Highlight currently focused/viewed file in file tree

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

@@ -58,6 +58,9 @@ export default {
     hasDiff() {
       return hasDiff(this.file);
     },
+    isActive() {
+      return this.currentDiffFileId === this.file.file_hash;
+    },
     isFileTooLarge() {
       return this.file.viewer.error === diffViewerErrors.too_large;
     },
@@ -143,7 +146,7 @@ export default {
   <div
     :id="file.file_hash"
     :class="{
-      'is-active': currentDiffFileId === file.file_hash,
+      'is-active': isActive,
     }"
     class="diff-file file-holder"
   >
@@ -153,6 +156,7 @@ export default {
       :collapsible="true"
       :expanded="!isCollapsed"
       :add-merge-request-buttons="true"
+      :is-active="isActive"
       class="js-file-title file-title"
       @toggleFile="handleToggle"
       @showForkMessage="showForkMessage"

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

@@ -55,6 +55,11 @@ export default {
       type: Boolean,
       required: true,
     },
+    isActive: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
   },
   computed: {
     ...mapGetters('diffs', ['diffHasExpandedDiscussions', 'diffHasDiscussions']),
@@ -158,6 +163,9 @@ export default {
   <div
     ref="header"
     class="js-file-title file-title file-title-flex-parent"
+    :class="{
+      'is-active': isActive,
+    }"
     @click.self="handleToggleFile"
   >
     <div class="file-header-content">

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

@@ -26,7 +26,7 @@ export default {
     };
   },
   computed: {
-    ...mapState('diffs', ['tree', 'renderTreeList']),
+    ...mapState('diffs', ['tree', 'renderTreeList', 'currentDiffFileId', 'viewedDiffFileIds']),
     ...mapGetters('diffs', ['allBlobs']),
     filteredTreeList() {
       const search = this.search.toLowerCase().trim();
@@ -96,6 +96,8 @@ export default {
           :level="0"
           :hide-file-stats="hideFileStats"
           :file-row-component="$options.DiffFileRow"
+          :active-file="currentDiffFileId"
+          :viewed-files="viewedDiffFileIds"
           @toggleTreeOpen="toggleTreeOpen"
           @clickFile="scrollToFile"
         />

app/assets/javascripts/diffs/store/modules/diff_state.js

@@ -26,6 +26,7 @@ export default () => ({
   showTreeList: true,
   currentDiffFileId: '',
   projectPath: '',
+  viewedDiffFileIds: [],
   commentForms: [],
   highlightedRow: null,
   renderTreeList: true,

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

@@ -284,6 +284,9 @@ export default {
   },
   [types.UPDATE_CURRENT_DIFF_FILE_ID](state, fileId) {
     state.currentDiffFileId = fileId;
+    if (!state.viewedDiffFileIds.includes(fileId)) {
+      state.viewedDiffFileIds = [fileId, ...state.viewedDiffFileIds];
+    }
   },
   [types.OPEN_DIFF_FILE_COMMENT_FORM](state, formData) {
     state.commentForms.push({

