Linking to a single line number in Web IDE

Introduces linking to a file(s) in Editor Lite.
The functionality is available in all Editor Lite instances
using the base extension (both single-file editor and WebIDE),
or any of its derivatives.

app/assets/javascripts/blob_edit/edit_blob.js

@@ -43,7 +43,7 @@ export default class EditBlob {
       blobPath: fileNameEl.value,
       blobContent: editorEl.innerText,
     });
-    this.editor.use(new FileTemplateExtension());
+    this.editor.use(new FileTemplateExtension({ instance: this.editor }));
 
     fileNameEl.addEventListener('change', () => {
       this.editor.updateModelLanguage(fileNameEl.value);

app/assets/javascripts/editor/extensions/editor_lite_extension_base.js

-import { ERROR_INSTANCE_REQUIRED_FOR_EXTENSION } from '../constants';
+import { Range } from 'monaco-editor';
+import { ERROR_INSTANCE_REQUIRED_FOR_EXTENSION, EDITOR_TYPE_CODE } from '../constants';
+
+const hashRegexp = new RegExp('#?L', 'g');
+
+const createAnchor = (href) => {
+  const fragment = new DocumentFragment();
+  const el = document.createElement('a');
+  el.classList.add('link-anchor');
+  el.href = href;
+  fragment.appendChild(el);
+  el.addEventListener('contextmenu', (e) => {
+    e.stopPropagation();
+  });
+  return fragment;
+};
 
 export class EditorLiteExtension {
   constructor({ instance, ...options } = {}) {
     if (instance) {
       Object.assign(instance, options);
+      EditorLiteExtension.highlightLines(instance);
+      if (instance.getEditorType && instance.getEditorType() === EDITOR_TYPE_CODE) {
+        EditorLiteExtension.setupLineLinking(instance);
+      }
     } else if (Object.entries(options).length) {
       throw new Error(ERROR_INSTANCE_REQUIRED_FOR_EXTENSION);
     }
   }
+
+  static highlightLines(instance) {
+    const { hash } = window.location;
+    if (!hash) {
+      return;
+    }
+    const [start, end] = hash.replace(hashRegexp, '').split('-');
+    let startLine = start ? parseInt(start, 10) : null;
+    let endLine = end ? parseInt(end, 10) : startLine;
+    if (endLine < startLine) {
+      [startLine, endLine] = [endLine, startLine];
+    }
+    if (startLine) {
+      window.requestAnimationFrame(() => {
+        instance.revealLineInCenter(startLine);
+        Object.assign(instance, {
+          lineDecorations: instance.deltaDecorations(
+            [],
+            [
+              {
+                range: new Range(startLine, 1, endLine, 1),
+                options: { isWholeLine: true, className: 'active-line-text' },
+              },
+            ],
+          ),
+        });
+      });
+    }
+  }
+
+  static onMouseMoveHandler(e) {
+    const target = e.target.element;
+    if (target.classList.contains('line-numbers')) {
+      const lineNum = e.target.position.lineNumber;
+      const hrefAttr = `#L${lineNum}`;
+      let el = target.querySelector('a');
+      if (!el) {
+        el = createAnchor(hrefAttr);
+        target.appendChild(el);
+      }
+    }
+  }
+
+  static setupLineLinking(instance) {
+    instance.onMouseMove(EditorLiteExtension.onMouseMoveHandler);
+    instance.onMouseDown((e) => {
+      const isCorrectAnchor = e.target.element.classList.contains('link-anchor');
+      if (!isCorrectAnchor) {
+        return;
+      }
+      if (instance.lineDecorations) {
+        instance.deltaDecorations(instance.lineDecorations, []);
+      }
+    });
+  }
 }

app/assets/javascripts/ide/lib/editor_options.js

@@ -7,6 +7,7 @@ export const defaultEditorOptions = {
     enabled: false,
   },
   wordWrap: 'on',
+  glyphMargin: true,
 };
 
 export const defaultDiffOptions = {
@@ -21,6 +22,7 @@ export const defaultDiffEditorOptions = {
   readOnly: false,
   renderLineHighlight: 'none',
   hideCursorInOverviewRuler: true,
+  glyphMargin: true,
 };
 
 export const defaultModelOptions = {

app/assets/javascripts/pipeline_editor/components/editor/text_editor.vue

@@ -27,7 +27,7 @@ export default {
     registerCiSchema() {
       const editorInstance = this.$refs.editor.getEditor();
 
