Source Editor refactoring integration

app/assets/javascripts/blob_edit/edit_blob.js

 import $ from 'jquery';
+import { SourceEditorExtension } from '~/editor/extensions/source_editor_extension_base';
 import { FileTemplateExtension } from '~/editor/extensions/source_editor_file_template_ext';
 import SourceEditor from '~/editor/source_editor';
 import { getBlobLanguage } from '~/editor/utils';
@@ -26,23 +27,29 @@ export default class EditBlob {
     this.editor.focus();
   }
 
-  fetchMarkdownExtension() {
-    import('~/editor/extensions/source_editor_markdown_ext')
-      .then(({ EditorMarkdownExtension: MarkdownExtension } = {}) => {
-        this.editor.use(
-          new MarkdownExtension({
-            instance: this.editor,
-            previewMarkdownPath: this.options.previewMarkdownPath,
-          }),
-        );
-        this.hasMarkdownExtension = true;
-        addEditorMarkdownListeners(this.editor);
-      })
-      .catch((e) =>
-        createFlash({
-          message: `${BLOB_EDITOR_ERROR}: ${e}`,
-        }),
-      );
+  async fetchMarkdownExtension() {
+    try {
+      const [
+        { EditorMarkdownExtension: MarkdownExtension },
+        { EditorMarkdownPreviewExtension: MarkdownLivePreview },
+      ] = await Promise.all([
+        import('~/editor/extensions/source_editor_markdown_ext'),
+        import('~/editor/extensions/source_editor_markdown_livepreview_ext'),
+      ]);
+      this.editor.use([
+        { definition: MarkdownExtension },
+        {
+          definition: MarkdownLivePreview,
+          setupOptions: { previewMarkdownPath: this.options.previewMarkdownPath },
+        },
+      ]);
+    } catch (e) {
+      createFlash({
+        message: `${BLOB_EDITOR_ERROR}: ${e}`,
+      });
+    }
+    this.hasMarkdownExtension = true;
+    addEditorMarkdownListeners(this.editor);
   }
 
   configureMonacoEditor() {
@@ -60,7 +67,7 @@ export default class EditBlob {
       blobPath: fileNameEl.value,
       blobContent: editorEl.innerText,
     });
-    this.editor.use(new FileTemplateExtension({ instance: this.editor }));
+    this.editor.use([{ definition: SourceEditorExtension }, { definition: FileTemplateExtension }]);
 
     fileNameEl.addEventListener('change', () => {
       this.editor.updateModelLanguage(fileNameEl.value);

app/assets/javascripts/editor/constants.js

@@ -42,6 +42,10 @@ export const EDITOR_EXTENSION_STORE_IS_MISSING_ERROR = s__(
 // EXTENSIONS' CONSTANTS
 //
 
+// Source Editor Base Extension
+export const EXTENSION_BASE_LINE_LINK_ANCHOR_CLASS = 'link-anchor';
+export const EXTENSION_BASE_LINE_NUMBERS_CLASS = 'line-numbers';
+
 // For CI config schemas the filename must match
 // '*.gitlab-ci.yml' regardless of project configuration.
 // https://gitlab.com/gitlab-org/gitlab/-/issues/293641

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

@@ -6,6 +6,16 @@
 //
 
 export class MyFancyExtension {
+  /**
+   * A required getter returning the extension's name
+   * We have to provide it for every extension instead of relying on the built-in
+   * `name` prop because the prop does not survive the webpack's minification
+   * and the name mangling.
+   * @returns {string}
+   */
+  static get extensionName() {
+    return 'MyFancyExtension';
+  }
   /**
    * THE LIFE-CYCLE CALLBACKS
    */

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

 import ciSchemaPath from '~/editor/schema/ci.json';
 import { registerSchema } from '~/ide/utils';
-import { SourceEditorExtension } from './source_editor_extension_base';
 
-export class CiSchemaExtension extends SourceEditorExtension {
-  /**
-   * Registers a syntax schema to the editor based on project
-   * identifier and commit.
-   *
-   * The schema is added to the file that is currently edited
-   * in the editor.
-   *
-   * @param {Object} opts
-   * @param {String} opts.projectNamespace
-   * @param {String} opts.projectPath
-   * @param {String?} opts.ref - Current ref. Defaults to main
-   */
-  registerCiSchema() {
-    // In order for workers loaded from `data://` as the
-    // ones loaded by monaco editor, we use absolute URLs
-    // to fetch schema files, hence the `gon.gitlab_url`
-    // reference. This prevents error:
-    //   "Failed to execute 'fetch' on 'WorkerGlobalScope'"
-    const absoluteSchemaUrl = gon.gitlab_url + ciSchemaPath;
-    const modelFileName = this.getModel().uri.path.split('/').pop();
+export class CiSchemaExtension {
+  static get extensionName() {
+    return 'CiSchema';
+  }
+  // eslint-disable-next-line class-methods-use-this
+  provides() {
+    return {
+      registerCiSchema: (instance) => {
+        // In order for workers loaded from `data://` as the
+        // ones loaded by monaco editor, we use absolute URLs
+        // to fetch schema files, hence the `gon.gitlab_url`
+        // reference. This prevents error:
+        //   "Failed to execute 'fetch' on 'WorkerGlobalScope'"
+        const absoluteSchemaUrl = gon.gitlab_url + ciSchemaPath;
+        const modelFileName = instance.getModel().uri.path.split('/').pop();
 
-    registerSchema({
-      uri: absoluteSchemaUrl,
-      fileMatch: [modelFileName],
-    });
+        registerSchema({
+          uri: absoluteSchemaUrl,
+          fileMatch: [modelFileName],
+        });
+      },
+    };
   }
 }

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

 import { Range } from 'monaco-editor';
-import { waitForCSSLoaded } from '~/helpers/startup_css_helper';
-import { ERROR_INSTANCE_REQUIRED_FOR_EXTENSION, EDITOR_TYPE_CODE } from '../constants';
+import {
+  EDITOR_TYPE_CODE,
+  EXTENSION_BASE_LINE_LINK_ANCHOR_CLASS,
+  EXTENSION_BASE_LINE_NUMBERS_CLASS,
+} 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.classList.add(EXTENSION_BASE_LINE_LINK_ANCHOR_CLASS);
   el.href = href;
   fragment.appendChild(el);
   el.addEventListener('contextmenu', (e) => {
@@ -17,38 +20,46 @@ const createAnchor = (href) => {
 };
 
 export class SourceEditorExtension {
-  constructor({ instance, ...options } = {}) {
-    if (instance) {
-      Object.assign(instance, options);
-      SourceEditorExtension.highlightLines(instance);
-      if (instance.getEditorType && instance.getEditorType() === EDITOR_TYPE_CODE) {
-        SourceEditorExtension.setupLineLinking(instance);
-      }
-      SourceEditorExtension.deferRerender(instance);
-    } else if (Object.entries(options).length) {
-      throw new Error(ERROR_INSTANCE_REQUIRED_FOR_EXTENSION);
+  static get extensionName() {
+    return 'BaseExtension';
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  onUse(instance) {
+    SourceEditorExtension.highlightLines(instance);
+    if (instance.getEditorType && instance.getEditorType() === EDITOR_TYPE_CODE) {
+      SourceEditorExtension.setupLineLinking(instance);
     }
   }
 
-  static deferRerender(instance) {
-    waitForCSSLoaded(() => {
-      instance.layout();
-    });
+  static onMouseMoveHandler(e) {
+    const target = e.target.element;
+    if (target.classList.contains(EXTENSION_BASE_LINE_NUMBERS_CLASS)) {
+      const lineNum = e.target.position.lineNumber;
+      const hrefAttr = `#L${lineNum}`;
+      let lineLink = target.querySelector('a');
+      if (!lineLink) {
+        lineLink = createAnchor(hrefAttr);
+        target.appendChild(lineLink);
+      }
+    }
   }
 
-  static removeHighlights(instance) {
-    Object.assign(instance, {
-      lineDecorations: instance.deltaDecorations(instance.lineDecorations || [], []),
+  static setupLineLinking(instance) {
+    instance.onMouseMove(SourceEditorExtension.onMouseMoveHandler);
+    instance.onMouseDown((e) => {
+      const isCorrectAnchor = e.target.element.classList.contains(
+        EXTENSION_BASE_LINE_LINK_ANCHOR_CLASS,
+      );
+      if (!isCorrectAnchor) {
+        return;
+      }
+      if (instance.lineDecorations) {
+        instance.deltaDecorations(instance.lineDecorations, []);
+      }
     });
   }
 
-  /**
-   * Returns a function that can only be invoked once between
-   * each browser screen repaint.
-   * @param {Object} instance - The Source Editor instance
-   * @param {Array} bounds - The [start, end] array with start
-   * and end coordinates for highlighting
-   */
   static highlightLines(instance, bounds = null) {
     const [start, end] =
       bounds && Array.isArray(bounds)
@@ -74,29 +85,29 @@ export class SourceEditorExtension {
     }
   }
 
-  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);
-      }
-    }
-  }
+  // eslint-disable-next-line class-methods-use-this
+  provides() {
+    return {
+      /**
+       * Removes existing line decorations and updates the reference on the instance
+       * @param {module:source_editor_instance~EditorInstance} instance - The Source Editor instance
+       */
+      removeHighlights: (instance) => {
+        Object.assign(instance, {
+          lineDecorations: instance.deltaDecorations(instance.lineDecorations || [], []),
+        });
+      },
 
-  static setupLineLinking(instance) {
-    instance.onMouseMove(SourceEditorExtension.onMouseMoveHandler);
-    instance.onMouseDown((e) => {
-      const isCorrectAnchor = e.target.element.classList.contains('link-anchor');
-      if (!isCorrectAnchor) {
-        return;
-      }
-      if (instance.lineDecorations) {
-        instance.deltaDecorations(instance.lineDecorations, []);
-      }
-    });
+      /**
+       * Returns a function that can only be invoked once between
+       * each browser screen repaint.
+       * @param {Array} bounds - The [start, end] array with start
+       * @param {module:source_editor_instance~EditorInstance} instance - The Source Editor instance
+       * and end coordinates for highlighting
+       */
+      highlightLines(instance, bounds = null) {
+        SourceEditorExtension.highlightLines(instance, bounds);
+      },
+    };
   }
 }

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

 import { Position } from 'monaco-editor';
-import { SourceEditorExtension } from './source_editor_extension_base';
 
-export class FileTemplateExtension extends SourceEditorExtension {
-  navigateFileStart() {
-    this.setPosition(new Position(1, 1));
+export class FileTemplateExtension {
+  static get extensionName() {
+    return 'FileTemplate';
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  provides() {
+    return {
+      navigateFileStart: (instance) => {
+        instance.setPosition(new Position(1, 1));
+      },
+    };
   }
 }

