Add option to expand diff to full file

The user can also toggle between the diff changes and
the full file diff.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/19054

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

@@ -5,7 +5,7 @@ import { polyfillSticky } from '~/lib/utils/sticky';
 import ClipboardButton from '~/vue_shared/components/clipboard_button.vue';
 import Icon from '~/vue_shared/components/icon.vue';
 import FileIcon from '~/vue_shared/components/file_icon.vue';
-import { GlTooltipDirective } from '@gitlab/ui';
+import { GlButton, GlTooltipDirective, GlTooltip, GlLoadingIcon } from '@gitlab/ui';
 import { truncateSha } from '~/lib/utils/text_utility';
 import { __, s__, sprintf } from '~/locale';
 import { diffViewerModes } from '~/ide/constants';
@@ -14,6 +14,9 @@ import DiffStats from './diff_stats.vue';
 
 export default {
   components: {
+    GlTooltip,
+    GlLoadingIcon,
+    GlButton,
     ClipboardButton,
     EditButton,
     Icon,
@@ -125,12 +128,15 @@ export default {
     isModeChanged() {
       return this.diffFile.viewer.name === diffViewerModes.mode_changed;
     },
+    showExpandDiffToFullFileEnabled() {
+      return gon.features.expandDiffFullFile && !this.diffFile.is_fully_expanded;
+    },
   },
   mounted() {
     polyfillSticky(this.$refs.header);
   },
   methods: {
-    ...mapActions('diffs', ['toggleFileDiscussions']),
+    ...mapActions('diffs', ['toggleFileDiscussions', 'toggleFullDiff']),
     handleToggleFile(e, checkTarget) {
       if (
         !checkTarget ||
@@ -240,12 +246,30 @@ export default {
         v-html="viewReplacedFileButtonText"
       >
       </a>
-      <a
+      <gl-tooltip :target="() => $refs.viewButton" placement="bottom">
+        <span v-html="viewFileButtonText"></span>
+      </gl-tooltip>
+      <gl-button
+        ref="viewButton"
         :href="diffFile.view_path"
-        class="btn view-file js-view-file-button"
-        v-html="viewFileButtonText"
+        target="blank"
+        class="view-file js-view-file-button"
       >
-      </a>
+        <icon name="external-link" />
+      </gl-button>
+      <gl-button
+        v-if="showExpandDiffToFullFileEnabled"
+        class="expand-file js-expand-file"
+        @click="toggleFullDiff(diffFile.file_path)"
+      >
+        <template v-if="diffFile.isShowingFullFile">
+          {{ s__('MRDiff|Show changes only') }}
+        </template>
+        <template v-else>
+          {{ s__('MRDiff|Show full file') }}
+        </template>
+        <gl-loading-icon v-if="diffFile.isLoadingFullFile" inline />
+      </gl-button>
 
       <a
         v-if="diffFile.external_url"

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

 <script>
+import { GlTooltipDirective, GlButton } from '@gitlab/ui';
+import Icon from '~/vue_shared/components/icon.vue';
+
 export default {
+  components: {
+    GlButton,
+    Icon,
+  },
+  directives: {
+    GlTooltip: GlTooltipDirective,
+  },
   props: {
     editPath: {
       type: String,
@@ -27,5 +37,13 @@ export default {
 </script>
 
 <template>
-  <a :href="editPath" class="btn btn-default js-edit-blob" @click="handleEditClick"> Edit </a>
+  <gl-button
+    v-gl-tooltip.bottom
+    :href="editPath"
+    :title="__('Edit file')"
+    class="js-edit-blob"
+    @click.native="handleEditClick"
+  >
+    <icon name="pencil" />
+  </gl-button>
 </template>

app/assets/javascripts/diffs/constants.js

@@ -42,3 +42,8 @@ export const INITIAL_TREE_WIDTH = 320;
 export const MIN_TREE_WIDTH = 240;
 export const MAX_TREE_WIDTH = 400;
 export const TREE_HIDE_STATS_WIDTH = 260;
+
+export const OLD_LINE_KEY = 'old_line';
+export const NEW_LINE_KEY = 'new_line';
+export const TYPE_KEY = 'type';
+export const LEFT_LINE_KEY = 'left';

app/assets/javascripts/diffs/store/actions.js

@@ -309,5 +309,40 @@ export const cacheTreeListWidth = (_, size) => {
   localStorage.setItem(TREE_LIST_WIDTH_STORAGE_KEY, size);
 };
 