-      editorInstance.use(new CiSchemaExtension());
+      editorInstance.use(new CiSchemaExtension({ instance: editorInstance }));
       editorInstance.registerCiSchema({
         projectPath: this.projectPath,
         projectNamespace: this.projectNamespace,

app/assets/stylesheets/framework/editor-lite.scss

@@ -24,3 +24,53 @@
 [id^='editor-lite-'] {
   height: 500px;
 }
+
+.monaco-editor.gl-editor-lite {
+  .margin-view-overlays {
+    .line-numbers {
+      @include gl-display-flex;
+      @include gl-justify-content-end;
+      @include gl-relative;
+
+      &::before {
+        @include gl-visibility-hidden;
+        @include gl-align-self-center;
+        @include gl-bg-gray-400;
+        @include gl-mr-2;
+        @include gl-w-4;
+        @include gl-h-4;
+        mask-image: asset_url('icons-stacked.svg#link');
+        mask-repeat: no-repeat;
+        mask-size: cover;
+        mask-position: center;
+        content: '';
+      }
+
+      &:hover {
+        @include gl-text-decoration-underline;
+        cursor: pointer !important;
+      }
+
+      &:hover::before {
+        @include gl-visibility-visible;
+      }
+
+      &:focus::before {
+        @include gl-visibility-visible;
+        outline: auto;
+      }
+
+      .link-anchor {
+        @include gl-display-block;
+        @include gl-absolute;
+        @include gl-w-full;
+        @include gl-h-full;
+      }
+    }
+  }
+}
+
+.active-line-text {
+  @include gl-bg-orange-600;
+  @include gl-opacity-3;
+}

changelogs/unreleased/21762-link-to-a-line.yml

+---
+title: Linking to a single line number in Web IDE
+merge_request: 56159
+author:
+type: added

doc/user/project/repository/web_editor.md

@@ -56,6 +56,24 @@ NOTE:
 The **Set up CI/CD** button does not appear on an empty repository. For the button
 to display, add a file to your repository.
 
+## Highlight lines
+
+Web Editor enables you to highlight a single line by adding specially formatted
+hash information to the URL's file path segment. For example, the file path segment
+`MY_FILE.js#L3` instructs the Web Editor to highlight line 3.
+
+The Web Editor also enables you to highlight multiple lines using a similar pattern. In
+this case, the file path segment `MY_FILE.js#L3-10` instructs the Web Editor to
+highlight lines 3 to 10 of the file.
+
+You don't need to construct these lines manually. Instead, you can:
+
+1. Hover over the number of a line you want to be highlighted when sharing.
+1. Right-click the number with your mouse.
+1. Click **Copy Link Address** in the context menu.
+
+   ![Link to a line](img/web_editor_line_link_v13_10.png)
+
 ## Upload a file
 
 The ability to create a file is great when the content is text. However, this

doc/user/project/web_ide/index.md

@@ -66,9 +66,6 @@ Monaco uses the [Monarch](https://microsoft.github.io/monaco-editor/monarch.html
 
 If you are missing Syntax Highlighting support for any language, we prepared a short guide on how to [add support for a missing language Syntax Highlighting.](https://gitlab.com/gitlab-org/gitlab/-/blob/master/app/assets/javascripts/ide/lib/languages/README.md)
 
-NOTE:
-Single file editing is based on the [Ace Editor](https://ace.c9.io).
-
 ### Themes
 
 > - [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/2389) in GitLab 13.0.
@@ -82,6 +79,12 @@ You can pick a theme from your [profile preferences](../../profile/preferences.m
 |-------------------------------------------------------------|-----------------------------------------|
 | ![Solarized Dark Theme](img/solarized_dark_theme_v13_1.png) | ![Dark Theme](img/dark_theme_v13_0.png) |
 
+## Highlight lines
+
+WebIDE is built with the [Web Editor](../repository/web_editor.md). This enables WebIDE to share the
+same core features for highlighting and linking to particular lines in the edited files
+[described for the Web Editor](../repository/web_editor.md#highlight-lines).
+
 ## Schema based validation
 
 > - Support for validation based on predefined schemas [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/218472) in GitLab 13.2.