Merge branch '21636-deleting-source-project-with-existing-fork-closes-all-related-merge-requests' into 'master'

Deleting source project with existing fork link should closes all
related merge requests, and does not render `invalid` template for merge
requests with deleted source project.
The merge request without source project can be edited but can't be reopened.

Closes #21636 

See merge request !6177

8 files changed, 127 insertions, 21 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 195362046dc..4cad8707015 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -127,6 +127,7 @@ v 8.12.0 (unreleased)
   - Allow bulk update merge requests from merge requests index page
   - Add notification_settings API calls !5632 (mahcsig)
   - Remove duplication between project builds and admin builds view !5680 (Katarzyna Kobierska Ula Budziszewska)
+  - Deleting source project with existing fork link will close all related merge requests !6177 (Katarzyna Kobierska Ula Budziszeska)
 
 v 8.11.6 (unreleased)
   - Fix an error where we were unable to create a CommitStatus for running state
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 8895cb955bd..aa8645ba8cc 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -428,17 +428,11 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def validates_merge_request
-    # If source project was removed (Ex. mr from fork to origin)
-    return invalid_mr unless @merge_request.source_project
-
     # Show git not found page
     # if there is no saved commits between source & target branch
     if @merge_request.commits.blank?
       # and if target branch doesn't exist
       return invalid_mr unless @merge_request.target_branch_exists?
-
-      # or if source branch doesn't exist
-      return invalid_mr unless @merge_request.source_branch_exists?
     end
   end
 
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index b0b1313f94a..f7d1253d957 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -316,6 +316,10 @@ class MergeRequest < ActiveRecord::Base
     closed? && forked_source_project_missing?
   end
 
+  def closed_without_source_project?
+    closed? && !source_project
+  end
+
   def forked_source_project_missing?
     return false unless for_fork?
     return true unless source_project
@@ -323,6 +327,12 @@ class MergeRequest < ActiveRecord::Base
     !source_project.forked_from?(target_project)
   end
 
+  def reopenable?
+    return false if closed_without_fork? || closed_without_source_project? || merged?
+
+    closed?
+  end
+
   def ensure_merge_request_diff
     merge_request_diff || create_merge_request_diff
   end
diff --git a/app/services/projects/destroy_service.rb b/app/services/projects/destroy_service.rb
index 8a53f65aec1..a08c6fcd94b 100644
--- a/app/services/projects/destroy_service.rb
+++ b/app/services/projects/destroy_service.rb
@@ -27,6 +27,8 @@ module Projects
       # Git data (e.g. a list of branch names).
       flush_caches(project, wiki_path)
 
+      Projects::UnlinkForkService.new(project, current_user).execute
+
       Project.transaction do
         project.destroy!
 
diff --git a/app/views/projects/merge_requests/_discussion.html.haml b/app/views/projects/merge_requests/_discussion.html.haml
index d070979bcfe..3900b4f6f17 100644
--- a/app/views/projects/merge_requests/_discussion.html.haml
+++ b/app/views/projects/merge_requests/_discussion.html.haml
@@ -2,7 +2,7 @@
   - if can?(current_user, :update_merge_request, @merge_request)
     - if @merge_request.open?
       = link_to 'Close merge request', merge_request_path(@merge_request, merge_request: {state_event: :close }), method: :put, class: "btn btn-nr btn-comment btn-close close-mr-link js-note-target-close", title: "Close merge request", data: {original_text: "Close merge request", alternative_text: "Comment & close merge request"}
-    - if @merge_request.closed?
+    - if @merge_request.reopenable?
       = link_to 'Reopen merge request', merge_request_path(@merge_request, merge_request: {state_event: :reopen }), method: :put, class: "btn btn-nr btn-comment btn-reopen reopen-mr-link js-note-target-reopen", title: "Reopen merge request", data: {original_text: "Reopen merge request", alternative_text: "Comment & reopen merge request"}
   %comment-and-resolve-btn{ "inline-template" => true, ":discussion-id" => "" }
     %button.btn.btn-nr.btn-default.append-right-10.js-comment-resolve-button{ "v-if" => "showButton", type: "submit", data: { namespace_path: "#{@merge_request.project.namespace.path}", project_path: "#{@merge_request.project.path}" } }
diff --git a/app/views/projects/merge_requests/_show.html.haml b/app/views/projects/merge_requests/_show.html.haml
index 4b4d418e8ec..d03ff9ec7e8 100644
--- a/app/views/projects/merge_requests/_show.html.haml
+++ b/app/views/projects/merge_requests/_show.html.haml
@@ -29,17 +29,19 @@
             %ul.dropdown-menu.dropdown-menu-align-right
               %li= link_to "Email Patches", merge_request_path(@merge_request, format: :patch)
               %li= link_to "Plain Diff",    merge_request_path(@merge_request, format: :diff)
-      .normal
-        %span Request to merge
-        %span.label-branch= source_branch_with_namespace(@merge_request)
-        %span into
-        %span.label-branch
-          = link_to @merge_request.target_branch, namespace_project_commits_path(@project.namespace, @project, @merge_request.target_branch)
-        - if @merge_request.open? && @merge_request.diverged_from_target_branch?
-          %span (#{pluralize(@merge_request.diverged_commits_count, 'commit')} behind)
+      - unless @merge_request.closed_without_fork?
+        .normal
+          %span Request to merge
+          %span.label-branch= source_branch_with_namespace(@merge_request)
+          %span into
+          %span.label-branch
+            = link_to @merge_request.target_branch, namespace_project_commits_path(@project.namespace, @project, @merge_request.target_branch)
+          - if @merge_request.open? && @merge_request.diverged_from_target_branch?
+            %span (#{pluralize(@merge_request.diverged_commits_count, 'commit')} behind)
 