+export const requestFullDiff = ({ commit }, filePath) => commit(types.REQUEST_FULL_DIFF, filePath);
+export const receiveFullDiffSucess = ({ commit }, { filePath, data }) =>
+  commit(types.RECEIVE_FULL_DIFF_SUCCESS, { filePath, data });
+export const receiveFullDiffError = ({ commit }, filePath) => {
+  commit(types.RECEIVE_FULL_DIFF_ERROR, filePath);
+  createFlash(s__('MergeRequest|Error loading full diff. Please try again.'));
+};
+
+export const fetchFullDiff = ({ dispatch }, file) =>
+  axios
+    .get(file.context_lines_path, {
+      params: {
+        full: true,
+        from_merge_request: true,
+      },
+    })
+    .then(({ data }) => dispatch('receiveFullDiffSucess', { filePath: file.file_path, data }))
+    .then(() => scrollToElement(`#${file.file_hash}`))
+    .catch(() => dispatch('receiveFullDiffError', file.file_path));
+
+export const toggleFullDiff = ({ dispatch, getters, state }, filePath) => {
+  const file = state.diffFiles.find(f => f.file_path === filePath);
+
+  dispatch('requestFullDiff', filePath);
+
+  if (file.isShowingFullFile) {
+    dispatch('loadCollapsedDiff', file)
+      .then(() => dispatch('assignDiscussionsToDiff', getters.getDiffFileDiscussions(file)))
+      .then(() => scrollToElement(`#${file.file_hash}`))
+      .catch(() => dispatch('receiveFullDiffError', filePath));
+  } else {
+    dispatch('fetchFullDiff', file);
+  }
+};
+
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
 export default () => {};

app/assets/javascripts/diffs/store/mutation_types.js

@@ -23,3 +23,7 @@ export const SET_TREE_DATA = 'SET_TREE_DATA';
 export const SET_RENDER_TREE_LIST = 'SET_RENDER_TREE_LIST';
 export const SET_SHOW_WHITESPACE = 'SET_SHOW_WHITESPACE';
 export const TOGGLE_FILE_FINDER_VISIBLE = 'TOGGLE_FILE_FINDER_VISIBLE';
+
+export const REQUEST_FULL_DIFF = 'REQUEST_FULL_DIFF';
+export const RECEIVE_FULL_DIFF_SUCCESS = 'RECEIVE_FULL_DIFF_SUCCESS';
+export const RECEIVE_FULL_DIFF_ERROR = 'RECEIVE_FULL_DIFF_ERROR';

app/assets/javascripts/diffs/store/mutations.js

@@ -6,8 +6,10 @@ import {
   addContextLines,
   prepareDiffData,
   isDiscussionApplicableToLine,
+  convertExpandLines,
 } from './utils';
 import * as types from './mutation_types';
+import { OLD_LINE_KEY, NEW_LINE_KEY, TYPE_KEY, LEFT_LINE_KEY } from '../constants';
 
