Pass project into predicates for feature flags

We've added a pair of feature flag checks that are gated on project, but
in order to get at the project object. we have to go through the
diff_file object because of the Grape abstractions in play..

app/serializers/diff_file_entity.rb

@@ -53,7 +53,7 @@ class DiffFileEntity < DiffFileBaseEntity
   end
 
   # Used for inline diffs
-  expose :highlighted_diff_lines, using: DiffLineEntity, if: -> (diff_file, options) { inline_diff_view?(options) && diff_file.text? } do |diff_file|
+  expose :highlighted_diff_lines, using: DiffLineEntity, if: -> (diff_file, options) { inline_diff_view?(options, diff_file) && diff_file.text? } do |diff_file|
     diff_file.diff_lines_for_serializer
   end
 
@@ -62,19 +62,19 @@ class DiffFileEntity < DiffFileBaseEntity
   end
 
   # Used for parallel diffs
-  expose :parallel_diff_lines, using: DiffLineParallelEntity, if: -> (diff_file, options) { parallel_diff_view?(options) && diff_file.text? }
+  expose :parallel_diff_lines, using: DiffLineParallelEntity, if: -> (diff_file, options) { parallel_diff_view?(options, diff_file) && diff_file.text? }
 
   private
 
-  def parallel_diff_view?(options)
-    return true unless Feature.enabled?(:single_mr_diff_view)
+  def parallel_diff_view?(options, diff_file)
+    return true unless Feature.enabled?(:single_mr_diff_view, diff_file.repository.project)
 
     # If we're not rendering inline, we must be rendering parallel
-    !inline_diff_view?(options)
+    !inline_diff_view?(options, diff_file)
   end
 
-  def inline_diff_view?(options)
-    return true unless Feature.enabled?(:single_mr_diff_view)
+  def inline_diff_view?(options, diff_file)
+    return true unless Feature.enabled?(:single_mr_diff_view, diff_file.repository.project)
 
     # If nothing is present, inline will be the default.
     options.fetch(:diff_view, :inline).to_sym == :inline

spec/features/merge_request/maintainer_edits_fork_spec.rb

@@ -20,7 +20,7 @@ describe 'a maintainer edits files on a source-branch of an MR from a fork', :js
   end
 
   before do
-    stub_feature_flags(web_ide_default: false, single_mr_diff_view: false, code_navigation: false)
+    stub_feature_flags(web_ide_default: false, single_mr_diff_view: { enabled: false, thing: target_project }, code_navigation: false)
 
     target_project.add_maintainer(user)
     sign_in(user)

spec/features/merge_request/user_interacts_with_batched_mr_diffs_spec.rb

@@ -10,7 +10,7 @@ describe 'Batch diffs', :js do
   let(:merge_request) { create(:merge_request, source_project: project, source_branch: 'master', target_branch: 'empty-branch') }
 
   before do
-    stub_feature_flags(single_mr_diff_view: true)
+    stub_feature_flags(single_mr_diff_view: { enabled: true, thing: project })
     stub_feature_flags(diffs_batch_load: true)
 
     sign_in(project.owner)

spec/support/shared_examples/serializers/diff_file_entity_shared_examples.rb

@@ -60,7 +60,7 @@ RSpec.shared_examples 'diff file entity' do
 
     context 'when the `single_mr_diff_view` feature is disabled' do
       before do
-        stub_feature_flags(single_mr_diff_view: false)
+        stub_feature_flags(single_mr_diff_view: { enabled: false, thing: project })
       end
 
       it 'contains both kinds of diffs' do