CodeMirror 6 for VE 2017 wikitext editor

Add new temporary ext.CodeMirror.visualEditor.init RL module which
selects the temporary ext.CodeMirror.visualEditor.v6 or non-v6 based on
$wgCodeMirrorV6. This will allow us to deploy CM6 further.

As a result of this work, the core CodeMirror class now has knowledge
of ve.ui.Surface.

Other changes:
* Add Compartment for specialCharsExtension so it can be disabled in VE.
* Add option to mediaWikiLang() to disable template folding.
* Add support for RTL wikis where $wgCodeMirrorRTL is enabled.
* Make CodeMirror.logUsage() and setCodeMirrorPreference() static.
* Fix unit and linting tests.

Some code courtesy of Fandom, GPLv2-or-later; see:
https://github.com/Wikia/mediawiki-extensions-CodeMirror/commit/ef297c48c

Bug: T357482
Change-Id: I15453b33e77e1c1b4d5e5183e41e53d56ff14c3e

.eslintignore

@@ -1,4 +1,3 @@
 /resources/lib/
-/resources/dist/
 /vendor
 /docs

extension.json

@@ -278,6 +278,34 @@
 			"packageFiles": [
 				"codemirror.wikieditor.mediawiki.init.js"
 			]
+		},
+		"ext.CodeMirror.v6.visualEditor": {
+			"dependencies": [
+				"ext.visualEditor.mwcore",
+				"ext.visualEditor.mwmeta",
+				"mediawiki.api",
+				"user.options",
+				"ext.CodeMirror.v6"
+			],
+			"scripts": [
+				"ve-cm/ve.ui.CodeMirrorAction.v6.js",
+				"ve-cm/ve.ui.CodeMirrorTool.v6.js"
+			],
+			"styles": [
+				"ve-cm/ve.ui.CodeMirror.v6.less"
+			],
+			"messages": [
+				"codemirror-toggle-label"
+			]
+		},
+		"ext.CodeMirror.visualEditor.init": {
+			"packageFiles": [
+				"ve-cm/ve.ui.CodeMirror.init.js",
+				{
+					"name": "ext.CodeMirror.data.js",
+					"callback": "MediaWiki\\Extension\\CodeMirror\\DataScript::makeScript"
+				}
+			]
 		}
 	},
 	"ResourceFileModulePaths": {
@@ -333,7 +361,7 @@
 		},
 		"VisualEditor": {
 			"PluginModules": [
-				"ext.CodeMirror.visualEditor"
+				"ext.CodeMirror.visualEditor.init"
 			]
 		},
 		"EventLogging": {

includes/DataScript.php

@@ -58,8 +58,10 @@ class DataScript {
 
 		// initialize configuration
 		$config = [
+			'useV6' => $mwConfig->get( 'CodeMirrorV6' ),
 			'lineNumberingNamespaces' => $mwConfig->get( 'CodeMirrorLineNumberingNamespaces' ),
 			'templateFoldingNamespaces' => $mwConfig->get( 'CodeMirrorTemplateFoldingNamespaces' ),
+			'isSupportedRtlWiki' => $mwConfig->get( 'CodeMirrorRTL' ),
 			'pluginModules' => $registry->getAttribute( 'CodeMirrorPluginModules' ),
 			'tagModes' => $tagModes,
 			'tags' => array_fill_keys( $tagNames, true ),

jsdoc.json

@@ -44,7 +44,8 @@
 				"TagStyle": "https://codemirror.net/docs/ref/#language.TagStyle",
 				"Tooltip": "https://codemirror.net/docs/ref/#view.Tooltip",
 				"Tree": "https://lezer.codemirror.net/docs/ref/#common.Tree",
-				"ViewUpdate": "https://codemirror.net/docs/ref/#view.ViewUpdate"
+				"ViewUpdate": "https://codemirror.net/docs/ref/#view.ViewUpdate",
+				"ve.ui.Surface": "https://doc.wikimedia.org/visualeditor-standalone/master/ve.ui.Surface.html"
 			}
 		}
 	}

