Show merge requests which close current issue

CHANGELOG

@@ -3,6 +3,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 v 8.1.0 (unreleased)
   - Fix error preventing displaying of commit data for a directory with a leading dot (Stan Hu)
   - Speed up load times of issue detail pages by roughly 1.5x
+  - If a merge request is to close an issue, show this on the issue page (Zeger-Jan van de Weg)
   - Make diff file view easier to use on mobile screens (Stan Hu)
   - Improved performance of finding users by username or Email address
   - Fix bug where merge request comments created by API would not trigger notifications (Stan Hu)

app/assets/stylesheets/pages/issues.scss

@@ -132,6 +132,11 @@ form.edit-issue {
   }
 }
 
+.issue-closed-by-widget {
+  padding: 16px 0;
+  margin: 0px;
+}
+
 .issue-form .select2-container {
   width: 250px !important;
 }

app/controllers/projects/issues_controller.rb

@@ -14,6 +14,9 @@ class Projects::IssuesController < Projects::ApplicationController
   # Allow issues bulk update
   before_action :authorize_admin_issues!, only: [:bulk_update]
 
+  # Cross-reference merge requests
+  before_action :closed_by_merge_requests, only: [:show]
+
   respond_to :html
 
   def index
@@ -112,6 +115,10 @@ class Projects::IssuesController < Projects::ApplicationController
     render nothing: true
   end
 
+  def closed_by_merge_requests
+    @closed_by_mr = @issue.closed_by_merge_requests(current_user)
+  end
+
   protected
 
   def issue

app/helpers/issues_helper.rb

@@ -83,6 +83,10 @@ module IssuesHelper
     end
   end
 
+  def merge_requests_sentence(merge_requests)
+    merge_requests.map(&:to_reference).to_sentence
+  end
+
   # Required for Gitlab::Markdown::IssueReferenceFilter
   module_function :url_for_issue
 end

app/models/issue.rb

@@ -95,4 +95,14 @@ class Issue < ActiveRecord::Base
   def source_project
     project
   end
+
+  # From all notes on this issue, we'll select the system notes about linked
+  # merge requests. Of those, the MRs closing `self` are returned.
+  def closed_by_merge_requests(current_user)
+    notes.system.flat_map do |note|
+      ext = Gitlab::ReferenceExtractor.new(self.project, current_user)
+      ext.analyze(note.note)
+      ext.merge_requests
+    end.uniq.select { |mr| mr.closes_issue?(self) }
+  end
 end

app/models/merge_request.rb

@@ -294,6 +294,10 @@ class MergeRequest < ActiveRecord::Base
     target_project
   end
 
+  def closes_issue?(issue)
+    closes_issues.include?(issue)
+  end
+
   # Return the set of issues that will be closed if this merge request is accepted.
   def closes_issues(current_user = self.author)
     if target_branch == project.default_branch

app/views/projects/issues/_closed_by_box.html.haml

+.issue-closed-by-widget 
+  %i.fa.fa-check
+  - if @closed_by_mr.count == 1
+    This issue will be closed when #{gfm(@closed_by_mr.first.to_reference)} is accepted.
+  -else 
+    This issue will be closed when any of merge requests #{gfm(merge_requests_sentence(@closed_by_mr.sort))} is accepted.

app/views/projects/issues/show.html.haml

@@ -46,6 +46,7 @@
                 = markdown(@issue.description)
             %textarea.hidden.js-task-list-field
               = @issue.description
-
+  - if @closed_by_mr.present?
+    = render 'projects/issues/closed_by_box'
   .issue-discussion
     = render 'projects/issues/discussion'