From fc1df8c8307fc5022f9e8aae04164c089d8fdf2e Mon Sep 17 00:00:00 2001
From: GitLab Bot <gitlab-bot@gitlab.com>
Date: Tue, 17 Mar 2020 09:09:20 +0000
Subject: Add latest changes from gitlab-org/gitlab@master

---
 .vale.ini                                          |  39 +-
 app/assets/javascripts/api.js                      |   6 +-
 .../components/enable_review_app_button.vue        |   8 +-
 .../ide/components/commit_sidebar/list.vue         |   2 +-
 .../javascripts/ide/components/pipelines/list.vue  |   3 +-
 app/assets/javascripts/lib/utils/icon_utils.js     |  44 +-
 .../page_bundles/_ide_monaco_overrides.scss        | 146 +++++
 app/assets/stylesheets/page_bundles/ide.scss       | 224 +------
 app/services/system_note_service.rb                |   4 +
 app/services/system_notes/issuables_service.rb     |   6 +
 changelogs/unreleased/stop_environments.yml        |   5 +
 doc/.linting/vale/styles/gitlab/Contractions.yml   |  53 --
 doc/.linting/vale/styles/gitlab/FirstPerson.yml    |  13 -
 .../vale/styles/gitlab/InternalLinkExtension.yml   |  11 -
 doc/.linting/vale/styles/gitlab/LatinTerms.yml     |  17 -
 doc/.linting/vale/styles/gitlab/OxfordComma.yml    |  11 -
 doc/.linting/vale/styles/gitlab/RelativeLinks.yml  |  11 -
 .../vale/styles/gitlab/SentenceSpacing.yml         |  15 -
 doc/.linting/vale/styles/gitlab/Substitutions.yml  |  13 -
 doc/.vale/gitlab/Contractions.yml                  |  53 ++
 doc/.vale/gitlab/FirstPerson.yml                   |  13 +
 doc/.vale/gitlab/InternalLinkExtension.yml         |  11 +
 doc/.vale/gitlab/LatinTerms.yml                    |  17 +
 doc/.vale/gitlab/OxfordComma.yml                   |  11 +
 doc/.vale/gitlab/RelativeLinks.yml                 |  11 +
 doc/.vale/gitlab/SentenceSpacing.yml               |  15 +
 doc/.vale/gitlab/Substitutions.yml                 |  13 +
 doc/ci/review_apps/img/enable_review_app_v12_8.png | Bin 17151 -> 14013 bytes
 doc/development/contributing/issue_workflow.md     |   2 +
 doc/development/event_tracking/backend.md          |   5 +
 doc/development/event_tracking/frontend.md         |   5 +
 doc/development/event_tracking/index.md            |   5 +
 doc/policy/maintenance.md                          |  10 +-
 lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml  |   1 +
 lib/gitlab/import_export/group/tree_restorer.rb    |  25 +-
 lib/gitlab/import_export/json/legacy_reader.rb     | 104 +++
 lib/gitlab/import_export/project/tree_loader.rb    |  74 ---
 lib/gitlab/import_export/project/tree_restorer.rb  |  22 +-
 lib/gitlab/import_export/reader.rb                 |   8 +
 lib/gitlab/import_export/relation_tree_restorer.rb |  34 +-
 lib/gitlab/import_export/relation_tree_saver.rb    |   2 +-
 .../gitlab/import_export/invalid_json/project.json |   3 +
 spec/frontend/__mocks__/mousetrap/index.js         |   6 +
 spec/frontend/diffs/components/app_spec.js         | 723 +++++++++++++++++++++
 spec/frontend/diffs/create_diffs_store.js          |  15 +
 .../pipelines/__snapshots__/list_spec.js.snap      |   1 +
 spec/frontend/lib/utils/icon_utils_spec.js         |  72 +-
 .../frontend/mocks/ce/diffs/workers/tree_worker.js |   8 +
 spec/javascripts/diffs/components/app_spec.js      | 718 --------------------
 spec/javascripts/diffs/create_diffs_store.js       |  16 +-
 .../import_export/json/legacy_reader_spec.rb       | 149 +++++
 .../import_export/project/tree_loader_spec.rb      |  49 --
 .../import_export/project/tree_restorer_spec.rb    |   3 +-
 .../import_export/relation_tree_restorer_spec.rb   |  27 +-
 spec/services/system_note_service_spec.rb          |  10 +
 .../system_notes/issuables_service_spec.rb         |  12 +
 56 files changed, 1538 insertions(+), 1346 deletions(-)
 create mode 100644 app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss
 create mode 100644 changelogs/unreleased/stop_environments.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/Contractions.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/FirstPerson.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/InternalLinkExtension.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/LatinTerms.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/OxfordComma.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/RelativeLinks.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/SentenceSpacing.yml
 delete mode 100644 doc/.linting/vale/styles/gitlab/Substitutions.yml
 create mode 100644 doc/.vale/gitlab/Contractions.yml
 create mode 100644 doc/.vale/gitlab/FirstPerson.yml
 create mode 100644 doc/.vale/gitlab/InternalLinkExtension.yml
 create mode 100644 doc/.vale/gitlab/LatinTerms.yml
 create mode 100644 doc/.vale/gitlab/OxfordComma.yml
 create mode 100644 doc/.vale/gitlab/RelativeLinks.yml
 create mode 100644 doc/.vale/gitlab/SentenceSpacing.yml
 create mode 100644 doc/.vale/gitlab/Substitutions.yml
 create mode 100644 doc/development/event_tracking/backend.md
 create mode 100644 doc/development/event_tracking/frontend.md
 create mode 100644 doc/development/event_tracking/index.md
 create mode 100644 lib/gitlab/import_export/json/legacy_reader.rb
 delete mode 100644 lib/gitlab/import_export/project/tree_loader.rb
 create mode 100644 spec/fixtures/lib/gitlab/import_export/invalid_json/project.json
 create mode 100644 spec/frontend/__mocks__/mousetrap/index.js
 create mode 100644 spec/frontend/diffs/components/app_spec.js
 create mode 100644 spec/frontend/diffs/create_diffs_store.js
 create mode 100644 spec/frontend/mocks/ce/diffs/workers/tree_worker.js
 delete mode 100644 spec/javascripts/diffs/components/app_spec.js
 create mode 100644 spec/lib/gitlab/import_export/json/legacy_reader_spec.rb
 delete mode 100644 spec/lib/gitlab/import_export/project/tree_loader_spec.rb

diff --git a/.vale.ini b/.vale.ini
index 89a669ec7ff..13b198b9148 100644
--- a/.vale.ini
+++ b/.vale.ini
@@ -1,40 +1,9 @@
-# Vale configuration file, taken from https://errata-ai.github.io/vale/config/
+# Vale configuration file.
+#
+# For more information, see https://errata-ai.gitbook.io/vale/getting-started/configuration.
 
-# The relative path to the folder containing linting rules (styles)
-# -----------------------------------------------------------------
-StylesPath = doc/.linting/vale/styles
-
-# Minimum alert level
-# -------------------
-# The minimum alert level to display (suggestion, warning, or error).
-# If integrated into CI, builds fail by default on error-level alerts,
-# unless you execute Vale with the --no-exit flag
+StylesPath = doc/.vale
 MinAlertLevel = suggestion
 
-# Should Vale parse any file formats other than .md files as Markdown?
-# --------------------------------------------------------------------
-[formats]
-mdx = md
-
-# What file types should Vale test?
-# ----------------------------------
 [*.md]
-
-# Styles to load
-# --------------
-# What styles, located in the StylesPath folder, should Vale load?
-# Vale also currently includes write-good, proselint, joblint, and vale
 BasedOnStyles = gitlab
-
-# Enabling or disabling specific rules in a style
-# -----------------------------------------------
-# To disable a rule in an enabled style, use the following format:
-# {style}.{filename} = NO
-# To enable a single rule in a disabled style, use the following format:
-# vale.Editorializing = YES
-
-# Altering the severity of a rule in a style
-# ------------------------------------------
-# To change the reporting level (suggestion, warning, error) of a rule,
-# use the following format: {style}.{filename} = {level}
-# vale.Hedging = error
diff --git a/app/assets/javascripts/api.js b/app/assets/javascripts/api.js
index dc6ea148047..022d79ecf49 100644
--- a/app/assets/javascripts/api.js
+++ b/app/assets/javascripts/api.js
@@ -1,5 +1,3 @@
-import $ from 'jquery';
-import _ from 'underscore';
 import axios from './lib/utils/axios_utils';
 import { joinPaths } from './lib/utils/url_utility';
 import flash from '~/flash';
@@ -70,7 +68,7 @@ const Api = {
   },
 
   // Return groups list. Filtered by query
-  groups(query, options, callback = $.noop) {
+  groups(query, options, callback = () => {}) {
     const url = Api.buildUrl(Api.groupsPath);
     return axios
       .get(url, {
@@ -108,7 +106,7 @@ const Api = {
   },
 
   // Return projects list. Filtered by query
-  projects(query, options, callback = _.noop) {
+  projects(query, options, callback = () => {}) {
     const url = Api.buildUrl(Api.projectsPath);
     const defaults = {
       search: query,
diff --git a/app/assets/javascripts/environments/components/enable_review_app_button.vue b/app/assets/javascripts/environments/components/enable_review_app_button.vue
index 2f9e9cb628f..8fbbc5189bf 100644
--- a/app/assets/javascripts/environments/components/enable_review_app_button.vue
+++ b/app/assets/javascripts/environments/components/enable_review_app_button.vue
@@ -26,15 +26,17 @@ export default {
   modalInfo: {
     closeText: s__('EnableReviewApp|Close'),
     copyToClipboardText: s__('EnableReviewApp|Copy snippet text'),
-    copyString: `deploy_review
+    copyString: `deploy_review:
   stage: deploy
   script:
     - echo "Deploy a review app"
   environment:
     name: review/$CI_COMMIT_REF_NAME
     url: https://$CI_ENVIRONMENT_SLUG.example.com
-  only: branches
-  except: master`,
+  only:
+    - branches
+  except:
+    - master`,
     id: 'enable-review-app-info',
     title: s__('ReviewApp|Enable Review App'),
   },
diff --git a/app/assets/javascripts/ide/components/commit_sidebar/list.vue b/app/assets/javascripts/ide/components/commit_sidebar/list.vue
index 2e273d45506..a15e22d4742 100644
--- a/app/assets/javascripts/ide/components/commit_sidebar/list.vue
+++ b/app/assets/javascripts/ide/components/commit_sidebar/list.vue
@@ -94,7 +94,7 @@ export default {
             data-boundary="viewport"
             @click="openDiscardModal"
           >
-            <icon :size="16" name="remove-all" class="ml-auto mr-auto" />
+            <icon :size="16" name="remove-all" class="ml-auto mr-auto position-top-0" />
           </button>
         </div>
       </div>
diff --git a/app/assets/javascripts/ide/components/pipelines/list.vue b/app/assets/javascripts/ide/components/pipelines/list.vue
index b61d0a47795..3a63fc32639 100644
--- a/app/assets/javascripts/ide/components/pipelines/list.vue
+++ b/app/assets/javascripts/ide/components/pipelines/list.vue
@@ -59,7 +59,7 @@ export default {
     <gl-loading-icon v-if="showLoadingIcon" :size="2" class="prepend-top-default" />
     <template v-else-if="hasLoadedPipeline">
       <header v-if="latestPipeline" class="ide-tree-header ide-pipeline-header">
-        <ci-icon :status="latestPipeline.details.status" :size="24" />
+        <ci-icon :status="latestPipeline.details.status" :size="24" class="d-flex" />
         <span class="prepend-left-8">
           <strong> {{ __('Pipeline') }} </strong>
           <a
@@ -76,6 +76,7 @@ export default {
         :help-page-path="links.ciHelpPagePath"
         :empty-state-svg-path="pipelinesEmptyStateSvgPath"
         :can-set-ci="true"
+        class="mb-auto mt-auto"
       />
       <div v-else-if="latestPipeline.yamlError" class="bs-callout bs-callout-danger">
         <p class="append-bottom-0">{{ __('Found errors in your .gitlab-ci.yml:') }}</p>
diff --git a/app/assets/javascripts/lib/utils/icon_utils.js b/app/assets/javascripts/lib/utils/icon_utils.js
index 7b8dd9bbef7..97ee773358d 100644
--- a/app/assets/javascripts/lib/utils/icon_utils.js
+++ b/app/assets/javascripts/lib/utils/icon_utils.js
@@ -1,18 +1,40 @@
-/* eslint-disable import/prefer-default-export */
-
+import { memoize } from 'lodash';
 import axios from '~/lib/utils/axios_utils';
 