resources/.eslintrc.json

@@ -13,7 +13,8 @@
 		"commonjs": true
 	},
 	"globals": {
-		"Tree": "readonly"
+		"Tree": "readonly",
+		"ve": "readonly"
 	},
 	"rules": {
 		"max-len": "off",

resources/codemirror.js

@@ -37,10 +37,23 @@ class CodeMirror {
 	/**
 	 * Instantiate a new CodeMirror instance.
 	 *
-	 * @param {HTMLTextAreaElement|jQuery|string} textarea Textarea to add syntax highlighting to.
+	 * @param {HTMLTextAreaElement|jQuery|string|ve.ui.Surface} textarea Textarea to
+	 *   add syntax highlighting to.
 	 * @constructor
 	 */
 	constructor( textarea ) {
+		if ( textarea.constructor.name === 'VeUiMWWikitextSurface' ) {
+			/**
+			 * The VisualEditor surface CodeMirror is bound to.
+			 *
+			 * @type {ve.ui.Surface}
+			 */
+			this.surface = textarea;
+
+			// Let the content editable mimic the textarea.
+			// eslint-disable-next-line no-jquery/variable-pattern
+			textarea = this.surface.getView().$attachedRootNode;
+		}
 		/**
 		 * The textarea that CodeMirror is bound to.
 		 *
@@ -64,7 +77,9 @@ class CodeMirror {
 		 *
 		 * @type {boolean}
 		 */
-		this.readOnly = this.$textarea.prop( 'readonly' );
+		this.readOnly = this.surface ?
+			this.surface.getModel().isReadOnly() :
+			this.$textarea.prop( 'readonly' );
 		/**
 		 * The [edit recovery]{@link https://www.mediawiki.org/wiki/Manual:Edit_Recovery} handler.
 		 *
@@ -78,11 +93,17 @@ class CodeMirror {
 		 */
 		this.textSelection = null;
 		/**
-		 * Language direction extension.
+		 * Compartment for the language direction Extension.
 		 *
 		 * @type {Compartment}
 		 */
 		this.dirCompartment = new Compartment();
+		/**
+		 * Compartment for the special characters Extension.
+		 *
+		 * @type {Compartment}
+		 */
+		this.specialCharsCompartment = new Compartment();
 	}
 
 	/**
@@ -97,7 +118,7 @@ class CodeMirror {
 		const extensions = [
 			this.contentAttributesExtension,
 			this.phrasesExtension,
-			this.specialCharsExtension,
+			this.specialCharsCompartment.of( this.specialCharsExtension ),
 			this.heightExtension,
 			this.updateExtension,
 			this.bracketMatchingExtension,
@@ -187,7 +208,7 @@ class CodeMirror {
 	get heightExtension() {
 		return EditorView.theme( {
 			'&': {
-				height: `${ this.$textarea.outerHeight() }px`
+				height: this.surface ? '100%' : `${ this.$textarea.outerHeight() }px`
 			},
 			'.cm-scroller': {
 				overflow: 'auto'
@@ -205,7 +226,9 @@ class CodeMirror {
 	 */
 	get contentAttributesExtension() {
 		const classList = [];
-		// T245568: Sync text editor font preferences with CodeMirror
+		// T245568: Sync text editor font preferences with CodeMirror,
+		// but don't do this for the 2017 wikitext editor.
+		if ( !this.surface ) {
 			const fontClass = Array.from( this.$textarea[ 0 ].classList )
 				.find( ( style ) => style.startsWith( 'mw-editfont-' ) );
 			if ( fontClass ) {
@@ -219,6 +242,7 @@ class CodeMirror {
 			) {
 				classList.push( 'cm-mw-colorblind-colors' );
 			}
+		}
 
 		return [
 			// .cm-content element (the contenteditable area)
@@ -379,7 +403,9 @@ class CodeMirror {
 
 		// Set up the initial EditorState of CodeMirror with contents of the native textarea.
 		this.state = EditorState.create( {
-			doc: this.$textarea.textSelection( 'getContents' ),
+			doc: this.surface ?
+				this.surface.getDom() :
+				this.$textarea.textSelection( 'getContents' ),
 			extensions
 		} );
 
@@ -387,6 +413,7 @@ class CodeMirror {
 		this.addCodeMirrorToDom();
 
