New: add rule "require-named-capture-group" (fixes #11381)

docs/rules/require-named-capture-group.md

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+# Suggest using named capture group in regular expression (require-named-capture-group)
+
+With the landing of ECMAScript 2018, named capture group can be used in regular expression, which can improve the readability.
+
+```js
+const regex = /(?<year>[0-9]{4})/;
+```
+
+## Rule Details
+
+This rule is aimed at using named capture group instead of numbered capture group in regular expression.
+
+Examples of **incorrect** code for this rule:
+
+```js
+/*eslint require-named-capture-group: "error"*/
+
+const foo = /(ba[rz])/;
+const bar = new RegExp('(ba[rz])');
+const baz = RegExp('(ba[rz])');
+
+foo.exec('bar')[1]; // Retrieve the group result.
+```
+
+Examples of **correct** code for this rule:
+
+```js
+/*eslint require-named-capture-group: "error"*/
+
+const foo = /(?<id>ba[rz])/;
+const bar = new RegExp('(?<id>ba[rz])');
+const baz = RegExp('(?<id>ba[rz])');
+
+foo.exec('bar').groups.id; // Retrieve the group result.
+```
+
+## When Not To Use It
+
+If you are targeting ECMAScript 2017 and/or older environments, you can disable this rule, because this ECMAScript feature is only supported in ECMAScript 2018 and/or newer environments.
+
+## Related Rules
+
+* [no-invalid-regexp](./no-invalid-regexp.md)

lib/rules/require-named-capture-group.js

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+/**
+ * @fileoverview Rule to enforce requiring named capture groups in regular expression.
+ * @author Pig Fang <https://github.com/g-plane>
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const regexpp = require("regexpp");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const parser = new regexpp.RegExpParser();
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "enforce using named capture group in regular expression",
+            category: "Best Practices",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/require-named-capture-group"
+        },
+
+        schema: [],
+
+        messages: {
+            required: "Capture group '{{group}}' in regular expression should be named."
+        }
+    },
+
+    create(context) {
+        /**
+         * Function to check regular expression.
+         *
+         * @param {string} regex The regular expression to be check.
+         * @param {ASTNode} node AST node which contains regular expression.
+         * @returns {void}
+         */
+        function checkRegex(regex, node) {
+            const ast = parser.parsePattern(regex);
+            regexpp.visitRegExpAST(ast, {
+                onCapturingGroupEnter(group) {
+                    if (!group.name) {
+                        context.report({
+                            node,
+                            messageId: "required",
+                            data: {
+                                group: group.raw
+                            }
+                        });
+                    }
+                }
+            });
+        }
+
+        return {
+            Literal(node) {
+                if (node.regex) {
+                    checkRegex(node.regex.pattern, node);
+                }
+            },
+            "NewExpression, CallExpression"(node) {
+                const { callee, arguments: [firstArg] } = node;
+                if (
+                    callee.type === "Identifier" &&
+                    callee.name === "RegExp" &&
+                    firstArg &&
+                    firstArg.type === "Literal" &&
+                    typeof firstArg.value === "string"
+                ) {
+                    checkRegex(firstArg.value, node);
+                }
+            }
+        }
+    }
+}

tests/lib/rules/require-named-capture-group.js

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+/**
+ * @fileoverview Tests for require-named-capture-group rule.
+ * @author Pig Fang <https://github.com/g-plane>
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const rule = require("../../../lib/rules/require-named-capture-group"),
+    RuleTester = require("../../../lib/testers/rule-tester");
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 2018 } });
+
+ruleTester.run("require-named-capture-group", rule, {
+    valid: [
+        "/normal_regex/",
+        "/(?:[0-9]{4})/",
+        "/(?<year>[0-9]{4})/",
+        "new RegExp()",
+        "new RegExp(foo)",
+        "new RegExp('')",
+        "new RegExp('(?<year>[0-9]{4})')",
+        "RegExp()",
+        "RegExp(foo)",
+        "RegExp('')",
+        "RegExp('(?<year>[0-9]{4})')"
+    ],
+
+    invalid: [
+        {
+            code: "/([0-9]{4})/",
+            errors: [{ messageId: "required", type: "Literal", data: { group: '([0-9]{4})' } }]
+        },
+        {
+            code: "new RegExp('([0-9]{4})')",
+            errors: [{ messageId: "required", type: "NewExpression", data: { group: '([0-9]{4})' } }]
+        },
+        {
+            code: "RegExp('([0-9]{4})')",
+            errors: [{ messageId: "required", type: "CallExpression", data: { group: '([0-9]{4})' } }]
+        },
+        {
+            code: "/([0-9]{4})-(\\w{5})/",
+            errors: [
+                { messageId: "required", type: "Literal", data: { group: '([0-9]{4})' } },
+                { messageId: "required", type: "Literal", data: { group: '(\\w{5})' } },
+            ]
+        }
+    ]
+});