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

-import { EditorMarkdownPreviewExtension } from '~/editor/extensions/source_editor_markdown_livepreview_ext';
-
-export class EditorMarkdownExtension extends EditorMarkdownPreviewExtension {
-  getSelectedText(selection = this.getSelection()) {
-    const { startLineNumber, endLineNumber, startColumn, endColumn } = selection;
-    const valArray = this.getValue().split('\n');
-    let text = '';
-    if (startLineNumber === endLineNumber) {
-      text = valArray[startLineNumber - 1].slice(startColumn - 1, endColumn - 1);
-    } else {
-      const startLineText = valArray[startLineNumber - 1].slice(startColumn - 1);
-      const endLineText = valArray[endLineNumber - 1].slice(0, endColumn - 1);
-
-      for (let i = startLineNumber, k = endLineNumber - 1; i < k; i += 1) {
-        text += `${valArray[i]}`;
-        if (i !== k - 1) text += `\n`;
-      }
-      text = text
-        ? [startLineText, text, endLineText].join('\n')
-        : [startLineText, endLineText].join('\n');
-    }
-    return text;
+export class EditorMarkdownExtension {
+  static get extensionName() {
+    return 'EditorMarkdown';
   }
 
-  replaceSelectedText(text, select = undefined) {
-    const forceMoveMarkers = !select;
-    this.executeEdits('', [{ range: this.getSelection(), text, forceMoveMarkers }]);
-  }
-
-  moveCursor(dx = 0, dy = 0) {
-    const pos = this.getPosition();
-    pos.column += dx;
-    pos.lineNumber += dy;
-    this.setPosition(pos);
-  }
+  // eslint-disable-next-line class-methods-use-this
+  provides() {
+    return {
+      getSelectedText: (instance, selection = instance.getSelection()) => {
+        const { startLineNumber, endLineNumber, startColumn, endColumn } = selection;
+        const valArray = instance.getValue().split('\n');
+        let text = '';
+        if (startLineNumber === endLineNumber) {
+          text = valArray[startLineNumber - 1].slice(startColumn - 1, endColumn - 1);
+        } else {
+          const startLineText = valArray[startLineNumber - 1].slice(startColumn - 1);
+          const endLineText = valArray[endLineNumber - 1].slice(0, endColumn - 1);
 
-  /**
-   * Adjust existing selection to select text within the original selection.
-   * - If `selectedText` is not supplied, we fetch selected text with
-   *
-   * ALGORITHM:
-   *
-   * MULTI-LINE SELECTION
-   * 1. Find line that contains `toSelect` text.
-   * 2. Using the index of this line and the position of `toSelect` text in it,
-   * construct:
-   *   * newStartLineNumber
-   *   * newStartColumn
-   *
-   * SINGLE-LINE SELECTION
-   * 1. Use `startLineNumber` from the current selection as `newStartLineNumber`
-   * 2. Find the position of `toSelect` text in it to get `newStartColumn`
-   *
-   * 3. `newEndLineNumber` — Since this method is supposed to be used with
-   * markdown decorators that are pretty short, the `newEndLineNumber` is
-   * suggested to be assumed the same as the startLine.
-   * 4. `newEndColumn` — pretty obvious
-   * 5. Adjust the start and end positions of the current selection
-   * 6. Re-set selection on the instance
-   *
-   * @param {string} toSelect - New text to select within current selection.
-   * @param {string} selectedText - Currently selected text. It's just a
-   * shortcut: If it's not supplied, we fetch selected text from the instance
-   */
-  selectWithinSelection(toSelect, selectedText) {
-    const currentSelection = this.getSelection();
-    if (currentSelection.isEmpty() || !toSelect) {
-      return;
-    }
-    const text = selectedText || this.getSelectedText(currentSelection);
-    let lineShift;
-    let newStartLineNumber;
-    let newStartColumn;
+          for (let i = startLineNumber, k = endLineNumber - 1; i < k; i += 1) {
+            text += `${valArray[i]}`;
+            if (i !== k - 1) text += `\n`;
+          }
+          text = text
+            ? [startLineText, text, endLineText].join('\n')
+            : [startLineText, endLineText].join('\n');
+        }
+        return text;
+      },
+      replaceSelectedText: (instance, text, select) => {
+        const forceMoveMarkers = !select;
+        instance.executeEdits('', [{ range: instance.getSelection(), text, forceMoveMarkers }]);
+      },
+      moveCursor: (instance, dx = 0, dy = 0) => {
+        const pos = instance.getPosition();
+        pos.column += dx;
+        pos.lineNumber += dy;
+        instance.setPosition(pos);
+      },
+      /**
+       * Adjust existing selection to select text within the original selection.
+       * - If `selectedText` is not supplied, we fetch selected text with
+       *
+       * ALGORITHM:
+       *
+       * MULTI-LINE SELECTION
+       * 1. Find line that contains `toSelect` text.
+       * 2. Using the index of this line and the position of `toSelect` text in it,
+       * construct:
+       *   * newStartLineNumber
+       *   * newStartColumn
+       *
+       * SINGLE-LINE SELECTION
+       * 1. Use `startLineNumber` from the current selection as `newStartLineNumber`
+       * 2. Find the position of `toSelect` text in it to get `newStartColumn`
+       *
+       * 3. `newEndLineNumber` — Since this method is supposed to be used with
+       * markdown decorators that are pretty short, the `newEndLineNumber` is
+       * suggested to be assumed the same as the startLine.
+       * 4. `newEndColumn` — pretty obvious
+       * 5. Adjust the start and end positions of the current selection
+       * 6. Re-set selection on the instance
+       *
+       * @param {module:source_editor_instance~EditorInstance} instance - The Source Editor instance. Is passed automatically.
+       * @param {string} toSelect - New text to select within current selection.
+       * @param {string} selectedText - Currently selected text. It's just a
+       * shortcut: If it's not supplied, we fetch selected text from the instance
+       */
+      selectWithinSelection: (instance, toSelect, selectedText) => {
+        const currentSelection = instance.getSelection();
+        if (currentSelection.isEmpty() || !toSelect) {
+          return;
+        }
+        const text = selectedText || instance.getSelectedText(currentSelection);
+        let lineShift;
+        let newStartLineNumber;
+        let newStartColumn;
 
-    const textLines = text.split('\n');
+        const textLines = text.split('\n');
 
-    if (textLines.length > 1) {
-      // Multi-line selection
-      lineShift = textLines.findIndex((line) => line.indexOf(toSelect) !== -1);
-      newStartLineNumber = currentSelection.startLineNumber + lineShift;
-      newStartColumn = textLines[lineShift].indexOf(toSelect) + 1;
-    } else {
-      // Single-line selection
-      newStartLineNumber = currentSelection.startLineNumber;
-      newStartColumn = currentSelection.startColumn + text.indexOf(toSelect);
-    }
+        if (textLines.length > 1) {
+          // Multi-line selection
+          lineShift = textLines.findIndex((line) => line.indexOf(toSelect) !== -1);
+          newStartLineNumber = currentSelection.startLineNumber + lineShift;
+          newStartColumn = textLines[lineShift].indexOf(toSelect) + 1;
+        } else {
+          // Single-line selection
+          newStartLineNumber = currentSelection.startLineNumber;
+          newStartColumn = currentSelection.startColumn + text.indexOf(toSelect);
+        }
 
-    const newEndLineNumber = newStartLineNumber;
-    const newEndColumn = newStartColumn + toSelect.length;
+        const newEndLineNumber = newStartLineNumber;
+        const newEndColumn = newStartColumn + toSelect.length;
 
-    const newSelection = currentSelection
-      .setStartPosition(newStartLineNumber, newStartColumn)
-      .setEndPosition(newEndLineNumber, newEndColumn);
+        const newSelection = currentSelection
+          .setStartPosition(newStartLineNumber, newStartColumn)
+          .setEndPosition(newEndLineNumber, newEndColumn);
 
-    this.setSelection(newSelection);
+        instance.setSelection(newSelection);
+      },
+    };
   }
 }

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

@@ -12,9 +12,8 @@ import {
   EXTENSION_MARKDOWN_PREVIEW_PANEL_PARENT_CLASS,
   EXTENSION_MARKDOWN_PREVIEW_UPDATE_DELAY,
 } from '../constants';
-import { SourceEditorExtension } from './source_editor_extension_base';
 
-const getPreview = (text, previewMarkdownPath) => {
+const fetchPreview = (text, previewMarkdownPath) => {
   return axios
     .post(previewMarkdownPath, {
       text,
@@ -34,19 +33,20 @@ const setupDomElement = ({ injectToEl = null } = {}) => {
   return previewEl;
 };
 
-export class EditorMarkdownPreviewExtension extends SourceEditorExtension {
-  constructor({ instance, previewMarkdownPath, ...args } = {}) {
-    super({ instance, ...args });
-    Object.assign(instance, {
-      previewMarkdownPath,
-      preview: {
-        el: undefined,
-        action: undefined,
-        shown: false,
-        modelChangeListener: undefined,
-      },
-    });
-    this.setupPreviewAction.call(instance);
+export class EditorMarkdownPreviewExtension {
+  static get extensionName() {
+    return 'EditorMarkdownPreview';
+  }
+
+  onSetup(instance, setupOptions) {
+    this.preview = {
+      el: undefined,
+      action: undefined,
+      shown: false,
+      modelChangeListener: undefined,
+      path: setupOptions.previewMarkdownPath,
+    };
+    this.setupPreviewAction(instance);
 
     instance.getModel().onDidChangeLanguage(({ newLanguage, oldLanguage } = {}) => {
       if (newLanguage === 'markdown' && oldLanguage !== newLanguage) {
@@ -68,43 +68,31 @@ export class EditorMarkdownPreviewExtension extends SourceEditorExtension {
     });
   }
 
-  static togglePreviewLayout() {
-    const { width, height } = this.getLayoutInfo();
+  togglePreviewLayout(instance) {
+    const { width, height } = instance.getLayoutInfo();
     const newWidth = this.preview.shown
       ? width / EXTENSION_MARKDOWN_PREVIEW_PANEL_WIDTH
       : width * EXTENSION_MARKDOWN_PREVIEW_PANEL_WIDTH;
-    this.layout({ width: newWidth, height });
+    instance.layout({ width: newWidth, height });
   }
 
-  static togglePreviewPanel() {
-    const parentEl = this.getDomNode().parentElement;
+  togglePreviewPanel(instance) {
+    const parentEl = instance.getDomNode().parentElement;
     const { el: previewEl } = this.preview;
     parentEl.classList.toggle(EXTENSION_MARKDOWN_PREVIEW_PANEL_PARENT_CLASS);
 
     if (previewEl.style.display === 'none') {
       // Show the preview panel
-      this.fetchPreview();
+      this.fetchPreview(instance);
     } else {
       // Hide the preview panel
       previewEl.style.display = 'none';
     }
   }
 
-  cleanup() {
-    if (this.preview.modelChangeListener) {
-      this.preview.modelChangeListener.dispose();
-    }
-    this.preview.action.dispose();
-    if (this.preview.shown) {
-      EditorMarkdownPreviewExtension.togglePreviewPanel.call(this);
-      EditorMarkdownPreviewExtension.togglePreviewLayout.call(this);
-    }
-    this.preview.shown = false;
-  }
-
-  fetchPreview() {
+  fetchPreview(instance) {
     const { el: previewEl } = this.preview;
-    getPreview(this.getValue(), this.previewMarkdownPath)
+    fetchPreview(instance.getValue(), this.preview.path)
       .then((data) => {
         previewEl.innerHTML = sanitize(data);
         syntaxHighlight(previewEl.querySelectorAll('.js-syntax-highlight'));
@@ -113,10 +101,10 @@ export class EditorMarkdownPreviewExtension extends SourceEditorExtension {
       .catch(() => createFlash(BLOB_PREVIEW_ERROR));
   }
 
