Remove unused data from discussions endpoint

We don't need a series of attributes to render diff files on
discussions.json request. Therefore this MR removes lots of unnecessary
attributes from the request, mainly the highlighted diff lines, which
are pretty expensive.

1 files changed, 46 insertions, 0 deletions

diff --git a/spec/support/shared_examples/serializers/diff_file_entity_examples.rb b/spec/support/shared_examples/serializers/diff_file_entity_examples.rb
new file mode 100644
index 00000000000..b8065886c42
--- /dev/null
+++ b/spec/support/shared_examples/serializers/diff_file_entity_examples.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+shared_examples 'diff file base entity' do
+  it 'exposes essential attributes' do
+    expect(subject).to include(:content_sha, :submodule, :submodule_link,
+                               :submodule_tree_url, :old_path_html,
+                               :new_path_html, :blob, :can_modify_blob,
+                               :file_hash, :file_path, :old_path, :new_path,
+                               :collapsed, :text, :diff_refs, :stored_externally,
+                               :external_storage, :renamed_file, :deleted_file,
+                               :mode_changed, :a_mode, :b_mode, :new_file)
+  end
+
+  # Converted diff files from GitHub import does not contain blob file
+  # and content sha.
+  context 'when diff file does not have a blob and content sha' do
+    it 'exposes some attributes as nil' do
+      allow(diff_file).to receive(:content_sha).and_return(nil)
+      allow(diff_file).to receive(:blob).and_return(nil)
+
+      expect(subject[:context_lines_path]).to be_nil
+      expect(subject[:view_path]).to be_nil
+      expect(subject[:highlighted_diff_lines]).to be_nil
+      expect(subject[:can_modify_blob]).to be_nil
+    end
+  end
+end
+
+shared_examples 'diff file entity' do
+  it_behaves_like 'diff file base entity'
+
+  it 'exposes correct attributes' do
+    expect(subject).to include(:too_large, :added_lines, :removed_lines,
+                               :context_lines_path, :highlighted_diff_lines,
+                               :parallel_diff_lines)
+  end
+
+  it 'includes viewer' do
+    expect(subject[:viewer].with_indifferent_access)
+        .to match_schema('entities/diff_viewer')
+  end
+end
+
+shared_examples 'diff file discussion entity' do
+  it_behaves_like 'diff file base entity'
+end