 /**
- * Retrieve SVG icon path content from gitlab/svg sprite icons
- * @param {String} name
+ * Resolves to a DOM that contains GitLab icons
+ * in svg format. Memoized to avoid duplicate requests
  */
-export const getSvgIconPathContent = name =>
+const getSvgDom = memoize(() =>
   axios
     .get(gon.sprite_icons)
-    .then(({ data: svgs }) =>
-      new DOMParser()
-        .parseFromString(svgs, 'text/xml')
-        .querySelector(`#${name} path`)
-        .getAttribute('d'),
-    )
+    .then(({ data: svgs }) => new DOMParser().parseFromString(svgs, 'text/xml'))
+    .catch(() => {
+      getSvgDom.cache.clear();
+    }),
+);
+
+/**
+ * Clears the memoized SVG content.
+ *
+ * You probably don't need to invoke this function unless
+ * sprite_icons are updated.
+ */
+export const clearSvgIconPathContentCache = () => {
+  getSvgDom.cache.clear();
+};
+
+/**
+ * Retrieve SVG icon path content from gitlab/svg sprite icons.
+ *
+ * Content loaded is cached.
+ *
+ * @param {String} name - Icon name
+ * @returns A promise that resolves to the svg path
+ */
+export const getSvgIconPathContent = name =>
+  getSvgDom()
+    .then(doc => {
+      return doc.querySelector(`#${name} path`).getAttribute('d');
+    })
     .catch(() => null);
diff --git a/app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss b/app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss
new file mode 100644
index 00000000000..c47901dc177
--- /dev/null
+++ b/app/assets/stylesheets/page_bundles/_ide_monaco_overrides.scss
@@ -0,0 +1,146 @@
+
+// stylelint-disable selector-class-pattern
+// stylelint-disable selector-max-compound-selectors
+// stylelint-disable stylelint-gitlab/duplicate-selectors
+// stylelint-disable stylelint-gitlab/utility-classes
+
+.blob-editor-container {
+  flex: 1;
+  height: 0;
+  display: flex;
+  flex-direction: column;
+  justify-content: center;
+
+  .vertical-center {
+    min-height: auto;
+  }
+
+  .monaco-editor .lines-content .cigr {
+    display: none;
+  }
+
+  .monaco-editor .selected-text {
+    z-index: 1;
+  }
+
+  .monaco-editor .view-lines {
+    z-index: 2;
+  }
+
+  .is-readonly,
+  .editor.original {
+    .view-lines {
+      cursor: default;
+    }
+
+    .cursors-layer {
+      display: none;
+    }
+  }
+
+  .is-deleted {
+    .editor.modified {
+      .margin-view-overlays,
+      .lines-content,
+      .decorationsOverviewRuler {
+        // !important to override monaco inline styles
+        display: none !important;
+      }
+    }
+
+    .diffOverviewRuler.modified {
+      // !important to override monaco inline styles
+      display: none !important;
+    }
+  }
+
+  .is-added {
+    .editor.original {
+      .margin-view-overlays,
+      .lines-content,
+      .decorationsOverviewRuler {
+        // !important to override monaco inline styles
+        display: none !important;
+      }
+    }
+
+    .diffOverviewRuler.original {
+      // !important to override monaco inline styles
+      display: none !important;
+    }
+  }
+
+  .monaco-diff-editor.vs {
+    .editor.modified {
+      box-shadow: none;
+    }
+
+    .diagonal-fill {
+      display: none !important;
+    }
+
+    .diffOverview {
+      background-color: $white-light;
+      border-left: 1px solid $white-dark;
+      cursor: ns-resize;
+    }
+
+    .diffViewport {
+      display: none;
+    }
+
+    .char-insert {
+      background-color: $line-added-dark;
+    }
+
+    .char-delete {
+      background-color: $line-removed-dark;
+    }
+
+    .line-numbers {
+      color: $black-transparent;
+    }
+
+    .view-overlays {
+      .line-insert {
+        background-color: $line-added;
+      }
+
+      .line-delete {
+        background-color: $line-removed;
+      }
+    }
+
+    .margin {
+      background-color: $white-light;
+      border-right: 1px solid $gray-100;
+
+      .line-insert {
+        border-right: 1px solid $line-added-dark;
+      }
+
+      .line-delete {
+        border-right: 1px solid $line-removed-dark;
+      }
+    }
+
+    .margin-view-overlays .insert-sign,
+    .margin-view-overlays .delete-sign {
+      opacity: 0.4;
+    }
+  }
+}
+
+.multi-file-editor-holder {
+  height: 100%;
+  min-height: 0; // firefox fix
+
+  &.is-readonly .vs,
+  .vs .editor.original {
+    .monaco-editor,
+    .monaco-editor-background,
+    .monaco-editor .inputarea.ime-input {
+      background-color: $gray-50;
+    }
+  }
+}
diff --git a/app/assets/stylesheets/page_bundles/ide.scss b/app/assets/stylesheets/page_bundles/ide.scss
index a748c669ee8..c37f75d1533 100644
--- a/app/assets/stylesheets/page_bundles/ide.scss
+++ b/app/assets/stylesheets/page_bundles/ide.scss
@@ -1,6 +1,7 @@
 @import 'framework/variables';
 @import 'framework/mixins';
 @import './ide_mixins';
+@import './ide_monaco_overrides';
 
 $search-list-icon-width: 18px;
 $ide-activity-bar-width: 60px;
@@ -16,11 +17,6 @@ $ide-commit-header-height: 48px;
   display: inline-block;
 }
 
-.fade-enter,
-.fade-leave-to {
-  opacity: 0;
-}
-
 .commit-message {
   @include str-truncated(250px);
 }
@@ -49,10 +45,6 @@ $ide-commit-header-height: 48px;
   flex-direction: column;
   flex: 1;
   min-height: 0; // firefox fix
-
-  a {
-    color: $gl-text-color;
-  }
 }
 
 .multi-file-loading-container {
@@ -160,157 +152,6 @@ $ide-commit-header-height: 48px;
   height: 0;
 }
 
-// stylelint-disable selector-class-pattern
-// stylelint-disable selector-max-compound-selectors
-// stylelint-disable stylelint-gitlab/duplicate-selectors
-// stylelint-disable stylelint-gitlab/utility-classes
-
-.blob-editor-container {
-  flex: 1;
-  height: 0;
-  display: flex;
-  flex-direction: column;
-  justify-content: center;
-
-  .vertical-center {
-    min-height: auto;
-  }
-
-  .monaco-editor .lines-content .cigr {
-    display: none;
-  }
-
-  .monaco-editor .selected-text {
-    z-index: 1;
-  }
-
-  .monaco-editor .view-lines {
-    z-index: 2;
-  }
-
-  .is-readonly,
-  .editor.original {
-    .view-lines {
-      cursor: default;
-    }
-
-    .cursors-layer {
-      display: none;
-    }
-  }
-
-  .is-deleted {
-    .editor.modified {
-      .margin-view-overlays,
-      .lines-content,
-      .decorationsOverviewRuler {
-        // !important to override monaco inline styles
-        display: none !important;
-      }
-    }
-
-    .diffOverviewRuler.modified {
-      // !important to override monaco inline styles
-      display: none !important;
-    }
-  }
-
-  .is-added {
-    .editor.original {
-      .margin-view-overlays,
-      .lines-content,
-      .decorationsOverviewRuler {
-        // !important to override monaco inline styles
-        display: none !important;
-      }
-    }
-
-    .diffOverviewRuler.original {
-      // !important to override monaco inline styles
-      display: none !important;
-    }
-  }
-
-  .monaco-diff-editor.vs {
-    .editor.modified {
-      box-shadow: none;
-    }
-
-    .diagonal-fill {
-      display: none !important;
-    }
-
-    .diffOverview {
-      background-color: $white-light;
-      border-left: 1px solid $white-dark;
-      cursor: ns-resize;
-    }
-
-    .diffViewport {
-      display: none;
-    }
-
-    .char-insert {
-      background-color: $line-added-dark;
-    }
-
-    .char-delete {
-      background-color: $line-removed-dark;
-    }
-
-    .line-numbers {
-      color: $black-transparent;
-    }
-
-    .view-overlays {
-      .line-insert {
-        background-color: $line-added;
-      }
-
-      .line-delete {
-        background-color: $line-removed;
-      }
-    }
-
-    .margin {
-      background-color: $white-light;
-      border-right: 1px solid $gray-100;
-
-      .line-insert {
-        border-right: 1px solid $line-added-dark;
-      }
-
-      .line-delete {
-        border-right: 1px solid $line-removed-dark;
-      }
-    }
-
-    .margin-view-overlays .insert-sign,
-    .margin-view-overlays .delete-sign {
-      opacity: 0.4;
-    }
-  }
-}
-
-.multi-file-editor-holder {
-  height: 100%;
-  min-height: 0; // firefox fix
-
-  &.is-readonly .vs,
-  .vs .editor.original {
-    .monaco-editor,
-    .monaco-editor-background,
-    .monaco-editor .inputarea.ime-input {
-      background-color: $gray-50;
-    }
-  }
-}
-
-// stylelint-enable selector-class-pattern
-// stylelint-enable selector-max-compound-selectors
-// stylelint-enable stylelint-gitlab/duplicate-selectors
-// stylelint-enable stylelint-gitlab/utility-classes
-
 .preview-container {
   flex-grow: 1;
   position: relative;
@@ -671,10 +512,6 @@ $ide-commit-header-height: 48px;
   width: $ide-commit-row-height;
   height: $ide-commit-row-height;
   color: inherit;
-
-  > svg {
-    top: 0;
-  }
 }
 
 .ide-commit-file-count {
@@ -864,39 +701,39 @@ $ide-commit-header-height: 48px;
     margin-left: auto;
   }
 
-  .ide-nav-dropdown {
-    width: 100%;
-    margin-bottom: 12px;
+  button {
+    color: $gl-text-color;
+  }
+}
 
-    .dropdown-menu {
-      width: 385px;
-      max-height: initial;
-    }
+.ide-nav-dropdown {
+  width: 100%;
+  margin-bottom: 12px;
 
-    .dropdown-menu-toggle {
-      svg {
-        vertical-align: middle;
-        color: $gray-700;
+  .dropdown-menu {
+    width: 385px;
+    max-height: initial;
+  }
 
-        &:hover {
-          color: $gray-700;
-        }
-      }
+  .dropdown-menu-toggle {
+    svg {
+      vertical-align: middle;
+      color: $gray-700;
 
       &:hover {
-        background-color: $white-normal;
+        color: $gray-700;
       }
     }
 
-    &.show {
-      .dropdown-menu-toggle {
-        background-color: $white-dark;
-      }
+    &:hover {
+      background-color: $white-normal;
     }
   }
 
-  button {
-    color: $gl-text-color;
+  &.show {
+    .dropdown-menu-toggle {
+      background-color: $white-dark;
+    }
   }
 }
 
@@ -945,6 +782,8 @@ $ide-commit-header-height: 48px;
   transform: translateY(0);
 }
 
+.fade-enter,
+.fade-leave-to,
 .commit-form-slide-up-enter,
 .commit-form-slide-up-leave-to {
   opacity: 0;
@@ -1063,9 +902,6 @@ $ide-commit-header-height: 48px;
   @include ide-trace-view();
 
   .empty-state {
-    margin-top: auto;
-    margin-bottom: auto;
-
     p {
       margin: $grid-size 0;
       text-align: center;
@@ -1092,10 +928,6 @@ $ide-commit-header-height: 48px;
   min-height: 55px;
   padding-left: $gl-padding;
   padding-right: $gl-padding;
-
-  .ci-status-icon {
-    display: flex;
-  }
 }
 
 .ide-job-item {
@@ -1135,7 +967,7 @@ $ide-commit-header-height: 48px;
 }
 
 .ide-nav-form {
-  .nav-links li {
+  li {
     width: 50%;
     padding-left: 0;
     padding-right: 0;
@@ -1222,10 +1054,6 @@ $ide-commit-header-height: 48px;
     background-color: $blue-500;
     outline: 0;
   }
-
-  svg {
-    fill: currentColor;
-  }
 }
 
 .ide-new-btn {
diff --git a/app/services/system_note_service.rb b/app/services/system_note_service.rb
index 8a0f44b4e93..1b9f5971f73 100644
--- a/app/services/system_note_service.rb
+++ b/app/services/system_note_service.rb
@@ -241,6 +241,10 @@ module SystemNoteService
   def zoom_link_removed(issue, project, author)
     ::SystemNotes::ZoomService.new(noteable: issue, project: project, author: author).zoom_link_removed
   end
+
+  def auto_resolve_prometheus_alert(noteable, project, author)
+    ::SystemNotes::IssuablesService.new(noteable: noteable, project: project, author: author).auto_resolve_prometheus_alert
+  end
 end
 
 SystemNoteService.prepend_if_ee('EE::SystemNoteService')
diff --git a/app/services/system_notes/issuables_service.rb b/app/services/system_notes/issuables_service.rb
index b555760f88e..275c64bea89 100644
--- a/app/services/system_notes/issuables_service.rb
+++ b/app/services/system_notes/issuables_service.rb
@@ -288,6 +288,12 @@ module SystemNotes
       create_note(NoteSummary.new(noteable, project, author, body, action: 'closed'))
     end
 
+    def auto_resolve_prometheus_alert
+      body = 'automatically closed this issue because the alert resolved.'
+
+      create_note(NoteSummary.new(noteable, project, author, body, action: 'closed'))
+    end
+
     private
 
