feat: add enforceInClassFields option to no-underscore-dangle

docs/src/rules/no-underscore-dangle.md

@@ -54,6 +54,7 @@ This rule has an object option:
 * `"allowAfterSuper": false` (default) disallows dangling underscores in members of the `super` object
 * `"allowAfterThisConstructor": false` (default) disallows dangling underscores in members of the `this.constructor` object
 * `"enforceInMethodNames": false` (default) allows dangling underscores in method names
+* `"enforceInClassFields": false` (default) allows dangling underscores in es2022 class fields names
 * `"allowFunctionParams": true` (default) allows dangling underscores in function parameter names
 
 ### allow
@@ -124,6 +125,34 @@ const o = {
 };
 ```
 
+### enforceInClassFields
+
+Examples of **incorrect** code for this rule with the `{ "enforceInClassFields": true }` option:
+
+```js
+/*eslint no-underscore-dangle: ["error", { "enforceInClassFields": true }]*/
+
+class Foo {
+    _bar;
+}
+
+class Foo {
+    _bar = () => {};
+}
+
+class Foo {
+    bar_;
+}
+
+class Foo {
+    #_bar;
+}
+
+class Foo {
+    #bar_;
+}
+```
+
 ### allowFunctionParams
 
 Examples of **incorrect** code for this rule with the `{ "allowFunctionParams": false }` option:

lib/rules/no-underscore-dangle.js

@@ -49,6 +49,10 @@ module.exports = {
                     allowFunctionParams: {
                         type: "boolean",
                         default: true
+                    },
+                    enforceInClassFields: {
+                        type: "boolean",
+                        default: false
                     }
                 },
                 additionalProperties: false
@@ -68,6 +72,7 @@ module.exports = {
         const allowAfterSuper = typeof options.allowAfterSuper !== "undefined" ? options.allowAfterSuper : false;
         const allowAfterThisConstructor = typeof options.allowAfterThisConstructor !== "undefined" ? options.allowAfterThisConstructor : false;
         const enforceInMethodNames = typeof options.enforceInMethodNames !== "undefined" ? options.enforceInMethodNames : false;
+        const enforceInClassFields = typeof options.enforceInClassFields !== "undefined" ? options.enforceInClassFields : false;
         const allowFunctionParams = typeof options.allowFunctionParams !== "undefined" ? options.allowFunctionParams : true;
 
         //-------------------------------------------------------------------------
@@ -261,6 +266,30 @@ module.exports = {
             }
         }
 
+        /**
+         * Check if a class field has a dangling underscore
+         * @param {ASTNode} node node to evaluate
+         * @returns {void}
+         * @private
+         */
+        function checkForDanglingUnderscoreInClassField(node) {
+            const identifier = node.key.name;
+
+            if (typeof identifier !== "undefined" && hasDanglingUnderscore(identifier) &&
+                enforceInClassFields &&
+                !isAllowed(identifier)) {
+                context.report({
+                    node,
+                    messageId: "unexpectedUnderscore",
+                    data: {
+                        identifier: node.key.type === "PrivateIdentifier"
+                            ? `#${identifier}`
+                            : identifier
+                    }
+                });
+            }
+        }
+
         //--------------------------------------------------------------------------
         // Public API
         //--------------------------------------------------------------------------
@@ -270,7 +299,7 @@ module.exports = {
             VariableDeclarator: checkForDanglingUnderscoreInVariableExpression,
             MemberExpression: checkForDanglingUnderscoreInMemberExpression,
             MethodDefinition: checkForDanglingUnderscoreInMethod,
-            PropertyDefinition: checkForDanglingUnderscoreInMethod,
+            PropertyDefinition: checkForDanglingUnderscoreInClassField,
             Property: checkForDanglingUnderscoreInMethod,
             FunctionExpression: checkForDanglingUnderscoreInFunction,
             ArrowFunctionExpression: checkForDanglingUnderscoreInFunction

tests/lib/rules/no-underscore-dangle.js

@@ -71,7 +71,9 @@ ruleTester.run("no-underscore-dangle", rule, {
         { code: "function foo( { _bar = 0 } = {}) {}", options: [{ allowFunctionParams: false }], parserOptions: { ecmaVersion: 6 } },
         { code: "function foo(...[_bar]) {}", options: [{ allowFunctionParams: false }], parserOptions: { ecmaVersion: 2016 } },
         { code: "class foo { _field; }", parserOptions: { ecmaVersion: 2022 } },
-        { code: "class foo { #_field; }", parserOptions: { ecmaVersion: 2022 } }
+        { code: "class foo { _field; }", options: [{ enforceInClassFields: false }], parserOptions: { ecmaVersion: 2022 } },
+        { code: "class foo { #_field; }", parserOptions: { ecmaVersion: 2022 } },
+        { code: "class foo { #_field; }", options: [{ enforceInClassFields: false }], parserOptions: { ecmaVersion: 2022 } }
     ],
     invalid: [
         { code: "var _foo = 1", errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_foo" }, type: "VariableDeclarator" }] },
@@ -109,6 +111,30 @@ ruleTester.run("no-underscore-dangle", rule, {
             options: [{ enforceInMethodNames: true }],
             parserOptions: { ecmaVersion: 2022 },
             errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "#bar_" } }]
+        },
+        {
+            code: "class foo { _field; }",
+            options: [{ enforceInClassFields: true }],
+            parserOptions: { ecmaVersion: 2022 },
+            errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "_field" } }]
+        },
+        {
+            code: "class foo { #_field; }",
+            options: [{ enforceInClassFields: true }],
+            parserOptions: { ecmaVersion: 2022 },
+            errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "#_field" } }]
+        },
+        {
+            code: "class foo { field_; }",
+            options: [{ enforceInClassFields: true }],
+            parserOptions: { ecmaVersion: 2022 },
+            errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "field_" } }]
+        },
+        {
+            code: "class foo { #field_; }",
+            options: [{ enforceInClassFields: true }],
+            parserOptions: { ecmaVersion: 2022 },
+            errors: [{ messageId: "unexpectedUnderscore", data: { identifier: "#field_" } }]
         }
     ]
 });