Merge branch '19315-can-edit-merge-request-with-deleted-fork' into 'master'

User can edit closed MR with deleted fork

## What does this MR do?
User can edit closed MR with deleted fork (can't change "Target branch"). When fork is deleted "Reopen" button is hidden.

## What are the relevant issue numbers?
Closes #19315 

## Screenshots (if relevant)
* hidden Reopen button and information about deleted fork
![Zrzut_ekranu_2016-08-12_o_13.19.24](/uploads/d288c5625e788382e31b2979acb601df/Zrzut_ekranu_2016-08-12_o_13.19.24.png)

* editable fields for closed MR without fork
![Zrzut_ekranu_2016-08-05_o_12.24.38](/uploads/1549e54d4bc2a9939ef296ce66139706/Zrzut_ekranu_2016-08-05_o_12.24.38.png)


## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [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)

cc @ubudzisz @yorickpeterse @grzesiek @tmaczukin

See merge request !5496

10 files changed, 232 insertions, 18 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 76f05d9123e..c7559c17605 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -43,6 +43,7 @@ v 8.12.0 (unreleased)
   - Use the default branch for displaying the project icon instead of master !5792 (Hannes Rosenögger)
   - Adds response mime type to transaction metric action when it's not HTML
   - Fix hover leading space bug in pipeline graph !5980
+  - User can edit closed MR with deleted fork (Katarzyna Kobierska Ula Budziszewska) !5496
 
 v 8.11.4 (unreleased)
   - Fix broken gitlab:backup:restore because of bad permissions on repo storage !6098 (Dirk Hörner)
diff --git a/app/helpers/merge_requests_helper.rb b/app/helpers/merge_requests_helper.rb
index db6e731c744..a9e175c3f5c 100644
--- a/app/helpers/merge_requests_helper.rb
+++ b/app/helpers/merge_requests_helper.rb
@@ -98,6 +98,6 @@ module MergeRequestsHelper
   end
 
   def merge_request_button_visibility(merge_request, closed)
-    return 'hidden' if merge_request.closed? == closed || (merge_request.merged? == closed && !merge_request.closed?)
+    return 'hidden' if merge_request.closed? == closed || (merge_request.merged? == closed && !merge_request.closed?) || merge_request.closed_without_fork?
   end
 end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 1d05e4a85d1..a8dd4a306cf 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -91,13 +91,13 @@ class MergeRequest < ActiveRecord::Base
     end
   end
 
-  validates :source_project, presence: true, unless: [:allow_broken, :importing?]
+  validates :source_project, presence: true, unless: [:allow_broken, :importing?, :closed_without_fork?]
   validates :source_branch, presence: true
   validates :target_project, presence: true
   validates :target_branch, presence: true
   validates :merge_user, presence: true, if: :merge_when_build_succeeds?
-  validate :validate_branches, unless: [:allow_broken, :importing?]
-  validate :validate_fork
+  validate :validate_branches, unless: [:allow_broken, :importing?, :closed_without_fork?]
+  validate :validate_fork, unless: :closed_without_fork?
 
   scope :by_branch, ->(branch_name) { where("(source_branch LIKE :branch) OR (target_branch LIKE :branch)", branch: branch_name) }
   scope :cared, ->(user) { where('assignee_id = :user OR author_id = :user', user: user.id) }
@@ -305,19 +305,22 @@ class MergeRequest < ActiveRecord::Base
 
   def validate_fork
     return true unless target_project && source_project
+    return true if target_project == source_project
+    return true unless forked_source_project_missing?
 
-    if target_project == source_project
-      true
-    else
-      # If source and target projects are different
-      # we should check if source project is actually a fork of target project
-      if source_project.forked_from?(target_project)
-        true
-      else
-        errors.add :validate_fork,
-                   'Source project is not a fork of target project'
-      end
-    end
+    errors.add :validate_fork,
+               'Source project is not a fork of the target project'
+  end
+
+  def closed_without_fork?
+    closed? && forked_source_project_missing?
+  end
+
+  def forked_source_project_missing?
+    return false unless for_fork?
+    return true unless source_project
+
+    !source_project.forked_from?(target_project)
   end
 
   def ensure_merge_request_diff
diff --git a/app/services/merge_requests/update_service.rb b/app/services/merge_requests/update_service.rb
index 30c5f24988c..398ec47f0ea 100644
--- a/app/services/merge_requests/update_service.rb
+++ b/app/services/merge_requests/update_service.rb
@@ -11,6 +11,10 @@ module MergeRequests
       params.except!(:target_project_id)
       params.except!(:source_branch)
 