     def cross_reference_note_content(gfm_reference)
diff --git a/changelogs/unreleased/stop_environments.yml b/changelogs/unreleased/stop_environments.yml
new file mode 100644
index 00000000000..ea92be202af
--- /dev/null
+++ b/changelogs/unreleased/stop_environments.yml
@@ -0,0 +1,5 @@
+---
+title: 'Fixes stop_review job upon expired artifacts from previous stages'
+merge_request: 27258
+author: Jack Lei
+type: fixed
diff --git a/doc/.linting/vale/styles/gitlab/Contractions.yml b/doc/.linting/vale/styles/gitlab/Contractions.yml
deleted file mode 100644
index 5f389bd1ea4..00000000000
--- a/doc/.linting/vale/styles/gitlab/Contractions.yml
+++ /dev/null
@@ -1,53 +0,0 @@
----
-# Checks for use of common and uncommon contractions.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: substitution
-message: Use "%s" instead of "%s" in most cases.
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
-level: suggestion
-nonword: false
-ignorecase: true
-swap:
-
-  # Common contractions are ok
-  it is: it's
-  can not: can't
-  cannot: can't
-  do not: don't
-  have not: haven't
-  that is: that's
-  we are: we're
-  will not: won't
-  would not: wouldn't
-  you are: you're
-  you have: you've
-
-  # Uncommon contractions are not ok
-  aren't: are not
-  couldn't: could not
-  didn't: did not
-  doesn't: does not
-  hasn't: has not
-  how'll: how will
-  how's: how is
-  isn't: is not
-  it'll: it will
-  shouldn't: should not
-  that'll: that will
-  they'll: they will
-  they're: they are
-  wasn't: was not
-  weren't: were not
-  we'll: we will
-  we've: we have
-  what's: what is
-  what'll: what will
-  when's: when is
-  when'll: when will
-  where's: where is
-  where'll: where will
-  who's: who is
-  who'll: who will
-  why's: why is
-  why'll: why will
diff --git a/doc/.linting/vale/styles/gitlab/FirstPerson.yml b/doc/.linting/vale/styles/gitlab/FirstPerson.yml
deleted file mode 100644
index 18c5265b0a6..00000000000
--- a/doc/.linting/vale/styles/gitlab/FirstPerson.yml
+++ /dev/null
@@ -1,13 +0,0 @@
-# Checks for use of first person pronouns.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: existence
-message: '`%s` is a first-person pronoun. Use second- or third-person pronouns (like we, you, us, one) instead.'
-level: warning
-ignorecase: true
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
-tokens:
-  - '\bI[ ,;:?!"]|\bI\x27.{1,2}'
-  - me
-  - myself
-  - mine
diff --git a/doc/.linting/vale/styles/gitlab/InternalLinkExtension.yml b/doc/.linting/vale/styles/gitlab/InternalLinkExtension.yml
deleted file mode 100644
index d07a2600798..00000000000
--- a/doc/.linting/vale/styles/gitlab/InternalLinkExtension.yml
+++ /dev/null
@@ -1,11 +0,0 @@
----
-# Checks that internal links have .md extenstion and not .html extension.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: existence
-message: Link %s must use the .md file extension.
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#links-to-internal-documentation
-level: error
-scope: raw
-raw:
-  - '\[.+\]\((https?:){0}[\w\/\.-]+(\.html).*\)'
diff --git a/doc/.linting/vale/styles/gitlab/LatinTerms.yml b/doc/.linting/vale/styles/gitlab/LatinTerms.yml
deleted file mode 100644
index 8412631f8fe..00000000000
--- a/doc/.linting/vale/styles/gitlab/LatinTerms.yml
+++ /dev/null
@@ -1,17 +0,0 @@
----
-# Checks for use of latin terms..
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: substitution
-message: Use "%s" instead of "%s," but consider rewriting the sentence.
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
-level: warning
-nonword: true
-ignorecase: true
-swap:
-  e\.g\.: for example
-  e\. g\.: for example
-  i\.e\.: that is
-  i\. e\.: that is
-  etc\.: and so on
-  et cetera: and so on
diff --git a/doc/.linting/vale/styles/gitlab/OxfordComma.yml b/doc/.linting/vale/styles/gitlab/OxfordComma.yml
deleted file mode 100644
index 4b37ba8c2b9..00000000000
--- a/doc/.linting/vale/styles/gitlab/OxfordComma.yml
+++ /dev/null
@@ -1,11 +0,0 @@
----
-# Checks for the lack of an Oxford comma. In some cases, will catch overly
-# complex sentence structures with lots of commas.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: existence
-message: Use a comma before the last "and" or "or" in a list of four or more items.
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#punctuation
-level: warning
-raw:
-  - '(?:[\w-_` ]+,){2,}(?:[\w-_` ]+) (and |or )'
diff --git a/doc/.linting/vale/styles/gitlab/RelativeLinks.yml b/doc/.linting/vale/styles/gitlab/RelativeLinks.yml
deleted file mode 100644
index 95bd60dd6e4..00000000000
--- a/doc/.linting/vale/styles/gitlab/RelativeLinks.yml
+++ /dev/null
@@ -1,11 +0,0 @@
----
-# Checks for the presence of absolute hyperlinks that should be relative.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: existence
-message: Link %s must be relative.
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#links-to-internal-documentation
-level: error
-scope: raw
-raw:
-  - '\[.+\]\(https?:\/\/docs\.gitlab\.com\/ee.*\)'
diff --git a/doc/.linting/vale/styles/gitlab/SentenceSpacing.yml b/doc/.linting/vale/styles/gitlab/SentenceSpacing.yml
deleted file mode 100644
index b061f7f6f9e..00000000000
--- a/doc/.linting/vale/styles/gitlab/SentenceSpacing.yml
+++ /dev/null
@@ -1,15 +0,0 @@
----
-# Check for the following in common content scenarios:
-#
-# - No spaces.
-# - More than one space.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: existence
-message: '"%s" must contain one and only one space.'
-link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#punctuation
-level: error
-nonword: true
-tokens:
-  - '[a-z][.?!,][A-Z]'
-  - '[\w.?!,\(\)\-":] {2,}[\w.?!,\(\)\-":]'
diff --git a/doc/.linting/vale/styles/gitlab/Substitutions.yml b/doc/.linting/vale/styles/gitlab/Substitutions.yml
deleted file mode 100644
index b32a03e17d5..00000000000
--- a/doc/.linting/vale/styles/gitlab/Substitutions.yml
+++ /dev/null
@@ -1,13 +0,0 @@
----
-# Checks for use of some of the top misused terms at GitLab.
-#
-# For a list of all options, see https://errata-ai.github.io/vale/styles/
-extends: substitution
-message: Use "%s" instead of "%s".
-link: https://about.gitlab.com/handbook/communication/#top-misused-terms
-level: error
-ignorecase: true
-swap:
-  GitLabber: GitLab team member
-  self hosted: self-managed
-  self-hosted: self-managed
diff --git a/doc/.vale/gitlab/Contractions.yml b/doc/.vale/gitlab/Contractions.yml
new file mode 100644
index 00000000000..5f389bd1ea4
--- /dev/null
+++ b/doc/.vale/gitlab/Contractions.yml
@@ -0,0 +1,53 @@
+---
+# Checks for use of common and uncommon contractions.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: substitution
+message: Use "%s" instead of "%s" in most cases.
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
+level: suggestion
+nonword: false
+ignorecase: true
+swap:
+
+  # Common contractions are ok
+  it is: it's
+  can not: can't
+  cannot: can't
+  do not: don't
+  have not: haven't
+  that is: that's
+  we are: we're
+  will not: won't
+  would not: wouldn't
+  you are: you're
+  you have: you've
+
+  # Uncommon contractions are not ok
+  aren't: are not
+  couldn't: could not
+  didn't: did not
+  doesn't: does not
+  hasn't: has not
+  how'll: how will
+  how's: how is
+  isn't: is not
+  it'll: it will
+  shouldn't: should not
+  that'll: that will
+  they'll: they will
+  they're: they are
+  wasn't: was not
+  weren't: were not
+  we'll: we will
+  we've: we have
+  what's: what is
+  what'll: what will
+  when's: when is
+  when'll: when will
+  where's: where is
+  where'll: where will
+  who's: who is
+  who'll: who will
+  why's: why is
+  why'll: why will
diff --git a/doc/.vale/gitlab/FirstPerson.yml b/doc/.vale/gitlab/FirstPerson.yml
new file mode 100644
index 00000000000..18c5265b0a6
--- /dev/null
+++ b/doc/.vale/gitlab/FirstPerson.yml
@@ -0,0 +1,13 @@
+# Checks for use of first person pronouns.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: existence
+message: '`%s` is a first-person pronoun. Use second- or third-person pronouns (like we, you, us, one) instead.'
+level: warning
+ignorecase: true
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
+tokens:
+  - '\bI[ ,;:?!"]|\bI\x27.{1,2}'
+  - me
+  - myself
+  - mine
diff --git a/doc/.vale/gitlab/InternalLinkExtension.yml b/doc/.vale/gitlab/InternalLinkExtension.yml
new file mode 100644
index 00000000000..d07a2600798
--- /dev/null
+++ b/doc/.vale/gitlab/InternalLinkExtension.yml
@@ -0,0 +1,11 @@
+---
+# Checks that internal links have .md extenstion and not .html extension.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: existence
+message: Link %s must use the .md file extension.
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#links-to-internal-documentation
+level: error
+scope: raw
+raw:
+  - '\[.+\]\((https?:){0}[\w\/\.-]+(\.html).*\)'
diff --git a/doc/.vale/gitlab/LatinTerms.yml b/doc/.vale/gitlab/LatinTerms.yml
new file mode 100644
index 00000000000..8412631f8fe
--- /dev/null
+++ b/doc/.vale/gitlab/LatinTerms.yml
@@ -0,0 +1,17 @@
+---
+# Checks for use of latin terms..
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: substitution
+message: Use "%s" instead of "%s," but consider rewriting the sentence.
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#language
+level: warning
+nonword: true
+ignorecase: true
+swap:
+  e\.g\.: for example
+  e\. g\.: for example
+  i\.e\.: that is
+  i\. e\.: that is
+  etc\.: and so on
+  et cetera: and so on
diff --git a/doc/.vale/gitlab/OxfordComma.yml b/doc/.vale/gitlab/OxfordComma.yml
new file mode 100644
index 00000000000..4b37ba8c2b9
--- /dev/null
+++ b/doc/.vale/gitlab/OxfordComma.yml
@@ -0,0 +1,11 @@
+---
+# Checks for the lack of an Oxford comma. In some cases, will catch overly
+# complex sentence structures with lots of commas.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: existence
+message: Use a comma before the last "and" or "or" in a list of four or more items.
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#punctuation
+level: warning
+raw:
+  - '(?:[\w-_` ]+,){2,}(?:[\w-_` ]+) (and |or )'
diff --git a/doc/.vale/gitlab/RelativeLinks.yml b/doc/.vale/gitlab/RelativeLinks.yml
new file mode 100644
index 00000000000..95bd60dd6e4
--- /dev/null
+++ b/doc/.vale/gitlab/RelativeLinks.yml
@@ -0,0 +1,11 @@
+---
+# Checks for the presence of absolute hyperlinks that should be relative.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: existence
+message: Link %s must be relative.
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#links-to-internal-documentation
+level: error
+scope: raw
+raw:
+  - '\[.+\]\(https?:\/\/docs\.gitlab\.com\/ee.*\)'
diff --git a/doc/.vale/gitlab/SentenceSpacing.yml b/doc/.vale/gitlab/SentenceSpacing.yml
new file mode 100644
index 00000000000..b061f7f6f9e
--- /dev/null
+++ b/doc/.vale/gitlab/SentenceSpacing.yml
@@ -0,0 +1,15 @@
+---
+# Check for the following in common content scenarios:
+#
+# - No spaces.
+# - More than one space.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: existence
+message: '"%s" must contain one and only one space.'
+link: https://docs.gitlab.com/ee/development/documentation/styleguide.html#punctuation
+level: error
+nonword: true
+tokens:
+  - '[a-z][.?!,][A-Z]'
+  - '[\w.?!,\(\)\-":] {2,}[\w.?!,\(\)\-":]'
diff --git a/doc/.vale/gitlab/Substitutions.yml b/doc/.vale/gitlab/Substitutions.yml
new file mode 100644
index 00000000000..b32a03e17d5
--- /dev/null
+++ b/doc/.vale/gitlab/Substitutions.yml
@@ -0,0 +1,13 @@
+---
+# Checks for use of some of the top misused terms at GitLab.
+#
+# For a list of all options, see https://errata-ai.github.io/vale/styles/
+extends: substitution
+message: Use "%s" instead of "%s".
+link: https://about.gitlab.com/handbook/communication/#top-misused-terms
+level: error
+ignorecase: true
+swap:
+  GitLabber: GitLab team member
+  self hosted: self-managed
+  self-hosted: self-managed
diff --git a/doc/ci/review_apps/img/enable_review_app_v12_8.png b/doc/ci/review_apps/img/enable_review_app_v12_8.png
index 7d40f49725f..264e4834e72 100644
Binary files a/doc/ci/review_apps/img/enable_review_app_v12_8.png and b/doc/ci/review_apps/img/enable_review_app_v12_8.png differ
diff --git a/doc/development/contributing/issue_workflow.md b/doc/development/contributing/issue_workflow.md
index 4d84e921acf..46d1d4c2414 100644
--- a/doc/development/contributing/issue_workflow.md
+++ b/doc/development/contributing/issue_workflow.md
@@ -81,6 +81,8 @@ already reserved for category labels).
 The descriptions on the [labels page](https://gitlab.com/groups/gitlab-org/-/labels)
 explain what falls under each type label.
 
+The GitLab handbook documents [when something is a bug and when it is a feature request.](https://about.gitlab.com/handbook/product/product-management/process/feature-or-bug.html)
+
 ### Facet labels
 
 Sometimes it's useful to refine the type of an issue. In those cases, you can
diff --git a/doc/development/event_tracking/backend.md b/doc/development/event_tracking/backend.md
new file mode 100644
index 00000000000..dc4d7279671
--- /dev/null
+++ b/doc/development/event_tracking/backend.md
@@ -0,0 +1,5 @@
+---
+redirect_to: '../../telemetry/backend.md'
+---
+
+This document was moved to [another location](../../telemetry/backend.md).
diff --git a/doc/development/event_tracking/frontend.md b/doc/development/event_tracking/frontend.md
new file mode 100644
index 00000000000..0e98daf15bb
--- /dev/null
+++ b/doc/development/event_tracking/frontend.md
@@ -0,0 +1,5 @@
+---
+redirect_to: '../../telemetry/frontend.md'
+---
+
+This document was moved to [another location](../../telemetry/frontend.md).
diff --git a/doc/development/event_tracking/index.md b/doc/development/event_tracking/index.md
new file mode 100644
index 00000000000..ae555e99c6b
--- /dev/null
+++ b/doc/development/event_tracking/index.md
@@ -0,0 +1,5 @@
+---
+redirect_to: '../../telemetry/index.md'
+---
+
+This document was moved to [another location](../../telemetry/index.md).
diff --git a/doc/policy/maintenance.md b/doc/policy/maintenance.md
index 1739c07ccd5..028e372985d 100644
--- a/doc/policy/maintenance.md
+++ b/doc/policy/maintenance.md
@@ -127,7 +127,7 @@ one major version. For example, it is safe to:
   - `9.5.5` -> `9.5.9`
   - `10.6.3` -> `10.6.6`
   - `11.11.1` -> `11.11.8`
-  - `12.0.4` -> `12.0.9`
+  - `12.0.4` -> `12.0.12`
 - Upgrade the minor version:
   - `8.9.4` -> `8.12.3`
   - `9.2.3` -> `9.5.5`
@@ -144,9 +144,10 @@ It's also important to ensure that any background migrations have been fully com
 before upgrading to a new major version. To see the current size of the `background_migration` queue,
 [Check for background migrations before upgrading](../update/README.md#checking-for-background-migrations-before-upgrading).
 
-To ensure background migrations are successful, increment by one minor version during the version jump before installing newer releases.
+From version 12 onwards, an additional step is required. More significant migrations may occur during major release upgrades. To ensure these are successful, increment to the first minor version (`x.0.x`) during the major version jump. Then proceed with upgrading to a newer release.
+
+For example: `11.11.x` -> `12.0.x` -> `12.8.x`
 
-For example: `11.11.x` -> `12.0.x`
 Please see the table below for some examples:
 
 | Latest stable version | Your version | Recommended upgrade path | Note |
@@ -154,7 +155,8 @@ Please see the table below for some examples:
 | 9.4.5                 | 8.13.4       | `8.13.4` -> `8.17.7` -> `9.4.5`                          | `8.17.7` is the last version in version `8` |
 | 10.1.4                | 8.13.4       | `8.13.4 -> 8.17.7 -> 9.5.10 -> 10.1.4`                   | `8.17.7` is the last version in version `8`, `9.5.10` is the last version in version `9` |
 | 11.3.4                | 8.13.4       | `8.13.4` -> `8.17.7` -> `9.5.10` -> `10.8.7` -> `11.3.4` | `8.17.7` is the last version in version `8`, `9.5.10` is the last version in version `9`, `10.8.7` is the last version in version `10` |
-| 12.5.8                | 11.3.4       | `11.3.4` -> `11.11.8` -> `12.0.9` -> `12.5.8`            | `11.11.8` is the last version in version `11` |
+| 12.5.8                | 11.3.4       | `11.3.4` -> `11.11.8` -> `12.0.12` -> `12.5.8`            | `11.11.8` is the last version in version `11`. `12.0.x` [is a required step.](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/23211#note_272842444) |
+| 12.8.5                | 9.2.6       | `9.2.6` -> `9.5.10` -> `10.8.7` -> `11.11.8` -> `12.0.12` -> `12.8.5` | Four intermediate versions required: the final 9.5, 10.8, 11.11 releases, plus 12.0 |
 