 		// Hide native textarea and sync CodeMirror contents upon submission.
+		if ( !this.surface ) {
 			this.$textarea.hide();
 			if ( this.$textarea[ 0 ].form ) {
 				this.$textarea[ 0 ].form.addEventListener( 'submit', () => {
@@ -397,6 +424,7 @@ class CodeMirror {
 					}
 				} );
 			}
+		}
 
 		// Register $.textSelection() on the .cm-editor element.
 		$( this.view.dom ).textSelection( 'register', this.cmTextSelection );
@@ -426,7 +454,9 @@ class CodeMirror {
 
 		this.view = new EditorView( {
 			state: this.state,
-			parent: this.$textarea.parent()[ 0 ]
+			parent: this.surface ?
+				this.surface.getView().$element[ 0 ] :
+				this.$textarea.parent()[ 0 ]
 		} );
 	}
 
@@ -443,7 +473,9 @@ class CodeMirror {
 		$( this.view.dom ).textSelection( 'unregister' );
 		this.$textarea.textSelection( 'unregister' );
 		this.$textarea.unwrap( '.ext-codemirror-wrapper' );
+		if ( !this.surface ) {
 			this.$textarea.val( this.view.state.doc.toString() );
+		}
 		this.view.destroy();
 		this.view = null;
 		this.$textarea.show();
@@ -470,8 +502,10 @@ class CodeMirror {
 	 *
 	 * @param {Object} data
 	 * @stable to call
+	 * @internal
+	 * @ignore
 	 */
-	logUsage( data ) {
+	static logUsage( data ) {
 		/* eslint-disable camelcase */
 		const event = Object.assign( {
 			session_token: mw.user.sessionId(),
@@ -491,7 +525,7 @@ class CodeMirror {
 	 * @param {boolean} prefValue True, if CodeMirror should be enabled by default, otherwise false.
 	 * @stable to call and override
 	 */
-	setCodeMirrorPreference( prefValue ) {
+	static setCodeMirrorPreference( prefValue ) {
 		// Skip for unnamed users
 		if ( !mw.user.isNamed() ) {
 			return;

resources/codemirror.mediawiki.js

@@ -1262,6 +1262,7 @@ class CodeMirrorModeMediaWiki {
  * @param {Object} [config] Configuration options for the MediaWiki mode.
  * @param {boolean} [config.bidiIsolation=false] Enable bidi isolation around HTML tags.
  *   This should generally always be enabled on RTL pages, but it comes with a performance cost.
+ * @param {boolean} [config.templateFolding=true] Enable template folding.
  * @param {Object|null} [mwConfig] Ignore; used only by unit tests.
  * @return {LanguageSupport}
  * @stable to call
@@ -1277,10 +1278,11 @@ const mediaWikiLang = ( config = { bidiIsolation: false }, mwConfig = null ) =>
 		)
 	) ];
 
-	// Add template folding if in supported namespace.
-	const templateFoldingNs = mwConfig.templateFoldingNamespaces;
 	// Set to [] to disable everywhere, or null to enable everywhere.
-	if ( !templateFoldingNs || templateFoldingNs.includes( mw.config.get( 'wgNamespaceNumber' ) ) ) {
+	const templateFoldingNs = mwConfig.templateFoldingNamespaces;
+	const shouldUseFolding = !templateFoldingNs || templateFoldingNs.includes( mw.config.get( 'wgNamespaceNumber' ) );
+	// Add template folding if in supported namespace.
+	if ( shouldUseFolding && ( config.templateFolding || config.templateFolding === undefined ) ) {
 		langExtension.push( templateFoldingExtension );
 	}
 

resources/codemirror.wikieditor.js

@@ -63,7 +63,7 @@ class CodeMirrorWikiEditor extends CodeMirror {
 	setCodeMirrorPreference( prefValue ) {
 		// Save state for function updateToolbarButton()
 		this.useCodeMirror = prefValue;
-		super.setCodeMirrorPreference( prefValue );
+		CodeMirror.setCodeMirrorPreference( prefValue );
 	}
 