-  setupPreviewAction() {
-    if (this.getAction(EXTENSION_MARKDOWN_PREVIEW_ACTION_ID)) return;
+  setupPreviewAction(instance) {
+    if (instance.getAction(EXTENSION_MARKDOWN_PREVIEW_ACTION_ID)) return;
 
-    this.preview.action = this.addAction({
+    this.preview.action = instance.addAction({
       id: EXTENSION_MARKDOWN_PREVIEW_ACTION_ID,
       label: __('Preview Markdown'),
       keybindings: [
@@ -128,27 +116,52 @@ export class EditorMarkdownPreviewExtension extends SourceEditorExtension {
 
       // Method that will be executed when the action is triggered.
       // @param ed The editor instance is passed in as a convenience
-      run(instance) {
-        instance.togglePreview();
+      run(inst) {
+        inst.togglePreview();
       },
     });
   }
 
-  togglePreview() {
-    if (!this.preview?.el) {
-      this.preview.el = setupDomElement({ injectToEl: this.getDomNode().parentElement });
-    }
-    EditorMarkdownPreviewExtension.togglePreviewLayout.call(this);
-    EditorMarkdownPreviewExtension.togglePreviewPanel.call(this);
+  provides() {
+    return {
+      markdownPreview: this.preview,
 
-    if (!this.preview?.shown) {
-      this.preview.modelChangeListener = this.onDidChangeModelContent(
-        debounce(this.fetchPreview.bind(this), EXTENSION_MARKDOWN_PREVIEW_UPDATE_DELAY),
-      );
-    } else {
-      this.preview.modelChangeListener.dispose();
-    }
+      cleanup: (instance) => {
+        if (this.preview.modelChangeListener) {
+          this.preview.modelChangeListener.dispose();
+        }
+        this.preview.action.dispose();
+        if (this.preview.shown) {
+          this.togglePreviewPanel(instance);
+          this.togglePreviewLayout(instance);
+        }
+        this.preview.shown = false;
+      },
+
+      fetchPreview: (instance) => this.fetchPreview(instance),
 
-    this.preview.shown = !this.preview?.shown;
+      setupPreviewAction: (instance) => this.setupPreviewAction(instance),
+
+      togglePreview: (instance) => {
+        if (!this.preview?.el) {
+          this.preview.el = setupDomElement({ injectToEl: instance.getDomNode().parentElement });
+        }
+        this.togglePreviewLayout(instance);
+        this.togglePreviewPanel(instance);
+
+        if (!this.preview?.shown) {
+          this.preview.modelChangeListener = instance.onDidChangeModelContent(
+            debounce(
+              this.fetchPreview.bind(this, instance),
+              EXTENSION_MARKDOWN_PREVIEW_UPDATE_DELAY,
+            ),
+          );
+        } else {
+          this.preview.modelChangeListener.dispose();
+        }
+
+        this.preview.shown = !this.preview?.shown;
+      },
+    };
   }
 }

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

+/**
+ * A WebIDE Extension options for Source Editor
+ * @typedef {Object} WebIDEExtensionOptions
+ * @property {Object} modelManager The root manager for WebIDE models
+ * @property {Object} store The state store for communication
+ * @property {Object} file
+ * @property {Object} options The Monaco editor options
+ */
+
 import { debounce } from 'lodash';
 import { KeyCode, KeyMod, Range } from 'monaco-editor';
 import { EDITOR_TYPE_DIFF } from '~/editor/constants';
-import { SourceEditorExtension } from '~/editor/extensions/source_editor_extension_base';
 import Disposable from '~/ide/lib/common/disposable';
 import { editorOptions } from '~/ide/lib/editor_options';
 import keymap from '~/ide/lib/keymap.json';
@@ -11,154 +19,168 @@ const isDiffEditorType = (instance) => {
 };
 
 export const UPDATE_DIMENSIONS_DELAY = 200;
+const defaultOptions = {
+  modelManager: undefined,
+  store: undefined,
+  file: undefined,
+  options: {},
+};
 
-export class EditorWebIdeExtension extends SourceEditorExtension {
-  constructor({ instance, modelManager, ...options } = {}) {
-    super({
-      instance,
-      ...options,
-      modelManager,
-      disposable: new Disposable(),
-      debouncedUpdate: debounce(() => {
-        instance.updateDimensions();
-      }, UPDATE_DIMENSIONS_DELAY),
-    });
-
-    window.addEventListener('resize', instance.debouncedUpdate, false);
-
-    instance.onDidDispose(() => {
-      window.removeEventListener('resize', instance.debouncedUpdate);
-
-      // catch any potential errors with disposing the error
-      // this is mainly for tests caused by elements not existing
-      try {
-        instance.disposable.dispose();
-      } catch (e) {
-        if (process.env.NODE_ENV !== 'test') {
-          // eslint-disable-next-line no-console
-          console.error(e);
-        }
-      }
-    });
+const addActions = (instance, store) => {
+  const getKeyCode = (key) => {
+    const monacoKeyMod = key.indexOf('KEY_') === 0;
 
-    EditorWebIdeExtension.addActions(instance);
-  }
+    return monacoKeyMod ? KeyCode[key] : KeyMod[key];
+  };
 
-  static addActions(instance) {
-    const { store } = instance;
-    const getKeyCode = (key) => {
-      const monacoKeyMod = key.indexOf('KEY_') === 0;
+  keymap.forEach((command) => {
+    const { bindings, id, label, action } = command;
 
-      return monacoKeyMod ? KeyCode[key] : KeyMod[key];
-    };
+    const keybindings = bindings.map((binding) => {
+      const keys = binding.split('+');
 
-    keymap.forEach((command) => {
-      const { bindings, id, label, action } = command;
-
-      const keybindings = bindings.map((binding) => {
-        const keys = binding.split('+');
-
-        // eslint-disable-next-line no-bitwise
-        return keys.length > 1 ? getKeyCode(keys[0]) | getKeyCode(keys[1]) : getKeyCode(keys[0]);
-      });
-
-      instance.addAction({
-        id,
-        label,
-        keybindings,
-        run() {
-          store.dispatch(action.name, action.params);
-          return null;
-        },
-      });
+      // eslint-disable-next-line no-bitwise
+      return keys.length > 1 ? getKeyCode(keys[0]) | getKeyCode(keys[1]) : getKeyCode(keys[0]);
     });
-  }
-
-  createModel(file, head = null) {
-    return this.modelManager.addModel(file, head);
-  }
-
-  attachModel(model) {
-    if (isDiffEditorType(this)) {
-      this.setModel({
-        original: model.getOriginalModel(),
-        modified: model.getModel(),
-      });
 
-      return;
-    }
-
-    this.setModel(model.getModel());
+    instance.addAction({
+      id,
+      label,
+      keybindings,
+      run() {
+        store.dispatch(action.name, action.params);
+        return null;
+      },
+    });
+  });
+};
 
-    this.updateOptions(
-      editorOptions.reduce((acc, obj) => {
-        Object.keys(obj).forEach((key) => {
-          Object.assign(acc, {
-            [key]: obj[key](model),
-          });
-        });
-        return acc;
-      }, {}),
-    );
-  }
+const renderSideBySide = (domElement) => {
+  return domElement.offsetWidth >= 700;
+};
 
-  attachMergeRequestModel(model) {
-    this.setModel({
-      original: model.getBaseModel(),
-      modified: model.getModel(),
+const updateInstanceDimensions = (instance) => {
+  instance.layout();
+  if (isDiffEditorType(instance)) {
+    instance.updateOptions({
+      renderSideBySide: renderSideBySide(instance.getDomNode()),
     });
   }
+};
 
-  updateDimensions() {
-    this.layout();
-    this.updateDiffView();
+export class EditorWebIdeExtension {
+  static get extensionName() {
+    return 'EditorWebIde';
   }
 
-  setPos({ lineNumber, column }) {
-    this.revealPositionInCenter({
-      lineNumber,
-      column,
-    });
-    this.setPosition({
-      lineNumber,
-      column,
-    });
+  /**
+   * Set up the WebIDE extension for Source Editor
+   * @param {module:source_editor_instance~EditorInstance} instance - The Source Editor instance
+   * @param {WebIDEExtensionOptions} setupOptions
+   */
+  onSetup(instance, setupOptions = defaultOptions) {
+    this.modelManager = setupOptions.modelManager;
+    this.store = setupOptions.store;
+    this.file = setupOptions.file;
+    this.options = setupOptions.options;
+
+    this.disposable = new Disposable();
+    this.debouncedUpdate = debounce(() => {
+      updateInstanceDimensions(instance);
+    }, UPDATE_DIMENSIONS_DELAY);
+
+    addActions(instance, setupOptions.store);
   }
 
-  onPositionChange(cb) {
-    if (!this.onDidChangeCursorPosition) {
-      return;
-    }
+  onUse(instance) {
+    window.addEventListener('resize', this.debouncedUpdate, false);
 
-    this.disposable.add(this.onDidChangeCursorPosition((e) => cb(this, e)));
+    instance.onDidDispose(() => {
+      this.onUnuse();
+    });
   }
 
-  updateDiffView() {
-    if (!isDiffEditorType(this)) {
-      return;
+  onUnuse() {
+    window.removeEventListener('resize', this.debouncedUpdate);
+
+    // catch any potential errors with disposing the error
+    // this is mainly for tests caused by elements not existing
+    try {
+      this.disposable.dispose();
+    } catch (e) {
+      if (process.env.NODE_ENV !== 'test') {
+        // eslint-disable-next-line no-console
+        console.error(e);
+      }
     }
-
-    this.updateOptions({
-      renderSideBySide: EditorWebIdeExtension.renderSideBySide(this.getDomNode()),
-    });
   }
 
-  replaceSelectedText(text) {
-    let selection = this.getSelection();
-    const range = new Range(
-      selection.startLineNumber,
-      selection.startColumn,
-      selection.endLineNumber,
-      selection.endColumn,
-    );
+  provides() {
+    return {
+      createModel: (instance, file, head = null) => {
+        return this.modelManager.addModel(file, head);
+      },
+      attachModel: (instance, model) => {
+        if (isDiffEditorType(instance)) {
+          instance.setModel({
+            original: model.getOriginalModel(),
+            modified: model.getModel(),
+          });
 
-    this.executeEdits('', [{ range, text }]);
+          return;
+        }
 
-    selection = this.getSelection();
-    this.setPosition({ lineNumber: selection.endLineNumber, column: selection.endColumn });
-  }
+        instance.setModel(model.getModel());
+
+        instance.updateOptions(
+          editorOptions.reduce((acc, obj) => {
+            Object.keys(obj).forEach((key) => {
+              Object.assign(acc, {
+                [key]: obj[key](model),
+              });
+            });
+            return acc;
+          }, {}),
+        );
+      },
+      attachMergeRequestModel: (instance, model) => {
+        instance.setModel({
+          original: model.getBaseModel(),
+          modified: model.getModel(),
+        });
+      },
+      updateDimensions: (instance) => updateInstanceDimensions(instance),
+      setPos: (instance, { lineNumber, column }) => {
+        instance.revealPositionInCenter({
+          lineNumber,
+          column,
+        });
+        instance.setPosition({
+          lineNumber,
+          column,
+        });
+      },
+      onPositionChange: (instance, cb) => {
+        if (typeof instance.onDidChangeCursorPosition !== 'function') {
+          return;
+        }
 
