Add changelog entry, improve specs and model code

CHANGELOG

@@ -17,6 +17,7 @@ v 8.7.0 (unreleased)
   - Add links to CI setup documentation from project settings and builds pages
   - Handle nil descriptions in Slack issue messages (Stan Hu)
   - Add default scope to projects to exclude projects pending deletion
+  - Allow to close merge requests which source projects(forks) are deleted.
   - Ensure empty recipients are rejected in BuildsEmailService
   - API: Ability to filter milestones by state `active` and `closed` (Robert Schilling)
   - Implement 'Groups View' as an option for dashboard preferences !3379 (Elias W.)

app/models/merge_request.rb

@@ -128,7 +128,7 @@ class MergeRequest < ActiveRecord::Base
   validates :target_project, presence: true
   validates :target_branch, presence: true
   validates :merge_user, presence: true, if: :merge_when_build_succeeds?
-  validate :validate_branches
+  validate :validate_branches, unless: :allow_broken
   validate :validate_fork
 
   scope :by_branch, ->(branch_name) { where("(source_branch LIKE :branch) OR (target_branch LIKE :branch)", branch: branch_name) }
@@ -213,14 +213,12 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def validate_branches
-    return if allow_broken
-
     if target_project == source_project && target_branch == source_branch
       errors.add :branch_conflict, "You can not use same project/branch for source and target"
     end
 
     if opened? || reopened?
-      similar_mrs = self.target_project.merge_requests.where(source_branch: source_branch, target_branch: target_branch, source_project_id: source_project.id).opened
+      similar_mrs = self.target_project.merge_requests.where(source_branch: source_branch, target_branch: target_branch, source_project_id: source_project.try(:id)).opened
       similar_mrs = similar_mrs.where('id not in (?)', self.id) if self.id
       if similar_mrs.any?
         errors.add :validate_branches,
@@ -346,12 +344,9 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def hook_attrs
-    source_hook_attrs = source_project.hook_attrs if source_project.present?
-    target_hook_attrs = target_project.hook_attrs if target_project.present?
-
     attrs = {
-      source: source_hook_attrs,
+      source: source_project.try(:hook_attrs),
-      target: target_hook_attrs,
+      target: target_project.hook_attrs,
       last_commit: nil,
       work_in_progress: work_in_progress?
     }

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -161,17 +161,16 @@ describe Projects::MergeRequestsController do
     context 'there is no source project' do
       let(:project)       { create(:project) }
       let(:fork_project)  { create(:forked_project_with_submodules) }
-      let(:merge_request) { create(:merge_request_with_diffs, source_project: fork_project, source_branch: 'add-submodule-version-bump', target_branch: 'master', target_project: project) }
+      let(:merge_request) { create(:merge_request, source_project: fork_project, source_branch: 'add-submodule-version-bump', target_branch: 'master', target_project: project) }
 
       before do
         fork_project.build_forked_project_link(forked_to_project_id: fork_project.id, forked_from_project_id: project.id)
         fork_project.save
         merge_request.reload
+        fork_project.destroy
       end
 
       it 'closes MR without errors' do
-        fork_project.destroy
-
         post :update,
             namespace_id: project.namespace.path,
             project_id: project.path,