+      if merge_request.closed_without_fork?
+        params.except!(:target_branch, :force_remove_source_branch)
+      end
+
       merge_request.merge_params['force_remove_source_branch'] = params.delete(:force_remove_source_branch)
 
       update(merge_request)
diff --git a/app/views/projects/merge_requests/show/_mr_title.html.haml b/app/views/projects/merge_requests/show/_mr_title.html.haml
index 098ce19da21..e35291dff7d 100644
--- a/app/views/projects/merge_requests/show/_mr_title.html.haml
+++ b/app/views/projects/merge_requests/show/_mr_title.html.haml
@@ -1,3 +1,7 @@
+- if @merge_request.closed_without_fork?
+  .alert.alert-danger
+    %p The source project of this merge request has been removed.
+
 .clearfix.detail-page-header
   .issuable-header
     .issuable-status-box.status-box{ class: status_box_class(@merge_request) }
diff --git a/app/views/shared/issuable/_form.html.haml b/app/views/shared/issuable/_form.html.haml
index 22594b46443..3856a4917b4 100644
--- a/app/views/shared/issuable/_form.html.haml
+++ b/app/views/shared/issuable/_form.html.haml
@@ -134,7 +134,7 @@
       title: 'Moving an issue will copy the discussion to a different project and close it here. All participants will be notified of the new location.' }
         = icon('question-circle')
 
-- if issuable.is_a?(MergeRequest)
+- if issuable.is_a?(MergeRequest) && !issuable.closed_without_fork?
   %hr
   - if @merge_request.new_record?
     .form-group
@@ -175,7 +175,7 @@
     = link_to 'Cancel', polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable.class]), class: 'btn btn-cancel'
   - else
     .pull-right
-      - if current_user.can?(:"destroy_#{issuable.to_ability_name}", @project)
+      - if can?(current_user, :"destroy_#{issuable.to_ability_name}", @project)
         = link_to 'Delete', polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable]), data: { confirm: "#{issuable.class.name.titleize} will be removed! Are you sure?" },
                                                                                                   method: :delete, class: 'btn btn-danger btn-grouped'
       = link_to 'Cancel', polymorphic_path([@project.namespace.becomes(Namespace), @project, issuable]), class: 'btn btn-grouped btn-cancel'
diff --git a/spec/controllers/projects/merge_requests_controller_spec.rb b/spec/controllers/projects/merge_requests_controller_spec.rb
index c64c2b075c5..a219400d75f 100644
--- a/spec/controllers/projects/merge_requests_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests_controller_spec.rb
@@ -170,6 +170,35 @@ describe Projects::MergeRequestsController do
         expect(response).to redirect_to([merge_request.target_project.namespace.becomes(Namespace), merge_request.target_project, merge_request])
         expect(merge_request.reload.closed?).to be_truthy
       end
+
+      it 'allows editing of a closed merge request' do
+        merge_request.close!
+
+        put :update,
+            namespace_id: project.namespace.path,
+            project_id: project.path,
+            id: merge_request.iid,
+            merge_request: {
+              title: 'New title'
+            }
+
+        expect(response).to redirect_to([merge_request.target_project.namespace.becomes(Namespace), merge_request.target_project, merge_request])
+        expect(merge_request.reload.title).to eq 'New title'
+      end
+
+      it 'does not allow to update target branch closed merge request' do
+        merge_request.close!
+
+        put :update,
+            namespace_id: project.namespace.path,
+            project_id: project.path,
+            id: merge_request.iid,
+            merge_request: {
+              target_branch: 'new_branch'
+            }
+
+        expect { merge_request.reload.target_branch }.not_to change { merge_request.target_branch }
+      end
     end
   end
 
