add eslint rule to disallow look behind regex feature, ignore in git and markdown fyi @lszomoru, @mjbvz

.eslintignore

@@ -9,6 +9,7 @@
 **/extensions/markdown-language-features/media/**
 **/extensions/markdown-language-features/notebook-out/**
 **/extensions/markdown-math/notebook-out/**
+**/extensions/notebook-renderers/renderer-out/index.js
 **/extensions/simple-browser/media/index.js
 **/extensions/typescript-language-features/test-workspace/**
 **/extensions/vscode-api-tests/testWorkspace/**

.eslintrc.json

@@ -194,6 +194,7 @@
 				"src/**/*.ts"
 			],
 			"rules": {
+				"code-no-look-behind-regex": "warn",
 				"code-import-patterns": [
 					"warn",
 					{

build/lib/eslint/code-no-look-behind-regex.js

@@ -0,0 +1,42 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+'use strict';
+Object.defineProperty(exports, "__esModule", { value: true });
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+const _positiveLookBehind = /\(\?<=.+/;
+const _negativeLookBehind = /\(\?<!.+/;
+function _containsLookBehind(pattern) {
+    if (typeof pattern !== 'string') {
+        return false;
+    }
+    return _positiveLookBehind.test(pattern) || _negativeLookBehind.test(pattern);
+}
+module.exports = {
+    create(context) {
+        return {
+            // /.../
+            ['Literal[regex]']: (node) => {
+                const pattern = node.regex?.pattern;
+                if (_containsLookBehind(pattern)) {
+                    context.report({
+                        node,
+                        message: 'Look behind assertions are not yet supported in all browsers'
+                    });
+                }
+            },
+            // new Regex("...")
+            ['NewExpression[callee.name="RegExp"] Literal']: (node) => {
+                if (_containsLookBehind(node.value)) {
+                    context.report({
+                        node,
+                        message: 'Look behind assertions are not yet supported in all browsers'
+                    });
+                }
+            }
+        };
+    }
+};

build/lib/eslint/code-no-look-behind-regex.ts

@@ -0,0 +1,52 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+'use strict';
+
+import * as eslint from 'eslint';
+import { TSESTree } from '@typescript-eslint/experimental-utils';
+import * as ESTree from 'estree';
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+const _positiveLookBehind = /\(\?<=.+/;
+const _negativeLookBehind = /\(\?<!.+/;
+
+function _containsLookBehind(pattern: string | unknown): boolean {
+	if (typeof pattern !== 'string') {
+		return false;
+	}
+	return _positiveLookBehind.test(pattern) || _negativeLookBehind.test(pattern);
+}
+
+module.exports = {
+
+	create(context: eslint.Rule.RuleContext) {
+		return {
+			// /.../
+			['Literal[regex]']: (node: any) => {
+				type RegexLiteral = TSESTree.Literal & { regex: { pattern: string; flags: string } };
+				const pattern = (<RegexLiteral>node).regex?.pattern;
+				if (_containsLookBehind(pattern)) {
+					context.report({
+						node,
+						message: 'Look behind assertions are not yet supported in all browsers'
+					});
+				}
+			},
+			// new Regex("...")
+			['NewExpression[callee.name="RegExp"] Literal']: (node: ESTree.Literal) => {
+				if (_containsLookBehind(node.value)) {
+					context.report({
+						node,
+						message: 'Look behind assertions are not yet supported in all browsers'
+					});
+				}
+			}
+		};
+	}
+};

extensions/git/src/git.ts

@@ -480,6 +480,7 @@ export class Git {
 			const repoUri = Uri.file(repoPath);
 			const pathUri = Uri.file(repositoryPath);
 			if (repoUri.authority.length !== 0 && pathUri.authority.length === 0) {
+				// eslint-disable-next-line code-no-look-behind-regex
 				let match = /(?<=^\/?)([a-zA-Z])(?=:\/)/.exec(pathUri.path);
 				if (match !== null) {
 					const [, letter] = match;

extensions/markdown-language-features/src/features/documentLinkProvider.ts

@@ -104,6 +104,7 @@ export function stripAngleBrackets(link: string) {
 }
 
 const linkPattern = /(\[((!\[[^\]]*?\]\(\s*)([^\s\(\)]+?)\s*\)\]|(?:\\\]|[^\]])*\])\(\s*)(([^\s\(\)]|\([^\s\(\)]*?\))+)\s*(".*?")?\)/g;
+// eslint-disable-next-line code-no-look-behind-regex
 const referenceLinkPattern = /((?<=^|[^\]])\[((?:\\\]|[^\]])+)\])(?!:)(?:[^\[]|$|\[\s*?([^\s\]]*?)\])/g;
 const definitionPattern = /^([\t ]*\[(?!\^)((?:\\\]|[^\]])+)\]:\s*)([^<]\S*|<[^>]+>)/gm;
 const inlineCodePattern = /(?:^|[^`])(`+)(?:.+?|.*?(?:(?:\r?\n).+?)*?)(?:\r?\n)?\1(?:$|[^`])/gm;

extensions/markdown-language-features/src/test/inMemoryDocument.ts

@@ -48,6 +48,7 @@ export class InMemoryDocument implements vscode.TextDocument {
 		const before = this._contents.slice(0, offset);
 		const newLines = before.match(/\r\n|\n/g);
 		const line = newLines ? newLines.length : 0;
+		// eslint-disable-next-line code-no-look-behind-regex
 		const preCharacters = before.match(/(?<=\r\n|\n|^).*$/g);
 		return new vscode.Position(line, preCharacters ? preCharacters[0].length : 0);
 	}