✨ es/no-regexp-prototype-flags

docs/rules/no-regexp-prototype-flags.md

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+# es/no-regexp-prototype-flags
+> disallow the `RegExp.prototype.flags` property
+
+- ✅ The following configurations enable this rule: `plugin:es/no-new-in-es2015`, `plugin:es/restrict-to-es3`, and `plugin:es/restrict-to-es5`
+
+This rule reports ES2015 `RegExp.prototype.flags` property as errors.
+
+This rule is silent by default because it's hard to know types. You need to configure [the aggressive mode](../#the-aggressive-mode) or TypeScript in order to enable this rule.
+
+## 💡 Examples
+
+⛔ Examples of **incorrect** code for this rule:
+
+<eslint-playground type="bad" code="/*eslint es/no-regexp-prototype-flags: [error, { aggressive: true }] */
+/foo/u.flags
+new RegExp(pattern, flags).flags
+" />
+
+## 🔧 Options
+
+This rule has an option.
+
+```yml
+rules:
+  es/no-regexp-prototype-flags: [error, { aggressive: false }]
+```
+
+### aggressive: boolean
+
+Configure the aggressive mode for only this rule.
+This is prior to the `settings.es.aggressive` setting.
+
+## 📚 References
+
+- [Rule source](https://github.com/mysticatea/eslint-plugin-es/blob/v4.1.0/lib/rules/no-regexp-prototype-flags.js)
+- [Test source](https://github.com/mysticatea/eslint-plugin-es/blob/v4.1.0/tests/lib/rules/no-regexp-prototype-flags.js)

lib/rules/no-regexp-prototype-flags.js

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+/**
+ * @author Toru Nagashima <https://github.com/mysticatea>
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+const {
+    definePrototypeMethodHandler,
+} = require("../util/define-prototype-method-handler")
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow the `RegExp.prototype.flags` property.",
+            category: "ES2015",
+            recommended: false,
+            url:
+                "http://mysticatea.github.io/eslint-plugin-es/rules/no-regexp-prototype-flags.html",
+        },
+        fixable: null,
+        messages: {
+            forbidden: "ES2015 '{{name}}' property is forbidden.",
+        },
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    aggressive: { type: "boolean" },
+                },
+                additionalProperties: false,
+            },
+        ],
+        type: "problem",
+    },
+    create(context) {
+        return definePrototypeMethodHandler(context, {
+            RegExp: ["flags"],
+        })
+    },
+}

tests/lib/rules/no-regexp-prototype-flags.js

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+/**
+ * @author Toru Nagashima <https://github.com/mysticatea>
+ * See LICENSE file in root directory for full license.
+ */
+"use strict"
+
+const path = require("path")
+const RuleTester = require("../../tester")
+const rule = require("../../../lib/rules/no-regexp-prototype-flags.js")
+const ruleId = "no-regexp-prototype-flags"
+
+new RuleTester().run(ruleId, rule, {
+    valid: [
+        "foo.global",
+        "foo.flags",
+        { code: "foo.global", settings: { es: { aggressive: true } } },
+        {
+            code: "foo.flags",
+            options: [{ aggressive: false }],
+            settings: { es: { aggressive: true } },
+        },
+    ],
+    invalid: [
+        {
+            code: "foo.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+            settings: { es: { aggressive: true } },
+        },
+        {
+            code: "foo.flags",
+            options: [{ aggressive: true }],
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+            settings: { es: { aggressive: false } },
+        },
+    ],
+})
+
+// -----------------------------------------------------------------------------
+// TypeScript
+// -----------------------------------------------------------------------------
+const parser = require.resolve("@typescript-eslint/parser")
+const tsconfigRootDir = path.resolve(__dirname, "../../fixtures")
+const project = "tsconfig.json"
+const filename = path.join(tsconfigRootDir, "test.ts")
+
+new RuleTester({ parser }).run(`${ruleId} TS`, rule, {
+    valid: [
+        { filename, code: "foo.global" },
+        { filename, code: "foo.flags" },
+        { filename, code: "let foo = {}; foo.flags" },
+        {
+            filename,
+            code: "foo.global",
+            settings: { es: { aggressive: true } },
+        },
+
+        // `RegExp` is unknown type if tsconfig.json is not configured.
+        { filename, code: "new RegExp('').flags" },
+        { filename, code: "let foo = new RegExp(''); foo.flags" },
+    ],
+    invalid: [
+        {
+            filename,
+            code: "/foo/.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+        },
+        {
+            filename,
+            code: "new RegExp('').flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+            settings: { es: { aggressive: true } },
+        },
+        {
+            filename,
+            code: "let foo = new RegExp(''); foo.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+            settings: { es: { aggressive: true } },
+        },
+        {
+            filename,
+            code: "foo.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+            settings: { es: { aggressive: true } },
+        },
+    ],
+})
+
+new RuleTester({
+    parser,
+    parserOptions: { tsconfigRootDir, project },
+}).run(`${ruleId} TS Full Type Information`, rule, {
+    valid: [
+        { filename, code: "foo.global" },
+        { filename, code: "foo.flags" },
+        { filename, code: "let foo = {}; foo.flags" },
+        {
+            filename,
+            code: "foo.global",
+            settings: { es: { aggressive: true } },
+        },
+    ],
+    invalid: [
+        {
+            filename,
+            code: "/foo/.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+        },
+        {
+            filename,
+            code: "new RegExp('').flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+        },
+        {
+            filename,
+            code: "let foo = new RegExp(''); foo.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+        },
+        {
+            filename,
+            code: "foo.flags",
+            errors: ["ES2015 'RegExp.prototype.flags' property is forbidden."],
+            settings: { es: { aggressive: true } },
+        },
+    ],
+})