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index d67f71bbb9c..901b7bad007 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -962,4 +962,80 @@ describe MergeRequest, models: true do
       expect(merge_request.conflicts_can_be_resolved_in_ui?).to be_truthy
     end
   end
+
+  describe "#forked_source_project_missing?" do
+    let(:project)      { create(:project) }
+    let(:fork_project) { create(:project, forked_from_project: project) }
+    let(:user)         { create(:user) }
+    let(:unlink_project) { Projects::UnlinkForkService.new(fork_project, user) }
+
+    context "when the fork exists" do
+      let(:merge_request) do
+        create(:merge_request,
+          source_project: fork_project,
+          target_project: project)
+      end
+
+      it { expect(merge_request.forked_source_project_missing?).to be_falsey }
+    end
+
+    context "when the source project is the same as the target project" do
+      let(:merge_request) { create(:merge_request, source_project: project) }
+
+      it { expect(merge_request.forked_source_project_missing?).to be_falsey }
+    end
+
+    context "when the fork does not exist" do
+      let(:merge_request) do
+        create(:merge_request,
+          source_project: fork_project,
+          target_project: project)
+      end
+
+      it "returns true" do
+        unlink_project.execute
+        merge_request.reload
+
+        expect(merge_request.forked_source_project_missing?).to be_truthy
+      end
+    end
+  end
+
+  describe "#closed_without_fork?" do
+    let(:project)      { create(:project) }
+    let(:fork_project) { create(:project, forked_from_project: project) }
+    let(:user)         { create(:user) }
+    let(:unlink_project) { Projects::UnlinkForkService.new(fork_project, user) }
+
+    context "when the merge request is closed" do
+      let(:closed_merge_request) do
+        create(:closed_merge_request,
+          source_project: fork_project,
+          target_project: project)
+      end
+
+      it "returns false if the fork exist" do
+        expect(closed_merge_request.closed_without_fork?).to be_falsey
+      end
+
+      it "returns true if the fork does not exist" do
+        unlink_project.execute
+        closed_merge_request.reload
+
+        expect(closed_merge_request.closed_without_fork?).to be_truthy
+      end
+    end
+
+    context "when the merge request is open" do
+      let(:open_merge_request) do
+        create(:merge_request,
+          source_project: fork_project,
+          target_project: project)
+      end
+
+      it "returns false" do
+        expect(open_merge_request.closed_without_fork?).to be_falsey
+      end
+    end
+  end
 end
diff --git a/spec/views/projects/merge_requests/edit.html.haml_spec.rb b/spec/views/projects/merge_requests/edit.html.haml_spec.rb
new file mode 100644
index 00000000000..31bbb150698
--- /dev/null
+++ b/spec/views/projects/merge_requests/edit.html.haml_spec.rb
@@ -0,0 +1,53 @@
+require 'spec_helper'
+
+describe 'projects/merge_requests/edit.html.haml' do
+  include Devise::TestHelpers
+
+  let(:user) { create(:user) }
+  let(:project) { create(:project) }
+  let(:fork_project) { create(:project, forked_from_project: project) }
+  let(:unlink_project) { Projects::UnlinkForkService.new(fork_project, user) }
+
+  let(:closed_merge_request) do
+    create(:closed_merge_request,
+      source_project: fork_project,
+      target_project: project,
+      author: user)
+  end
+
+  before do
+    assign(:project, project)
+    assign(:merge_request, closed_merge_request)
+
+    allow(view).to receive(:can?).and_return(true)
+    allow(view).to receive(:current_user)
+      .and_return(User.find(closed_merge_request.author_id))
+  end
+
+  context 'when a merge request without fork' do
+    it "shows editable fields" do
+      unlink_project.execute
+      closed_merge_request.reload
+
+      render
+
+      expect(rendered).to have_field('merge_request[title]')
+      expect(rendered).to have_field('merge_request[description]')
+      expect(rendered).to have_selector('#merge_request_assignee_id', visible: false)
+      expect(rendered).to have_selector('#merge_request_milestone_id', visible: false)
+      expect(rendered).not_to have_selector('#merge_request_target_branch', visible: false)
+    end
+  end
+
+  context 'when a merge request with an existing source project is closed' do
+    it "shows editable fields" do
+      render
+
+      expect(rendered).to have_field('merge_request[title]')
+      expect(rendered).to have_field('merge_request[description]')
+      expect(rendered).to have_selector('#merge_request_assignee_id', visible: false)
+      expect(rendered).to have_selector('#merge_request_milestone_id', visible: false)
+      expect(rendered).to have_selector('#merge_request_target_branch', visible: false)
+    end
+  end
+end
diff --git a/spec/views/projects/merge_requests/show.html.haml_spec.rb b/spec/views/projects/merge_requests/show.html.haml_spec.rb
new file mode 100644
index 00000000000..fe0780e72df
--- /dev/null
+++ b/spec/views/projects/merge_requests/show.html.haml_spec.rb
@@ -0,0 +1,44 @@
+require 'spec_helper'
+
+describe 'projects/merge_requests/show.html.haml' do
+  include Devise::TestHelpers
+
+  let(:user) { create(:user) }
+  let(:project) { create(:project) }
+  let(:fork_project) { create(:project, forked_from_project: project) }
+  let(:unlink_project) { Projects::UnlinkForkService.new(fork_project, user) }
+
+  let(:closed_merge_request) do
+    create(:closed_merge_request,
+      source_project: fork_project,
+      target_project: project,
+      author: user)
+  end
+
+  before do
+    assign(:project, project)
+    assign(:merge_request, closed_merge_request)
+    assign(:commits_count, 0)
+
+    allow(view).to receive(:can?).and_return(true)
+  end
+
+  context 'when the merge request is closed' do
+    it 'shows the "Reopen" button' do
+      render
+
+      expect(rendered).to have_css('a', visible: true, text: 'Reopen')
+      expect(rendered).to have_css('a', visible: false, text: 'Close')
+    end
+
+    it 'does not show the "Reopen" button when the source project does not exist' do
+      unlink_project.execute
+      closed_merge_request.reload
+
+      render
+
+      expect(rendered).to have_css('a', visible: false, text: 'Reopen')
+      expect(rendered).to have_css('a', visible: false, text: 'Close')
+    end
+  end
+end