app/assets/javascripts/vue_shared/components/file_row.vue

@@ -18,6 +18,16 @@ export default {
       type: Number,
       required: true,
     },
+    activeFile: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    viewedFiles: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   computed: {
     isTree() {
@@ -34,8 +44,8 @@ export default {
     fileClass() {
       return {
         'file-open': this.isBlob && this.file.opened,
-        'is-active': this.isBlob && this.file.active,
-        folder: this.isTree,
+        'is-active': this.isBlob && (this.file.active || this.activeFile === this.file.fileHash),
+        'is-viewed': this.isBlob && this.viewedFiles.includes(this.file.fileHash),
         'is-open': this.file.opened,
       };
     },
@@ -107,15 +117,23 @@ export default {
     v-else
     :class="fileClass"
     :title="file.name"
-    class="file-row"
+    class="file-row text-left px-1 py-2 ml-n2 d-flex align-items-center"
     role="button"
     @click="clickFile"
     @mouseleave="$emit('mouseleave', $event)"
   >
-    <div class="file-row-name-container">
-      <span ref="textOutput" :style="levelIndentation" class="file-row-name str-truncated">
+    <div class="file-row-name-container w-100 d-flex align-items-center">
+      <span
+        ref="textOutput"
+        :style="levelIndentation"
+        class="file-row-name str-truncated d-inline-block"
+        :class="[
+          { 'folder font-weight-normal': isTree },
+          fileClass['is-viewed'] ? 'font-weight-normal' : 'font-weight-bold',
+        ]"
+      >
         <file-icon
-          class="file-row-icon"
+          class="file-row-icon align-middle mr-1"
           :class="{ 'text-secondary': file.type === 'tree' }"
           :file-name="file.name"
           :loading="file.loading"
@@ -132,14 +150,8 @@ export default {
 
 <style>
 .file-row {
-  display: flex;
-  align-items: center;
   height: 32px;
-  padding: 4px 8px;
-  margin-left: -8px;
-  margin-right: -8px;
   border-radius: 3px;
-  text-align: left;
   cursor: pointer;
 }
 
@@ -157,24 +169,15 @@ export default {
 }
 
 .file-row-name-container {
-  display: flex;
-  width: 100%;
-  align-items: center;
   overflow: visible;
 }
 
 .file-row-name {
-  display: inline-block;
   flex: 1;
   max-width: inherit;
-  height: 19px;
+  height: 20px;
   line-height: 16px;
   text-overflow: ellipsis;
   white-space: nowrap;
 }
-
-.file-row-name .file-row-icon {
-  margin-right: 2px;
-  vertical-align: middle;
-}
 </style>

app/assets/stylesheets/pages/diff.scss

@@ -69,6 +69,11 @@
     }
   }
 
+  .file-title.is-active,
+  .file-title-flex-parent.is-active {
+    background-color: $gray-200;
+  }
+
   @media (min-width: map-get($grid-breakpoints, md)) {
     &.conflict .file-title,
     &.conflict .file-title-flex-parent {

changelogs/unreleased/24629.yml

+---
+title: Highlight currently focused/viewed file in file tree
+merge_request: 27703
+author:
+type: changed

spec/frontend/diffs/components/diff_file_header_spec.js

@@ -61,6 +61,7 @@ describe('DiffFileHeader component', () => {
   const findTitleLink = () => wrapper.find({ ref: 'titleWrapper' });
   const findExpandButton = () => wrapper.find({ ref: 'expandDiffToFullFileButton' });
   const findFileActions = () => wrapper.find('.file-actions');
+  const findActiveHeader = () => wrapper.find('.is-active');
   const findModeChangedLine = () => wrapper.find({ ref: 'fileMode' });
   const findLfsLabel = () => wrapper.find('.label-lfs');
   const findToggleDiscussionsButton = () => wrapper.find({ ref: 'toggleDiscussionsButton' });
@@ -143,6 +144,11 @@ describe('DiffFileHeader component', () => {
     expect(wrapper.find(ClipboardButton).exists()).toBe(true);
   });
 
+  it('contains a active header class if this is the active file header', () => {
+    createComponent({ isActive: true });
+    expect(findActiveHeader().exists()).toBe(true);
+  });
+
   describe('for submodule', () => {
     const submoduleDiffFile = {
       ...diffFile,

spec/frontend/vue_shared/components/file_row_spec.js

@@ -72,6 +72,19 @@ describe('File row component', () => {
     });
   });
 
+  it('is marked as viewed if clicked', () => {
+    createComponent({
+      file: {
+        ...file(),
+        type: 'blob',
+        fileHash: '#123456789',
+      },
+      level: 0,
+      viewedFiles: ['#123456789'],
+    });
+    expect(wrapper.classes()).toContain('is-viewed');
+  });
+
   it('indents row based on level', () => {
     createComponent({
       file: file('t4'),