 More information about the release procedures can be found in our
 [release documentation](https://gitlab.com/gitlab-org/release/docs). You may also want to read our
diff --git a/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml b/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml
index bbfcf53b3d4..c6c8256b4bb 100644
--- a/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml
+++ b/lib/gitlab/ci/templates/Jobs/Deploy.gitlab-ci.yml
@@ -40,6 +40,7 @@ stop_review:
   environment:
     name: review/$CI_COMMIT_REF_NAME
     action: stop
+  dependencies: []
   when: manual
   allow_failure: true
   only:
diff --git a/lib/gitlab/import_export/group/tree_restorer.rb b/lib/gitlab/import_export/group/tree_restorer.rb
index cbaa6929efa..247e39a68b9 100644
--- a/lib/gitlab/import_export/group/tree_restorer.rb
+++ b/lib/gitlab/import_export/group/tree_restorer.rb
@@ -17,9 +17,17 @@ module Gitlab
         end
 
         def restore
-          @tree_hash = @group_hash || read_tree_hash
-          @group_members = @tree_hash.delete('members')
-          @children = @tree_hash.delete('children')
+          @relation_reader ||=
+            if @group_hash.present?
+              ImportExport::JSON::LegacyReader::User.new(@group_hash, reader.group_relation_names)
+            else
+              ImportExport::JSON::LegacyReader::File.new(@path, reader.group_relation_names)
+            end
+
+          @group_members = @relation_reader.consume_relation('members')
+          @children = @relation_reader.consume_attribute('children')
+          @relation_reader.consume_attribute('name')
+          @relation_reader.consume_attribute('path')
 
           if members_mapper.map && restorer.restore
             @children&.each do |group_hash|
@@ -45,21 +53,12 @@ module Gitlab
 
         private
 
-        def read_tree_hash
-          json = IO.read(@path)
-          ActiveSupport::JSON.decode(json)
-        rescue => e
-          @shared.error(e)
-
-          raise Gitlab::ImportExport::Error.new('Incorrect JSON format')
-        end
-
         def restorer
           @relation_tree_restorer ||= RelationTreeRestorer.new(
             user:             @user,
             shared:           @shared,
             importable:       @group,
-            tree_hash:        @tree_hash.except('name', 'path'),
+            relation_reader:  @relation_reader,
             members_mapper:   members_mapper,
             object_builder:   object_builder,
             relation_factory: relation_factory,
diff --git a/lib/gitlab/import_export/json/legacy_reader.rb b/lib/gitlab/import_export/json/legacy_reader.rb
new file mode 100644
index 00000000000..477e41ae3eb
--- /dev/null
+++ b/lib/gitlab/import_export/json/legacy_reader.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module ImportExport
+    module JSON
+      class LegacyReader
+        class File < LegacyReader
+          def initialize(path, relation_names)
+            @path = path
+            super(relation_names)
+          end
+
+          def valid?
+            ::File.exist?(@path)
+          end
+
+          private
+
+          def tree_hash
+            @tree_hash ||= read_hash
+          end
+
+          def read_hash
+            ActiveSupport::JSON.decode(IO.read(@path))
+          rescue => e
+            Gitlab::ErrorTracking.log_exception(e)
+            raise Gitlab::ImportExport::Error.new('Incorrect JSON format')
+          end
+        end
+
+        class User < LegacyReader
+          def initialize(tree_hash, relation_names)
+            @tree_hash = tree_hash
+            super(relation_names)
+          end
+
+          def valid?
+            @tree_hash.present?
+          end
+
+          protected
+
+          attr_reader :tree_hash
+        end
+
+        def initialize(relation_names)
+          @relation_names = relation_names.map(&:to_s)
+        end
+
+        def valid?
+          raise NotImplementedError
+        end
+
+        def legacy?
+          true
+        end
+
+        def root_attributes(excluded_attributes = [])
+          attributes.except(*excluded_attributes.map(&:to_s))
+        end
+
+        def consume_relation(key)
+          value = relations.delete(key)
+
+          return value unless block_given?
+
+          return if value.nil?
+
+          if value.is_a?(Array)
+            value.each.with_index do |item, idx|
+              yield(item, idx)
+            end
+          else
+            yield(value, 0)
+          end
+        end
+
+        def consume_attribute(key)
+          attributes.delete(key)
+        end
+
+        def sort_ci_pipelines_by_id
+          relations['ci_pipelines']&.sort_by! { |hash| hash['id'] }
+        end
+
+        private
+
+        attr_reader :relation_names
+
+        def tree_hash
+          raise NotImplementedError
+        end
+
+        def attributes
+          @attributes ||= tree_hash.slice!(*relation_names)
+        end
+
+        def relations
+          @relations ||= tree_hash.extract!(*relation_names)
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/import_export/project/tree_loader.rb b/lib/gitlab/import_export/project/tree_loader.rb
deleted file mode 100644
index 6d4737a2d00..00000000000
--- a/lib/gitlab/import_export/project/tree_loader.rb
+++ /dev/null
@@ -1,74 +0,0 @@
-# frozen_string_literal: true
-
-module Gitlab
-  module ImportExport
-    module Project
-      class TreeLoader
-        def load(path, dedup_entries: false)
-          tree_hash = ActiveSupport::JSON.decode(IO.read(path))
-
-          if dedup_entries
-            dedup_tree(tree_hash)
-          else
-            tree_hash
-          end
-        end
-
-        private
-
-        # This function removes duplicate entries from the given tree recursively
-        # by caching nodes it encounters repeatedly. We only consider nodes for
-        # which there can actually be multiple equivalent instances (e.g. strings,
-        # hashes and arrays, but not `nil`s, numbers or booleans.)
-        #
-        # The algorithm uses a recursive depth-first descent with 3 cases, starting
-        # with a root node (the tree/hash itself):
-        # - a node has already been cached; in this case we return it from the cache
-        # - a node has not been cached yet but should be; descend into its children
-        # - a node is neither cached nor qualifies for caching; this is a no-op
-        def dedup_tree(node, nodes_seen = {})
-          if nodes_seen.key?(node) && distinguishable?(node)
-            yield nodes_seen[node]
-          elsif should_dedup?(node)
-            nodes_seen[node] = node
-
-            case node
-            when Array
-              node.each_index do |idx|
-                dedup_tree(node[idx], nodes_seen) do |cached_node|
-                  node[idx] = cached_node
-                end
-              end
-            when Hash
-              node.each do |k, v|
-                dedup_tree(v, nodes_seen) do |cached_node|
-                  node[k] = cached_node
-                end
-              end
-            end
-          else
-            node
-          end
-        end
-
-        # We do not need to consider nodes for which there cannot be multiple instances
-        def should_dedup?(node)
-          node && !(node.is_a?(Numeric) || node.is_a?(TrueClass) || node.is_a?(FalseClass))
-        end
-
-        # We can only safely de-dup values that are distinguishable. True value objects
-        # are always distinguishable by nature. Hashes however can represent entities,
-        # which are identified by ID, not value. We therefore disallow de-duping hashes
-        # that do not have an `id` field, since we might risk dropping entities that
-        # have equal attributes yet different identities.
-        def distinguishable?(node)
-          if node.is_a?(Hash)
-            node.key?('id')
-          else
-            true
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/import_export/project/tree_restorer.rb b/lib/gitlab/import_export/project/tree_restorer.rb
index 295e0d5f348..f8d25e14c02 100644
--- a/lib/gitlab/import_export/project/tree_restorer.rb
+++ b/lib/gitlab/import_export/project/tree_restorer.rb
@@ -4,8 +4,6 @@ module Gitlab
   module ImportExport
     module Project
       class TreeRestorer
-        LARGE_PROJECT_FILE_SIZE_BYTES = 500.megabyte
-
         attr_reader :user
         attr_reader :shared
         attr_reader :project
@@ -14,12 +12,12 @@ module Gitlab
           @user = user
           @shared = shared
           @project = project
-          @tree_loader = TreeLoader.new
         end
 
         def restore
-          @tree_hash = read_tree_hash
-          @project_members = @tree_hash.delete('project_members')
+          @relation_reader = ImportExport::JSON::LegacyReader::File.new(File.join(shared.export_path, 'project.json'), reader.project_relation_names)
+
+          @project_members = @relation_reader.consume_relation('project_members')
 
           if relation_tree_restorer.restore
             import_failure_service.with_retry(action: 'set_latest_merge_request_diff_ids!') do
@@ -37,24 +35,12 @@ module Gitlab
 
         private
 
-        def large_project?(path)
-          File.size(path) >= LARGE_PROJECT_FILE_SIZE_BYTES
-        end
-
-        def read_tree_hash
-          path = File.join(@shared.export_path, 'project.json')
-          @tree_loader.load(path, dedup_entries: large_project?(path))
-        rescue => e
-          Rails.logger.error("Import/Export error: #{e.message}") # rubocop:disable Gitlab/RailsLogger
-          raise Gitlab::ImportExport::Error.new('Incorrect JSON format')
-        end
-
         def relation_tree_restorer
           @relation_tree_restorer ||= RelationTreeRestorer.new(
             user: @user,
             shared: @shared,
             importable: @project,
-            tree_hash: @tree_hash,
+            relation_reader: @relation_reader,
             object_builder: object_builder,
             members_mapper: members_mapper,
             relation_factory: relation_factory,
diff --git a/lib/gitlab/import_export/reader.rb b/lib/gitlab/import_export/reader.rb
index 1390770acef..8d36d05ca6f 100644
--- a/lib/gitlab/import_export/reader.rb
+++ b/lib/gitlab/import_export/reader.rb
@@ -17,10 +17,18 @@ module Gitlab
         tree_by_key(:project)
       end
 
+      def project_relation_names
+        attributes_finder.find_relations_tree(:project).keys
+      end
+
       def group_tree
         tree_by_key(:group)
       end
 
+      def group_relation_names
+        attributes_finder.find_relations_tree(:group).keys
+      end
+
       def group_members_tree
         tree_by_key(:group_members)
       end
diff --git a/lib/gitlab/import_export/relation_tree_restorer.rb b/lib/gitlab/import_export/relation_tree_restorer.rb
index 8359eefc846..466cb03862e 100644
--- a/lib/gitlab/import_export/relation_tree_restorer.rb
+++ b/lib/gitlab/import_export/relation_tree_restorer.rb
@@ -9,13 +9,13 @@ module Gitlab
       attr_reader :user
       attr_reader :shared
       attr_reader :importable
-      attr_reader :tree_hash
+      attr_reader :relation_reader
 
-      def initialize(user:, shared:, importable:, tree_hash:, members_mapper:, object_builder:, relation_factory:, reader:)
+      def initialize(user:, shared:, importable:, relation_reader:, members_mapper:, object_builder:, relation_factory:, reader:)
         @user = user
         @shared = shared
         @importable = importable
-        @tree_hash = tree_hash
+        @relation_reader = relation_reader
         @members_mapper = members_mapper
         @object_builder = object_builder
         @relation_factory = relation_factory
@@ -30,7 +30,7 @@ module Gitlab
             bulk_inserts_enabled = @importable.class == ::Project &&
               Feature.enabled?(:import_bulk_inserts, @importable.group)
             BulkInsertableAssociations.with_bulk_insert(enabled: bulk_inserts_enabled) do
-              update_relation_hashes!
+              fix_ci_pipelines_not_sorted_on_legacy_project_json!
               create_relations!
             end
           end
@@ -57,18 +57,8 @@ module Gitlab
       end
 
       def process_relation!(relation_key, relation_definition)
-        data_hashes = @tree_hash.delete(relation_key)
-        return unless data_hashes
-
-        # we do not care if we process array or hash
-        data_hashes = [data_hashes] unless data_hashes.is_a?(Array)
-
-        relation_index = 0
-
-        # consume and remove objects from memory
-        while data_hash = data_hashes.shift
+        @relation_reader.consume_relation(relation_key) do |data_hash, relation_index|
           process_relation_item!(relation_key, relation_definition, relation_index, data_hash)
-          relation_index += 1
         end
       end
 
@@ -103,10 +93,7 @@ module Gitlab
       end
 
       def update_params!
-        params = @tree_hash.reject do |key, _|
-          relations.include?(key)
-        end
-
+        params = @relation_reader.root_attributes(relations.keys)
         params = params.merge(present_override_params)
 
         # Cleaning all imported and overridden params
@@ -223,8 +210,13 @@ module Gitlab
         }
       end
 
-      def update_relation_hashes!
-        @tree_hash['ci_pipelines']&.sort_by! { |hash| hash['id'] }
+      # Temporary fix for https://gitlab.com/gitlab-org/gitlab/-/issues/27883 when import from legacy project.json
+      # This should be removed once legacy JSON format is deprecated.
+      # Ndjson export file will fix the order during project export.
+      def fix_ci_pipelines_not_sorted_on_legacy_project_json!
+        return unless relation_reader.legacy?
+
+        relation_reader.sort_ci_pipelines_by_id
       end
     end
   end
diff --git a/lib/gitlab/import_export/relation_tree_saver.rb b/lib/gitlab/import_export/relation_tree_saver.rb
index a0452071ccf..ed5392c13d0 100644
--- a/lib/gitlab/import_export/relation_tree_saver.rb
+++ b/lib/gitlab/import_export/relation_tree_saver.rb
@@ -18,7 +18,7 @@ module Gitlab
       def save(tree, dir_path, filename)
         mkdir_p(dir_path)
 
-        tree_json = JSON.generate(tree)
+        tree_json = ::JSON.generate(tree)
 