-  static renderSideBySide(domElement) {
-    return domElement.offsetWidth >= 700;
+        this.disposable.add(instance.onDidChangeCursorPosition((e) => cb(instance, e)));
+      },
+      replaceSelectedText: (instance, text) => {
+        let selection = instance.getSelection();
+        const range = new Range(
+          selection.startLineNumber,
+          selection.startColumn,
+          selection.endLineNumber,
+          selection.endColumn,
+        );
+
+        instance.executeEdits('', [{ range, text }]);
+
+        selection = instance.getSelection();
+        instance.setPosition({ lineNumber: selection.endLineNumber, column: selection.endColumn });
+      },
+    };
   }
 }

app/assets/javascripts/editor/source_editor.js

 import { editor as monacoEditor, Uri } from 'monaco-editor';
+import { waitForCSSLoaded } from '~/helpers/startup_css_helper';
 import { defaultEditorOptions } from '~/ide/lib/editor_options';
 import languages from '~/ide/lib/languages';
 import { registerLanguages } from '~/ide/utils';
@@ -11,10 +12,39 @@ import {
   EDITOR_TYPE_DIFF,
 } from './constants';
 import { clearDomElement, setupEditorTheme, getBlobLanguage } from './utils';
+import EditorInstance from './source_editor_instance';
+
+const instanceRemoveFromRegistry = (editor, instance) => {
+  const index = editor.instances.findIndex((inst) => inst === instance);
+  editor.instances.splice(index, 1);
+};
+
+const instanceDisposeModels = (editor, instance, model) => {
+  const instanceModel = instance.getModel() || model;
+  if (!instanceModel) {
+    return;
+  }
+  if (instance.getEditorType() === EDITOR_TYPE_DIFF) {
+    const { original, modified } = instanceModel;
+    if (original) {
+      original.dispose();
+    }
+    if (modified) {
+      modified.dispose();
+    }
+  } else {
+    instanceModel.dispose();
+  }
+};
 
 export default class SourceEditor {
+  /**
+   * Constructs a global editor.
+   * @param {Object} options - Monaco config options used to create the editor
+   */
   constructor(options = {}) {
     this.instances = [];
+    this.extensionsStore = new Map();
     this.options = {
       extraEditorClassName: 'gl-source-editor',
       ...defaultEditorOptions,
@@ -26,19 +56,6 @@ export default class SourceEditor {
     registerLanguages(...languages);
   }
 
-  static mixIntoInstance(source, inst) {
-    if (!inst) {
-      return;
-    }
-    const isClassInstance = source.constructor.prototype !== Object.prototype;
-    const sanitizedSource = isClassInstance ? source.constructor.prototype : source;
-    Object.getOwnPropertyNames(sanitizedSource).forEach((prop) => {
-      if (prop !== 'constructor') {
-        Object.assign(inst, { [prop]: source[prop] });
-      }
-    });
-  }
-
   static prepareInstance(el) {
     if (!el) {
       throw new Error(SOURCE_EDITOR_INSTANCE_ERROR_NO_EL);
@@ -78,71 +95,17 @@ export default class SourceEditor {
     return diffModel;
   }
 
-  static convertMonacoToELInstance = (inst) => {
-    const sourceEditorInstanceAPI = {
-      updateModelLanguage: (path) => {
-        return SourceEditor.instanceUpdateLanguage(inst, path);
-      },
-      use: (exts = []) => {
-        return SourceEditor.instanceApplyExtension(inst, exts);
-      },
-    };
-    const handler = {
-      get(target, prop, receiver) {
-        if (Reflect.has(sourceEditorInstanceAPI, prop)) {
-          return sourceEditorInstanceAPI[prop];
-        }
-        return Reflect.get(target, prop, receiver);
-      },
-    };
-    return new Proxy(inst, handler);
-  };
-
-  static instanceUpdateLanguage(inst, path) {
-    const lang = getBlobLanguage(path);
-    const model = inst.getModel();
-    return monacoEditor.setModelLanguage(model, lang);
-  }
-
-  static instanceApplyExtension(inst, exts = []) {
-    const extensions = [].concat(exts);
-    extensions.forEach((extension) => {
-      SourceEditor.mixIntoInstance(extension, inst);
-    });
-    return inst;
-  }
-
-  static instanceRemoveFromRegistry(editor, instance) {
-    const index = editor.instances.findIndex((inst) => inst === instance);
-    editor.instances.splice(index, 1);
-  }
-
-  static instanceDisposeModels(editor, instance, model) {
-    const instanceModel = instance.getModel() || model;
-    if (!instanceModel) {
-      return;
-    }
-    if (instance.getEditorType() === EDITOR_TYPE_DIFF) {
-      const { original, modified } = instanceModel;
-      if (original) {
-        original.dispose();
-      }
-      if (modified) {
-        modified.dispose();
-      }
-    } else {
-      instanceModel.dispose();
-    }
-  }
-
   /**
-   * Creates a monaco instance with the given options.
-   *
-   * @param {Object} options Options used to initialize monaco.
-   * @param {Element} options.el The element which will be used to create the monacoEditor.
+   * Creates a Source Editor Instance with the given options.
+   * @param {Object} options Options used to initialize the instance.
+   * @param {Element} options.el The element to attach the instance for.
    * @param {string} options.blobPath The path used as the URI of the model. Monaco uses the extension of this path to determine the language.
    * @param {string} options.blobContent The content to initialize the monacoEditor.
+   * @param {string} options.blobOriginalContent The original blob's content. Is used when creating a Diff Instance.
    * @param {string} options.blobGlobalId This is used to help globally identify monaco instances that are created with the same blobPath.
+   * @param {Boolean} options.isDiff Flag to enable creation of a Diff Instance?
+   * @param {...*} options.instanceOptions Configuration options used to instantiate an instance.
+   * @returns {EditorInstance}
    */
   createInstance({
     el = undefined,
@@ -156,13 +119,18 @@ export default class SourceEditor {
     SourceEditor.prepareInstance(el);
 
     const createEditorFn = isDiff ? 'createDiffEditor' : 'create';
-    const instance = SourceEditor.convertMonacoToELInstance(
+    const instance = new EditorInstance(
       monacoEditor[createEditorFn].call(this, el, {
         ...this.options,
         ...instanceOptions,
       }),
+      this.extensionsStore,
     );
 
+    waitForCSSLoaded(() => {
+      instance.layout();
+    });
+
     let model;
     if (instanceOptions.model !== null) {
       model = SourceEditor.createEditorModel({
@@ -176,8 +144,8 @@ export default class SourceEditor {
     }
 
     instance.onDidDispose(() => {
-      SourceEditor.instanceRemoveFromRegistry(this, instance);
-      SourceEditor.instanceDisposeModels(this, instance, model);
+      instanceRemoveFromRegistry(this, instance);
+      instanceDisposeModels(this, instance, model);
     });
 
     this.instances.push(instance);
@@ -185,6 +153,11 @@ export default class SourceEditor {
     return instance;
   }
 
+  /**
+   * Create a Diff Instance
+   * @param {Object} args Options to be passed further down to createInstance() with the same signature
+   * @returns {EditorInstance}
+   */
   createDiffInstance(args) {
     return this.createInstance({
       ...args,
@@ -192,6 +165,10 @@ export default class SourceEditor {
     });
   }
 
+  /**
+   * Dispose global editor
+   * Automatically disposes all the instances registered for this editor
+   */
   dispose() {
     this.instances.forEach((instance) => instance.dispose());
   }

app/assets/javascripts/editor/source_editor_extension.js

@@ -5,10 +5,10 @@ export default class EditorExtension {
     if (typeof definition !== 'function') {
       throw new Error(EDITOR_EXTENSION_DEFINITION_ERROR);
     }
-    this.name = definition.name; // both class- and fn-based extensions have a name
     this.setupOptions = setupOptions;
     // eslint-disable-next-line new-cap
     this.obj = new definition();
+    this.extensionName = definition.extensionName || this.obj.extensionName; // both class- and fn-based extensions have a name
   }
 
   get api() {

app/assets/javascripts/editor/source_editor_instance.js

@@ -13,7 +13,7 @@
  * A Source Editor Extension
  * @typedef {Object} SourceEditorExtension
  * @property {Object} obj
- * @property {string} name
+ * @property {string} extensionName
  * @property {Object} api
  */
 
@@ -43,12 +43,12 @@ const utils = {
     }
   },
 
-  getStoredExtension: (extensionsStore, name) => {
+  getStoredExtension: (extensionsStore, extensionName) => {
     if (!extensionsStore) {
       logError(EDITOR_EXTENSION_STORE_IS_MISSING_ERROR);
       return undefined;
     }
-    return extensionsStore.get(name);
+    return extensionsStore.get(extensionName);
   },
 };
 
@@ -73,30 +73,18 @@ export default class EditorInstance {
         if (methodExtension) {
           const extension = extensionsStore.get(methodExtension);
 
-          return (...args) => extension.api[prop].call(seInstance, receiver, ...args);
+          if (typeof extension.api[prop] === 'function') {
+            return extension.api[prop].bind(extension.obj, receiver);
+          }
+
+          return extension.api[prop];
         }
         return Reflect.get(seInstance[prop] ? seInstance : target, prop, receiver);
       },
-      set(target, prop, value) {
-        Object.assign(seInstance, {
-          [prop]: value,
-        });
-        return true;
-      },
     };
     const instProxy = new Proxy(rootInstance, getHandler);
 
-    /**
-     * Main entry point to apply an extension to the instance
-     * @param {SourceEditorExtensionDefinition}
-     */
-    this.use = EditorInstance.useUnuse.bind(instProxy, extensionsStore, this.useExtension);
-
-    /**
-     * Main entry point to un-use an extension and remove it from the instance
-     * @param {SourceEditorExtension}
-     */
-    this.unuse = EditorInstance.useUnuse.bind(instProxy, extensionsStore, this.unuseExtension);
+    this.dispatchExtAction = EditorInstance.useUnuse.bind(instProxy, extensionsStore);
 
     return instProxy;
   }
@@ -141,7 +129,7 @@ export default class EditorInstance {
     }
 