 export default {
   [types.SET_BASE_CONFIG](state, options) {
@@ -248,4 +250,54 @@ export default {
   [types.TOGGLE_FILE_FINDER_VISIBLE](state, visible) {
     state.fileFinderVisible = visible;
   },
+  [types.REQUEST_FULL_DIFF](state, filePath) {
+    const file = findDiffFile(state.diffFiles, filePath, 'file_path');
+
+    file.isLoadingFullFile = true;
+  },
+  [types.RECEIVE_FULL_DIFF_ERROR](state, filePath) {
+    const file = findDiffFile(state.diffFiles, filePath, 'file_path');
+
+    file.isLoadingFullFile = false;
+  },
+  [types.RECEIVE_FULL_DIFF_SUCCESS](state, { filePath, data }) {
+    const file = findDiffFile(state.diffFiles, filePath, 'file_path');
+
+    file.isShowingFullFile = true;
+    file.isLoadingFullFile = false;
+
+    file.highlighted_diff_lines = convertExpandLines({
+      diffLines: file.highlighted_diff_lines,
+      typeKey: [TYPE_KEY],
+      oldLineKey: [OLD_LINE_KEY],
+      newLineKey: [NEW_LINE_KEY],
+      data,
+      mapLine: ({ line, oldLine, newLine }) => ({
+        ...line,
+        old_line: oldLine,
+        new_line: newLine,
+        line_code: `${file.file_hash}_${oldLine}_${newLine}`,
+      }),
+    });
+
+    file.parallel_diff_lines = convertExpandLines({
+      diffLines: file.parallel_diff_lines,
+      typeKey: [LEFT_LINE_KEY, TYPE_KEY],
+      oldLineKey: [LEFT_LINE_KEY, OLD_LINE_KEY],
+      newLineKey: [LEFT_LINE_KEY, NEW_LINE_KEY],
+      data,
+      mapLine: ({ line, oldLine, newLine }) => ({
+        left: {
+          ...line,
+          old_line: oldLine,
+          line_code: `${file.file_hash}_${oldLine}_${newLine}`,
+        },
+        right: {
+          ...line,
+          new_line: newLine,
+          line_code: `${file.file_hash}_${newLine}_${oldLine}`,
+        },
+      }),
+    });
+  },
 };

app/assets/javascripts/diffs/store/utils.js

@@ -15,8 +15,8 @@ import {
   TREE_TYPE,
 } from '../constants';
 
-export function findDiffFile(files, hash) {
-  return files.filter(file => file.file_hash === hash)[0];
+export function findDiffFile(files, match, matchKey = 'file_hash') {
+  return files.find(file => file[matchKey] === match);
 }
 
 export const getReversePosition = linePosition => {
@@ -250,6 +250,8 @@ export function prepareDiffData(diffData) {
       renderIt: showingLines < LINES_TO_BE_RENDERED_DIRECTLY,
       collapsed:
         file.viewer.name === diffViewerModes.text && showingLines > MAX_LINES_TO_BE_RENDERED,
+      isShowingFullFile: false,
+      isLoadingFullFile: false,
       discussions: [],
     });
   }
@@ -411,3 +413,37 @@ export const getDiffMode = diffFile => {
     diffModes.replaced
   );
 };
+
+export const convertExpandLines = ({
+  diffLines,
+  data,
+  typeKey,
+  oldLineKey,
+  newLineKey,
+  mapLine,
+}) => {
+  const dataLength = data.length;
+
+  return diffLines.reduce((acc, line, i) => {
+    if (_.property(typeKey)(line) === 'match') {
+      const beforeLine = diffLines[i - 1];
+      const afterLine = diffLines[i + 1];
+      const beforeLineIndex = _.property(newLineKey)(beforeLine) || 0;
+      const afterLineIndex = _.property(newLineKey)(afterLine) - 1 || dataLength;
+
+      acc.push(
+        ...data.slice(beforeLineIndex, afterLineIndex).map((l, index) => ({
+          ...mapLine({
+            line: { ...l, hasForm: false, discussions: [] },
+            oldLine: (_.property(oldLineKey)(beforeLine) || 0) + index + 1,
+            newLine: (_.property(newLineKey)(beforeLine) || 0) + index + 1,
+          }),
+        })),
+      );
+    } else {
+      acc.push(line);
+    }
+
+    return acc;
+  }, []);
+};

app/assets/stylesheets/pages/diff.scss

@@ -53,6 +53,10 @@
       background-color: $gray-normal;
     }
 
+    a {
+      color: $gray-700;
+    }
+
     svg {
       vertical-align: middle;
       top: -1px;

app/controllers/projects/merge_requests_controller.rb

@@ -18,6 +18,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
 
   before_action only: [:show] do
     push_frontend_feature_flag(:diff_tree_filtering, default_enabled: true)
+    push_frontend_feature_flag(:expand_diff_full_file)
   end
 
   def index

app/serializers/diff_file_entity.rb

@@ -7,7 +7,7 @@ class DiffFileEntity < DiffFileBaseEntity
   expose :added_lines
   expose :removed_lines
 