         File.write(File.join(dir_path, filename), tree_json)
       end
diff --git a/spec/fixtures/lib/gitlab/import_export/invalid_json/project.json b/spec/fixtures/lib/gitlab/import_export/invalid_json/project.json
new file mode 100644
index 00000000000..83cb34eea91
--- /dev/null
+++ b/spec/fixtures/lib/gitlab/import_export/invalid_json/project.json
@@ -0,0 +1,3 @@
+{
+  "invalid" json
+}
diff --git a/spec/frontend/__mocks__/mousetrap/index.js b/spec/frontend/__mocks__/mousetrap/index.js
new file mode 100644
index 00000000000..63c92fa9a09
--- /dev/null
+++ b/spec/frontend/__mocks__/mousetrap/index.js
@@ -0,0 +1,6 @@
+/* global Mousetrap */
+// `mousetrap` uses amd which webpack understands but Jest does not
+// Thankfully it also writes to a global export so we can es6-ify it
+import 'mousetrap';
+
+export default Mousetrap;
diff --git a/spec/frontend/diffs/components/app_spec.js b/spec/frontend/diffs/components/app_spec.js
new file mode 100644
index 00000000000..15f91871437
--- /dev/null
+++ b/spec/frontend/diffs/components/app_spec.js
@@ -0,0 +1,723 @@
+import Vuex from 'vuex';
+import { shallowMount, createLocalVue } from '@vue/test-utils';
+import { GlLoadingIcon } from '@gitlab/ui';
+import MockAdapter from 'axios-mock-adapter';
+import { TEST_HOST } from 'spec/test_constants';
+import Mousetrap from 'mousetrap';
+import App from '~/diffs/components/app.vue';
+import NoChanges from '~/diffs/components/no_changes.vue';
+import DiffFile from '~/diffs/components/diff_file.vue';
+import CompareVersions from '~/diffs/components/compare_versions.vue';
+import HiddenFilesWarning from '~/diffs/components/hidden_files_warning.vue';
+import CommitWidget from '~/diffs/components/commit_widget.vue';
+import TreeList from '~/diffs/components/tree_list.vue';
+import { INLINE_DIFF_VIEW_TYPE, PARALLEL_DIFF_VIEW_TYPE } from '~/diffs/constants';
+import createDiffsStore from '../create_diffs_store';
+import axios from '~/lib/utils/axios_utils';
+import diffsMockData from '../mock_data/merge_request_diffs';
+
+const mergeRequestDiff = { version_index: 1 };
+const TEST_ENDPOINT = `${TEST_HOST}/diff/endpoint`;
+
+describe('diffs/components/app', () => {
+  const oldMrTabs = window.mrTabs;
+  let store;
+  let wrapper;
+  let mock;
+
+  function createComponent(props = {}, extendStore = () => {}) {
+    const localVue = createLocalVue();
+
+    localVue.use(Vuex);
+
+    store = createDiffsStore();
+    store.state.diffs.isLoading = false;
+
+    extendStore(store);
+
+    wrapper = shallowMount(localVue.extend(App), {
+      localVue,
+      propsData: {
+        endpoint: TEST_ENDPOINT,
+        endpointMetadata: `${TEST_HOST}/diff/endpointMetadata`,
+        endpointBatch: `${TEST_HOST}/diff/endpointBatch`,
+        projectPath: 'namespace/project',
+        currentUser: {},
+        changesEmptyStateIllustration: '',
+        dismissEndpoint: '',
+        showSuggestPopover: true,
+        ...props,
+      },
+      store,
+      methods: {
+        isLatestVersion() {
+          return true;
+        },
+      },
+    });
+  }
+
+  function getOppositeViewType(currentViewType) {
+    return currentViewType === INLINE_DIFF_VIEW_TYPE
+      ? PARALLEL_DIFF_VIEW_TYPE
+      : INLINE_DIFF_VIEW_TYPE;
+  }
+
+  beforeEach(() => {
+    // setup globals (needed for component to mount :/)
+    window.mrTabs = {
+      resetViewContainer: jest.fn(),
+    };
+    window.mrTabs.expandViewContainer = jest.fn();
+    mock = new MockAdapter(axios);
+    mock.onGet(TEST_ENDPOINT).reply(200, {});
+  });
+
+  afterEach(() => {
+    // reset globals
+    window.mrTabs = oldMrTabs;
+
+    // reset component
+    wrapper.destroy();
+
+    mock.restore();
+  });
+
+  describe('fetch diff methods', () => {
+    beforeEach(done => {
+      const fetchResolver = () => {
+        store.state.diffs.retrievingBatches = false;
+        store.state.notes.discussions = 'test';
+        return Promise.resolve({ real_size: 100 });
+      };
+      jest.spyOn(window, 'requestIdleCallback').mockImplementation(fn => fn());
+      createComponent();
+      jest.spyOn(wrapper.vm, 'fetchDiffFiles').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'fetchDiffFilesMeta').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'fetchDiffFilesBatch').mockImplementation(fetchResolver);
+      jest.spyOn(wrapper.vm, 'setDiscussions').mockImplementation(() => {});
+      jest.spyOn(wrapper.vm, 'startRenderDiffsQueue').mockImplementation(() => {});
+      jest.spyOn(wrapper.vm, 'unwatchDiscussions').mockImplementation(() => {});
+      jest.spyOn(wrapper.vm, 'unwatchRetrievingBatches').mockImplementation(() => {});
+      store.state.diffs.retrievingBatches = true;
+      store.state.diffs.diffFiles = [];
+      wrapper.vm.$nextTick(done);
+    });
+
+    describe('when the diff view type changes and it should load a single diff view style', () => {
+      const noLinesDiff = {
+        highlighted_diff_lines: [],
+        parallel_diff_lines: [],
+      };
+      const parallelLinesDiff = {
+        highlighted_diff_lines: [],
+        parallel_diff_lines: ['line'],
+      };
+      const inlineLinesDiff = {
+        highlighted_diff_lines: ['line'],
+        parallel_diff_lines: [],
+      };
+      const fullDiff = {
+        highlighted_diff_lines: ['line'],
+        parallel_diff_lines: ['line'],
+      };
+
+      function expectFetchToOccur({
+        vueInstance,
+        done = () => {},
+        batch = false,
+        existingFiles = 1,
+      } = {}) {
+        vueInstance.$nextTick(() => {
+          expect(vueInstance.diffFiles.length).toEqual(existingFiles);
+
+          if (!batch) {
+            expect(vueInstance.fetchDiffFiles).toHaveBeenCalled();
+            expect(vueInstance.fetchDiffFilesBatch).not.toHaveBeenCalled();
+          } else {
+            expect(vueInstance.fetchDiffFiles).not.toHaveBeenCalled();
+            expect(vueInstance.fetchDiffFilesBatch).toHaveBeenCalled();
+          }
+
+          done();
+        });
+      }
+
+      beforeEach(() => {
+        wrapper.vm.glFeatures.singleMrDiffView = true;
+      });
+
+      it('fetches diffs if it has none', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: false, existingFiles: 0, done });
+      });
+
+      it('fetches diffs if it has both view styles, but no lines in either', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffFiles.push(noLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, done });
+      });
+
+      it('fetches diffs if it only has inline view style', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffFiles.push(inlineLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, done });
+      });
+
+      it('fetches diffs if it only has parallel view style', done => {
+        wrapper.vm.isLatestVersion = () => false;
+
+        store.state.diffs.diffFiles.push(parallelLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, done });
+      });
+
+      it('fetches batch diffs if it has none', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, existingFiles: 0, done });
+      });
+
+      it('fetches batch diffs if it has both view styles, but no lines in either', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(noLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
+      });
+
+      it('fetches batch diffs if it only has inline view style', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(inlineLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
+      });
+
+      it('fetches batch diffs if it only has parallel view style', done => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(parallelLinesDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
+      });
+
+      it('does not fetch diffs if it has already fetched both styles of diff', () => {
+        wrapper.vm.glFeatures.diffsBatchLoad = false;
+
+        store.state.diffs.diffFiles.push(fullDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expect(wrapper.vm.diffFiles.length).toEqual(1);
+        expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
+      });
+
+      it('does not fetch batch diffs if it has already fetched both styles of diff', () => {
+        wrapper.vm.glFeatures.diffsBatchLoad = true;
+
+        store.state.diffs.diffFiles.push(fullDiff);
+        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
+
+        expect(wrapper.vm.diffFiles.length).toEqual(1);
+        expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
+      });
+    });
+
+    it('calls fetchDiffFiles if diffsBatchLoad is not enabled', done => {
+      expect(wrapper.vm.diffFilesLength).toEqual(0);
+      wrapper.vm.glFeatures.diffsBatchLoad = false;
+      wrapper.vm.fetchData(false);
+
+      expect(wrapper.vm.fetchDiffFiles).toHaveBeenCalled();
+      setImmediate(() => {
+        expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesMeta).not.toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
+        expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
+        expect(wrapper.vm.diffFilesLength).toEqual(100);
+        expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
+
+        done();
+      });
+    });
+
+    it('calls batch methods if diffsBatchLoad is enabled, and not latest version', done => {
+      expect(wrapper.vm.diffFilesLength).toEqual(0);
+      wrapper.vm.glFeatures.diffsBatchLoad = true;
+      wrapper.vm.isLatestVersion = () => false;
+      wrapper.vm.fetchData(false);
+
+      expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
+      setImmediate(() => {
+        expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
+        expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
+        expect(wrapper.vm.diffFilesLength).toEqual(100);
+        expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
+        done();
+      });
+    });
+
+    it('calls batch methods if diffsBatchLoad is enabled, and latest version', done => {
+      expect(wrapper.vm.diffFilesLength).toEqual(0);
+      wrapper.vm.glFeatures.diffsBatchLoad = true;
+      wrapper.vm.fetchData(false);
+
+      expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
+      setImmediate(() => {
+        expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
+        expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
+        expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
+        expect(wrapper.vm.diffFilesLength).toEqual(100);
+        expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
+        done();
+      });
+    });
+  });
+
+  it('adds container-limiting classes when showFileTree is false with inline diffs', () => {
+    createComponent({}, ({ state }) => {
+      state.diffs.showTreeList = false;
+      state.diffs.isParallelView = false;
+    });
+
+    expect(wrapper.contains('.container-limited.limit-container-width')).toBe(true);
+  });
+
+  it('does not add container-limiting classes when showFileTree is false with inline diffs', () => {
+    createComponent({}, ({ state }) => {
+      state.diffs.showTreeList = true;
+      state.diffs.isParallelView = false;
+    });
+
+    expect(wrapper.contains('.container-limited.limit-container-width')).toBe(false);
+  });
+
+  it('does not add container-limiting classes when isFluidLayout', () => {
+    createComponent({ isFluidLayout: true }, ({ state }) => {
+      state.diffs.isParallelView = false;
+    });
+
+    expect(wrapper.contains('.container-limited.limit-container-width')).toBe(false);
+  });
+
+  it('displays loading icon on loading', () => {
+    createComponent({}, ({ state }) => {
+      state.diffs.isLoading = true;
+    });
+
+    expect(wrapper.contains(GlLoadingIcon)).toBe(true);
+  });
+
+  it('displays loading icon on batch loading', () => {
+    createComponent({}, ({ state }) => {
+      state.diffs.isBatchLoading = true;
+    });
+
+    expect(wrapper.contains(GlLoadingIcon)).toBe(true);
+  });
+
+  it('displays diffs container when not loading', () => {
+    createComponent();
+
+    expect(wrapper.contains(GlLoadingIcon)).toBe(false);
+    expect(wrapper.contains('#diffs')).toBe(true);
+  });
+
+  it('does not show commit info', () => {
+    createComponent();
+
+    expect(wrapper.contains('.blob-commit-info')).toBe(false);
+  });
+
+  describe('row highlighting', () => {
+    beforeEach(() => {
+      window.location.hash = 'ABC_123';
+    });
+
+    it('sets highlighted row if hash exists in location object', done => {
+      createComponent({
+        shouldShow: true,
+      });
+
+      // Component uses $nextTick so we wait until that has finished
+      setImmediate(() => {
+        expect(store.state.diffs.highlightedRow).toBe('ABC_123');
+
+        done();
+      });
+    });
+
+    it('marks current diff file based on currently highlighted row', () => {
+      createComponent({
+        shouldShow: true,
+      });
+
+      // Component uses $nextTick so we wait until that has finished
+      return wrapper.vm.$nextTick().then(() => {
+        expect(store.state.diffs.currentDiffFileId).toBe('ABC');
+      });
+    });
+  });
+
+  describe('resizable', () => {
+    afterEach(() => {
+      localStorage.removeItem('mr_tree_list_width');
+    });
+
+    it('sets initial width when no localStorage has been set', () => {
+      createComponent();
+
+      expect(wrapper.vm.treeWidth).toEqual(320);
+    });
+
+    it('sets initial width to localStorage size', () => {
+      localStorage.setItem('mr_tree_list_width', '200');
+
+      createComponent();
+
+      expect(wrapper.vm.treeWidth).toEqual(200);
+    });
+
+    it('sets width of tree list', () => {
+      createComponent();
+
+      expect(wrapper.find('.js-diff-tree-list').element.style.width).toEqual('320px');
+    });
+  });
+
+  it('marks current diff file based on currently highlighted row', done => {
+    createComponent({
+      shouldShow: true,
+    });
+
+    // Component uses $nextTick so we wait until that has finished
+    setImmediate(() => {
+      expect(store.state.diffs.currentDiffFileId).toBe('ABC');
+
+      done();
+    });
+  });
+
+  describe('empty state', () => {
+    it('renders empty state when no diff files exist', () => {
+      createComponent();
+
+      expect(wrapper.contains(NoChanges)).toBe(true);
+    });
+
+    it('does not render empty state when diff files exist', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.diffFiles.push({
+          id: 1,
+        });
+      });
+
+      expect(wrapper.contains(NoChanges)).toBe(false);
+      expect(wrapper.findAll(DiffFile).length).toBe(1);
+    });
+
+    it('does not render empty state when versions match', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.startVersion = mergeRequestDiff;
+        state.diffs.mergeRequestDiff = mergeRequestDiff;
+      });
+
+      expect(wrapper.contains(NoChanges)).toBe(false);
+    });
+  });
+
+  describe('keyboard shortcut navigation', () => {
+    const mappings = {
+      '[': -1,
+      k: -1,
+      ']': +1,
+      j: +1,
+    };
+    let spy;
+
+    describe('visible app', () => {
+      beforeEach(() => {
+        spy = jest.fn();
+
+        createComponent({
+          shouldShow: true,
+        });
+        wrapper.setMethods({
+          jumpToFile: spy,
+        });
+      });
+
+      it.each(Object.keys(mappings))(
+        'calls `jumpToFile()` with correct parameter whenever pre-defined %s is pressed',
+        key => {
+          return wrapper.vm.$nextTick().then(() => {
+            expect(spy).not.toHaveBeenCalled();
+
+            Mousetrap.trigger(key);
+
+            expect(spy).toHaveBeenCalledWith(mappings[key]);
+          });
+        },
+      );
+
+      it('does not call `jumpToFile()` when unknown key is pressed', done => {
+        wrapper.vm
+          .$nextTick()
+          .then(() => {
+            Mousetrap.trigger('d');
+
+            expect(spy).not.toHaveBeenCalled();
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+    });
+
+    describe('hideen app', () => {
+      beforeEach(() => {
+        spy = jest.fn();
+
+        createComponent({
+          shouldShow: false,
+        });
+        wrapper.setMethods({
+          jumpToFile: spy,
+        });
+      });
+
+      it('stops calling `jumpToFile()` when application is hidden', done => {
+        wrapper.vm
+          .$nextTick()
+          .then(() => {
+            Object.keys(mappings).forEach(key => {
+              Mousetrap.trigger(key);
+
+              expect(spy).not.toHaveBeenCalled();
+            });
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+    });
+  });
+
+  describe('jumpToFile', () => {
+    let spy;
+
+    beforeEach(() => {
+      spy = jest.fn();
+
+      createComponent({}, () => {
+        store.state.diffs.diffFiles = [
+          { file_hash: '111', file_path: '111.js' },
+          { file_hash: '222', file_path: '222.js' },
+          { file_hash: '333', file_path: '333.js' },
+        ];
+      });
+
+      wrapper.setMethods({
+        scrollToFile: spy,
+      });
+    });
+
+    afterEach(() => {
+      wrapper.destroy();
+    });
+
+    it('jumps to next and previous files in the list', done => {
+      wrapper.vm
+        .$nextTick()
+        .then(() => {
+          wrapper.vm.jumpToFile(+1);
+
+          expect(spy.mock.calls[spy.mock.calls.length - 1]).toEqual(['222.js']);
+          store.state.diffs.currentDiffFileId = '222';
+          wrapper.vm.jumpToFile(+1);
+
+          expect(spy.mock.calls[spy.mock.calls.length - 1]).toEqual(['333.js']);
+          store.state.diffs.currentDiffFileId = '333';
+          wrapper.vm.jumpToFile(-1);
+
+          expect(spy.mock.calls[spy.mock.calls.length - 1]).toEqual(['222.js']);
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+
+    it('does not jump to previous file from the first one', done => {
+      wrapper.vm
+        .$nextTick()
+        .then(() => {
+          store.state.diffs.currentDiffFileId = '333';
+
+          expect(wrapper.vm.currentDiffIndex).toEqual(2);
+
+          wrapper.vm.jumpToFile(+1);
+
+          expect(wrapper.vm.currentDiffIndex).toEqual(2);
+          expect(spy).not.toHaveBeenCalled();
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+
+    it('does not jump to next file from the last one', done => {
+      wrapper.vm
+        .$nextTick()
+        .then(() => {
+          expect(wrapper.vm.currentDiffIndex).toEqual(0);
+
+          wrapper.vm.jumpToFile(-1);
+
+          expect(wrapper.vm.currentDiffIndex).toEqual(0);
+          expect(spy).not.toHaveBeenCalled();
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+  });
+
+  describe('diffs', () => {
+    it('should render compare versions component', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.mergeRequestDiffs = diffsMockData;
+        state.diffs.targetBranchName = 'target-branch';
+        state.diffs.mergeRequestDiff = mergeRequestDiff;
+      });
+
+      expect(wrapper.contains(CompareVersions)).toBe(true);
+      expect(wrapper.find(CompareVersions).props()).toEqual(
+        expect.objectContaining({
+          targetBranch: {
+            branchName: 'target-branch',
+            versionIndex: -1,
+            path: '',
+          },
+          mergeRequestDiffs: diffsMockData,
+          mergeRequestDiff,
+        }),
+      );
+    });
+
+    it('should render hidden files warning if render overflow warning is present', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.renderOverflowWarning = true;
+        state.diffs.realSize = '5';
+        state.diffs.plainDiffPath = 'plain diff path';
+        state.diffs.emailPatchPath = 'email patch path';
+        state.diffs.size = 1;
+      });
+
+      expect(wrapper.contains(HiddenFilesWarning)).toBe(true);
+      expect(wrapper.find(HiddenFilesWarning).props()).toEqual(
+        expect.objectContaining({
+          total: '5',
+          plainDiffPath: 'plain diff path',
+          emailPatchPath: 'email patch path',
+          visible: 1,
+        }),
+      );
+    });
+
+    it('should display commit widget if store has a commit', () => {
+      createComponent({}, () => {
+        store.state.diffs.commit = {
+          author: 'John Doe',
+        };
+      });
+
+      expect(wrapper.contains(CommitWidget)).toBe(true);
+    });
+
+    it('should display diff file if there are diff files', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.diffFiles.push({ sha: '123' });
+      });
+
+      expect(wrapper.contains(DiffFile)).toBe(true);
+    });
+
+    it('should render tree list', () => {
+      createComponent();
+
+      expect(wrapper.find(TreeList).exists()).toBe(true);
+    });
+  });
+
+  describe('hideTreeListIfJustOneFile', () => {
+    let toggleShowTreeList;
+
+    beforeEach(() => {
+      toggleShowTreeList = jest.fn();
+    });
+
+    afterEach(() => {
+      localStorage.removeItem('mr_tree_show');
+    });
+
+    it('calls toggleShowTreeList when only 1 file', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.diffFiles.push({ sha: '123' });
+      });
+
+      wrapper.setMethods({
+        toggleShowTreeList,
+      });
+
+      wrapper.vm.hideTreeListIfJustOneFile();
+
+      expect(toggleShowTreeList).toHaveBeenCalledWith(false);
+    });
+
+    it('does not call toggleShowTreeList when more than 1 file', () => {
+      createComponent({}, ({ state }) => {
+        state.diffs.diffFiles.push({ sha: '123' });
+        state.diffs.diffFiles.push({ sha: '124' });
+      });
+
+      wrapper.setMethods({
+        toggleShowTreeList,
+      });
+
+      wrapper.vm.hideTreeListIfJustOneFile();
+
+      expect(toggleShowTreeList).not.toHaveBeenCalled();
+    });
+
+    it('does not call toggleShowTreeList when localStorage is set', () => {
+      localStorage.setItem('mr_tree_show', 'true');
+
+      createComponent({}, ({ state }) => {
+        state.diffs.diffFiles.push({ sha: '123' });
+      });
+
+      wrapper.setMethods({
+        toggleShowTreeList,
+      });
+
+      wrapper.vm.hideTreeListIfJustOneFile();
+
+      expect(toggleShowTreeList).not.toHaveBeenCalled();
+    });
+  });
+});
diff --git a/spec/frontend/diffs/create_diffs_store.js b/spec/frontend/diffs/create_diffs_store.js
new file mode 100644
index 00000000000..aacde99964c
--- /dev/null
+++ b/spec/frontend/diffs/create_diffs_store.js
@@ -0,0 +1,15 @@
+import Vue from 'vue';
+import Vuex from 'vuex';
+import diffsModule from '~/diffs/store/modules';
+import notesModule from '~/notes/stores/modules';
+
+Vue.use(Vuex);
+
+export default function createDiffsStore() {
+  return new Vuex.Store({
+    modules: {
+      diffs: diffsModule(),
+      notes: notesModule(),
+    },
+  });
+}
diff --git a/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap b/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap
index 177cd4559ca..efa58a4a47b 100644
--- a/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap
+++ b/spec/frontend/ide/components/pipelines/__snapshots__/list_spec.js.snap
@@ -8,6 +8,7 @@ exports[`IDE pipelines list when loaded renders empty state when no latestPipeli
    
