Merge branch '54786-mr-empty-file-display' into 'master'

Display empty files properly on MR diffs

Closes #54786

See merge request gitlab-org/gitlab-ce!23671

app/assets/javascripts/diffs/components/diff_content.vue

 <script>
 import { mapActions, mapGetters, mapState } from 'vuex';
 import DiffViewer from '~/vue_shared/components/diff_viewer/diff_viewer.vue';
+import EmptyFileViewer from '~/vue_shared/components/diff_viewer/viewers/empty_file.vue';
 import InlineDiffView from './inline_diff_view.vue';
 import ParallelDiffView from './parallel_diff_view.vue';
 import NoteForm from '../../notes/components/note_form.vue';
@@ -17,6 +18,7 @@ export default {
     NoteForm,
     DiffDiscussions,
     ImageDiffOverlay,
+    EmptyFileViewer,
   },
   props: {
     diffFile: {
@@ -75,14 +77,15 @@ export default {
   <div class="diff-content">
     <div class="diff-viewer">
       <template v-if="isTextFile">
+        <empty-file-viewer v-if="diffFile.empty" />
         <inline-diff-view
-          v-if="isInlineView"
+          v-else-if="isInlineView"
           :diff-file="diffFile"
           :diff-lines="diffFile.highlighted_diff_lines || []"
           :help-page-path="helpPagePath"
         />
         <parallel-diff-view
-          v-if="isParallelView"
+          v-else-if="isParallelView"
           :diff-file="diffFile"
           :diff-lines="diffFile.parallel_diff_lines || []"
           :help-page-path="helpPagePath"

app/assets/javascripts/vue_shared/components/diff_viewer/viewers/empty_file.vue

+<template>
+  <div class="nothing-here-block">{{ __('Empty file') }}</div>
+</template>

app/serializers/diff_file_entity.rb

@@ -5,6 +5,7 @@ class DiffFileEntity < DiffFileBaseEntity
   include IconsHelper
 
   expose :too_large?, as: :too_large
+  expose :empty?, as: :empty
   expose :added_lines
   expose :removed_lines
 

changelogs/unreleased/54786-mr-empty-file-display.yml

+---
+title: Display empty files properly on MR diffs
+merge_request: 23671
+author: Sean Nichols
+type: fixed

lib/gitlab/diff/file.rb

@@ -255,6 +255,10 @@ module Gitlab
       end
       # rubocop: enable CodeReuse/ActiveRecord
 
+      def empty?
+        valid_blobs.map(&:empty?).all?
+      end
+
       def raw_binary?
         try_blobs(:raw_binary?)
       end

locale/gitlab.pot

@@ -2668,6 +2668,9 @@ msgstr ""
 msgid "Embed"
 msgstr ""
 
+msgid "Empty file"
+msgstr ""
+
 msgid "Enable"
 msgstr ""
 

spec/javascripts/diffs/components/diff_content_spec.js

@@ -50,6 +50,45 @@ describe('DiffContent', () => {
     });
   });
 
+  describe('empty files', () => {
+    beforeEach(() => {
+      vm.diffFile.empty = true;
+      vm.diffFile.highlighted_diff_lines = [];
+      vm.diffFile.parallel_diff_lines = [];
+    });
+
+    it('should render a message', done => {
+      vm.$nextTick(() => {
+        const block = vm.$el.querySelector('.diff-viewer .nothing-here-block');
+
+        expect(block).not.toBe(null);
+        expect(block.textContent.trim()).toContain('Empty file');
+
+        done();
+      });
+    });
+
+    it('should not render multiple messages', done => {
+      vm.diffFile.mode_changed = true;
+      vm.diffFile.b_mode = '100755';
+      vm.diffFile.viewer.name = 'mode_changed';
+
+      vm.$nextTick(() => {
+        expect(vm.$el.querySelectorAll('.nothing-here-block').length).toBe(1);
+
+        done();
+      });
+    });
+
+    it('should not render diff table', done => {
+      vm.$nextTick(() => {
+        expect(vm.$el.querySelector('table')).toBe(null);
+
+        done();
+      });
+    });
+  });
+
   describe('Non-Text diffs', () => {
     beforeEach(() => {
       vm.diffFile.viewer.name = 'image';

spec/lib/gitlab/diff/file_spec.rb

@@ -583,6 +583,12 @@ describe Gitlab::Diff::File do
       end
     end
 
+    describe '#empty?' do
+      it 'returns true' do
+        expect(diff_file.empty?).to be_truthy
+      end
+    end
+
     describe '#different_type?' do
       it 'returns false' do
         expect(diff_file).not_to be_different_type
@@ -662,4 +668,87 @@ describe Gitlab::Diff::File do
       end
     end
   end
+
+  describe '#empty?' do
+    let(:project) do
+      create(:project, :custom_repo, files: {})
+    end
+    let(:branch_name) { 'master' }
+
+    def create_file(file_name, content)
+      Files::CreateService.new(
+        project,
+        project.owner,
+        commit_message: 'Update',
+        start_branch: branch_name,
+        branch_name: branch_name,
+        file_path: file_name,
+        file_content: content
+      ).execute
+
+      project.commit(branch_name).diffs.diff_files.first
+    end
+
+    def update_file(file_name, content)
+      Files::UpdateService.new(
+        project,
+        project.owner,
+        commit_message: 'Update',
+        start_branch: branch_name,
+        branch_name: branch_name,
+        file_path: file_name,
+        file_content: content
+      ).execute
+
+      project.commit(branch_name).diffs.diff_files.first
+    end
+
+    def delete_file(file_name)
+      Files::DeleteService.new(
+        project,
+        project.owner,
+        commit_message: 'Update',
+        start_branch: branch_name,
+        branch_name: branch_name,
+        file_path: file_name
+      ).execute
+
+      project.commit(branch_name).diffs.diff_files.first
+    end
+
+    context 'when empty file is created' do
+      it 'returns true' do
+        diff_file = create_file('empty.md', '')
+
+        expect(diff_file.empty?).to be_truthy
+      end
+    end
+
+    context 'when empty file is deleted' do
+      it 'returns true' do
+        create_file('empty.md', '')
+        diff_file = delete_file('empty.md')
+
+        expect(diff_file.empty?).to be_truthy
+      end
+    end
+
+    context 'when file with content is truncated' do
+      it 'returns false' do
+        create_file('with-content.md', 'file content')
+        diff_file = update_file('with-content.md', '')
+
+        expect(diff_file.empty?).to be_falsey
+      end
+    end
+
+    context 'when empty file has content added' do
+      it 'returns false' do
+        create_file('empty.md', '')
+        diff_file = update_file('empty.md', 'new content')
+
+        expect(diff_file.empty?).to be_falsey
+      end
+    end
+  end
 end

spec/support/shared_examples/serializers/diff_file_entity_examples.rb

@@ -32,7 +32,7 @@ shared_examples 'diff file entity' do
   it 'exposes correct attributes' do
     expect(subject).to include(:too_large, :added_lines, :removed_lines,
                                :context_lines_path, :highlighted_diff_lines,
-                               :parallel_diff_lines)
+                               :parallel_diff_lines, :empty)
   end
 
   it 'includes viewer' do