-  expose :load_collapsed_diff_url, if: -> (diff_file, options) { diff_file.viewer.collapsed? && options[:merge_request] } do |diff_file|
+  expose :load_collapsed_diff_url, if: -> (diff_file, options) { options[:merge_request] } do |diff_file|
     merge_request = options[:merge_request]
     project = merge_request.target_project
 
@@ -57,6 +57,10 @@ class DiffFileEntity < DiffFileBaseEntity
     diff_file.diff_lines_for_serializer
   end
 
+  expose :is_fully_expanded, if: -> (diff_file, _) { Feature.enabled?(:expand_diff_full_file) && diff_file.text? } do |diff_file|
+    diff_file.fully_expanded?
+  end
+
   # Used for parallel diffs
   expose :parallel_diff_lines, using: DiffLineParallelEntity, if: -> (diff_file, _) { diff_file.text? }
 end

changelogs/unreleased/expand-diff-to-full-file.yml

+---
+title: Allow expanding a diff to display full file
+merge_request: 24406
+author:
+type: added

lib/gitlab/diff/file.rb

@@ -329,6 +329,16 @@ module Gitlab
         lines
       end
 
+      def fully_expanded?
+        return true if binary?
+
+        lines = diff_lines_for_serializer
+
+        return true if lines.nil?
+
+        lines.none? { |line| line.type.to_s == 'match' }
+      end
+
       private
 
       def total_blob_lines(blob)

locale/gitlab.pot

@@ -2929,6 +2929,9 @@ msgstr ""
 msgid "Edit environment"
 msgstr ""
 
+msgid "Edit file"
+msgstr ""
+
 msgid "Edit files in the editor and commit changes here"
 msgstr ""
 
@@ -4521,6 +4524,12 @@ msgstr ""
 msgid "Logs"
 msgstr ""
 
+msgid "MRDiff|Show changes only"
+msgstr ""
+
+msgid "MRDiff|Show full file"
+msgstr ""
+
 msgid "Make sure you're logged into the account that owns the projects you'd like to import."
 msgstr ""
 
@@ -4689,6 +4698,9 @@ msgstr ""
 msgid "MergeRequest| %{paragraphStart}changed the description %{descriptionChangedTimes} times %{timeDifferenceMinutes}%{paragraphEnd}"
 msgstr ""
 
+msgid "MergeRequest|Error loading full diff. Please try again."
+msgstr ""
+
 msgid "MergeRequest|Filter files"
 msgstr ""
 

spec/features/merge_request/maintainer_edits_fork_spec.rb

@@ -26,7 +26,7 @@ describe 'a maintainer edits files on a source-branch of an MR from a fork', :js
     visit project_merge_request_path(target_project, merge_request)
     click_link 'Changes'
     wait_for_requests
-    first('.js-file-title').click_link 'Edit'
+    first('.js-file-title').find('.js-edit-blob').click
     wait_for_requests
   end
 

spec/javascripts/diffs/components/diff_file_header_spec.js

@@ -23,6 +23,9 @@ describe('diff_file_header', () => {
   });
 
   beforeEach(() => {
+    gon.features = {
+      expandDiffFullFile: true,
+    };
     const diffFile = diffDiscussionMock.diff_file;
 
     diffFile.added_lines = 2;
@@ -382,7 +385,7 @@ describe('diff_file_header', () => {
         props.diffFile.edit_path = '/';
         vm = mountComponentWithStore(Component, { props, store });
 
-        expect(vm.$el.querySelector('.js-edit-blob')).toContainText('Edit');
+        expect(vm.$el.querySelector('.js-edit-blob')).not.toBe(null);
       });
 