-    = render "projects/merge_requests/show/how_to_merge"
-    = render "projects/merge_requests/widget/show.html.haml"
+    - unless @merge_request.closed_without_source_project?
+      = render "projects/merge_requests/show/how_to_merge"
+      = render "projects/merge_requests/widget/show.html.haml"
 
     - if @merge_request.source_branch_exists? && @merge_request.mergeable? && @merge_request.can_be_merged_by?(current_user)
       .light.prepend-top-default.append-bottom-default
@@ -53,10 +55,11 @@
           = link_to namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#notes', action: 'notes', toggle: 'tab' } do
             Discussion
             %span.badge= @merge_request.mr_and_commit_notes.user.count
-        %li.commits-tab
-          = link_to commits_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#commits', action: 'commits', toggle: 'tab' } do
-            Commits
-            %span.badge= @commits_count
+        - unless @merge_request.closed_without_source_project?
+          %li.commits-tab
+            = link_to commits_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#commits', action: 'commits', toggle: 'tab' } do
+              Commits
+              %span.badge= @commits_count
         - if @pipeline
           %li.pipelines-tab
             = link_to pipelines_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: '#pipelines', action: 'pipelines', toggle: 'tab' } do
diff --git a/spec/controllers/projects_controller_spec.rb b/spec/controllers/projects_controller_spec.rb
index ffe0641ddd7..b0f740f48f7 100644
--- a/spec/controllers/projects_controller_spec.rb
+++ b/spec/controllers/projects_controller_spec.rb
@@ -181,6 +181,25 @@ describe ProjectsController do
       expect(response).to have_http_status(302)
       expect(response).to redirect_to(dashboard_projects_path)
     end
+
+    context "when the project is forked" do
+      let(:project)      { create(:project) }
+      let(:fork_project) { create(:project, forked_from_project: project) }
+      let(:merge_request) do
+        create(:merge_request,
+          source_project: fork_project,
+          target_project: project)
+      end
+
+      it "closes all related merge requests" do
+        project.merge_requests << merge_request
+        sign_in(admin)
+
+        delete :destroy, namespace_id: fork_project.namespace.path, id: fork_project.path
+
+        expect(merge_request.reload.state).to eq('closed')
+      end
+    end
   end
 
   describe "POST #toggle_star" do
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 5bf3b8e609e..3b815ded2d3 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -1038,4 +1038,81 @@ describe MergeRequest, models: true do
       end
     end
   end
+
+  describe '#closed_without_source_project?' do
+    let(:project)      { create(:project) }
+    let(:user)         { create(:user) }
+    let(:fork_project) { create(:project, forked_from_project: project, namespace: user.namespace) }
+    let(:destroy_service) { Projects::DestroyService.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 source project exists' do
+        expect(closed_merge_request.closed_without_source_project?).to be_falsey
+      end
+
+      it 'returns true if the source project does not exist' do
+        destroy_service.execute
+        closed_merge_request.reload
+
+        expect(closed_merge_request.closed_without_source_project?).to be_truthy
+      end
+    end
+
+    context 'when the merge request is open' do
+      it 'returns false' do
+        expect(subject.closed_without_source_project?).to be_falsey
+      end
+    end
+  end
+
+  describe '#reopenable?' do
+    context 'when the merge request is closed' do
+      it 'returns true' do
+        subject.close
+
+        expect(subject.reopenable?).to be_truthy
+      end
+
+      context 'forked project' do
+        let(:project)      { create(:project) }
+        let(:user)         { create(:user) }
+        let(:fork_project) { create(:project, forked_from_project: project, namespace: user.namespace) }
+        let(:merge_request) do
+          create(:closed_merge_request,
+            source_project: fork_project,
+            target_project: project)
+        end
+
+        it 'returns false if unforked' do
+          Projects::UnlinkForkService.new(fork_project, user).execute
+
+          expect(merge_request.reload.reopenable?).to be_falsey
+        end
+
+        it 'returns false if the source project is deleted' do
+          Projects::DestroyService.new(fork_project, user).execute
+
+          expect(merge_request.reload.reopenable?).to be_falsey
+        end
+
+        it 'returns false if the merge request is merged' do
+          merge_request.update_attributes(state: 'merged')
+
+          expect(merge_request.reload.reopenable?).to be_falsey
+        end
+      end
+    end
+
+    context 'when the merge request is opened' do
+      it 'returns false' do
+        expect(subject.reopenable?).to be_falsey
+      end
+    end
+  end
 end