Merge branch '23341-fix-viewing-mr-from-deleted-project' into 'master'

Fix a 500 error viewing an MR with a deleted source project

## What does this MR do?

Allows merged MRs to be shown without any 500 errors if the source project is removed

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

https://gitlab.com/gitlab-org/gitlab-ce/commit/31c37c6c38258684fc92e0d91119c33872e39034 fixed this for closed MRs only. I had trouble understanding the introduced helper and logic, so reverted it and keyed everything on the existence of the source project or branch directly.

commits.json returns a 500 error for a closed or merged MR; the approach taken in the above MR was to hide the commits... tab, so I've run with that.

For merged MRs, the commits (but not the pipeline data) are in the target project, so we *could* do better, but it's a fairly nasty intervention to make it happen.

## Why was this MR needed?

Viewing merged MRs should work even if the fork they came from has been deleted or unlinked.

## Screenshots (if relevant)

![Screen_Shot_2016-10-19_at_17.56.37](/uploads/1aeadd5147b9a4ad29b946b1c7ea52cb/Screen_Shot_2016-10-19_at_17.56.37.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) 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
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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 it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Closes #23341

See merge request !6991

7 files changed, 48 insertions, 70 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 98cffab8c03..4f163f323e6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -39,6 +39,7 @@ Please view this file on the master branch, on stable branches it's out of date.
   - ProjectCacheWorker updates caches at most once per 15 minutes per project
   - Fix Error 500 when viewing old merge requests with bad diff data
   - Create a new /templates namespace for the /licenses, /gitignores and /gitlab_ci_ymls API endpoints. !5717 (tbalthazar)
+  - Fix viewing merged MRs when the source project has been removed !6991
   - Speed-up group milestones show page
   - Fix inconsistent options dropdown caret on mobile viewports (ClemMakesApps)
   - Extract project#update_merge_requests and SystemHooks to its own worker from GitPushService
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 0f593d1a936..2ee53f7ceda 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -398,7 +398,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
 
       status ||= "preparing"
     else
-      ci_service = @merge_request.source_project.ci_service
+      ci_service = @merge_request.source_project.try(:ci_service)
       status = ci_service.commit_status(merge_request.diff_head_sha, merge_request.source_branch) if ci_service
 
       if ci_service.respond_to?(:commit_coverage)
@@ -554,7 +554,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   def define_pipelines_vars
     @pipelines = @merge_request.all_pipelines
 
-    if @pipelines.any?
+    if @pipelines.present?
       @pipeline = @pipelines.first
       @statuses = @pipeline.statuses.relevant
     end
diff --git a/app/helpers/merge_requests_helper.rb b/app/helpers/merge_requests_helper.rb
index 249cb44e9d5..a6659ea2fd1 100644
--- a/app/helpers/merge_requests_helper.rb
+++ b/app/helpers/merge_requests_helper.rb
@@ -86,11 +86,15 @@ module MergeRequestsHelper
   end
 
   def source_branch_with_namespace(merge_request)
-    branch = link_to(merge_request.source_branch, namespace_project_commits_path(merge_request.source_project.namespace, merge_request.source_project, merge_request.source_branch))
+    namespace = merge_request.source_project_namespace
+    branch = merge_request.source_branch
+
+    if merge_request.source_branch_exists?
+      namespace = link_to(namespace, project_path(merge_request.source_project))
+      branch = link_to(branch, namespace_project_commits_path(merge_request.source_project.namespace, merge_request.source_project, merge_request.source_branch))
+    end
 
     if merge_request.for_fork?
-      namespace = link_to(merge_request.source_project_namespace,
-        project_path(merge_request.source_project))
       namespace + ":" + branch
     else
       branch
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 0cc0b3c2a0e..c476a3bb14e 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -326,21 +326,17 @@ 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?
+    return true unless source_project_missing?
 
     errors.add :validate_fork,
                'Source project is not a fork of the target project'
   end
 
   def closed_without_fork?
-    closed? && forked_source_project_missing?
+    closed? && source_project_missing?
   end
 