       it('should not show edit button when file is deleted', () => {
@@ -576,4 +579,66 @@ describe('diff_file_header', () => {
       });
     });
   });
+
+  describe('expand full file button', () => {
+    beforeEach(() => {
+      props.addMergeRequestButtons = true;
+      props.diffFile.edit_path = '/';
+    });
+
+    it('does not render button', () => {
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file')).toBe(null);
+    });
+
+    it('renders button', () => {
+      props.diffFile.is_fully_expanded = false;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file')).not.toBe(null);
+    });
+
+    it('shows fully expanded text', () => {
+      props.diffFile.is_fully_expanded = false;
+      props.diffFile.isShowingFullFile = true;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file').textContent).toContain('Show changes only');
+    });
+
+    it('shows expand text', () => {
+      props.diffFile.is_fully_expanded = false;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file').textContent).toContain('Show full file');
+    });
+
+    it('renders loading icon', () => {
+      props.diffFile.is_fully_expanded = false;
+      props.diffFile.isLoadingFullFile = true;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      expect(vm.$el.querySelector('.js-expand-file .loading-container')).not.toBe(null);
+    });
+
+    it('calls toggleFullDiff on click', () => {
+      props.diffFile.is_fully_expanded = false;
+
+      vm = mountComponentWithStore(Component, { props, store });
+
+      spyOn(vm.$store, 'dispatch').and.stub();
+
+      vm.$el.querySelector('.js-expand-file').click();
+
+      expect(vm.$store.dispatch).toHaveBeenCalledWith(
+        'diffs/toggleFullDiff',
+        props.diffFile.file_path,
+      );
+    });
+  });
 });

spec/javascripts/diffs/mock_data/diff_discussions.js

@@ -288,6 +288,7 @@ export default {
     external_storage: null,
     old_path_html: 'CHANGELOG_OLD',
     new_path_html: 'CHANGELOG',
+    is_fully_expanded: true,
     context_lines_path:
       '/gitlab-org/gitlab-test/blob/c48ee0d1bf3b30453f5b32250ce03134beaa6d13/CHANGELOG/diff',
     highlighted_diff_lines: [

spec/javascripts/diffs/store/actions_spec.js

@@ -30,6 +30,11 @@ import actions, {
   setRenderTreeList,
   setShowWhitespace,
   setRenderIt,
+  requestFullDiff,
+  receiveFullDiffSucess,
+  receiveFullDiffError,
+  fetchFullDiff,
+  toggleFullDiff,
 } from '~/diffs/store/actions';
 import eventHub from '~/notes/event_hub';
 import * as types from '~/diffs/store/mutation_types';
@@ -847,4 +852,129 @@ describe('DiffsStoreActions', () => {
       testAction(setRenderIt, 'file', {}, [{ type: types.RENDER_FILE, payload: 'file' }], [], done);
     });
   });
+
+  describe('requestFullDiff', () => {
+    it('commits REQUEST_FULL_DIFF', done => {
+      testAction(
+        requestFullDiff,
+        'file',
+        {},
+        [{ type: types.REQUEST_FULL_DIFF, payload: 'file' }],
+        [],
+        done,
+      );
+    });
+  });
+
+  describe('receiveFullDiffSucess', () => {
+    it('commits REQUEST_FULL_DIFF', done => {
+      testAction(
+        receiveFullDiffSucess,
+        { filePath: 'test', data: 'test' },
+        {},
+        [{ type: types.RECEIVE_FULL_DIFF_SUCCESS, payload: { filePath: 'test', data: 'test' } }],
+        [],
+        done,
+      );
+    });
+  });
+
+  describe('receiveFullDiffError', () => {
+    it('commits REQUEST_FULL_DIFF', done => {
+      testAction(
+        receiveFullDiffError,
+        'file',
+        {},
+        [{ type: types.RECEIVE_FULL_DIFF_ERROR, payload: 'file' }],
+        [],
+        done,
+      );
+    });
+  });
+
+  describe('fetchFullDiff', () => {
+    let mock;
+    let scrollToElementSpy;
+
+    beforeEach(() => {
+      scrollToElementSpy = spyOnDependency(actions, 'scrollToElement').and.stub();
+
+      mock = new MockAdapter(axios);
+    });
+
+    afterEach(() => {
+      mock.restore();
+    });
+
+    describe('success', () => {
+      beforeEach(() => {
+        mock.onGet(`${gl.TEST_HOST}/context`).replyOnce(200, ['test']);
+      });
+
+      it('dispatches receiveFullDiffSucess', done => {
+        testAction(
+          fetchFullDiff,
+          { context_lines_path: `${gl.TEST_HOST}/context`, file_path: 'test', file_hash: 'test' },
+          null,
+          [],
+          [{ type: 'receiveFullDiffSucess', payload: { filePath: 'test', data: ['test'] } }],
+          done,
+        );
+      });
+
+      it('scrolls to element', done => {
+        fetchFullDiff(
+          { dispatch() {} },
+          { context_lines_path: `${gl.TEST_HOST}/context`, file_path: 'test', file_hash: 'test' },
+        )
+          .then(() => {
+            expect(scrollToElementSpy).toHaveBeenCalledWith('#test');
+
+            done();
+          })
+          .catch(done.fail);
+      });
+    });
+
+    describe('error', () => {
+      beforeEach(() => {
+        mock.onGet(`${gl.TEST_HOST}/context`).replyOnce(500);
+      });
+
+      it('dispatches receiveFullDiffError', done => {
+        testAction(
+          fetchFullDiff,
+          { context_lines_path: `${gl.TEST_HOST}/context`, file_path: 'test', file_hash: 'test' },
+          null,
+          [],
+          [{ type: 'receiveFullDiffError', payload: 'test' }],
+          done,
+        );
+      });
+    });
+  });
+
+  describe('toggleFullDiff', () => {
+    let state;
+
+    beforeEach(() => {
+      state = {
+        diffFiles: [{ file_path: 'test', isShowingFullFile: false }],
+      };
+    });
+
+    it('dispatches fetchFullDiff when file is not expanded', done => {
+      testAction(
+        toggleFullDiff,
+        'test',
+        state,
+        [],
+        [
+          { type: 'requestFullDiff', payload: 'test' },
+          { type: 'fetchFullDiff', payload: state.diffFiles[0] },
+        ],
+        done,
+      );
+    });
+  });
 });