     // Existing Extension Path
-    const existingExt = utils.getStoredExtension(extensionsStore, definition.name);
+    const existingExt = utils.getStoredExtension(extensionsStore, definition.extensionName);
     if (existingExt) {
       if (isEqual(extension.setupOptions, existingExt.setupOptions)) {
         return existingExt;
@@ -168,14 +156,14 @@ export default class EditorInstance {
    * @param {Map} extensionsStore - The global registry for the extension instances
    */
   registerExtension(extension, extensionsStore) {
-    const { name } = extension;
+    const { extensionName } = extension;
     const hasExtensionRegistered =
-      extensionsStore.has(name) &&
-      isEqual(extension.setupOptions, extensionsStore.get(name).setupOptions);
+      extensionsStore.has(extensionName) &&
+      isEqual(extension.setupOptions, extensionsStore.get(extensionName).setupOptions);
     if (hasExtensionRegistered) {
       return;
     }
-    extensionsStore.set(name, extension);
+    extensionsStore.set(extensionName, extension);
     const { obj: extensionObj } = extension;
     if (extensionObj.onUse) {
       extensionObj.onUse(this);
@@ -187,7 +175,7 @@ export default class EditorInstance {
    * @param {SourceEditorExtension} extension - Instance of Source Editor extension
    */
   registerExtensionMethods(extension) {
-    const { api, name } = extension;
+    const { api, extensionName } = extension;
 
     if (!api) {
       return;
@@ -197,7 +185,7 @@ export default class EditorInstance {
       if (this[prop]) {
         logError(sprintf(EDITOR_EXTENSION_NAMING_CONFLICT_ERROR, { prop }));
       } else {
-        this.methods[prop] = name;
+        this.methods[prop] = extensionName;
       }
     }, this);
   }
@@ -215,10 +203,10 @@ export default class EditorInstance {
     if (!extension) {
       throw new Error(EDITOR_EXTENSION_NOT_SPECIFIED_FOR_UNUSE_ERROR);
     }
-    const { name } = extension;
-    const existingExt = utils.getStoredExtension(extensionsStore, name);
+    const { extensionName } = extension;
+    const existingExt = utils.getStoredExtension(extensionsStore, extensionName);
     if (!existingExt) {
-      throw new Error(sprintf(EDITOR_EXTENSION_NOT_REGISTERED_ERROR, { name }));
+      throw new Error(sprintf(EDITOR_EXTENSION_NOT_REGISTERED_ERROR, { extensionName }));
     }
     const { obj: extensionObj } = existingExt;
     if (extensionObj.onBeforeUnuse) {
@@ -235,12 +223,12 @@ export default class EditorInstance {
    * @param {SourceEditorExtension} extension - Instance of Source Editor extension to un-use
    */
   unregisterExtensionMethods(extension) {
-    const { api, name } = extension;
+    const { api, extensionName } = extension;
     if (!api) {
       return;
     }
     Object.keys(api).forEach((method) => {
-      utils.removeExtFromMethod(method, name, this.methods);
+      utils.removeExtFromMethod(method, extensionName, this.methods);
     });
   }
 
@@ -259,6 +247,24 @@ export default class EditorInstance {
     monacoEditor.setModelLanguage(model, lang);
   }
 
+  /**
+   * Main entry point to apply an extension to the instance
+   * @param {SourceEditorExtensionDefinition[]|SourceEditorExtensionDefinition} extDefs - The extension(s) to use
+   * @returns {EditorExtension|*}
+   */
+  use(extDefs) {
+    return this.dispatchExtAction(this.useExtension, extDefs);
+  }
+
+  /**
+   * Main entry point to remove an extension to the instance
+   * @param {SourceEditorExtension[]|SourceEditorExtension} exts -
+   * @returns {*}
+   */
+  unuse(exts) {
+    return this.dispatchExtAction(this.unuseExtension, exts);
+  }
+
   /**
    * Get the methods returned by extensions.
    * @returns {Array}

app/assets/javascripts/ide/components/repo_editor.vue

@@ -7,6 +7,7 @@ import {
   EDITOR_CODE_INSTANCE_FN,
   EDITOR_DIFF_INSTANCE_FN,
 } from '~/editor/constants';
+import { SourceEditorExtension } from '~/editor/extensions/source_editor_extension_base';
 import { EditorWebIdeExtension } from '~/editor/extensions/source_editor_webide_ext';
 import SourceEditor from '~/editor/source_editor';
 import createFlash from '~/flash';
@@ -302,30 +303,32 @@ export default {
           ...instanceOptions,
           ...this.editorOptions,
         });
-
-        this.editor.use(
-          new EditorWebIdeExtension({
-            instance: this.editor,
-            modelManager: this.modelManager,
-            store: this.$store,
-            file: this.file,
-            options: this.editorOptions,
-          }),
-        );
+        this.editor.use([
+          {
+            definition: SourceEditorExtension,
+          },
+          {
+            definition: EditorWebIdeExtension,
+            setupOptions: {
+              modelManager: this.modelManager,
+              store: this.$store,
+              file: this.file,
+              options: this.editorOptions,
+            },
+          },
+        ]);
 
         if (
           this.fileType === MARKDOWN_FILE_TYPE &&
           this.editor?.getEditorType() === EDITOR_TYPE_CODE &&
           this.previewMarkdownPath
         ) {
-          import('~/editor/extensions/source_editor_markdown_ext')
-            .then(({ EditorMarkdownExtension: MarkdownExtension } = {}) => {
-              this.editor.use(
-                new MarkdownExtension({
-                  instance: this.editor,
-                  previewMarkdownPath: this.previewMarkdownPath,
-                }),
-              );
+          import('~/editor/extensions/source_editor_markdown_livepreview_ext')
+            .then(({ EditorMarkdownPreviewExtension: MarkdownLivePreview }) => {
+              this.editor.use({
+                definition: MarkdownLivePreview,
+                setupOptions: { previewMarkdownPath: this.previewMarkdownPath },
+              });
             })
             .catch((e) =>
               createFlash({

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

@@ -19,7 +19,7 @@ export default {
       if (this.glFeatures.schemaLinting) {
         const editorInstance = this.$refs.editor.getEditor();
 
-        editorInstance.use(new CiSchemaExtension({ instance: editorInstance }));
+        editorInstance.use({ definition: CiSchemaExtension });
         editorInstance.registerCiSchema();
       }
     },

spec/frontend/blob_edit/edit_blob_spec.js

 import waitForPromises from 'helpers/wait_for_promises';
 import EditBlob from '~/blob_edit/edit_blob';
+import { SourceEditorExtension } from '~/editor/extensions/source_editor_extension_base';
 import { FileTemplateExtension } from '~/editor/extensions/source_editor_file_template_ext';
 import { EditorMarkdownExtension } from '~/editor/extensions/source_editor_markdown_ext';
+import { EditorMarkdownPreviewExtension } from '~/editor/extensions/source_editor_markdown_livepreview_ext';
 import SourceEditor from '~/editor/source_editor';
 
 jest.mock('~/editor/source_editor');
-jest.mock('~/editor/extensions/source_editor_markdown_ext');
+jest.mock('~/editor/extensions/source_editor_extension_base');
 jest.mock('~/editor/extensions/source_editor_file_template_ext');
+jest.mock('~/editor/extensions/source_editor_markdown_ext');
+jest.mock('~/editor/extensions/source_editor_markdown_livepreview_ext');
 
 const PREVIEW_MARKDOWN_PATH = '/foo/bar/preview_markdown';
+const defaultExtensions = [
+  { definition: SourceEditorExtension },
+  { definition: FileTemplateExtension },
+];
+const markdownExtensions = [
+  { definition: EditorMarkdownExtension },
+  {
+    definition: EditorMarkdownPreviewExtension,
+    setupOptions: { previewMarkdownPath: PREVIEW_MARKDOWN_PATH },
+  },
+];
 
 describe('Blob Editing', () => {
   const useMock = jest.fn();
@@ -29,7 +44,9 @@ describe('Blob Editing', () => {
     jest.spyOn(SourceEditor.prototype, 'createInstance').mockReturnValue(mockInstance);
   });
   afterEach(() => {
+    SourceEditorExtension.mockClear();
     EditorMarkdownExtension.mockClear();
+    EditorMarkdownPreviewExtension.mockClear();
     FileTemplateExtension.mockClear();
   });
 
@@ -45,26 +62,22 @@ describe('Blob Editing', () => {
     await waitForPromises();
   };
 
-  it('loads FileTemplateExtension by default', async () => {
+  it('loads SourceEditorExtension and FileTemplateExtension by default', async () => {
     await initEditor();
-    expect(useMock).toHaveBeenCalledWith(expect.any(FileTemplateExtension));
-    expect(FileTemplateExtension).toHaveBeenCalledTimes(1);
+    expect(useMock).toHaveBeenCalledWith(defaultExtensions);
   });
 
   describe('Markdown', () => {
-    it('does not load MarkdownExtension by default', async () => {
+    it('does not load MarkdownExtensions by default', async () => {
       await initEditor();
       expect(EditorMarkdownExtension).not.toHaveBeenCalled();
+      expect(EditorMarkdownPreviewExtension).not.toHaveBeenCalled();
     });
 
     it('loads MarkdownExtension only for the markdown files', async () => {
       await initEditor(true);
-      expect(useMock).toHaveBeenCalledWith(expect.any(EditorMarkdownExtension));
-      expect(EditorMarkdownExtension).toHaveBeenCalledTimes(1);
-      expect(EditorMarkdownExtension).toHaveBeenCalledWith({
-        instance: mockInstance,
-        previewMarkdownPath: PREVIEW_MARKDOWN_PATH,
-      });
+      expect(useMock).toHaveBeenCalledTimes(2);
+      expect(useMock.mock.calls[1]).toEqual([markdownExtensions]);
     });
   });
 

spec/frontend/editor/helpers.js

+/* eslint-disable max-classes-per-file */
+
+// Helpers
+export const spyOnApi = (extension, spiesObj = {}) => {
+  const origApi = extension.api;
+  if (extension?.obj) {
+    jest.spyOn(extension.obj, 'provides').mockReturnValue({
+      ...origApi,
+      ...spiesObj,
+    });
+  }
+};
+
+// Dummy Extensions
 export class SEClassExtension {
+  static get extensionName() {
+    return 'SEClassExtension';
+  }
+
   // eslint-disable-next-line class-methods-use-this
   provides() {
     return {
@@ -10,6 +28,7 @@ export class SEClassExtension {
 
 export function SEFnExtension() {
   return {
+    extensionName: 'SEFnExtension',
     fnExtMethod: () => 'fn own method',
     provides: () => {
       return {
@@ -21,6 +40,7 @@ export function SEFnExtension() {
 
 export const SEConstExt = () => {
   return {
+    extensionName: 'SEConstExt',
     provides: () => {
       return {
         constExtMethod: () => 'const own method',
@@ -29,36 +49,39 @@ export const SEConstExt = () => {
   };
 };
 