 	/**
@@ -193,7 +193,7 @@ class CodeMirrorWikiEditor extends CodeMirror {
 		}
 		this.updateToolbarButton();
 
-		this.logUsage( {
+		CodeMirror.logUsage( {
 			editor: 'wikitext',
 			enabled: this.useCodeMirror,
 			toggled: false,
@@ -235,7 +235,7 @@ class CodeMirrorWikiEditor extends CodeMirror {
 		}
 		this.updateToolbarButton();
 
-		this.logUsage( {
+		CodeMirror.logUsage( {
 			editor: 'wikitext',
 			enabled: this.useCodeMirror,
 			toggled: true,

resources/ve-cm/ve.ui.CodeMirror.init.js

@@ -0,0 +1,7 @@
+require( '../../ext.CodeMirror.data.js' );
+
+if ( mw.config.get( 'extCodeMirrorConfig' ).useV6 ) {
+	mw.loader.load( 'ext.CodeMirror.v6.visualEditor' );
+} else {
+	mw.loader.load( 'ext.CodeMirror.visualEditor' );
+}

resources/ve-cm/ve.ui.CodeMirror.v6.less

@@ -0,0 +1,131 @@
+.ve-init-mw-desktopArticleTarget {
+	.cm-editor {
+		background: transparent;
+		border: 0;
+		box-sizing: border-box;
+		height: auto;
+		left: 0;
+		pointer-events: none;
+		// stylelint-disable-next-line declaration-no-important
+		position: absolute !important;
+		top: 0;
+		width: 100%;
+
+		// Skin specific paddings
+		.skin-vector & {
+			padding: 0 1rem;
+
+			@media screen and ( min-width: 982px ) {
+				.skin-vector-legacy& {
+					padding: 0 1.5rem;
+				}
+			}
+		}
+
+		.skin-minerva &,
+		.skin-monobook & {
+			padding: 0;
+		}
+	}
+
+	.cm-gutters {
+		background-color: transparent;
+		padding-right: 8px;
+		/* @noflip */
+		border-right: 0;
+	}
+
+	/* RTL rules need to apply to the content, not the interface language */
+	.cm-editor[ dir='rtl' ] .cm-gutters {
+		/* @noflip */
+		padding-left: 8px;
+		/* @noflip */
+		padding-right: initial;
+	}
+
+	.cm-focused {
+		outline: 0;
+	}
+
+	.cm-line {
+		padding: 0;
+	}
+
+	.cm-content {
+		padding: 0;
+	}
+
+	.cm-gutterElement {
+		// stylelint-disable-next-line declaration-no-important
+		padding: 0 3px 0 4px !important;
+	}
+
+	.CodeMirror-selected {
+		display: none;
+	}
+
+	// Ensure surfaces are using identical font rules
+	.cm-scroller,
+	.cm-scroller *,
+	.ve-ui-mwWikitextSurface .ve-ce-paragraphNode {
+		// The following are already set by mw-editfont-monospace on the parent: font-size, font-family
+		word-wrap: break-word;
+		// Support: Chrome<76, Firefox<69
+		// Fallback for browsers which don't support break-spaces
+		white-space: pre-wrap;
+		word-break: normal;
+		-webkit-hyphens: manual;
+		-moz-hyphens: manual;
+		-ms-hyphens: manual;
+		hyphens: manual;
+		-webkit-font-variant-ligatures: contextual;
+		font-variant-ligatures: contextual;
+
+		// Monospace fonts can change width when bold
+		// stylelint-disable-next-line declaration-no-important
+		font-weight: normal !important;
+		// T252965
+		line-break: initial;
+	}
+
+	.cm-mw-section-1,
+	.cm-mw-section-1 ~ *,
+	.cm-mw-section-2,
+	.cm-mw-section-2 ~ *,
+	/* TODO: remove overqualified `span` after CM6 upgrade */
+	span.cm-mw-section-3 ~ *,
+	span.cm-mw-section-4 ~ *,
+	span.cm-mw-section-5 ~ *,
+	span.cm-mw-section-6 ~ * {
+		font-size: inherit;
+		line-height: inherit;
+		font-weight: inherit;
+	}
+
+	.mw-content-ltr .ve-ce-paragraphNode {
+		margin-left: 6px !important; /* stylelint-disable-line declaration-no-important */
+	}
+
+	.mw-content-rtl .ve-ce-paragraphNode {
+		/* @noflip */
+		margin-right: 6px !important; /* stylelint-disable-line declaration-no-important */
+	}
+
+	.cm-activeLineGutter {
+		background-color: transparent;
+		border-right: 0;
+	}
+}
+
+.ve-ce-documentNode-codeEditor-hide {
+	opacity: 0.4;
+
+	&::selection,
+	& *::selection {
+		background: #6da9f7 !important; /* stylelint-disable-line declaration-no-important */
+	}
+}
+
+.ve-ce-documentNode-codeEditor-webkit-hide {
+	-webkit-text-fill-color: transparent;
+}

