feat(no-regexp-lookbehind): add no-regexp-lookbehind

docs/no-regexp-lookbehind.md

@@ -0,0 +1,20 @@
+# no-regexp-lookbehind
+
+This prevents the use of the RegExp lookbehind feature
+
+```js
+/(?<=a>)b/
+
+new RegExp("/(?<=a)b")
+```
+
+These will not be allowed because they are not supported in the following browsers:
+
+ - Edge < 79
+ - Safari (any version at the time of writing)
+ - Firefox (any version at the time of writing)
+ - Chrome < 62
+
+## What is the Fix?
+
+You may be able to rewrite your experession using (Negative) Lookaheads, but if not then there is no solution for this, aside from pulling in a custom RegExp library.

lib/index.js

@@ -41,6 +41,7 @@ createRule('no-async-iteration', 'edge < 79, safari < 12, firefox < 57, chrome <
 createRule('no-async-generator', 'edge < 79, safari < 12, firefox < 57, chrome < 63', 'disallow the use of async generator functions')
 createRule('no-object-rest-spread', 'edge < 79, safari < 11.1, firefox < 55, chrome < 60', 'disallow object rest/spread patterns')
 createRule('no-regexp-s-flag', 'edge < 79, safari < 11.1, firefox > 0, chrome < 62', 'disallow the use of the RegExp `s` flag')
+createRule('no-regexp-lookbehind', 'edge < 79, safari > 0, firefox > 0, chrome < 62', 'disallow the use of RegExp lookbehinds')
 
 // ES2019
 createRule('no-optional-catch', 'edge < 79, safari < 11.1, firefox < 58, chrome < 66', 'always require catch() to have an argument')
@@ -61,7 +62,7 @@ createRule('no-do-expression', 'edge > 0, safari > 0, firefox > 0, chrome > 0',
 createRule('no-bind-operator', 'edge > 0, safari > 0, firefox > 0, chrome > 0', 'disallow the :: bind operator')
 createRule('no-pipeline-operator', 'edge > 0, safari > 0, firefox > 0, chrome > 0', 'disallow the > pipeline operator')
 
-const v2breakingRules = new Set(['no-nullish-coalescing', 'no-bigint'])
+const v2breakingRules = new Set(['no-nullish-coalescing', 'no-bigint', 'no-regexp-lookbehind'])
 
 module.exports.configs.recommended = {
   plugins: ['escompat'],

lib/rules/no-regexp-lookbehind.js

@@ -0,0 +1,28 @@
+const hasLookbehind = s => s.includes('(?<=') || s.includes('(?<!)')
+
+module.exports = (context, badBrowser) => ({
+  'Literal[regex]'(node) {
+    if (hasLookbehind(node.regex.pattern)) {
+      context.report(node, `RegExp lookbehinds are not supported in ${badBrowser}`)
+    }
+  },
+  'CallExpression[callee.name="RegExp"], NewExpression[callee.name="RegExp"]'(node) {
+    const [source] = node.arguments;
+    if (
+      source &&
+      (
+        (
+          source.type === 'Literal' &&
+          typeof source.value === 'string' &&
+          hasLookbehind(source.value)
+        ) ||
+        (
+          source.type === 'TemplateLiteral' &&
+          source.quasis.some(({value: {raw}}) => hasLookbehind(raw))
+        )
+      )
+    ) {
+      context.report(node, `RegExp lookbehinds are not supported in ${badBrowser}`)
+    }
+  }
+})

test/no-regexp-lookbehind.js

@@ -0,0 +1,49 @@
+var rule = require('../lib/rules/no-regexp-lookbehind')
+var RuleTester = require('eslint').RuleTester
+
+var ruleTester = new RuleTester({parserOptions: {ecmaVersion: 2020}})
+
+ruleTester.run('no-regexp-lookbehind', rule, {
+  valid: [
+    {code: '/(?:a)b/'},
+    {code: '/(?:a)b/g'},
+    {code: '/(?<named_group_not_checked_here>)/'},
+    {code: 'RegExp("(?:a)b", "g")'},
+    {code: 'RegExp("(?:a)b", "g")'},
+    {code: 'RegExp("(?<named-group-not-checked-here>)")'},
+  ],
+  invalid: [
+    {
+      code: '/(?<=a)b/',
+      errors: [
+        {
+          message: 'RegExp lookbehinds are not supported in undefined'
+        }
+      ]
+    },
+    {
+      code: 'new RegExp("/(?<=a)b")',
+      errors: [
+        {
+          message: 'RegExp lookbehinds are not supported in undefined'
+        }
+      ]
+    },
+    {
+      code: '/(?<=a)b/g',
+      errors: [
+        {
+          message: 'RegExp lookbehinds are not supported in undefined'
+        }
+      ]
+    },
+    {
+      code: 'new RegExp("/(?<=a)b", "g")',
+      errors: [
+        {
+          message: 'RegExp lookbehinds are not supported in undefined'
+        }
+      ]
+    },
+  ]
+})