spec/javascripts/diffs/store/mutations_spec.js

@@ -680,4 +680,66 @@ describe('DiffsStoreMutations', () => {
       expect(state.showWhitespace).toBe(false);
     });
   });
+
+  describe('REQUEST_FULL_DIFF', () => {
+    it('sets isLoadingFullFile to true', () => {
+      const state = {
+        diffFiles: [{ file_path: 'test', isLoadingFullFile: false }],
+      };
+
+      mutations[types.REQUEST_FULL_DIFF](state, 'test');
+
+      expect(state.diffFiles[0].isLoadingFullFile).toBe(true);
+    });
+  });
+
+  describe('RECEIVE_FULL_DIFF_ERROR', () => {
+    it('sets isLoadingFullFile to false', () => {
+      const state = {
+        diffFiles: [{ file_path: 'test', isLoadingFullFile: true }],
+      };
+
+      mutations[types.RECEIVE_FULL_DIFF_ERROR](state, 'test');
+
+      expect(state.diffFiles[0].isLoadingFullFile).toBe(false);
+    });
+  });
+
+  describe('RECEIVE_FULL_DIFF_SUCCESS', () => {
+    it('sets isLoadingFullFile to false', () => {
+      const state = {
+        diffFiles: [
+          {
+            file_path: 'test',
+            isLoadingFullFile: true,
+            isShowingFullFile: false,
+            highlighted_diff_lines: [],
+            parallel_diff_lines: [],
+          },
+        ],
+      };
+
+      mutations[types.RECEIVE_FULL_DIFF_SUCCESS](state, { filePath: 'test', data: [] });
+
+      expect(state.diffFiles[0].isLoadingFullFile).toBe(false);
+    });
+
+    it('sets isShowingFullFile to true', () => {
+      const state = {
+        diffFiles: [
+          {
+            file_path: 'test',
+            isLoadingFullFile: true,
+            isShowingFullFile: false,
+            highlighted_diff_lines: [],
+            parallel_diff_lines: [],
+          },
+        ],
+      };
+
+      mutations[types.RECEIVE_FULL_DIFF_SUCCESS](state, { filePath: 'test', data: [] });
+
+      expect(state.diffFiles[0].isShowingFullFile).toBe(true);
+    });
+  });
 });