-  def closed_without_source_project?
-    closed? && !source_project
-  end
-
-  def forked_source_project_missing?
+  def source_project_missing?
     return false unless for_fork?
     return true unless source_project
 
@@ -348,9 +344,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def reopenable?
-    return false if closed_without_fork? || closed_without_source_project? || merged?
-
-    closed?
+    closed? && !source_project_missing? && source_branch_exists?
   end
 
   def ensure_merge_request_diff
@@ -662,7 +656,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def has_ci?
-    source_project.ci_service && commits.any?
+    source_project.try(:ci_service) && commits.any?
   end
 
   def branch_missing?
@@ -694,12 +688,9 @@ class MergeRequest < ActiveRecord::Base
 
     @environments ||=
       begin
-        environments = source_project.environments_for(
-          source_branch, diff_head_commit)
-        environments += target_project.environments_for(
-          target_branch, diff_head_commit, with_tags: true)
-
-        environments.uniq
+        envs = target_project.environments_for(target_branch, diff_head_commit, with_tags: true)
+        envs.concat(source_project.environments_for(source_branch, diff_head_commit)) if source_project
+        envs.uniq
       end
   end
 
diff --git a/app/views/projects/merge_requests/_show.html.haml b/app/views/projects/merge_requests/_show.html.haml
index cd98aaf8d75..0e19d224fcd 100644
--- a/app/views/projects/merge_requests/_show.html.haml
+++ b/app/views/projects/merge_requests/_show.html.haml
@@ -26,19 +26,19 @@
             %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)
-      - 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)
+      .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_source_project?
+    - if @merge_request.source_branch_exists?
       = render "projects/merge_requests/show/how_to_merge"
-      = render "projects/merge_requests/widget/show.html.haml"
+
+    = 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
@@ -52,7 +52,7 @@
           = 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
-        - unless @merge_request.closed_without_source_project?
+        - if @merge_request.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
diff --git a/spec/features/merge_requests/created_from_fork_spec.rb b/spec/features/merge_requests/created_from_fork_spec.rb
index a506624b30d..cfc1244429f 100644
--- a/spec/features/merge_requests/created_from_fork_spec.rb
+++ b/spec/features/merge_requests/created_from_fork_spec.rb
@@ -25,6 +25,20 @@ feature 'Merge request created from fork' do
     expect(page).to have_content 'Test merge request'
   end
 
+  context 'source project is deleted' do
+    background do
+      MergeRequests::MergeService.new(project, user).execute(merge_request)
+      fork_project.destroy!
+    end
+
+    scenario 'user can access merge request' do
+      visit_merge_request(merge_request)
+
+      expect(page).to have_content 'Test merge request'
+      expect(page).to have_content "(removed):#{merge_request.source_branch}"
+    end
+  end
+
   context 'pipeline present in source project' do
     include WaitForAjax
 
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 6db5e7f7d80..6e5137602aa 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -1198,7 +1198,7 @@ describe MergeRequest, models: true do
     end
   end
 
-  describe "#forked_source_project_missing?" do
+  describe "#source_project_missing?" do
     let(:project)      { create(:project) }
     let(:fork_project) { create(:project, forked_from_project: project) }
     let(:user)         { create(:user) }
@@ -1211,13 +1211,13 @@ describe MergeRequest, models: true do
           target_project: project)
       end
 
-      it { expect(merge_request.forked_source_project_missing?).to be_falsey }
+      it { expect(merge_request.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 }
+      it { expect(merge_request.source_project_missing?).to be_falsey }
     end
 
     context "when the fork does not exist" do
@@ -1231,7 +1231,7 @@ describe MergeRequest, models: true do
         unlink_project.execute
         merge_request.reload
 
-        expect(merge_request.forked_source_project_missing?).to be_truthy
+        expect(merge_request.source_project_missing?).to be_truthy
       end
     end
   end
@@ -1274,38 +1274,6 @@ describe MergeRequest, models: true do
     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