Resolve "In Merge Request diff screen, master is not a hyperlink"

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

@@ -54,6 +54,9 @@ export default {
     showDropdowns() {
       return !this.commit && this.mergeRequestDiffs.length;
     },
+    baseVersionPath() {
+      return this.mergeRequestDiff.base_version_path;
+    },
   },
   methods: {
     ...mapActions('diffs', [
@@ -95,6 +98,7 @@ export default {
         and
         <compare-versions-dropdown
           :other-versions="comparableDiffs"
+          :base-version-path="baseVersionPath"
           :start-version="startVersion"
           :target-branch="targetBranch"
           class="mr-version-compare-dropdown"

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

@@ -34,14 +34,13 @@ export default {
       required: false,
       default: false,
     },
+    baseVersionPath: {
+      type: String,
+      required: false,
+      default: null,
+    },
   },
   computed: {
-    baseVersion() {
-      return {
-        name: 'hii',
-        versionIndex: -1,
-      };
-    },
     targetVersions() {
       if (this.mergeRequestVersion) {
         return this.otherVersions;
@@ -62,6 +61,9 @@ export default {
       );
     },
     href(version) {
+      if (this.isBase(version)) {
+        return this.baseVersionPath;
+      }
       if (this.showCommitCount) {
         return version.version_path;
       }

app/serializers/merge_request_diff_entity.rb

@@ -24,6 +24,14 @@ class MergeRequestDiffEntity < Grape::Entity
     short_sha(merge_request_diff.head_commit_sha)
   end
 
+  expose :base_version_path do |merge_request_diff|
+    project = merge_request.target_project
+
+    next unless project
+
+    merge_request_version_path(project, merge_request, merge_request_diff)
+  end
+
   expose :version_path do |merge_request_diff|
     start_sha = options[:start_sha]
     project = merge_request.target_project

changelogs/unreleased/52275-fix-master-to-be-hyperlink.yml

+---
+title: Resolve In Merge Request diff screen, master is not a hyperlink
+merge_request: 23874
+author:
+type: fixed

spec/javascripts/diffs/components/compare_versions_dropdown_spec.js

 // TODO: https://gitlab.com/gitlab-org/gitlab-ce/issues/48034
+import { shallowMount, createLocalVue } from '@vue/test-utils';
+import CompareVersionsDropdown from '~/diffs/components/compare_versions_dropdown.vue';
+import diffsMockData from '../mock_data/merge_request_diffs';
+
+describe('CompareVersionsDropdown', () => {
+  let wrapper;
+  const targetBranch = { branchName: 'tmp-wine-dev', versionIndex: -1 };
+
+  const factory = (options = {}) => {
+    const localVue = createLocalVue();
+
+    wrapper = shallowMount(CompareVersionsDropdown, { localVue, ...options });
+  };
+
+  afterEach(() => {
+    wrapper.destroy();
+  });
+
+  it('should render a correct base version link', () => {
+    factory({
+      propsData: {
+        baseVersionPath: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37',
+        otherVersions: diffsMockData.slice(1),
+        targetBranch,
+      },
+    });
+
+    const links = wrapper.findAll('a');
+    const lastLink = links.wrappers[links.length - 1];
+
+    expect(lastLink.attributes('href')).toEqual(wrapper.props('baseVersionPath'));
+  });
+});

spec/javascripts/diffs/components/compare_versions_spec.js

@@ -100,6 +100,12 @@ describe('CompareVersions', () => {
     });
   });
 
+  describe('baseVersionPath', () => {
+    it('should be set correctly from mergeRequestDiff', () => {
+      expect(vm.baseVersionPath).toEqual(vm.mergeRequestDiff.base_version_path);
+    });
+  });
+
   describe('isWhitespaceVisible', () => {
     const originalHref = window.location.href;
 

spec/javascripts/diffs/mock_data/merge_request_diffs.js

 export default [
   {
-    versionIndex: 4,
-    createdAt: '2018-10-23T11:49:16.611Z',
-    commitsCount: 4,
+    base_version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37',
+    version_index: 4,
+    created_at: '2018-10-23T11:49:16.611Z',
+    commits_count: 4,
     latest: true,
-    shortCommitSha: 'de7a8f7f',
-    versionPath: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37',
-    comparePath:
+    short_commit_sha: 'de7a8f7f',
+    version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37',
+    compare_path:
       '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37&start_sha=de7a8f7f20c3ea2e0bef3ba01cfd41c21f6b4995',
   },
   {
-    versionIndex: 3,
-    createdAt: '2018-10-23T11:46:40.617Z',
-    commitsCount: 3,
+    base_version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=36',
+    version_index: 3,
+    created_at: '2018-10-23T11:46:40.617Z',
+    commits_count: 3,
     latest: false,
-    shortCommitSha: 'e78fc18f',
-    versionPath: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=36',
-    comparePath:
+    short_commit_sha: 'e78fc18f',
+    version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=36',
+    compare_path:
       '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37&start_sha=e78fc18fa37acb2185c59ca94d4a964464feb50e',
   },
   {
-    versionIndex: 2,
-    createdAt: '2018-10-04T09:57:39.648Z',
-    commitsCount: 2,
+    base_version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=35',
+    version_index: 2,
+    created_at: '2018-10-04T09:57:39.648Z',
+    commits_count: 2,
     latest: false,
-    shortCommitSha: '48da7e7e',
-    versionPath: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=35',
-    comparePath:
+    short_commit_sha: '48da7e7e',
+    version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=35',
+    compare_path:
       '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37&start_sha=48da7e7e9a99d41c852578bd9cb541ca4d864b3e',
   },
   {
-    versionIndex: 1,
-    createdAt: '2018-09-25T20:30:39.493Z',
-    commitsCount: 1,
+    base_version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=20',
+    version_index: 1,
+    created_at: '2018-09-25T20:30:39.493Z',
+    commits_count: 1,
     latest: false,
-    shortCommitSha: '47bac2ed',
-    versionPath: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=20',
-    comparePath:
+    short_commit_sha: '47bac2ed',
+    version_path: '/gnuwget/wget2/merge_requests/6/diffs?diff_id=20',
+    compare_path:
       '/gnuwget/wget2/merge_requests/6/diffs?diff_id=37&start_sha=47bac2ed972c5bee344c1cea159a22cd7f711dc0',
   },
 ];