resources/ve-cm/ve.ui.CodeMirrorAction.v6.js

@@ -0,0 +1,253 @@
+/*!
+ * VisualEditor UserInterface CodeMirrorAction class.
+ */
+
+/**
+ * CodeMirror action
+ *
+ * @class
+ * @extends ve.ui.Action
+ * @constructor
+ * @param {ve.ui.Surface} surface Surface to act on
+ */
+ve.ui.CodeMirrorAction = function VeUiCodeMirrorAction() {
+	// Parent constructor
+	ve.ui.CodeMirrorAction.super.apply( this, arguments );
+};
+
+/* Inheritance */
+
+OO.inheritClass( ve.ui.CodeMirrorAction, ve.ui.Action );
+
+/* Static Properties */
+
+ve.ui.CodeMirrorAction.static.name = 'codeMirror';
+
+/**
+ * @inheritdoc
+ */
+ve.ui.CodeMirrorAction.static.methods = [ 'toggle' ];
+
+/* Methods */
+
+/**
+ * @method
+ * @param {boolean} [enable] State to force toggle to, inverts current state if undefined
+ * @return {boolean} Action was executed
+ */
+ve.ui.CodeMirrorAction.prototype.toggle = function ( enable ) {
+	const action = this,
+		surface = this.surface,
+		surfaceView = surface.getView(),
+		doc = surface.getModel().getDocument();
+
+	if ( !surface.mirror && enable !== false ) {
+		surface.mirror = true;
+		mw.loader.using( [
+			'ext.CodeMirror.v6',
+			'ext.CodeMirror.v6.lib',
+			'ext.CodeMirror.v6.mode.mediawiki',
+			'jquery.client'
+		] ).then( ( require ) => {
+			const CodeMirror = require( 'ext.CodeMirror.v6' );
+			const codeMirrorLib = require( 'ext.CodeMirror.v6.lib' );
+			const mediawikiLang = require( 'ext.CodeMirror.v6.mode.mediawiki' );
+
+			if ( !surface.mirror ) {
+				// Action was toggled to false since promise started
+				return;
+			}
+
+			// The VE/CM overlay technique only works with monospace fonts
+			// (as we use width-changing bold as a highlight) so revert any editfont user preference
+			surfaceView.$element.removeClass( 'mw-editfont-sans-serif mw-editfont-serif' )
+				.addClass( 'mw-editfont-monospace' );
+
+			if ( mw.user.options.get( 'usecodemirror-colorblind' ) ) {
+				surfaceView.$element.addClass( 'cm-mw-colorblind-colors' );
+			}
+
+			surface.mirror = new CodeMirror( surface );
+			const lineHeightExtension = codeMirrorLib.EditorView.theme( {
+				'.cm-content': {
+					lineHeight: 1.5
+				}
+			} );
+
+			const profile = $.client.profile();
+			const supportsTransparentText = 'WebkitTextFillColor' in document.body.style &&
+				// Disable on Firefox+OSX (T175223)
+				!( profile.layout === 'gecko' && profile.platform === 'mac' );
+
+			surfaceView.$documentNode.addClass(
+				supportsTransparentText ?
+					've-ce-documentNode-codeEditor-webkit-hide' :
+					've-ce-documentNode-codeEditor-hide'
+			);
+
+			// TODO: pass bidiIsolation option to mediawikiLang() when it's more stable.
+			surface.mirror.initialize( surface.mirror.defaultExtensions.concat( mediawikiLang( {
+				templateFolding: false