   <empty-state-stub
     cansetci="true"
+    class="mb-auto mt-auto"
     emptystatesvgpath="http://test.host"
     helppagepath="http://test.host"
   />
diff --git a/spec/frontend/lib/utils/icon_utils_spec.js b/spec/frontend/lib/utils/icon_utils_spec.js
index 816d634ad15..f798dc6744d 100644
--- a/spec/frontend/lib/utils/icon_utils_spec.js
+++ b/spec/frontend/lib/utils/icon_utils_spec.js
@@ -1,10 +1,14 @@
 import MockAdapter from 'axios-mock-adapter';
 import axios from '~/lib/utils/axios_utils';
-import * as iconUtils from '~/lib/utils/icon_utils';
+import { clearSvgIconPathContentCache, getSvgIconPathContent } from '~/lib/utils/icon_utils';
 
 describe('Icon utils', () => {
   describe('getSvgIconPathContent', () => {
     let spriteIcons;
+    let axiosMock;
+    const mockName = 'mockIconName';
+    const mockPath = 'mockPath';
+    const mockIcons = `<svg><symbol id="${mockName}"><path d="${mockPath}"/></symbol></svg>`;
 
     beforeAll(() => {
       spriteIcons = gon.sprite_icons;
@@ -15,45 +19,63 @@ describe('Icon utils', () => {
       gon.sprite_icons = spriteIcons;
     });
 
-    let axiosMock;
-    let mockEndpoint;
-    const mockName = 'mockIconName';
-    const mockPath = 'mockPath';
-    const getIcon = () => iconUtils.getSvgIconPathContent(mockName);
-
     beforeEach(() => {
       axiosMock = new MockAdapter(axios);
-      mockEndpoint = axiosMock.onGet(gon.sprite_icons);
     });
 
     afterEach(() => {
       axiosMock.restore();
+      clearSvgIconPathContentCache();
     });
 
-    it('extracts svg icon path content from sprite icons', () => {
-      mockEndpoint.replyOnce(
-        200,
-        `<svg><symbol id="${mockName}"><path d="${mockPath}"/></symbol></svg>`,
-      );
-
-      return getIcon().then(path => {
-        expect(path).toBe(mockPath);
+    describe('when the icons can be loaded', () => {
+      beforeEach(() => {
+        axiosMock.onGet(gon.sprite_icons).reply(200, mockIcons);
       });
-    });
 
-    it('returns null if icon path content does not exist', () => {
-      mockEndpoint.replyOnce(200, ``);
+      it('extracts svg icon path content from sprite icons', () => {
+        return getSvgIconPathContent(mockName).then(path => {
+          expect(path).toBe(mockPath);
+        });
+      });
 
-      return getIcon().then(path => {
-        expect(path).toBe(null);
+      it('returns null if icon path content does not exist', () => {
+        return getSvgIconPathContent('missing-icon').then(path => {
+          expect(path).toBe(null);
+        });
       });
     });
 
-    it('returns null if an http error occurs', () => {
-      mockEndpoint.replyOnce(500);
+    describe('when the icons cannot be loaded on the first 2 tries', () => {
+      beforeEach(() => {
+        axiosMock
+          .onGet(gon.sprite_icons)
+          .replyOnce(500)
+          .onGet(gon.sprite_icons)
+          .replyOnce(500)
+          .onGet(gon.sprite_icons)
+          .reply(200, mockIcons);
+      });
+
+      it('returns null', () => {
+        return getSvgIconPathContent(mockName).then(path => {
+          expect(path).toBe(null);
+        });
+      });
 
