Request visible batch of commit data first

app/assets/javascripts/repository/commits_service.js

@@ -52,14 +52,9 @@ export const loadCommits = async (projectPath, path, ref, offset) => {
   }
 
   // We fetch in batches of 25, so this ensures we don't refetch
-  Array.from(Array(COMMIT_BATCH_SIZE)).forEach((_, i) => {
-    addRequestedOffset(offset - i);
-    addRequestedOffset(offset + i);
-  });
+  Array.from(Array(COMMIT_BATCH_SIZE)).forEach((_, i) => addRequestedOffset(offset + i));
 
-  // Since a user could scroll either up or down, we want to support lazy loading in both directions
-  const commitsBatchUp = await fetchData(projectPath, path, ref, offset - COMMIT_BATCH_SIZE);
-  const commitsBatchDown = await fetchData(projectPath, path, ref, offset);
+  const commits = await fetchData(projectPath, path, ref, offset);
 
-  return commitsBatchUp.concat(commitsBatchDown);
+  return commits;
 };

app/assets/javascripts/repository/components/table/row.vue

@@ -13,7 +13,7 @@ import {
 import { escapeRegExp } from 'lodash';
 import paginatedTreeQuery from 'shared_queries/repository/paginated_tree.query.graphql';
 import { escapeFileUrl } from '~/lib/utils/url_utility';
-import { TREE_PAGE_SIZE } from '~/repository/constants';
+import { TREE_PAGE_SIZE, ROW_APPEAR_DELAY } from '~/repository/constants';
 import FileIcon from '~/vue_shared/components/file_icon.vue';
 import TimeagoTooltip from '~/vue_shared/components/time_ago_tooltip.vue';
 import glFeatureFlagMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
@@ -128,6 +128,7 @@ export default {
     return {
       commit: null,
       hasRowAppeared: false,
+      delayedRowAppear: null,
     };
   },
   computed: {
@@ -202,14 +203,19 @@ export default {
     rowAppeared() {
       this.hasRowAppeared = true;
 
+      if (this.commitInfo) {
+        return;
+      }
+
       if (this.glFeatures.lazyLoadCommits) {
-        this.$emit('row-appear', {
-          rowNumber: this.rowNumber,
-          hasCommit: Boolean(this.commitInfo),
-        });
+        this.delayedRowAppear = setTimeout(
+          () => this.$emit('row-appear', this.rowNumber),
+          ROW_APPEAR_DELAY,
+        );
       }
     },
     rowDisappeared() {
+      clearTimeout(this.delayedRowAppear);
       this.hasRowAppeared = false;
     },
   },

app/assets/javascripts/repository/components/tree_content.vue

@@ -3,7 +3,12 @@ import paginatedTreeQuery from 'shared_queries/repository/paginated_tree.query.g
 import createFlash from '~/flash';
 import glFeatureFlagMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
 import { __ } from '../../locale';
-import { TREE_PAGE_SIZE, TREE_INITIAL_FETCH_COUNT, TREE_PAGE_LIMIT } from '../constants';
+import {
+  TREE_PAGE_SIZE,
+  TREE_INITIAL_FETCH_COUNT,
+  TREE_PAGE_LIMIT,
+  COMMIT_BATCH_SIZE,
+} from '../constants';
 import getRefMixin from '../mixins/get_ref';
 import projectPathQuery from '../queries/project_path.query.graphql';
 import { readmeFile } from '../utils/readme';
@@ -151,11 +156,19 @@ export default {
         .concat(data.trees.pageInfo, data.submodules.pageInfo, data.blobs.pageInfo)
         .find(({ hasNextPage }) => hasNextPage);
     },
-    loadCommitData({ rowNumber = 0, hasCommit } = {}) {
-      if (!this.glFeatures.lazyLoadCommits || hasCommit || isRequested(rowNumber)) {
+    handleRowAppear(rowNumber) {
+      if (!this.glFeatures.lazyLoadCommits || isRequested(rowNumber)) {
         return;
       }
 
