Make merge request diff works with new FileCollection logic

app/controllers/projects/merge_requests_controller.rb

@@ -91,7 +91,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
     respond_to do |format|
       format.html { define_discussion_vars }
       format.json do
-        @diffs = @merge_request.diffs(diff_options)
+        @diffs = @merge_request_diff.diffs(diff_options)
 
         render json: { html: view_to_html_string("projects/merge_requests/show/_diffs") }
       end

app/models/merge_request.rb

@@ -172,10 +172,10 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def diffs(diff_options = nil)
-    if self.compare
-      self.compare.diffs(diff_options)
+    if compare
+      compare.diffs(diff_options)
     else
-      Gitlab::Diff::FileCollection::MergeRequest.new(self, diff_options: diff_options)
+      merge_request_diff.diffs(diff_options)
     end
   end
 

app/models/merge_request_diff.rb

@@ -141,7 +141,13 @@ class MergeRequestDiff < ActiveRecord::Base
     base_commit_sha? && head_commit_sha? && start_commit_sha?
   end
 
-  private
+  def diffs(diff_options = nil)
+    Gitlab::Diff::FileCollection::MergeRequestDiff.new(self, diff_options: diff_options)
+  end
+
+  def project
+    merge_request.target_project
+  end
 
   def compare
     @compare ||=
@@ -157,6 +163,8 @@ class MergeRequestDiff < ActiveRecord::Base
       end
   end
 
+  private
+
   def dump_commits(commits)
     commits.map(&:to_hash)
   end
@@ -229,10 +237,6 @@ class MergeRequestDiff < ActiveRecord::Base
     update_columns_serialized(new_attributes)
   end
 
-  def project
-    merge_request.target_project
-  end
-
   def repository
     project.repository
   end

app/views/projects/merge_requests/show/_diffs.html.haml

 - if @merge_request_diff.collected?
+  = render 'projects/merge_requests/show/versions'
   = render "projects/diffs/diffs", diffs: @diffs
 - elsif @merge_request_diff.empty?
   .nothing-here-block Nothing to merge from #{@merge_request.source_branch} into #{@merge_request.target_branch}

lib/gitlab/diff/file_collection/merge_request.rb → lib/gitlab/diff/file_collection/merge_request_diff.rb

 module Gitlab
   module Diff
     module FileCollection
-      class MergeRequest < Base
-        def initialize(merge_request, diff_options:)
-          @merge_request = merge_request
+      class MergeRequestDiff < Base
+        def initialize(merge_request_diff, diff_options:)
+          @merge_request_diff = merge_request_diff
 
-          super(merge_request,
-            project: merge_request.project,
+          super(merge_request_diff,
+            project: merge_request_diff.project,
             diff_options: diff_options,
-            diff_refs: merge_request.diff_refs)
+            diff_refs: merge_request_diff.diff_refs)
         end
 
         def diff_files
@@ -61,11 +61,11 @@ module Gitlab
         end
 
         def cacheable?
-          @merge_request.merge_request_diff.present?
+          @merge_request_diff.present?
         end
 
         def cache_key
-          [@merge_request.merge_request_diff, 'highlighted-diff-files', diff_options]
+          [@merge_request_diff, 'highlighted-diff-files', diff_options]
         end
       end
     end