-export function SEWithSetupExt() {
-  return {
-    onSetup: (instance, setupOptions = {}) => {
-      if (setupOptions && !Array.isArray(setupOptions)) {
-        Object.entries(setupOptions).forEach(([key, value]) => {
-          Object.assign(instance, {
-            [key]: value,
-          });
+export class SEWithSetupExt {
+  static get extensionName() {
+    return 'SEWithSetupExt';
+  }
+  // eslint-disable-next-line class-methods-use-this
+  onSetup(instance, setupOptions = {}) {
+    if (setupOptions && !Array.isArray(setupOptions)) {
+      Object.entries(setupOptions).forEach(([key, value]) => {
+        Object.assign(instance, {
+          [key]: value,
         });
-      }
-    },
-    provides: () => {
-      return {
-        returnInstanceAndProps: (instance, stringProp, objProp = {}) => {
-          return [stringProp, objProp, instance];
-        },
-        returnInstance: (instance) => {
-          return instance;
-        },
-        giveMeContext: () => {
-          return this;
-        },
-      };
-    },
-  };
+      });
+    }
+  }
+  provides() {
+    return {
+      returnInstanceAndProps: (instance, stringProp, objProp = {}) => {
+        return [stringProp, objProp, instance];
+      },
+      returnInstance: (instance) => {
+        return instance;
+      },
+      giveMeContext: () => {
+        return this;
+      },
+    };
+  }
 }
 
 export const conflictingExtensions = {
   WithInstanceExt: () => {
     return {
+      extensionName: 'WithInstanceExt',
       provides: () => {
         return {
           use: () => 'A conflict with instance',
@@ -69,6 +92,7 @@ export const conflictingExtensions = {
   },
   WithAnotherExt: () => {
     return {
+      extensionName: 'WithAnotherExt',
       provides: () => {
         return {
           shared: () => 'A conflict with extension',

spec/frontend/editor/source_editor_ci_schema_ext_spec.js

@@ -23,7 +23,7 @@ describe('~/editor/editor_ci_config_ext', () => {
       blobPath,
       blobContent: '',
     });
-    instance.use(new CiSchemaExtension());
+    instance.use({ definition: CiSchemaExtension });
   };
 
   beforeAll(() => {

spec/frontend/editor/source_editor_extension_spec.js

@@ -40,7 +40,7 @@ describe('Editor Extension', () => {
 
       expect(extension).toEqual(
         expect.objectContaining({
-          name: expectedName,
+          extensionName: expectedName,
           setupOptions,
         }),
       );

spec/frontend/editor/source_editor_instance_spec.js

@@ -32,11 +32,17 @@ describe('Source Editor Instance', () => {
   ];
 
   const fooFn = jest.fn();
+  const fooProp = 'foo';
   class DummyExt {
+    // eslint-disable-next-line class-methods-use-this
+    get extensionName() {
+      return 'DummyExt';
+    }
     // eslint-disable-next-line class-methods-use-this
     provides() {
       return {
         fooFn,
+        fooProp,
       };
     }
   }
@@ -64,7 +70,7 @@ describe('Source Editor Instance', () => {
   });
 
   describe('proxy', () => {
-    it('returns prop from an extension if extension provides it', () => {
+    it('returns a method from an extension if extension provides it', () => {
       seInstance = new SourceEditorInstance();
       seInstance.use({ definition: DummyExt });
 
@@ -73,6 +79,13 @@ describe('Source Editor Instance', () => {
       expect(fooFn).toHaveBeenCalled();
     });
 
+    it('returns a prop from an extension if extension provides it', () => {
+      seInstance = new SourceEditorInstance();
+      seInstance.use({ definition: DummyExt });
+
+      expect(seInstance.fooProp).toBe('foo');
+    });
+
     it.each`
       stringPropToPass | objPropToPass        | setupOptions
       ${undefined}     | ${undefined}         | ${undefined}
@@ -118,20 +131,20 @@ describe('Source Editor Instance', () => {
 
     it("correctly sets the context of the 'this' keyword for the extension's methods", () => {
       seInstance = new SourceEditorInstance();
-      seInstance.use({ definition: SEWithSetupExt });
+      const extension = seInstance.use({ definition: SEWithSetupExt });
 
-      expect(seInstance.giveMeContext().constructor).toEqual(SEWithSetupExt);
+      expect(seInstance.giveMeContext()).toEqual(extension.obj);
     });
 
     it('returns props from SE instance itself if no extension provides the prop', () => {
       seInstance = new SourceEditorInstance({
         use: fooFn,
       });
-      jest.spyOn(seInstance, 'use').mockImplementation(() => {});
-      expect(seInstance.use).not.toHaveBeenCalled();
+      const spy = jest.spyOn(seInstance.constructor.prototype, 'use').mockImplementation(() => {});
+      expect(spy).not.toHaveBeenCalled();
       expect(fooFn).not.toHaveBeenCalled();
       seInstance.use();
-      expect(seInstance.use).toHaveBeenCalled();
+      expect(spy).toHaveBeenCalled();
       expect(fooFn).not.toHaveBeenCalled();
     });
 

spec/frontend/editor/source_editor_markdown_ext_spec.js

@@ -9,7 +9,6 @@ describe('Markdown Extension for Source Editor', () => {
   let instance;
   let editorEl;
   let mockAxios;
-  const previewMarkdownPath = '/gitlab/fooGroup/barProj/preview_markdown';
   const firstLine = 'This is a';
   const secondLine = 'multiline';
   const thirdLine = 'string with some **markup**';
@@ -36,7 +35,7 @@ describe('Markdown Extension for Source Editor', () => {
       blobPath: markdownPath,
       blobContent: text,
     });
-    instance.use(new EditorMarkdownExtension({ instance, previewMarkdownPath }));
+    instance.use({ definition: EditorMarkdownExtension });
   });
 
   afterEach(() => {
@@ -164,13 +163,11 @@ describe('Markdown Extension for Source Editor', () => {
     });
 
     it('does not fail when only `toSelect` is supplied and fetches the text from selection', () => {
-      jest.spyOn(instance, 'getSelectedText');
       const toSelect = 'string';
       selectSecondAndThirdLines();
 
       instance.selectWithinSelection(toSelect);
 
-      expect(instance.getSelectedText).toHaveBeenCalled();
       expect(selectionToString()).toBe(`[3,1 -> 3,${toSelect.length + 1}]`);
     });
 

spec/frontend/editor/source_editor_markdown_livepreview_ext_spec.js

@@ -13,6 +13,7 @@ import SourceEditor from '~/editor/source_editor';
 import createFlash from '~/flash';
 import axios from '~/lib/utils/axios_utils';
 import syntaxHighlight from '~/syntax_highlight';
+import { spyOnApi } from './helpers';
 
 jest.mock('~/syntax_highlight');
 jest.mock('~/flash');
@@ -23,6 +24,7 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
   let editorEl;
   let panelSpy;
   let mockAxios;
+  let extension;
   const previewMarkdownPath = '/gitlab/fooGroup/barProj/preview_markdown';
   const firstLine = 'This is a';
   const secondLine = 'multiline';
@@ -47,8 +49,11 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
       blobPath: markdownPath,
       blobContent: text,
     });
-    instance.use(new EditorMarkdownPreviewExtension({ instance, previewMarkdownPath }));
-    panelSpy = jest.spyOn(EditorMarkdownPreviewExtension, 'togglePreviewPanel');
+    extension = instance.use({
+      definition: EditorMarkdownPreviewExtension,
+      setupOptions: { previewMarkdownPath },
+    });
+    panelSpy = jest.spyOn(extension.obj.constructor.prototype, 'togglePreviewPanel');
   });
 
   afterEach(() => {
@@ -57,14 +62,14 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     mockAxios.restore();
   });
 
-  it('sets up the instance', () => {
-    expect(instance.preview).toEqual({
+  it('sets up the preview on the instance', () => {
+    expect(instance.markdownPreview).toEqual({
       el: undefined,
       action: expect.any(Object),
       shown: false,
       modelChangeListener: undefined,
+      path: previewMarkdownPath,
     });
-    expect(instance.previewMarkdownPath).toBe(previewMarkdownPath);
   });
 
   describe('model language changes listener', () => {
@@ -72,14 +77,22 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     let actionSpy;
 
     beforeEach(async () => {
-      cleanupSpy = jest.spyOn(instance, 'cleanup');
-      actionSpy = jest.spyOn(instance, 'setupPreviewAction');
+      cleanupSpy = jest.fn();
+      actionSpy = jest.fn();
+      spyOnApi(extension, {
+        cleanup: cleanupSpy,
+        setupPreviewAction: actionSpy,
+      });
       await togglePreview();
     });
 
+    afterEach(() => {
+      jest.clearAllMocks();
+    });
+
     it('cleans up when switching away from markdown', () => {
-      expect(instance.cleanup).not.toHaveBeenCalled();
-      expect(instance.setupPreviewAction).not.toHaveBeenCalled();
+      expect(cleanupSpy).not.toHaveBeenCalled();
+      expect(actionSpy).not.toHaveBeenCalled();
 
       instance.updateModelLanguage(plaintextPath);
 
@@ -110,8 +123,12 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     let actionSpy;
 
     beforeEach(() => {
-      cleanupSpy = jest.spyOn(instance, 'cleanup');
-      actionSpy = jest.spyOn(instance, 'setupPreviewAction');
+      cleanupSpy = jest.fn();
+      actionSpy = jest.fn();
+      spyOnApi(extension, {
+        cleanup: cleanupSpy,
+        setupPreviewAction: actionSpy,
+      });
       instance.togglePreview();
     });
 
@@ -153,14 +170,17 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     });
 
     it('disposes the modelChange listener and does not fetch preview on content changes', () => {
-      expect(instance.preview.modelChangeListener).toBeDefined();
-      jest.spyOn(instance, 'fetchPreview');
+      expect(instance.markdownPreview.modelChangeListener).toBeDefined();
+      const fetchPreviewSpy = jest.fn();
+      spyOnApi(extension, {
+        fetchPreview: fetchPreviewSpy,
+      });
 
       instance.cleanup();
       instance.setValue('Foo Bar');
       jest.advanceTimersByTime(EXTENSION_MARKDOWN_PREVIEW_UPDATE_DELAY);
 
-      expect(instance.fetchPreview).not.toHaveBeenCalled();
+      expect(fetchPreviewSpy).not.toHaveBeenCalled();
     });
 
     it('removes the contextual menu action', () => {
@@ -172,13 +192,13 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     });
 
     it('toggles the `shown` flag', () => {
-      expect(instance.preview.shown).toBe(true);
+      expect(instance.markdownPreview.shown).toBe(true);
       instance.cleanup();
-      expect(instance.preview.shown).toBe(false);
+      expect(instance.markdownPreview.shown).toBe(false);
     });
 
     it('toggles the panel only if the preview is visible', () => {
-      const { el: previewEl } = instance.preview;
+      const { el: previewEl } = instance.markdownPreview;
       const parentEl = previewEl.parentElement;
 
       expect(previewEl).toBeVisible();
@@ -200,7 +220,7 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     it('toggles the layout only if the preview is visible', () => {
       const { width } = instance.getLayoutInfo();
 
-      expect(instance.preview.shown).toBe(true);
+      expect(instance.markdownPreview.shown).toBe(true);
 
       instance.cleanup();
 
@@ -234,13 +254,13 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     });
 
     it('puts the fetched content into the preview DOM element', async () => {
-      instance.preview.el = editorEl.parentElement;
+      instance.markdownPreview.el = editorEl.parentElement;
       await fetchPreview();
-      expect(instance.preview.el.innerHTML).toEqual(responseData);
+      expect(instance.markdownPreview.el.innerHTML).toEqual(responseData);
     });
 
     it('applies syntax highlighting to the preview content', async () => {
-      instance.preview.el = editorEl.parentElement;
+      instance.markdownPreview.el = editorEl.parentElement;
       await fetchPreview();
       expect(syntaxHighlight).toHaveBeenCalled();
     });
@@ -266,14 +286,17 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     });
 
     it('toggles preview when the action is triggered', () => {
-      jest.spyOn(instance, 'togglePreview').mockImplementation();
+      const togglePreviewSpy = jest.fn();
+      spyOnApi(extension, {
+        togglePreview: togglePreviewSpy,
+      });
 