-      return getIcon().then(path => {
-        expect(path).toBe(null);
+      it('extracts svg icon path content, after 2 attempts', () => {
+        return getSvgIconPathContent(mockName)
+          .then(path1 => {
+            expect(path1).toBe(null);
+            return getSvgIconPathContent(mockName);
+          })
+          .then(path2 => {
+            expect(path2).toBe(null);
+            return getSvgIconPathContent(mockName);
+          })
+          .then(path3 => {
+            expect(path3).toBe(mockPath);
+          });
       });
     });
   });
diff --git a/spec/frontend/mocks/ce/diffs/workers/tree_worker.js b/spec/frontend/mocks/ce/diffs/workers/tree_worker.js
new file mode 100644
index 00000000000..a33ddbbfe63
--- /dev/null
+++ b/spec/frontend/mocks/ce/diffs/workers/tree_worker.js
@@ -0,0 +1,8 @@
+/* eslint-disable class-methods-use-this */
+export default class TreeWorkerMock {
+  addEventListener() {}
+
+  terminate() {}
+
+  postMessage() {}
+}
diff --git a/spec/javascripts/diffs/components/app_spec.js b/spec/javascripts/diffs/components/app_spec.js
deleted file mode 100644
index 5f97182489e..00000000000
--- a/spec/javascripts/diffs/components/app_spec.js
+++ /dev/null
@@ -1,718 +0,0 @@
-import Vuex from 'vuex';
-import { shallowMount, createLocalVue } from '@vue/test-utils';
-import { GlLoadingIcon } from '@gitlab/ui';
-import { TEST_HOST } from 'spec/test_constants';
-import Mousetrap from 'mousetrap';
-import App from '~/diffs/components/app.vue';
-import NoChanges from '~/diffs/components/no_changes.vue';
-import DiffFile from '~/diffs/components/diff_file.vue';
-import CompareVersions from '~/diffs/components/compare_versions.vue';
-import HiddenFilesWarning from '~/diffs/components/hidden_files_warning.vue';
-import CommitWidget from '~/diffs/components/commit_widget.vue';
-import TreeList from '~/diffs/components/tree_list.vue';
-import { INLINE_DIFF_VIEW_TYPE, PARALLEL_DIFF_VIEW_TYPE } from '~/diffs/constants';
-import createDiffsStore from '../create_diffs_store';
-import diffsMockData from '../mock_data/merge_request_diffs';
-
-const mergeRequestDiff = { version_index: 1 };
-
-describe('diffs/components/app', () => {
-  const oldMrTabs = window.mrTabs;
-  let store;
-  let wrapper;
-
-  function createComponent(props = {}, extendStore = () => {}) {
-    const localVue = createLocalVue();
-
-    localVue.use(Vuex);
-
-    store = createDiffsStore();
-    store.state.diffs.isLoading = false;
-
-    extendStore(store);
-
-    wrapper = shallowMount(localVue.extend(App), {
-      localVue,
-      propsData: {
-        endpoint: `${TEST_HOST}/diff/endpoint`,
-        endpointMetadata: `${TEST_HOST}/diff/endpointMetadata`,
-        endpointBatch: `${TEST_HOST}/diff/endpointBatch`,
-        projectPath: 'namespace/project',
-        currentUser: {},
-        changesEmptyStateIllustration: '',
-        dismissEndpoint: '',
-        showSuggestPopover: true,
-        ...props,
-      },
-      store,
-      methods: {
-        isLatestVersion() {
-          return true;
-        },
-      },
-    });
-  }
-
-  function getOppositeViewType(currentViewType) {
-    return currentViewType === INLINE_DIFF_VIEW_TYPE
-      ? PARALLEL_DIFF_VIEW_TYPE
-      : INLINE_DIFF_VIEW_TYPE;
-  }
-
-  beforeEach(() => {
-    // setup globals (needed for component to mount :/)
-    window.mrTabs = jasmine.createSpyObj('mrTabs', ['resetViewContainer']);
-    window.mrTabs.expandViewContainer = jasmine.createSpy();
-  });
-
-  afterEach(() => {
-    // reset globals
-    window.mrTabs = oldMrTabs;
-
-    // reset component
-    wrapper.destroy();
-  });
-
-  describe('fetch diff methods', () => {
-    beforeEach(done => {
-      const fetchResolver = () => {
-        store.state.diffs.retrievingBatches = false;
-        store.state.notes.discussions = 'test';
-        return Promise.resolve({ real_size: 100 });
-      };
-      spyOn(window, 'requestIdleCallback').and.callFake(fn => fn());
-      createComponent();
-      spyOn(wrapper.vm, 'fetchDiffFiles').and.callFake(fetchResolver);
-      spyOn(wrapper.vm, 'fetchDiffFilesMeta').and.callFake(fetchResolver);
-      spyOn(wrapper.vm, 'fetchDiffFilesBatch').and.callFake(fetchResolver);
-      spyOn(wrapper.vm, 'setDiscussions');
-      spyOn(wrapper.vm, 'startRenderDiffsQueue');
-      spyOn(wrapper.vm, 'unwatchDiscussions');
-      spyOn(wrapper.vm, 'unwatchRetrievingBatches');
-      store.state.diffs.retrievingBatches = true;
-      store.state.diffs.diffFiles = [];
-      wrapper.vm.$nextTick(done);
-    });
-
-    describe('when the diff view type changes and it should load a single diff view style', () => {
-      const noLinesDiff = {
-        highlighted_diff_lines: [],
-        parallel_diff_lines: [],
-      };
-      const parallelLinesDiff = {
-        highlighted_diff_lines: [],
-        parallel_diff_lines: ['line'],
-      };
-      const inlineLinesDiff = {
-        highlighted_diff_lines: ['line'],
-        parallel_diff_lines: [],
-      };
-      const fullDiff = {
-        highlighted_diff_lines: ['line'],
-        parallel_diff_lines: ['line'],
-      };
-
-      function expectFetchToOccur({
-        vueInstance,
-        done = () => {},
-        batch = false,
-        existingFiles = 1,
-      } = {}) {
-        vueInstance.$nextTick(() => {
-          expect(vueInstance.diffFiles.length).toEqual(existingFiles);
-
-          if (!batch) {
-            expect(vueInstance.fetchDiffFiles).toHaveBeenCalled();
-            expect(vueInstance.fetchDiffFilesBatch).not.toHaveBeenCalled();
-          } else {
-            expect(vueInstance.fetchDiffFiles).not.toHaveBeenCalled();
-            expect(vueInstance.fetchDiffFilesBatch).toHaveBeenCalled();
-          }
-
-          done();
-        });
-      }
-
-      beforeEach(() => {
-        wrapper.vm.glFeatures.singleMrDiffView = true;
-      });
-
-      it('fetches diffs if it has none', done => {
-        wrapper.vm.isLatestVersion = () => false;
-
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, batch: false, existingFiles: 0, done });
-      });
-
-      it('fetches diffs if it has both view styles, but no lines in either', done => {
-        wrapper.vm.isLatestVersion = () => false;
-
-        store.state.diffs.diffFiles.push(noLinesDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, done });
-      });
-
-      it('fetches diffs if it only has inline view style', done => {
-        wrapper.vm.isLatestVersion = () => false;
-
-        store.state.diffs.diffFiles.push(inlineLinesDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, done });
-      });
-
-      it('fetches diffs if it only has parallel view style', done => {
-        wrapper.vm.isLatestVersion = () => false;
-
-        store.state.diffs.diffFiles.push(parallelLinesDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, done });
-      });
-
-      it('fetches batch diffs if it has none', done => {
-        wrapper.vm.glFeatures.diffsBatchLoad = true;
-
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, existingFiles: 0, done });
-      });
-
-      it('fetches batch diffs if it has both view styles, but no lines in either', done => {
-        wrapper.vm.glFeatures.diffsBatchLoad = true;
-
-        store.state.diffs.diffFiles.push(noLinesDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
-      });
-
-      it('fetches batch diffs if it only has inline view style', done => {
-        wrapper.vm.glFeatures.diffsBatchLoad = true;
-
-        store.state.diffs.diffFiles.push(inlineLinesDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
-      });
-
-      it('fetches batch diffs if it only has parallel view style', done => {
-        wrapper.vm.glFeatures.diffsBatchLoad = true;
-
-        store.state.diffs.diffFiles.push(parallelLinesDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expectFetchToOccur({ vueInstance: wrapper.vm, batch: true, done });
-      });
-
-      it('does not fetch diffs if it has already fetched both styles of diff', () => {
-        wrapper.vm.glFeatures.diffsBatchLoad = false;
-
-        store.state.diffs.diffFiles.push(fullDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expect(wrapper.vm.diffFiles.length).toEqual(1);
-        expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
-      });
-
-      it('does not fetch batch diffs if it has already fetched both styles of diff', () => {
-        wrapper.vm.glFeatures.diffsBatchLoad = true;
-
-        store.state.diffs.diffFiles.push(fullDiff);
-        store.state.diffs.diffViewType = getOppositeViewType(wrapper.vm.diffViewType);
-
-        expect(wrapper.vm.diffFiles.length).toEqual(1);
-        expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
-      });
-    });
-
-    it('calls fetchDiffFiles if diffsBatchLoad is not enabled', done => {
-      expect(wrapper.vm.diffFilesLength).toEqual(0);
-      wrapper.vm.glFeatures.diffsBatchLoad = false;
-      wrapper.vm.fetchData(false);
-
-      expect(wrapper.vm.fetchDiffFiles).toHaveBeenCalled();
-      setTimeout(() => {
-        expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesMeta).not.toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesBatch).not.toHaveBeenCalled();
-        expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
-        expect(wrapper.vm.diffFilesLength).toEqual(100);
-        expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
-
-        done();
-      });
-    });
-
-    it('calls batch methods if diffsBatchLoad is enabled, and not latest version', done => {
-      expect(wrapper.vm.diffFilesLength).toEqual(0);
-      wrapper.vm.glFeatures.diffsBatchLoad = true;
-      wrapper.vm.isLatestVersion = () => false;
-      wrapper.vm.fetchData(false);
-
-      expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
-      setTimeout(() => {
-        expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
-        expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
-        expect(wrapper.vm.diffFilesLength).toEqual(100);
-        expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
-        done();
-      });
-    });
-
-    it('calls batch methods if diffsBatchLoad is enabled, and latest version', done => {
-      expect(wrapper.vm.diffFilesLength).toEqual(0);
-      wrapper.vm.glFeatures.diffsBatchLoad = true;
-      wrapper.vm.fetchData(false);
-
-      expect(wrapper.vm.fetchDiffFiles).not.toHaveBeenCalled();
-      setTimeout(() => {
-        expect(wrapper.vm.startRenderDiffsQueue).toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesMeta).toHaveBeenCalled();
-        expect(wrapper.vm.fetchDiffFilesBatch).toHaveBeenCalled();
-        expect(wrapper.vm.unwatchDiscussions).toHaveBeenCalled();
-        expect(wrapper.vm.diffFilesLength).toEqual(100);
-        expect(wrapper.vm.unwatchRetrievingBatches).toHaveBeenCalled();
-        done();
-      });
-    });
-  });
-
-  it('adds container-limiting classes when showFileTree is false with inline diffs', () => {
-    createComponent({}, ({ state }) => {
-      state.diffs.showTreeList = false;
-      state.diffs.isParallelView = false;
-    });
-
-    expect(wrapper.contains('.container-limited.limit-container-width')).toBe(true);
-  });
-
-  it('does not add container-limiting classes when showFileTree is false with inline diffs', () => {
-    createComponent({}, ({ state }) => {
-      state.diffs.showTreeList = true;
-      state.diffs.isParallelView = false;
-    });
-
-    expect(wrapper.contains('.container-limited.limit-container-width')).toBe(false);
-  });
-
-  it('does not add container-limiting classes when isFluidLayout', () => {
-    createComponent({ isFluidLayout: true }, ({ state }) => {
-      state.diffs.isParallelView = false;
-    });
-
-    expect(wrapper.contains('.container-limited.limit-container-width')).toBe(false);
-  });
-
-  it('displays loading icon on loading', () => {
-    createComponent({}, ({ state }) => {
-      state.diffs.isLoading = true;
-    });
-
-    expect(wrapper.contains(GlLoadingIcon)).toBe(true);
-  });
-
-  it('displays loading icon on batch loading', () => {
-    createComponent({}, ({ state }) => {
-      state.diffs.isBatchLoading = true;
-    });
-
-    expect(wrapper.contains(GlLoadingIcon)).toBe(true);
-  });
-
-  it('displays diffs container when not loading', () => {
-    createComponent();
-
-    expect(wrapper.contains(GlLoadingIcon)).toBe(false);
-    expect(wrapper.contains('#diffs')).toBe(true);
-  });
-
-  it('does not show commit info', () => {
-    createComponent();
-
-    expect(wrapper.contains('.blob-commit-info')).toBe(false);
-  });
-
-  describe('row highlighting', () => {
-    beforeEach(() => {
-      window.location.hash = 'ABC_123';
-    });
-
-    it('sets highlighted row if hash exists in location object', done => {
-      createComponent({
-        shouldShow: true,
-      });
-
-      // Component uses $nextTick so we wait until that has finished
-      setTimeout(() => {
-        expect(store.state.diffs.highlightedRow).toBe('ABC_123');
-
-        done();
-      });
-    });
-
-    it('marks current diff file based on currently highlighted row', done => {
-      createComponent({
-        shouldShow: true,
-      });
-
-      // Component uses $nextTick so we wait until that has finished
-      setTimeout(() => {
-        expect(store.state.diffs.currentDiffFileId).toBe('ABC');
-
-        done();
-      });
-    });
-  });
-
-  describe('resizable', () => {
-    afterEach(() => {
-      localStorage.removeItem('mr_tree_list_width');
-    });
-
-    it('sets initial width when no localStorage has been set', () => {
-      createComponent();
-
-      expect(wrapper.vm.treeWidth).toEqual(320);
-    });
-
-    it('sets initial width to localStorage size', () => {
-      localStorage.setItem('mr_tree_list_width', '200');
-
-      createComponent();
-
-      expect(wrapper.vm.treeWidth).toEqual(200);
-    });
-
-    it('sets width of tree list', () => {
-      createComponent();
-
-      expect(wrapper.find('.js-diff-tree-list').element.style.width).toEqual('320px');
-    });
-  });
-
-  it('marks current diff file based on currently highlighted row', done => {
-    createComponent({
-      shouldShow: true,
-    });
-
-    // Component uses $nextTick so we wait until that has finished
-    setTimeout(() => {
-      expect(store.state.diffs.currentDiffFileId).toBe('ABC');
-
-      done();
-    });
-  });
-
-  describe('empty state', () => {
-    it('renders empty state when no diff files exist', () => {
-      createComponent();
-
-      expect(wrapper.contains(NoChanges)).toBe(true);
-    });
-
-    it('does not render empty state when diff files exist', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.diffFiles.push({
-          id: 1,
-        });
-      });
-
-      expect(wrapper.contains(NoChanges)).toBe(false);
-      expect(wrapper.findAll(DiffFile).length).toBe(1);
-    });
-
-    it('does not render empty state when versions match', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.startVersion = mergeRequestDiff;
-        state.diffs.mergeRequestDiff = mergeRequestDiff;
-      });
-
-      expect(wrapper.contains(NoChanges)).toBe(false);
-    });
-  });
-
-  describe('keyboard shortcut navigation', () => {
-    const mappings = {
-      '[': -1,
-      k: -1,
-      ']': +1,
-      j: +1,
-    };
-    let spy;
-
-    describe('visible app', () => {
-      beforeEach(() => {
-        spy = jasmine.createSpy('spy');
-
-        createComponent({
-          shouldShow: true,
-        });
-        wrapper.setMethods({
-          jumpToFile: spy,
-        });
-      });
-
-      it('calls `jumpToFile()` with correct parameter whenever pre-defined key is pressed', done => {
-        wrapper.vm
-          .$nextTick()
-          .then(() => {
-            Object.keys(mappings).forEach(function(key) {
-              Mousetrap.trigger(key);
-
-              expect(spy.calls.mostRecent().args).toEqual([mappings[key]]);
-            });
-
-            expect(spy.calls.count()).toEqual(Object.keys(mappings).length);
-          })
-          .then(done)
-          .catch(done.fail);
-      });
-
-      it('does not call `jumpToFile()` when unknown key is pressed', done => {
-        wrapper.vm
-          .$nextTick()
-          .then(() => {
-            Mousetrap.trigger('d');
-
-            expect(spy).not.toHaveBeenCalled();
-          })
-          .then(done)
-          .catch(done.fail);
-      });
-    });
-
-    describe('hideen app', () => {
-      beforeEach(() => {
-        spy = jasmine.createSpy('spy');
-
-        createComponent({
-          shouldShow: false,
-        });
-        wrapper.setMethods({
-          jumpToFile: spy,
-        });
-      });
-
-      it('stops calling `jumpToFile()` when application is hidden', done => {
-        wrapper.vm
-          .$nextTick()
-          .then(() => {
-            Object.keys(mappings).forEach(function(key) {
-              Mousetrap.trigger(key);
-
-              expect(spy).not.toHaveBeenCalled();
-            });
-          })
-          .then(done)
-          .catch(done.fail);
-      });
-    });
-  });
-
-  describe('jumpToFile', () => {
-    let spy;
-
-    beforeEach(() => {
-      spy = jasmine.createSpy();
-
-      createComponent({}, () => {
-        store.state.diffs.diffFiles = [
-          { file_hash: '111', file_path: '111.js' },
-          { file_hash: '222', file_path: '222.js' },
-          { file_hash: '333', file_path: '333.js' },
-        ];
-      });
-
-      wrapper.setMethods({
-        scrollToFile: spy,
-      });
-    });
-
-    afterEach(() => {
-      wrapper.destroy();
-    });
-
-    it('jumps to next and previous files in the list', done => {
-      wrapper.vm
-        .$nextTick()
-        .then(() => {
-          wrapper.vm.jumpToFile(+1);
-
-          expect(spy.calls.mostRecent().args).toEqual(['222.js']);
-          store.state.diffs.currentDiffFileId = '222';
-          wrapper.vm.jumpToFile(+1);
-
-          expect(spy.calls.mostRecent().args).toEqual(['333.js']);
-          store.state.diffs.currentDiffFileId = '333';
-          wrapper.vm.jumpToFile(-1);
-
-          expect(spy.calls.mostRecent().args).toEqual(['222.js']);
-        })
-        .then(done)
-        .catch(done.fail);
-    });
-
-    it('does not jump to previous file from the first one', done => {
-      wrapper.vm
-        .$nextTick()
-        .then(() => {
-          store.state.diffs.currentDiffFileId = '333';
-
-          expect(wrapper.vm.currentDiffIndex).toEqual(2);
-
-          wrapper.vm.jumpToFile(+1);
-
-          expect(wrapper.vm.currentDiffIndex).toEqual(2);
-          expect(spy).not.toHaveBeenCalled();
-        })
-        .then(done)
-        .catch(done.fail);
-    });
-
-    it('does not jump to next file from the last one', done => {
-      wrapper.vm
-        .$nextTick()
-        .then(() => {
-          expect(wrapper.vm.currentDiffIndex).toEqual(0);
-
-          wrapper.vm.jumpToFile(-1);
-
-          expect(wrapper.vm.currentDiffIndex).toEqual(0);
-          expect(spy).not.toHaveBeenCalled();
-        })
-        .then(done)
-        .catch(done.fail);
-    });
-  });
-
-  describe('diffs', () => {
-    it('should render compare versions component', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.mergeRequestDiffs = diffsMockData;
-        state.diffs.targetBranchName = 'target-branch';
-        state.diffs.mergeRequestDiff = mergeRequestDiff;
-      });
-
-      expect(wrapper.contains(CompareVersions)).toBe(true);
-      expect(wrapper.find(CompareVersions).props()).toEqual(
-        jasmine.objectContaining({
-          targetBranch: {
-            branchName: 'target-branch',
-            versionIndex: -1,
-            path: '',
-          },
-          mergeRequestDiffs: diffsMockData,
-          mergeRequestDiff,
-        }),
-      );
-    });
-
-    it('should render hidden files warning if render overflow warning is present', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.renderOverflowWarning = true;
-        state.diffs.realSize = '5';
-        state.diffs.plainDiffPath = 'plain diff path';
-        state.diffs.emailPatchPath = 'email patch path';
-        state.diffs.size = 1;
-      });
-
-      expect(wrapper.contains(HiddenFilesWarning)).toBe(true);
-      expect(wrapper.find(HiddenFilesWarning).props()).toEqual(
-        jasmine.objectContaining({
-          total: '5',
-          plainDiffPath: 'plain diff path',
-          emailPatchPath: 'email patch path',
-          visible: 1,
-        }),
-      );
-    });
-
-    it('should display commit widget if store has a commit', () => {
-      createComponent({}, () => {
-        store.state.diffs.commit = {
-          author: 'John Doe',
-        };
-      });
-
-      expect(wrapper.contains(CommitWidget)).toBe(true);
-    });
-
-    it('should display diff file if there are diff files', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.diffFiles.push({ sha: '123' });
-      });
-
-      expect(wrapper.contains(DiffFile)).toBe(true);
-    });
-
-    it('should render tree list', () => {
-      createComponent();
-
-      expect(wrapper.find(TreeList).exists()).toBe(true);
-    });
-  });
-
-  describe('hideTreeListIfJustOneFile', () => {
-    let toggleShowTreeList;
-
-    beforeEach(() => {
-      toggleShowTreeList = jasmine.createSpy('toggleShowTreeList');
-    });
-
-    afterEach(() => {
-      localStorage.removeItem('mr_tree_show');
-    });
-
-    it('calls toggleShowTreeList when only 1 file', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.diffFiles.push({ sha: '123' });
-      });
-
-      wrapper.setMethods({
-        toggleShowTreeList,
-      });
-
-      wrapper.vm.hideTreeListIfJustOneFile();
-
-      expect(toggleShowTreeList).toHaveBeenCalledWith(false);
-    });
-
-    it('does not call toggleShowTreeList when more than 1 file', () => {
-      createComponent({}, ({ state }) => {
-        state.diffs.diffFiles.push({ sha: '123' });
-        state.diffs.diffFiles.push({ sha: '124' });
-      });
-
-      wrapper.setMethods({
-        toggleShowTreeList,
-      });
-
-      wrapper.vm.hideTreeListIfJustOneFile();
-
-      expect(toggleShowTreeList).not.toHaveBeenCalled();
-    });
-
-    it('does not call toggleShowTreeList when localStorage is set', () => {
-      localStorage.setItem('mr_tree_show', 'true');
-
-      createComponent({}, ({ state }) => {
-        state.diffs.diffFiles.push({ sha: '123' });
-      });
-
-      wrapper.setMethods({
-        toggleShowTreeList,
-      });
-
-      wrapper.vm.hideTreeListIfJustOneFile();
-
-      expect(toggleShowTreeList).not.toHaveBeenCalled();
-    });
-  });
-});
diff --git a/spec/javascripts/diffs/create_diffs_store.js b/spec/javascripts/diffs/create_diffs_store.js
index aacde99964c..cfefd4238b8 100644
--- a/spec/javascripts/diffs/create_diffs_store.js
+++ b/spec/javascripts/diffs/create_diffs_store.js
@@ -1,15 +1 @@
-import Vue from 'vue';
-import Vuex from 'vuex';
-import diffsModule from '~/diffs/store/modules';
-import notesModule from '~/notes/stores/modules';
-
-Vue.use(Vuex);
-
-export default function createDiffsStore() {
-  return new Vuex.Store({
-    modules: {
-      diffs: diffsModule(),
-      notes: notesModule(),
-    },
-  });
-}
+export { default } from '../../frontend/diffs/create_diffs_store';
diff --git a/spec/lib/gitlab/import_export/json/legacy_reader_spec.rb b/spec/lib/gitlab/import_export/json/legacy_reader_spec.rb
new file mode 100644
index 00000000000..0009a5f81de
--- /dev/null
+++ b/spec/lib/gitlab/import_export/json/legacy_reader_spec.rb
@@ -0,0 +1,149 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::ImportExport::JSON::LegacyReader::User do
+  let(:relation_names) { [] }
+  let(:legacy_reader) { described_class.new(tree_hash, relation_names) }
+
+  describe '#valid?' do
+    subject { legacy_reader.valid? }
+
+    context 'tree_hash not present' do
+      let(:tree_hash) { nil }
+
+      it { is_expected.to be false }
+    end
+
+    context 'tree_hash presents' do
+      let(:tree_hash) { { "issues": [] } }
+
+      it { is_expected.to be true }
+    end
+  end
+end
+
+describe Gitlab::ImportExport::JSON::LegacyReader::File do
+  let(:fixture) { 'spec/fixtures/lib/gitlab/import_export/light/project.json' }
+  let(:project_tree) { JSON.parse(File.read(fixture)) }
+  let(:relation_names) { [] }
+  let(:legacy_reader) { described_class.new(path, relation_names) }
+
+  describe '#valid?' do
+    subject { legacy_reader.valid? }
+
+    context 'given valid path' do
+      let(:path) { fixture }
+
+      it { is_expected.to be true }
+    end
+
+    context 'given invalid path' do
+      let(:path) { 'spec/non-existing-folder/do-not-create-this-file.json' }
+
+      it { is_expected.to be false }
+    end
+  end
+
+  describe '#root_attributes' do
+    let(:path) { fixture }
+
+    subject { legacy_reader.root_attributes(excluded_attributes) }
+
+    context 'No excluded attributes' do
+      let(:excluded_attributes) { [] }
+      let(:relation_names) { [] }
+
+      it 'returns the whole tree from parsed JSON' do
+        expect(subject).to eq(project_tree)
+      end
+    end
+
+    context 'Some attributes are excluded' do
+      let(:excluded_attributes) { %w[milestones labels issues services snippets] }
+      let(:relation_names) { %w[import_type archived] }
+
+      it 'returns hash without excluded attributes and relations' do
+        expect(subject).not_to include('milestones', 'labels', 'issues', 'services', 'snippets', 'import_type', 'archived')
+      end
+    end
+  end
+
+  describe '#consume_relation' do
+    let(:path) { fixture }
+    let(:key) { 'description' }
+
+    context 'block not given' do
+      it 'returns value of the key' do
+        expect(legacy_reader).to receive(:relations).and_return({ key => 'test value' })
+        expect(legacy_reader.consume_relation(key)).to eq('test value')
+      end
+    end
+
+    context 'key has been consumed' do
+      before do
+        legacy_reader.consume_relation(key)
+      end
+
+      it 'does not yield' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.not_to yield_control
+      end
+    end
+
+    context 'value is nil' do
+      before do
+        expect(legacy_reader).to receive(:relations).and_return({ key => nil })
+      end
+
+      it 'does not yield' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.not_to yield_control
+      end
+    end
+
+    context 'value is not array' do
+      before do
+        expect(legacy_reader).to receive(:relations).and_return({ key => 'value' })
+      end
+
+      it 'yield the value with index 0' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.to yield_with_args('value', 0)
+      end
+    end
+
+    context 'value is an array' do
+      before do
+        expect(legacy_reader).to receive(:relations).and_return({ key => %w[item1 item2 item3] })
+      end
+
+      it 'yield each array element with index' do
+        expect do |blk|
+          legacy_reader.consume_relation(key, &blk)
+        end.to yield_successive_args(['item1', 0], ['item2', 1], ['item3', 2])
+      end
+    end
+  end
+
+  describe '#tree_hash' do
+    let(:path) { fixture }
+
+    subject { legacy_reader.send(:tree_hash) }
+
+    it 'parses the JSON into the expected tree' do
+      expect(subject).to eq(project_tree)
+    end
+
+    context 'invalid JSON' do
+      let(:path) { 'spec/fixtures/lib/gitlab/import_export/invalid_json/project.json' }
+
+      it 'raise Exception' do
+        expect { subject }.to raise_exception(Gitlab::ImportExport::Error, 'Incorrect JSON format')
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/import_export/project/tree_loader_spec.rb b/spec/lib/gitlab/import_export/project/tree_loader_spec.rb
deleted file mode 100644
index e683eefa7c0..00000000000
--- a/spec/lib/gitlab/import_export/project/tree_loader_spec.rb
+++ /dev/null
@@ -1,49 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe Gitlab::ImportExport::Project::TreeLoader do
-  let(:fixture) { 'spec/fixtures/lib/gitlab/import_export/with_duplicates.json' }
-  let(:project_tree) { JSON.parse(File.read(fixture)) }
-
-  context 'without de-duplicating entries' do
-    let(:parsed_tree) do
-      subject.load(fixture)
-    end
-
-    it 'parses the JSON into the expected tree' do
-      expect(parsed_tree).to eq(project_tree)
-    end
-
-    it 'does not de-duplicate entries' do
-      expect(parsed_tree['duped_hash_with_id']).not_to be(parsed_tree['array'][0]['duped_hash_with_id'])
-    end
-  end
-
-  context 'with de-duplicating entries' do
-    let(:parsed_tree) do
-      subject.load(fixture, dedup_entries: true)
-    end
-
-    it 'parses the JSON into the expected tree' do
-      expect(parsed_tree).to eq(project_tree)
-    end
-
-    it 'de-duplicates equal values' do
-      expect(parsed_tree['duped_hash_with_id']).to be(parsed_tree['array'][0]['duped_hash_with_id'])
-      expect(parsed_tree['duped_hash_with_id']).to be(parsed_tree['nested']['duped_hash_with_id'])
-      expect(parsed_tree['duped_array']).to be(parsed_tree['array'][1]['duped_array'])
-      expect(parsed_tree['duped_array']).to be(parsed_tree['nested']['duped_array'])
-    end
-
-    it 'does not de-duplicate hashes without IDs' do
-      expect(parsed_tree['duped_hash_no_id']).to eq(parsed_tree['array'][2]['duped_hash_no_id'])
-      expect(parsed_tree['duped_hash_no_id']).not_to be(parsed_tree['array'][2]['duped_hash_no_id'])
-    end
-
-    it 'keeps single entries intact' do
-      expect(parsed_tree['simple']).to eq(42)
-      expect(parsed_tree['nested']['array']).to eq(["don't touch"])
-    end
-  end
-end
diff --git a/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb b/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb
index 9c2b202d5bb..e38ef75d085 100644
--- a/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb
+++ b/spec/lib/gitlab/import_export/project/tree_restorer_spec.rb
@@ -783,7 +783,8 @@ describe Gitlab::ImportExport::Project::TreeRestorer do
     end
 