+			} ), lineHeightExtension ) );
+
+			// Disable the Extension that highlights special characters.
+			surface.mirror.view.dispatch( {
+				effects: surface.mirror.specialCharsCompartment.reconfigure(
+					codeMirrorLib.EditorView.editorAttributes.of( [] )
+				)
+			} );
+
+			// Account for the gutter width in the margin.
+			action.updateGutterWidth( doc.getDir() );
+
+			// Set focus on the surface view.
+			surfaceView.focus();
+
+			/* Events */
+
+			// As the action is regenerated each time, we need to store bound listeners
+			// in the mirror for later disconnection.
+			surface.mirror.veTransactionListener = action.onDocumentPrecommit.bind( action );
+			surface.mirror.veSelectListener = action.onSelect.bind( action );
+			surface.mirror.vePositionListener = action.onPosition.bind( action );
+
+			doc.on( 'precommit', surface.mirror.veTransactionListener );
+			surface.getModel().on( 'select', surface.mirror.veSelectListener );
+			surfaceView.on( 'position', surface.mirror.vePositionListener );
+		} );
+	} else if ( surface.mirror && enable !== true ) {
+		if ( surface.mirror !== true ) {
+			surfaceView.off( 'position', surface.mirror.vePositionListener );
+			doc.off( 'precommit', surface.mirror.veTransactionListener );
+			surface.getModel().off( 'select', surface.mirror.veSelectListener );
+
+			// Restore edit-font
+			// eslint-disable-next-line mediawiki/class-doc
+			surfaceView.$element.removeClass( 'mw-editfont-monospace' )
+				.addClass( 'mw-editfont-' + mw.user.options.get( 'editfont' ) );
+
+			surfaceView.$documentNode.removeClass(
+				've-ce-documentNode-codeEditor-webkit-hide',
+				've-ce-documentNode-codeEditor-hide'
+			);
+			// Reset gutter.
+			surfaceView.$documentNode.css( {
+				'margin-left': '',
+				'margin-right': ''
+			} );
+
+			// Set focus on the surface view.
+			surface.getView().focus();
+
+			surface.mirror.destroy();
+			surface.mirror.view = null;
+		}
+
+		surface.mirror = null;
+	}
+
+	return true;
+};
+
+/**
+ * Update margins to account for the CodeMirror gutter.
+ *
+ * @param {string} dir Document direction
+ */
+ve.ui.CodeMirrorAction.prototype.updateGutterWidth = function ( dir ) {
+	const guttersWidth = this.surface.mirror.view.dom.querySelector( '.cm-gutters' ).offsetWidth;
+	this.surface.getView().$documentNode.css( {
+		'margin-left': dir === 'rtl' ? 0 : guttersWidth - 6,
+		'margin-right': dir === 'rtl' ? guttersWidth - 6 : 0
+	} );
+	// Also update width of .cm-content due to apparent Chromium bug.
+	this.surface.mirror.view.contentDOM.style.width = 'calc(100% - ' + ( guttersWidth + 1 ) + 'px)';
+};
+
+/**
+ * Mirror document directionality changes to CodeMirror.
+ */
+ve.ui.CodeMirrorAction.prototype.onPosition = function () {