-      expect(instance.togglePreview).not.toHaveBeenCalled();
+      expect(togglePreviewSpy).not.toHaveBeenCalled();
 
       const action = instance.getAction(EXTENSION_MARKDOWN_PREVIEW_ACTION_ID);
       action.run();
 
-      expect(instance.togglePreview).toHaveBeenCalled();
+      expect(togglePreviewSpy).toHaveBeenCalled();
     });
   });
 
@@ -283,39 +306,39 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
     });
 
     it('toggles preview flag on instance', () => {
-      expect(instance.preview.shown).toBe(false);
+      expect(instance.markdownPreview.shown).toBe(false);
 
       instance.togglePreview();
-      expect(instance.preview.shown).toBe(true);
+      expect(instance.markdownPreview.shown).toBe(true);
 
       instance.togglePreview();
-      expect(instance.preview.shown).toBe(false);
+      expect(instance.markdownPreview.shown).toBe(false);
     });
 
     describe('panel DOM element set up', () => {
       it('sets up an element to contain the preview and stores it on instance', () => {
-        expect(instance.preview.el).toBeUndefined();
+        expect(instance.markdownPreview.el).toBeUndefined();
 
         instance.togglePreview();
 
-        expect(instance.preview.el).toBeDefined();
-        expect(instance.preview.el.classList.contains(EXTENSION_MARKDOWN_PREVIEW_PANEL_CLASS)).toBe(
-          true,
-        );
+        expect(instance.markdownPreview.el).toBeDefined();
+        expect(
+          instance.markdownPreview.el.classList.contains(EXTENSION_MARKDOWN_PREVIEW_PANEL_CLASS),
+        ).toBe(true);
       });
 
       it('re-uses existing preview DOM element on repeated calls', () => {
         instance.togglePreview();
-        const origPreviewEl = instance.preview.el;
+        const origPreviewEl = instance.markdownPreview.el;
         instance.togglePreview();
 
-        expect(instance.preview.el).toBe(origPreviewEl);
+        expect(instance.markdownPreview.el).toBe(origPreviewEl);
       });
 
       it('hides the preview DOM element by default', () => {
         panelSpy.mockImplementation();
         instance.togglePreview();
-        expect(instance.preview.el.style.display).toBe('none');
+        expect(instance.markdownPreview.el.style.display).toBe('none');
       });
     });
 
@@ -350,9 +373,9 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
 
       it('toggles visibility of the preview DOM element', async () => {
         await togglePreview();
-        expect(instance.preview.el.style.display).toBe('block');
+        expect(instance.markdownPreview.el.style.display).toBe('block');
         await togglePreview();
-        expect(instance.preview.el.style.display).toBe('none');
+        expect(instance.markdownPreview.el.style.display).toBe('none');
       });
 
       describe('hidden preview DOM element', () => {
@@ -367,9 +390,9 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
         });
 
         it('stores disposable listener for model changes', async () => {
-          expect(instance.preview.modelChangeListener).toBeUndefined();
+          expect(instance.markdownPreview.modelChangeListener).toBeUndefined();
           await togglePreview();
-          expect(instance.preview.modelChangeListener).toBeDefined();
+          expect(instance.markdownPreview.modelChangeListener).toBeDefined();
         });
       });
 
@@ -386,7 +409,7 @@ describe('Markdown Live Preview Extension for Source Editor', () => {
 
         it('disposes the model change event listener', () => {
           const disposeSpy = jest.fn();
-          instance.preview.modelChangeListener = {
+          instance.markdownPreview.modelChangeListener = {
             dispose: disposeSpy,
           };
           instance.togglePreview();

spec/frontend/editor/source_editor_yaml_ext_spec.js

@@ -2,6 +2,10 @@ import { Document } from 'yaml';
 import SourceEditor from '~/editor/source_editor';
 import { YamlEditorExtension } from '~/editor/extensions/source_editor_yaml_ext';
 import { SourceEditorExtension } from '~/editor/extensions/source_editor_extension_base';
+import { spyOnApi } from 'jest/editor/helpers';
+
+let baseExtension;
+let yamlExtension;
 
 const getEditorInstance = (editorInstanceOptions = {}) => {
   setFixtures('<div id="editor"></div>');
@@ -16,7 +20,10 @@ const getEditorInstance = (editorInstanceOptions = {}) => {
 const getEditorInstanceWithExtension = (extensionOptions = {}, editorInstanceOptions = {}) => {
   setFixtures('<div id="editor"></div>');
   const instance = getEditorInstance(editorInstanceOptions);
-  instance.use(new YamlEditorExtension({ instance, ...extensionOptions }));
+  [baseExtension, yamlExtension] = instance.use([
+    { definition: SourceEditorExtension },
+    { definition: YamlEditorExtension, setupOptions: extensionOptions },
+  ]);
 
   // Remove the below once
   // https://gitlab.com/gitlab-org/gitlab/-/issues/325992 is resolved
@@ -29,19 +36,16 @@ const getEditorInstanceWithExtension = (extensionOptions = {}, editorInstanceOpt
 
 describe('YamlCreatorExtension', () => {
   describe('constructor', () => {
-    it('saves constructor options', () => {
+    it('saves setupOptions options on the extension, but does not expose those to instance', () => {
+      const highlightPath = 'foo';
       const instance = getEditorInstanceWithExtension({
-        highlightPath: 'foo',
+        highlightPath,
         enableComments: true,
       });
-      expect(instance).toEqual(
-        expect.objectContaining({
-          options: expect.objectContaining({
-            highlightPath: 'foo',
-            enableComments: true,
-          }),
-        }),
-      );
+      expect(yamlExtension.obj.highlightPath).toBe(highlightPath);
+      expect(yamlExtension.obj.enableComments).toBe(true);
+      expect(instance.highlightPath).toBeUndefined();
+      expect(instance.enableComments).toBeUndefined();
     });
 
     it('dumps values loaded with the model constructor options', () => {
@@ -55,7 +59,7 @@ describe('YamlCreatorExtension', () => {
     it('registers the onUpdate() function', () => {
       const instance = getEditorInstance();
       const onDidChangeModelContent = jest.spyOn(instance, 'onDidChangeModelContent');
-      instance.use(new YamlEditorExtension({ instance }));
+      instance.use({ definition: YamlEditorExtension });
       expect(onDidChangeModelContent).toHaveBeenCalledWith(expect.any(Function));
     });
 
@@ -82,21 +86,21 @@ describe('YamlCreatorExtension', () => {
     it('should call transformComments if enableComments is true', () => {
       const instance = getEditorInstanceWithExtension({ enableComments: true });
       const transformComments = jest.spyOn(YamlEditorExtension, 'transformComments');
-      YamlEditorExtension.initFromModel(instance, model);
+      instance.initFromModel(model);
       expect(transformComments).toHaveBeenCalled();
     });
 
     it('should not call transformComments if enableComments is false', () => {
       const instance = getEditorInstanceWithExtension({ enableComments: false });
       const transformComments = jest.spyOn(YamlEditorExtension, 'transformComments');
-      YamlEditorExtension.initFromModel(instance, model);
+      instance.initFromModel(model);
       expect(transformComments).not.toHaveBeenCalled();
     });
 
     it('should call setValue with the stringified model', () => {
       const instance = getEditorInstanceWithExtension();
       const setValue = jest.spyOn(instance, 'setValue');
-      YamlEditorExtension.initFromModel(instance, model);
+      instance.initFromModel(model);
       expect(setValue).toHaveBeenCalledWith(doc.toString());
     });
   });
@@ -240,26 +244,35 @@ foo:
     it("should call setValue with the stringified doc if the editor's value is empty", () => {
       const instance = getEditorInstanceWithExtension();
       const setValue = jest.spyOn(instance, 'setValue');
-      const updateValue = jest.spyOn(instance, 'updateValue');
+      const updateValueSpy = jest.fn();
+      spyOnApi(yamlExtension, {
+        updateValue: updateValueSpy,
+      });
       instance.setDoc(doc);
       expect(setValue).toHaveBeenCalledWith(doc.toString());
-      expect(updateValue).not.toHaveBeenCalled();
+      expect(updateValueSpy).not.toHaveBeenCalled();
     });
 
     it("should call updateValue with the stringified doc if the editor's value is not empty", () => {
       const instance = getEditorInstanceWithExtension({}, { value: 'asjkdhkasjdh' });
       const setValue = jest.spyOn(instance, 'setValue');
-      const updateValue = jest.spyOn(instance, 'updateValue');
+      const updateValueSpy = jest.fn();
+      spyOnApi(yamlExtension, {
+        updateValue: updateValueSpy,
+      });
       instance.setDoc(doc);
       expect(setValue).not.toHaveBeenCalled();
-      expect(updateValue).toHaveBeenCalledWith(doc.toString());
+      expect(updateValueSpy).toHaveBeenCalledWith(instance, doc.toString());
     });
 
     it('should trigger the onUpdate method', () => {
       const instance = getEditorInstanceWithExtension();
-      const onUpdate = jest.spyOn(instance, 'onUpdate');
+      const onUpdateSpy = jest.fn();
+      spyOnApi(yamlExtension, {
+        onUpdate: onUpdateSpy,
+      });
       instance.setDoc(doc);
-      expect(onUpdate).toHaveBeenCalled();
+      expect(onUpdateSpy).toHaveBeenCalled();
     });
   });
 
@@ -320,9 +333,12 @@ foo:
     it('calls highlight', () => {
       const highlightPath = 'foo';
       const instance = getEditorInstanceWithExtension({ highlightPath });
-      instance.highlight = jest.fn();
+      // Here we do not spy on the public API method of the extension, but rather
+      // the public method of the extension's instance.
+      // This is required based on how `onUpdate` works
+      const highlightSpy = jest.spyOn(yamlExtension.obj, 'highlight');
       instance.onUpdate();
-      expect(instance.highlight).toHaveBeenCalledWith(highlightPath);
+      expect(highlightSpy).toHaveBeenCalledWith(instance, highlightPath);
     });
   });
 