     before do
-      expect(restorer).to receive(:read_tree_hash) { tree_hash }
+      allow_any_instance_of(Gitlab::ImportExport::JSON::LegacyReader::File).to receive(:valid?).and_return(true)
+      allow_any_instance_of(Gitlab::ImportExport::JSON::LegacyReader::File).to receive(:tree_hash) { tree_hash }
     end
 
     context 'no group visibility' do
diff --git a/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb b/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb
index 80901feb893..578418998c0 100644
--- a/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb
+++ b/spec/lib/gitlab/import_export/relation_tree_restorer_spec.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # This spec is a lightweight version of:
-#   * project_tree_restorer_spec.rb
+#   * project/tree_restorer_spec.rb
 #
 # In depth testing is being done in the above specs.
 # This spec tests that restore project works
@@ -25,7 +25,7 @@ describe Gitlab::ImportExport::RelationTreeRestorer do
     described_class.new(
       user:             user,
       shared:           shared,
-      tree_hash:        tree_hash,
+      relation_reader:  relation_reader,
       importable:       importable,
       object_builder:   object_builder,
       members_mapper:   members_mapper,
@@ -36,14 +36,7 @@ describe Gitlab::ImportExport::RelationTreeRestorer do
 
   subject { relation_tree_restorer.restore }
 
-  context 'when restoring a project' do
-    let(:path) { 'spec/fixtures/lib/gitlab/import_export/complex/project.json' }
-    let(:importable) { create(:project, :builds_enabled, :issues_disabled, name: 'project', path: 'project') }
-    let(:object_builder) { Gitlab::ImportExport::Project::ObjectBuilder }
-    let(:relation_factory) { Gitlab::ImportExport::Project::RelationFactory }
-    let(:reader) { Gitlab::ImportExport::Reader.new(shared: shared) }
-    let(:tree_hash) { importable_hash }
-
+  shared_examples 'import project successfully' do
     it 'restores project tree' do
       expect(subject).to eq(true)
     end
@@ -66,4 +59,18 @@ describe Gitlab::ImportExport::RelationTreeRestorer do
       end
     end
   end
+
+  context 'when restoring a project' do
+    let(:path) { 'spec/fixtures/lib/gitlab/import_export/complex/project.json' }
+    let(:importable) { create(:project, :builds_enabled, :issues_disabled, name: 'project', path: 'project') }
+    let(:object_builder) { Gitlab::ImportExport::Project::ObjectBuilder }
+    let(:relation_factory) { Gitlab::ImportExport::Project::RelationFactory }
+    let(:reader) { Gitlab::ImportExport::Reader.new(shared: shared) }
+
+    context 'using legacy reader' do
+      let(:relation_reader) { Gitlab::ImportExport::JSON::LegacyReader::File.new(path, reader.project_relation_names) }
+
+      it_behaves_like 'import project successfully'
+    end
+  end
 end
diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 3df620d1fea..5b87ec022ae 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -625,4 +625,14 @@ describe SystemNoteService do
       described_class.discussion_lock(issuable, double)
     end
   end
+
+  describe '.auto_resolve_prometheus_alert' do
+    it 'calls IssuableService' do
+      expect_next_instance_of(::SystemNotes::IssuablesService) do |service|
+        expect(service).to receive(:auto_resolve_prometheus_alert)
+      end
+
+      described_class.auto_resolve_prometheus_alert(noteable, project, author)
+    end
+  end
 end
diff --git a/spec/services/system_notes/issuables_service_spec.rb b/spec/services/system_notes/issuables_service_spec.rb
index c0aaa65971a..477f9eae39e 100644
--- a/spec/services/system_notes/issuables_service_spec.rb
+++ b/spec/services/system_notes/issuables_service_spec.rb
@@ -654,4 +654,16 @@ describe ::SystemNotes::IssuablesService do
           .to eq('resolved the corresponding error and closed the issue.')
     end
   end
+
+  describe '#auto_resolve_prometheus_alert' do
+    subject { service.auto_resolve_prometheus_alert }
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'closed' }
+    end
+
+    it 'creates the expected system note' do
+      expect(subject.note).to eq('automatically closed this issue because the alert resolved.')
+    end
+  end
 end
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