+	const codeMirrorLib = require( 'ext.CodeMirror.v6.lib' );
+	const veDir = this.surface.getView().getDocument().getDir();
+	const cmView = this.surface.mirror.view;
+	const cmDir = cmView.textDirection === codeMirrorLib.Direction.LTR ? 'ltr' : 'rtl';
+	if ( veDir !== cmDir ) {
+		cmView.dispatch( {
+			effects: this.surface.mirror.dirCompartment.reconfigure(
+				codeMirrorLib.EditorView.editorAttributes.of( { dir: veDir } )
+			)
+		} );
+		this.updateGutterWidth( veDir );
+	}
+};
+
+/**
+ * Handle select events from the surface model
+ *
+ * @param {ve.dm.Selection} selection
+ */
+ve.ui.CodeMirrorAction.prototype.onSelect = function ( selection ) {
+	const range = selection.getCoveringRange();
+
+	// Do not re-trigger bracket matching as long as something is selected
+	if ( !range || !range.isCollapsed() ) {
+		return;
+	}
+
+	const offset = this.surface.getModel().getSourceOffsetFromOffset( range.from );
+
+	this.surface.mirror.view.dispatch( {
+		selection: {
+			anchor: offset,
+			head: offset
+		}
+	} );
+};
+
+/**
+ * Handle precommit events from the document.
+ *
+ * The document is still in it's 'old' state before the transaction
+ * has been applied at this point.
+ *
+ * @param {ve.dm.Transaction} tx
+ */
+ve.ui.CodeMirrorAction.prototype.onDocumentPrecommit = function ( tx ) {
+	const replacements = [],
+		action = this,
+		store = this.surface.getModel().getDocument().getStore();
+	let offset = 0;
+
+	const documentNode = document.querySelector( '.ve-ce-documentNode' );
+	const guttersWidth = parseInt( document.querySelector( '.cm-gutters' ).offsetWidth );
+	const marginProperty = this.surface.getModel().getDocument().getDir() === 'rtl' ? 'margin-right' : 'margin-left';
+	// XXX: Why 6px?
+	documentNode.style[ marginProperty ] = ( guttersWidth - 6 ) + 'px';
+
+	tx.operations.forEach( ( op ) => {
+		if ( op.type === 'retain' ) {
+			offset += op.length;
+		} else if ( op.type === 'replace' ) {
+			replacements.push( {
+				from: action.surface.getModel().getSourceOffsetFromOffset( offset ),
+				to: action.surface.getModel().getSourceOffsetFromOffset( offset + op.remove.length ),
+				insert: new ve.dm.ElementLinearData( store, op.insert ).getSourceText()
+			} );
+			offset += op.remove.length;
+		}
+	} );
+
+	// Apply replacements in reverse to avoid having to shift offsets
+	for ( let i = replacements.length - 1; i >= 0; i-- ) {
+		this.surface.mirror.view.dispatch( { changes: replacements[ i ] } );
+	}
+};
+
+/* Registration */
+
+// eslint-disable-next-line no-jquery/no-global-selector
+const isRTL = $( '.mw-body-content .mw-parser-output' ).attr( 'dir' ) === 'rtl';
+if ( !isRTL || ( isRTL && mw.config.get( 'extCodeMirrorConfig' ).isSupportedRtlWiki ) ) {
+	ve.ui.actionFactory.register( ve.ui.CodeMirrorAction );
+}