@@ -350,8 +366,12 @@ foo:
 
     beforeEach(() => {
       instance = getEditorInstanceWithExtension({ highlightPath: highlightPathOnSetup }, { value });
-      highlightLinesSpy = jest.spyOn(SourceEditorExtension, 'highlightLines');
-      removeHighlightsSpy = jest.spyOn(SourceEditorExtension, 'removeHighlights');
+      highlightLinesSpy = jest.fn();
+      removeHighlightsSpy = jest.fn();
+      spyOnApi(baseExtension, {
+        highlightLines: highlightLinesSpy,
+        removeHighlights: removeHighlightsSpy,
+      });
     });
 
     afterEach(() => {
@@ -361,7 +381,7 @@ foo:
     it('saves the highlighted path in highlightPath', () => {
       const path = 'foo.bar';
       instance.highlight(path);
-      expect(instance.options.highlightPath).toEqual(path);
+      expect(yamlExtension.obj.highlightPath).toEqual(path);
     });
 
     it('calls highlightLines with a number of lines', () => {
@@ -374,14 +394,14 @@ foo:
       instance.highlight(null);
       expect(removeHighlightsSpy).toHaveBeenCalledWith(instance);
       expect(highlightLinesSpy).not.toHaveBeenCalled();
-      expect(instance.options.highlightPath).toBeNull();
+      expect(yamlExtension.obj.highlightPath).toBeNull();
     });
 
     it('throws an error if path is invalid and does not change the highlighted path', () => {
       expect(() => instance.highlight('invalidPath[0]')).toThrow(
         'The node invalidPath[0] could not be found inside the document.',
       );
-      expect(instance.options.highlightPath).toEqual(highlightPathOnSetup);
+      expect(yamlExtension.obj.highlightPath).toEqual(highlightPathOnSetup);
       expect(highlightLinesSpy).not.toHaveBeenCalled();
       expect(removeHighlightsSpy).not.toHaveBeenCalled();
     });

spec/frontend/ide/components/repo_editor_spec.js

@@ -9,7 +9,7 @@ import waitUsingRealTimer from 'helpers/wait_using_real_timer';
 import { exampleConfigs, exampleFiles } from 'jest/ide/lib/editorconfig/mock_data';
 import { EDITOR_CODE_INSTANCE_FN, EDITOR_DIFF_INSTANCE_FN } from '~/editor/constants';
 import { EditorMarkdownExtension } from '~/editor/extensions/source_editor_markdown_ext';
-import { EditorWebIdeExtension } from '~/editor/extensions/source_editor_webide_ext';
+import { EditorMarkdownPreviewExtension } from '~/editor/extensions/source_editor_markdown_livepreview_ext';
 import SourceEditor from '~/editor/source_editor';
 import RepoEditor from '~/ide/components/repo_editor.vue';
 import {
@@ -23,6 +23,8 @@ import service from '~/ide/services';
 import { createStoreOptions } from '~/ide/stores';
 import axios from '~/lib/utils/axios_utils';
 import ContentViewer from '~/vue_shared/components/content_viewer/content_viewer.vue';
+import SourceEditorInstance from '~/editor/source_editor_instance';
+import { spyOnApi } from 'jest/editor/helpers';
 import { file } from '../helpers';
 
 const PREVIEW_MARKDOWN_PATH = '/foo/bar/preview_markdown';
@@ -101,6 +103,7 @@ describe('RepoEditor', () => {
   let createDiffInstanceSpy;
   let createModelSpy;
   let applyExtensionSpy;
+  let extensionsStore;
 
   const waitForEditorSetup = () =>
     new Promise((resolve) => {
@@ -120,6 +123,7 @@ describe('RepoEditor', () => {
     });
     await waitForPromises();
     vm = wrapper.vm;
+    extensionsStore = wrapper.vm.globalEditor.extensionsStore;
     jest.spyOn(vm, 'getFileData').mockResolvedValue();
     jest.spyOn(vm, 'getRawFileData').mockResolvedValue();
   };
@@ -127,28 +131,12 @@ describe('RepoEditor', () => {
   const findEditor = () => wrapper.find('[data-testid="editor-container"]');
   const findTabs = () => wrapper.findAll('.ide-mode-tabs .nav-links li');
   const findPreviewTab = () => wrapper.find('[data-testid="preview-tab"]');
-  const expectEditorMarkdownExtension = (shouldHaveExtension) => {
-    if (shouldHaveExtension) {
-      expect(applyExtensionSpy).toHaveBeenCalledWith(
-        wrapper.vm.editor,
-        expect.any(EditorMarkdownExtension),
-      );
-      // TODO: spying on extensions causes Jest to blow up, so we have to assert on
-      // the public property the extension adds, as opposed to the args passed to the ctor
-      expect(wrapper.vm.editor.previewMarkdownPath).toBe(PREVIEW_MARKDOWN_PATH);
-    } else {
-      expect(applyExtensionSpy).not.toHaveBeenCalledWith(
-        wrapper.vm.editor,
-        expect.any(EditorMarkdownExtension),
-      );
-    }
-  };
 
   beforeEach(() => {
     createInstanceSpy = jest.spyOn(SourceEditor.prototype, EDITOR_CODE_INSTANCE_FN);
     createDiffInstanceSpy = jest.spyOn(SourceEditor.prototype, EDITOR_DIFF_INSTANCE_FN);
     createModelSpy = jest.spyOn(monacoEditor, 'createModel');
-    applyExtensionSpy = jest.spyOn(SourceEditor, 'instanceApplyExtension');
+    applyExtensionSpy = jest.spyOn(SourceEditorInstance.prototype, 'use');
     jest.spyOn(service, 'getFileData').mockResolvedValue();
     jest.spyOn(service, 'getRawFileData').mockResolvedValue();
   });
@@ -275,14 +263,13 @@ describe('RepoEditor', () => {
     );
 
     it('installs the WebIDE extension', async () => {
-      const extensionSpy = jest.spyOn(SourceEditor, 'instanceApplyExtension');
       await createComponent();
-      expect(extensionSpy).toHaveBeenCalled();
-      Reflect.ownKeys(EditorWebIdeExtension.prototype)
-        .filter((fn) => fn !== 'constructor')
-        .forEach((fn) => {
-          expect(vm.editor[fn]).toBe(EditorWebIdeExtension.prototype[fn]);
-        });
+      expect(applyExtensionSpy).toHaveBeenCalled();
+      const ideExtensionApi = extensionsStore.get('EditorWebIde').api;
+      Reflect.ownKeys(ideExtensionApi).forEach((fn) => {
+        expect(vm.editor[fn]).toBeDefined();
+        expect(vm.editor.methods[fn]).toBe('EditorWebIde');
+      });
     });
 
     it.each`
@@ -301,7 +288,20 @@ describe('RepoEditor', () => {
       async ({ activeFile, viewer, shouldHaveMarkdownExtension } = {}) => {
         await createComponent({ state: { viewer }, activeFile });
 
-        expectEditorMarkdownExtension(shouldHaveMarkdownExtension);
+        if (shouldHaveMarkdownExtension) {
+          expect(applyExtensionSpy).toHaveBeenCalledWith({
+            definition: EditorMarkdownPreviewExtension,
+            setupOptions: { previewMarkdownPath: PREVIEW_MARKDOWN_PATH },
+          });
+          // TODO: spying on extensions causes Jest to blow up, so we have to assert on
+          // the public property the extension adds, as opposed to the args passed to the ctor
+          expect(wrapper.vm.editor.markdownPreview.path).toBe(PREVIEW_MARKDOWN_PATH);
+        } else {
+          expect(applyExtensionSpy).not.toHaveBeenCalledWith(
+            wrapper.vm.editor,
+            expect.any(EditorMarkdownExtension),
+          );
+        }
       },
     );
   });
@@ -329,18 +329,6 @@ describe('RepoEditor', () => {
       expect(vm.model).toBe(existingModel);
     });
 
-    it('adds callback methods', () => {
-      jest.spyOn(vm.editor, 'onPositionChange');
-      jest.spyOn(vm.model, 'onChange');
-      jest.spyOn(vm.model, 'updateOptions');
-
-      vm.setupEditor();
-
-      expect(vm.editor.onPositionChange).toHaveBeenCalledTimes(1);
-      expect(vm.model.onChange).toHaveBeenCalledTimes(1);
-      expect(vm.model.updateOptions).toHaveBeenCalledWith(vm.rules);
-    });
-
     it('updates state with the value of the model', () => {
       const newContent = 'As Gregor Samsa\n awoke one morning\n';
       vm.model.setValue(newContent);
@@ -366,53 +354,48 @@ describe('RepoEditor', () => {
 
   describe('editor updateDimensions', () => {
     let updateDimensionsSpy;
-    let updateDiffViewSpy;
     beforeEach(async () => {
       await createComponent();
-      updateDimensionsSpy = jest.spyOn(vm.editor, 'updateDimensions');
-      updateDiffViewSpy = jest.spyOn(vm.editor, 'updateDiffView').mockImplementation();
+      const ext = extensionsStore.get('EditorWebIde');
+      updateDimensionsSpy = jest.fn();
+      spyOnApi(ext, {
+        updateDimensions: updateDimensionsSpy,
+      });
     });
 
     it('calls updateDimensions only when panelResizing is false', async () => {
       expect(updateDimensionsSpy).not.toHaveBeenCalled();
-      expect(updateDiffViewSpy).not.toHaveBeenCalled();
       expect(vm.$store.state.panelResizing).toBe(false); // default value
 
       vm.$store.state.panelResizing = true;
       await vm.$nextTick();
 
       expect(updateDimensionsSpy).not.toHaveBeenCalled();
-      expect(updateDiffViewSpy).not.toHaveBeenCalled();
 
       vm.$store.state.panelResizing = false;
       await vm.$nextTick();
 
       expect(updateDimensionsSpy).toHaveBeenCalledTimes(1);
-      expect(updateDiffViewSpy).toHaveBeenCalledTimes(1);
 
       vm.$store.state.panelResizing = true;
       await vm.$nextTick();
 
       expect(updateDimensionsSpy).toHaveBeenCalledTimes(1);
-      expect(updateDiffViewSpy).toHaveBeenCalledTimes(1);
     });
 
     it('calls updateDimensions when rightPane is toggled', async () => {
       expect(updateDimensionsSpy).not.toHaveBeenCalled();
-      expect(updateDiffViewSpy).not.toHaveBeenCalled();
       expect(vm.$store.state.rightPane.isOpen).toBe(false); // default value
 
       vm.$store.state.rightPane.isOpen = true;
       await vm.$nextTick();
 
       expect(updateDimensionsSpy).toHaveBeenCalledTimes(1);
-      expect(updateDiffViewSpy).toHaveBeenCalledTimes(1);
 
       vm.$store.state.rightPane.isOpen = false;
       await vm.$nextTick();
 
       expect(updateDimensionsSpy).toHaveBeenCalledTimes(2);
-      expect(updateDiffViewSpy).toHaveBeenCalledTimes(2);
     });
   });
 
@@ -447,7 +430,11 @@ describe('RepoEditor', () => {
         activeFile: dummyFile.markdown,
       });
 
-      updateDimensionsSpy = jest.spyOn(vm.editor, 'updateDimensions');
+      const ext = extensionsStore.get('EditorWebIde');
+      updateDimensionsSpy = jest.fn();
+      spyOnApi(ext, {
+        updateDimensions: updateDimensionsSpy,
+      });
 
       changeViewMode(FILE_VIEW_MODE_PREVIEW);
       await vm.$nextTick();

spec/frontend/pipeline_editor/components/editor/text_editor_spec.js

 import { shallowMount } from '@vue/test-utils';
 
 import { EDITOR_READY_EVENT } from '~/editor/constants';
-import { SourceEditorExtension } from '~/editor/extensions/source_editor_extension_base';
 import TextEditor from '~/pipeline_editor/components/editor/text_editor.vue';
 import {
   mockCiConfigPath,
@@ -59,10 +58,6 @@ describe('Pipeline Editor | Text editor component', () => {
 
   const findEditor = () => wrapper.findComponent(MockSourceEditor);
 
-  beforeEach(() => {
-    SourceEditorExtension.deferRerender = jest.fn();
-  });
-
   afterEach(() => {
     wrapper.destroy();