Merge branch 'assign-issues-for-merge-request-18876' into 'master'

Ability to bulk assign issues to author of merge request

## What does this MR do?
Provides a link to auto-assign issues to the author of a merge request, when they are mentioned as being closed by the MR.

## Are there points in the code the reviewer needs to double check?


## Why was this MR needed?
To help avoid working on a MR without having assigned related issues to self

## What are the relevant issue numbers?
Fixes #18876 

## Screenshots (if relevant)
![ScreenShot-P216](/uploads/1af5e71a0a0ff0a60c5d7b54c0e09d9c/ScreenShot-P216.png)

## Tasks
- [x] Refactor or move away from using `BulkUpdateService`
- [x] ~~Consider alternate link message when only a subset of issues will be assigned~~
- [x] Minimize repeated calls to expensive `closes_issues` method
- [x] Move away from using inflector for pluralization and fix flash message
- [x] Change auth `before_action` and fallback to error flash message
- [x] Shouldn't overwrite current assignee if one exists

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [x] ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5725

1 files changed, 49 insertions, 0 deletions

diff --git a/spec/services/merge_requests/assign_issues_service_spec.rb b/spec/services/merge_requests/assign_issues_service_spec.rb
new file mode 100644
index 00000000000..7aeb95a15ea
--- /dev/null
+++ b/spec/services/merge_requests/assign_issues_service_spec.rb
@@ -0,0 +1,49 @@
+require 'spec_helper'
+
+describe MergeRequests::AssignIssuesService, services: true do
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :public) }
+  let(:issue) { create(:issue, project: project) }
+  let(:merge_request) { create(:merge_request, :simple, source_project: project, author: user, description: "fixes #{issue.to_reference}") }
+  let(:service) { described_class.new(project, user, merge_request: merge_request) }
+
+  before do
+    project.team << [user, :developer]
+  end
+
+  it 'finds unassigned issues fixed in merge request' do
+    expect(service.assignable_issues.map(&:id)).to include(issue.id)
+  end
+
+  it 'ignores issues already assigned to any user' do
+    issue.update!(assignee: create(:user))
+
+    expect(service.assignable_issues).to be_empty
+  end
+
+  it 'ignores issues the user cannot update assignee on' do
+    project.team.truncate
+
+    expect(service.assignable_issues).to be_empty
+  end
+
+  it 'ignores all issues unless current_user is merge_request.author' do
+    merge_request.update!(author: create(:user))
+
+    expect(service.assignable_issues).to be_empty
+  end
+
+  it 'accepts precomputed data for closes_issues' do
+    issue2 = create(:issue, project: project)
+    service2 = described_class.new(project,
+                                   user,
+                                   merge_request: merge_request,
+                                   closes_issues: [issue, issue2])
+
+    expect(service2.assignable_issues.count).to eq 2
+  end
+
+  it 'assigns these to the merge request owner' do
+    expect { service.execute }.to change { issue.reload.assignee }.to(user)
+  end
+end