spec/javascripts/diffs/store/utils_spec.js

@@ -781,4 +781,49 @@ describe('DiffsStoreUtils', () => {
       ]);
     });
   });
+
+  describe('convertExpandLines', () => {
+    it('converts expanded lines to normal lines', () => {
+      const diffLines = [
+        {
+          type: 'match',
+          old_line: 1,
+          new_line: 1,
+        },
+        {
+          type: '',
+          old_line: 2,
+          new_line: 2,
+        },
+      ];
+
+      const lines = utils.convertExpandLines({
+        diffLines,
+        data: [{ text: 'expanded' }],
+        typeKey: 'type',
+        oldLineKey: 'old_line',
+        newLineKey: 'new_line',
+        mapLine: ({ line, oldLine, newLine }) => ({
+          ...line,
+          old_line: oldLine,
+          new_line: newLine,
+        }),
+      });
+
+      expect(lines).toEqual([
+        {
+          text: 'expanded',
+          new_line: 1,
+          old_line: 1,
+          discussions: [],
+          hasForm: false,
+        },
+        {
+          type: '',
+          old_line: 2,
+          new_line: 2,
+        },
+      ]);
+    });
+  });
 });

spec/lib/gitlab/diff/file_spec.rb

@@ -8,6 +8,47 @@ describe Gitlab::Diff::File do
   let(:diff) { commit.raw_diffs.first }
   let(:diff_file) { described_class.new(diff, diff_refs: commit.diff_refs, repository: project.repository) }
 
+  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
+
   describe '#diff_lines' do
     let(:diff_lines) { diff_file.diff_lines }
 
@@ -675,47 +716,6 @@ describe Gitlab::Diff::File do
     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', '')
@@ -751,4 +751,123 @@ describe Gitlab::Diff::File do
       end
     end
   end
+
+  describe '#fully_expanded?' do
+    let(:project) do
+      create(:project, :custom_repo, files: {})
+    end
+    let(:branch_name) { 'master' }
+
+    context 'when empty file is created' do
+      it 'returns true' do
+        diff_file = create_file('empty.md', '')
+
+        expect(diff_file.fully_expanded?).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.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when short file with last line removed' do
+      it 'returns true' do
+        create_file('with-content.md', (1..3).to_a.join("\n"))
+        diff_file = update_file('with-content.md', (1..2).to_a.join("\n"))
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when a single line is added to empty file' do
+      it 'returns true' do
+        create_file('empty.md', '')
+        diff_file = update_file('empty.md', 'new content')
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when single line file is changed' do
+      it 'returns true' do
+        create_file('file.md', 'foo')
+        diff_file = update_file('file.md', 'bar')
+
+        expect(diff_file.fully_expanded?).to be_truthy
+      end
+    end
+
+    context 'when long file is changed' do
+      before do
+        create_file('file.md', (1..999).to_a.join("\n"))
+      end
+
+      context 'when first line is removed' do
+        it 'returns true' do
+          diff_file = update_file('file.md', (2..999).to_a.join("\n"))
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when last line is removed' do
+        it 'returns true' do
+          diff_file = update_file('file.md', (1..998).to_a.join("\n"))
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when first and last lines are removed' do
+        it 'returns false' do
+          diff_file = update_file('file.md', (2..998).to_a.join("\n"))
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when first and last lines are changed' do
+        it 'returns false' do
+          content = (2..998).to_a
+          content.prepend('a')
+          content.append('z')
+          content = content.join("\n")
+
+          diff_file = update_file('file.md', content)
+
+          expect(diff_file.fully_expanded?).to be_falsey
+        end
+      end
+
+      context 'when every line are changed' do
+        it 'returns true' do
+          diff_file = update_file('file.md', "hi\n" * 999)
+
+          expect(diff_file.fully_expanded?).to be_truthy
+        end
+      end
+
+      context 'when all contents are cleared' do
+        it 'returns true' do
+          diff_file = update_file('file.md', "")
+
+          expect(diff_file.fully_expanded?).to be_truthy
+        end
+      end
+
+      context 'when file is binary' do
+        it 'returns true' do
+          diff_file = update_file('file.md', (1..998).to_a.join("\n"))
+          allow(diff_file).to receive(:binary?).and_return(true)
+
+          expect(diff_file.fully_expanded?).to be_truthy
+        end
+      end
+    end
+  end
 end