resources/ve-cm/ve.ui.CodeMirrorTool.v6.js

@@ -0,0 +1,93 @@
+/**
+ * VisualEditor UserInterface CodeMirror tool.
+ *
+ * @class
+ * @abstract
+ * @extends ve.ui.Tool
+ * @constructor
+ * @param {OO.ui.ToolGroup} toolGroup
+ * @param {Object} [config] Configuration options
+ */
+ve.ui.CodeMirrorTool = function VeUiCodeMirrorTool() {
+	// Parent constructor
+	ve.ui.CodeMirrorTool.super.apply( this, arguments );
+
+	this.extCodeMirror = require( 'ext.CodeMirror.v6' );
+
+	// Events
+	this.toolbar.connect( this, { surfaceChange: 'onSurfaceChange' } );
+};
+
+/* Inheritance */
+
+OO.inheritClass( ve.ui.CodeMirrorTool, ve.ui.Tool );
+
+/* Static properties */
+
+ve.ui.CodeMirrorTool.static.name = 'codeMirror';
+ve.ui.CodeMirrorTool.static.autoAddToCatchall = false;
+ve.ui.CodeMirrorTool.static.title = OO.ui.deferMsg( 'codemirror-toggle-label' );
+ve.ui.CodeMirrorTool.static.icon = 'highlight';
+ve.ui.CodeMirrorTool.static.group = 'utility';
+ve.ui.CodeMirrorTool.static.commandName = 'codeMirror';
+ve.ui.CodeMirrorTool.static.deactivateOnSelect = false;
+
+/**
+ * @inheritdoc
+ */
+ve.ui.CodeMirrorTool.prototype.onSelect = function () {
+	// Parent method
+	ve.ui.CodeMirrorTool.super.prototype.onSelect.apply( this, arguments );
+
+	const useCodeMirror = !!this.toolbar.surface.mirror;
+	this.setActive( useCodeMirror );
+
+	this.extCodeMirror.setCodeMirrorPreference( useCodeMirror );
+	this.extCodeMirror.logUsage( {
+		editor: 'wikitext-2017',
+		enabled: useCodeMirror,
+		toggled: true,
+		// eslint-disable-next-line camelcase
+		edit_start_ts_ms: ( this.toolbar.target.startTimeStamp * 1000 ) || 0
+	} );
+};
+
+/**
+ * @inheritdoc
+ */
+ve.ui.CodeMirrorTool.prototype.onSurfaceChange = function ( oldSurface, newSurface ) {
+	const isDisabled = newSurface.getMode() !== 'source';
+
+	this.setDisabled( isDisabled );
+	if ( !isDisabled ) {
+		const command = this.getCommand();
+		const surface = this.toolbar.getSurface();
+		const useCodeMirror = mw.user.options.get( 'usecodemirror' ) > 0;
+		command.execute( surface, [ useCodeMirror ] );
+		this.setActive( useCodeMirror );
+
+		if ( this.toolbar.target.startTimeStamp ) {
+			this.extCodeMirror.logUsage( {
+				editor: 'wikitext-2017',
+				enabled: useCodeMirror,
+				toggled: false,
+				// eslint-disable-next-line camelcase
+				edit_start_ts_ms: ( this.toolbar.target.startTimeStamp * 1000 ) || 0
+			} );
+		}
+	}
+};
+
+ve.ui.CodeMirrorTool.prototype.onUpdateState = function () {};
+
+/* Registration */
+
+ve.ui.toolFactory.register( ve.ui.CodeMirrorTool );
+
+/* Command */
+
+ve.ui.commandRegistry.register(
+	new ve.ui.Command(
+		'codeMirror', 'codeMirror', 'toggle'
+	)
+);

tests/jest/codemirror.test.js

@@ -60,7 +60,7 @@ describe( 'initialize', () => {
 
 describe( 'logUsage', () => {
 	it( 'should track usage of CodeMirror with the correct data', () => {
-		cm.logUsage( {
+		CodeMirror.logUsage( {
 			editor: 'wikitext',
 			enabled: true,
 			toggled: false
@@ -85,14 +85,14 @@ describe( 'setCodeMirrorPreference', () => {
 	} );
 
 	it( 'should save using the API with the correct value', () => {
-		cm.setCodeMirrorPreference( true );
+		CodeMirror.setCodeMirrorPreference( true );
 		expect( mw.Api.prototype.saveOption ).toHaveBeenCalledWith( 'usecodemirror', 1 );
 		expect( mw.user.options.set ).toHaveBeenCalledWith( 'usecodemirror', 1 );
 	} );
 
 	it( 'should not save preferences if the user is not named', () => {
 		mw.user.isNamed = jest.fn().mockReturnValue( false );
-		cm.setCodeMirrorPreference( true );
+		CodeMirror.setCodeMirrorPreference( true );
 		expect( mw.Api.prototype.saveOption ).toHaveBeenCalledTimes( 0 );
 		expect( mw.user.options.set ).toHaveBeenCalledTimes( 0 );
 	} );

tests/phpunit/DataScriptTest.php

@@ -15,6 +15,9 @@ class DataScriptTest extends \MediaWikiIntegrationTestCase {
 
 		$script = DataScript::makeScript( $context );
 		$this->assertStringContainsString( '"extCodeMirrorConfig":', $script );
+		$this->assertStringContainsString( '"lineNumberingNamespaces":', $script );
+		$this->assertStringContainsString( '"templateFoldingNamespaces":', $script );
+		$this->assertStringContainsString( '"isSupportedRtlWiki":', $script );
 		$this->assertStringContainsString( '"pluginModules":', $script );
 		$this->assertStringContainsString( '"tagModes":', $script );
 		$this->assertStringContainsString( '"tags":', $script );