+      // Since a user could scroll either up or down, we want to support lazy loading in both directions
+      this.loadCommitData(rowNumber);
+
+      if (rowNumber - COMMIT_BATCH_SIZE >= 0) {
+        this.loadCommitData(rowNumber - COMMIT_BATCH_SIZE);
+      }
+    },
+    loadCommitData(rowNumber) {
       loadCommits(this.projectPath, this.path, this.ref, rowNumber)
         .then(this.setCommitData)
         .catch(() => {});
@@ -182,7 +195,7 @@ export default {
       :has-more="hasShowMore"
       :commits="commits"
       @showMore="handleShowMore"
-      @row-appear="loadCommitData"
+      @row-appear="handleRowAppear"
     />
     <file-preview v-if="readme" :blob="readme" />
   </div>

app/assets/javascripts/repository/constants.js

@@ -23,3 +23,5 @@ export const I18N_COMMIT_DATA_FETCH_ERROR = __('An error occurred while fetching
 
 export const PDF_MAX_FILE_SIZE = 10000000; // 10 MB
 export const PDF_MAX_PAGE_LIMIT = 50;
+
+export const ROW_APPEAR_DELAY = 150;

spec/frontend/repository/commits_service_spec.js

@@ -52,13 +52,6 @@ describe('commits service', () => {
     expect(axios.get.mock.calls.length).toEqual(1);
   });
 
-  it('calls axios get twice if an offset is larger than 25', async () => {
-    await requestCommits(100);
-
-    expect(axios.get.mock.calls[0][1]).toEqual({ params: { format: 'json', offset: 75 } });
-    expect(axios.get.mock.calls[1][1]).toEqual({ params: { format: 'json', offset: 100 } });
-  });
-
   it('updates the list of requested offsets', async () => {
     await requestCommits(200);
 

spec/frontend/repository/components/table/row_spec.js

@@ -4,6 +4,7 @@ import { createMockDirective, getBinding } from 'helpers/vue_mock_directive';
 import TableRow from '~/repository/components/table/row.vue';
 import FileIcon from '~/vue_shared/components/file_icon.vue';
 import { FILE_SYMLINK_MODE } from '~/vue_shared/constants';
+import { ROW_APPEAR_DELAY } from '~/repository/constants';
 
 const COMMIT_MOCK = { lockLabel: 'Locked by Root', committedDate: '2019-01-01' };
 
@@ -17,12 +18,12 @@ function factory(propsData = {}) {
 
   vm = shallowMount(TableRow, {
     propsData: {
+      commitInfo: COMMIT_MOCK,
       ...propsData,
       name: propsData.path,
       projectPath: 'gitlab-org/gitlab-ce',
       url: `https://test.com`,
       totalEntries: 10,
-      commitInfo: COMMIT_MOCK,
       rowNumber: 123,
     },
     directives: {
@@ -251,6 +252,8 @@ describe('Repository table row component', () => {
   });
 
   describe('row visibility', () => {
+    beforeAll(() => jest.useFakeTimers());
+
     beforeEach(() => {
       factory({
         id: '1',
@@ -258,18 +261,20 @@ describe('Repository table row component', () => {
         path: 'test',
         type: 'tree',
         currentPath: '/',
+        commitInfo: null,
       });
     });
-    it('emits a `row-appear` event', () => {
+
+    afterAll(() => jest.useRealTimers());
+
+    it('emits a `row-appear` event', async () => {
       findIntersectionObserver().vm.$emit('appear');
-      expect(vm.emitted('row-appear')).toEqual([
-        [
-          {
-            hasCommit: true,
-            rowNumber: 123,
-          },
-        ],
-      ]);
+
+      jest.runAllTimers();
+
+      expect(setTimeout).toHaveBeenCalledTimes(1);
+      expect(setTimeout).toHaveBeenLastCalledWith(expect.any(Function), ROW_APPEAR_DELAY);
+      expect(vm.emitted('row-appear')).toEqual([[123]]);
     });
   });
 });

spec/frontend/repository/components/tree_content_spec.js

@@ -190,14 +190,28 @@ describe('Repository table component', () => {
     });
   });
 
-  it('loads commit data when row-appear event is emitted', () => {
+  describe('commit data', () => {
     const path = 'some/path';
-    const rowNumber = 1;
 
-    factory(path);
-    findFileTable().vm.$emit('row-appear', { hasCommit: false, rowNumber });
+    it('loads commit data for both top and bottom batches when row-appear event is emitted', () => {
+      const rowNumber = 50;
 
-    expect(isRequested).toHaveBeenCalledWith(rowNumber);
-    expect(loadCommits).toHaveBeenCalledWith('', path, '', rowNumber);
+      factory(path);
+      findFileTable().vm.$emit('row-appear', rowNumber);
+
+      expect(isRequested).toHaveBeenCalledWith(rowNumber);
+
+      expect(loadCommits.mock.calls).toEqual([
+        ['', path, '', rowNumber],
+        ['', path, '', rowNumber - 25],
+      ]);
+    });
+
+    it('loads commit data once if rowNumber is zero', () => {
+      factory(path);
+      findFileTable().vm.$emit('row-appear', 0);
+
+      expect(loadCommits.mock.calls).toEqual([['', path, '', 0]]);
+    });
   });
 });