Fix (engine): detecting restricted objects in firefox

packages/ckeditor5-engine/src/view/domconverter.ts

@@ -31,7 +31,8 @@ import {
 	isText,
 	isComment,
 	isValidAttributeName,
-	first
+	first,
+	env
 } from '@ckeditor/ckeditor5-utils';
 
 import type ViewNode from './node';
@@ -732,6 +733,11 @@ export default class DomConverter {
 	 * @returns View selection.
 	 */
 	public domSelectionToView( domSelection: DomSelection ): ViewSelection {
+		// https://github.com/ckeditor/ckeditor5/issues/9635
+		if ( isGeckoRestrictedDomSelection( domSelection ) ) {
+			return new ViewSelection( [] );
+		}
+
 		// DOM selection might be placed in fake selection container.
 		// If container contains fake selection - return corresponding view selection.
 		if ( domSelection.rangeCount === 1 ) {
@@ -1787,6 +1793,27 @@ function _logUnsafeElement( elementName: string ): void {
 	}
 }
 
+/**
+ * In certain cases, Firefox mysteriously assigns so called "restricted objects" to native DOM Range properties.
+ * Any attempt at accessing restricted object's properties causes errors.
+ * https://github.com/ckeditor/ckeditor5/issues/9635
+ */
+function isGeckoRestrictedDomSelection( domSelection: DomSelection ): boolean {
+	if ( !env.isGecko || !domSelection.rangeCount ) {
+		return false;
+	}
+
+	try {
+		const container = domSelection.getRangeAt( 0 ).startContainer;
+
+		Object.prototype.toString.call( container );
+	} catch ( error ) {
+		return true;
+	}
+
+	return false;
+}
+
 /**
  * Enum representing the type of the block filler.
  *

packages/ckeditor5-engine/tests/view/domconverter/dom-to-view.js

@@ -18,6 +18,7 @@ import { parse, stringify } from '../../../src/dev-utils/view';
 import testUtils from '@ckeditor/ckeditor5-core/tests/_utils/utils';
 import count from '@ckeditor/ckeditor5-utils/src/count';
 import createElement from '@ckeditor/ckeditor5-utils/src/dom/createelement';
+import env from '@ckeditor/ckeditor5-utils/src/env';
 
 describe( 'DomConverter', () => {
 	let converter, viewDocument;
@@ -1287,5 +1288,23 @@ describe( 'DomConverter', () => {
 
 			domContainer.remove();
 		} );
+
+		it( 'should detect "restricted objects" in Firefox DOM ranges and prevent an error being thrown', () => {
+			const domRangeStubWithRestrictedObject = document.createRange();
+
+			testUtils.sinon.stub( env, 'isGecko' ).value( true );
+
+			sinon.stub( domRangeStubWithRestrictedObject, 'startContainer' ).get( () => {
+				throw new Error( 'Permission denied to access property Symbol.toStringTag' );
+			} );
+
+			const domSelection = document.getSelection();
+
+			testUtils.sinon.stub( domSelection, 'getRangeAt' ).withArgs( 0 ).returns( domRangeStubWithRestrictedObject );
+
+			expect( () => {
+				converter.domSelectionToView( domSelection );
+			} ).to.not.throw();
+		} );
 	} );
 } );

packages/ckeditor5-engine/tests/view/observer/selectionobserver.js

@@ -3,7 +3,7 @@
  * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-oss-license
  */
 
-/* globals setTimeout, document, console, Event */
+/* globals setTimeout, document, console, Event, Selection */
 
 import testUtils from '@ckeditor/ckeditor5-core/tests/_utils/utils';
 
@@ -162,6 +162,34 @@ describe( 'SelectionObserver', () => {
 		changeDomSelection();
 	} );
 
+	describe( 'Restricted objects handling in Gecko', () => {
+		beforeEach( () => {
+			testUtils.sinon.stub( env, 'isGecko' ).value( true );
+		} );
+
+		it( 'should detect "restricted objects" in Firefox DOM ranges and prevent an error being thrown', done => {
+			const domRangeStubWithRestrictedObject = domDocument.createRange();
+
+			sinon.stub( domRangeStubWithRestrictedObject, 'startContainer' ).get( () => {
+				throw new Error( 'Permission denied to access property Symbol.toStringTag' );
+			} );
+
+			testUtils.sinon.stub( Selection.prototype, 'getRangeAt' ).returns( domRangeStubWithRestrictedObject );
+
+			expect( () => {
+				changeDomSelection();
+				setTimeout( done, 100 );
+			} ).to.not.throw();
+		} );
+
+		it( 'should do nothing in Firefox if the DOM selection is correct', done => {
+			expect( () => {
+				changeDomSelection();
+				setTimeout( done, 100 );
+			} ).to.not.throw();
+		} );
+	} );
+
 	it( 'should add only one #selectionChange listener to one document', done => {
 		// Add second roots to ensure that listener is added once.
 		createViewRoot( viewDocument, 'div', 'additional' );