feat: add Unicode flag suggestion in no-misleading-character-class

docs/src/rules/no-misleading-character-class.md

@@ -7,6 +7,8 @@ rule_type: problem
 
 <!--RECOMMENDED-->
 
+<!--SUGGESTIONS-->
+
 Disallows characters which are made with multiple code points in character class syntax.
 
 Unicode includes the characters which are made with multiple code points.

lib/rules/no-misleading-character-class.js

@@ -4,13 +4,16 @@
 "use strict";
 
 const { CALL, CONSTRUCT, ReferenceTracker, getStringIfConstant } = require("eslint-utils");
-const { RegExpParser, visitRegExpAST } = require("regexpp");
+const { RegExpValidator, RegExpParser, visitRegExpAST } = require("regexpp");
 const { isCombiningCharacter, isEmojiModifier, isRegionalIndicatorSymbol, isSurrogatePair } = require("./utils/unicode");
+const astUtils = require("./utils/ast-utils.js");
 
 //------------------------------------------------------------------------------
 // Helpers
 //------------------------------------------------------------------------------
 
+const REGEXPP_LATEST_ECMA_VERSION = 2022;
+
 /**
  * Iterate character sequences of a given nodes.
  *
@@ -109,35 +112,32 @@ module.exports = {
             url: "https://eslint.org/docs/rules/no-misleading-character-class"
         },
 
+        hasSuggestions: true,
+
         schema: [],
 
         messages: {
             surrogatePairWithoutUFlag: "Unexpected surrogate pair in character class. Use 'u' flag.",
             combiningClass: "Unexpected combined character in character class.",
             emojiModifier: "Unexpected modified Emoji in character class.",
             regionalIndicatorSymbol: "Unexpected national flag in character class.",
-            zwj: "Unexpected joined character sequence in character class."
+            zwj: "Unexpected joined character sequence in character class.",
+            suggestUnicodeFlag: "Add unicode 'u' flag to regex."
         }
     },
     create(context) {
+        const sourceCode = context.getSourceCode();
         const parser = new RegExpParser();
 
         /**
          * Verify a given regular expression.
          * @param {Node} node The node to report.
          * @param {string} pattern The regular expression pattern to verify.
          * @param {string} flags The flags of the regular expression.
+         * @param {Function} unicodeFixer Fixer for missing "u" flag.
          * @returns {void}
          */
-        function verify(node, pattern, flags) {
-            const has = {
-                surrogatePairWithoutUFlag: false,
-                combiningClass: false,
-                variationSelector: false,
-                emojiModifier: false,
-                regionalIndicatorSymbol: false,
-                zwj: false
-            };
+        function verify(node, pattern, flags, unicodeFixer) {
             let patternNode;
 
             try {
@@ -153,26 +153,75 @@ module.exports = {
                 return;
             }
 
+            const foundKinds = new Set();
+
             visitRegExpAST(patternNode, {
                 onCharacterClassEnter(ccNode) {
                     for (const chars of iterateCharacterSequence(ccNode.elements)) {
                         for (const kind of kinds) {
-                            has[kind] = has[kind] || hasCharacterSequence[kind](chars);
+                            if (hasCharacterSequence[kind](chars)) {
+                                foundKinds.add(kind);
+                            }
                         }
                     }
                 }
             });
 
-            for (const kind of kinds) {
-                if (has[kind]) {
-                    context.report({ node, messageId: kind });
+            for (const kind of foundKinds) {
+                let suggest;
+
+                if (kind === "surrogatePairWithoutUFlag") {
+                    suggest = [{
+                        messageId: "suggestUnicodeFlag",
+                        fix: unicodeFixer
+                    }];
                 }
+
+                context.report({
+                    node,
+                    messageId: kind,
+                    suggest
+                });
             }
         }
 
+        /**
+         * Checks if the given regular expression pattern would be valid with the `u` flag.
+         * @param {string} pattern The regular expression pattern to verify.
+         * @returns {boolean} `true` if the pattern would be valid with the `u` flag.
+         * `false` if the pattern would be invalid with the `u` flag or the configured
+         * ecmaVersion doesn't support the `u` flag.
+         */
+        function isValidWithUnicodeFlag(pattern) {
+            const { ecmaVersion } = context.parserOptions;
+
+            // ecmaVersion is unknown or it doesn't support the 'u' flag
+            if (typeof ecmaVersion !== "number" || ecmaVersion <= 5) {
+                return false;
+            }
+
+            const validator = new RegExpValidator({
+                ecmaVersion: Math.min(ecmaVersion + 2009, REGEXPP_LATEST_ECMA_VERSION)
+            });
+
+            try {
+                validator.validatePattern(pattern, void 0, void 0, /* uFlag = */ true);
+            } catch {
+                return false;
+            }
+
+            return true;
+        }
+
         return {
             "Literal[regex]"(node) {
-                verify(node, node.regex.pattern, node.regex.flags);
+                verify(node, node.regex.pattern, node.regex.flags, fixer => {
+                    if (!isValidWithUnicodeFlag(node.regex.pattern)) {
+                        return null;
+                    }
+
+                    return fixer.insertTextAfter(node, "u");
+                });
             },
             "Program"() {
                 const scope = context.getScope();
@@ -191,7 +240,31 @@ module.exports = {
                     const flags = getStringIfConstant(flagsNode, scope);
 
                     if (typeof pattern === "string") {
-                        verify(node, pattern, flags || "");
+                        verify(node, pattern, flags || "", fixer => {
+
+                            if (!isValidWithUnicodeFlag(pattern)) {
+                                return null;
+                            }
+
+                            if (node.arguments.length === 1) {
+                                const penultimateToken = sourceCode.getLastToken(node, { skip: 1 }); // skip closing parenthesis
+
+                                return fixer.insertTextAfter(
+                                    penultimateToken,
+                                    astUtils.isCommaToken(penultimateToken)
+                                        ? ' "u",'
+                                        : ', "u"'
+                                );
+                            }
+
+                            if ((flagsNode.type === "Literal" && typeof flagsNode.value === "string") || flagsNode.type === "TemplateLiteral") {
+                                const range = [flagsNode.range[0], flagsNode.range[1] - 1];
+
+                                return fixer.insertTextAfterRange(range, "u");
+                            }
+
+                            return null;
+                        });
                     }
                 }
             }