Fix: arrow-parens no reporting for comments inside (fixes #12995)

docs/rules/arrow-parens.md

@@ -159,6 +159,7 @@ Examples of **incorrect** code for this rule with the `"as-needed"` option:
 a.then((foo) => {});
 a.then((foo) => a);
 a((foo) => { if (true) {} });
+const f = /** @type {number} */(a) => a + a;
 ```
 
 Examples of **correct** code for this rule with the `"as-needed"` option:
@@ -177,6 +178,7 @@ a.then(foo => { if (true) {} });
 (a = 10) => a;
 ([a, b]) => a;
 ({a, b}) => a;
+const f = /** @type {number} */a => a + a;
 ```
 
 ### requireForBlockBody

lib/rules/arrow-parens.js

@@ -105,10 +105,23 @@ module.exports = {
                 ], `${shouldAddSpaceForAsync ? " " : ""}${paramToken.value}`);
             }
 
+            /**
+             * Checks whether there are comments inside the params or not.
+             * @returns {boolean} `true` if there are comments inside of parens, else `false`
+             */
+            function hasCommentsInParens() {
+                const closingParenToken = sourceCode.getTokenAfter(firstTokenOfParam, astUtils.isClosingParenToken);
+
+                return closingParenToken && sourceCode.commentsExistBetween(firstTokenOfParam, closingParenToken);
+            }
+
+            if (hasCommentsInParens()) {
+                return;
+            }
+
             // "as-needed", { "requireForBlockBody": true }: x => x
             if (
                 requireForBlockBody &&
-                node.params.length === 1 &&
                 node.params[0].type === "Identifier" &&
                 !node.params[0].typeAnnotation &&
                 node.body.type !== "BlockStatement" &&
@@ -144,7 +157,6 @@ module.exports = {
 
             // "as-needed": x => x
             if (asNeeded &&
-                node.params.length === 1 &&
                 node.params[0].type === "Identifier" &&
                 !node.params[0].typeAnnotation &&
                 !node.returnType
@@ -178,7 +190,7 @@ module.exports = {
         }
 
         return {
-            ArrowFunctionExpression: parens
+            "ArrowFunctionExpression[params.length=1]": parens
         };
     }
 };

tests/lib/rules/arrow-parens.js

@@ -29,6 +29,12 @@ const valid = [
     "(a) => {\n}",
     "a.then((foo) => {});",
     "a.then((foo) => { if (true) {}; });",
+    "const f = (/* */a) => a + a;",
+    "const f = (a/** */) => a + a;",
+    "const f = (a//\n) => a + a;",
+    "const f = (//\na) => a + a;",
+    "const f = (/*\n */a//\n) => a + a;",
+    "const f = (/** @type {number} */a/**hello*/) => a + a;",
     { code: "a.then(async (foo) => { if (true) {}; });", parserOptions: { ecmaVersion: 8 } },
 
     // "always" (explicit)
@@ -68,7 +74,61 @@ const valid = [
     { code: "async a => ({})", options: ["as-needed", { requireForBlockBody: true }], parserOptions: { ecmaVersion: 8 } },
     { code: "async a => a", options: ["as-needed", { requireForBlockBody: true }], parserOptions: { ecmaVersion: 8 } },
     { code: "(a: T) => a", options: ["as-needed", { requireForBlockBody: true }], parser: parser("identifer-type") },
-    { code: "(a): T => a", options: ["as-needed", { requireForBlockBody: true }], parser: parser("return-type") }
+    { code: "(a): T => a", options: ["as-needed", { requireForBlockBody: true }], parser: parser("return-type") },
+    {
+        code: "const f = (/** @type {number} */a/**hello*/) => a + a;",
+        options: ["as-needed"]
+    },
+    {
+        code: "const f = (/* */a) => a + a;",
+        options: ["as-needed"]
+    },
+    {
+        code: "const f = (a/** */) => a + a;",
+        options: ["as-needed"]
+    },
+    {
+        code: "const f = (a//\n) => a + a;",
+        options: ["as-needed"]
+    },
+    {
+        code: "const f = (//\na) => a + a;",
+        options: ["as-needed"]
+    },
+    {
+        code: "const f = (/*\n */a//\n) => a + a;",
+        options: ["as-needed"]
+    },
+    {
+        code: "var foo = (a,/**/) => b;",
+        parserOptions: { ecmaVersion: 2017 },
+        options: ["as-needed"]
+    },
+    {
+        code: "var foo = (a , /**/) => b;",
+        parserOptions: { ecmaVersion: 2017 },
+        options: ["as-needed"]
+    },
+    {
+        code: "var foo = (a\n,\n/**/) => b;",
+        parserOptions: { ecmaVersion: 2017 },
+        options: ["as-needed"]
+    },
+    {
+        code: "var foo = (a,//\n) => b;",
+        parserOptions: { ecmaVersion: 2017 },
+        options: ["as-needed"]
+    },
+    {
+        code: "const i = (a/**/,) => a + a;",
+        parserOptions: { ecmaVersion: 2017 },
+        options: ["as-needed"]
+    },
+    {
+        code: "const i = (a \n /**/,) => a + a;",
+        parserOptions: { ecmaVersion: 2017 },
+        options: ["as-needed"]
+    }
 ];
 
 const type = "ArrowFunctionExpression";
@@ -271,7 +331,58 @@ const invalid = [
             messageId: "unexpectedParensInline",
             type
         }]
+    },
+    {
+        code: "const f = /** @type {number} */(a)/**hello*/ => a + a;",
+        options: ["as-needed"],
+        output: "const f = /** @type {number} */a/**hello*/ => a + a;",
+        errors: [{
+            line: 1,
+            column: 33,
+            type,
+            messageId: "unexpectedParens",
+            endLine: 1,
+            endColumn: 34
+        }]
+    },
+    {
+        code: "const f = //\n(a) => a + a;",
+        output: "const f = //\na => a + a;",
+        options: ["as-needed"],
+        errors: [{
+            line: 2,
+            column: 2,
+            type,
+            messageId: "unexpectedParens",
+            endLine: 2,
+            endColumn: 3
+        }]
+    },
+    {
+        code: "var foo = /**/ a => b;",
+        output: "var foo = /**/ (a) => b;",
+        errors: [{
+            line: 1,
+            column: 16,
+            type: "ArrowFunctionExpression",
+            messageId: "expectedParens",
+            endLine: 1,
+            endColumn: 17
+        }]
+    },
+    {
+        code: "var bar = a /**/ =>  b;",
+        output: "var bar = (a) /**/ =>  b;",
+        errors: [{
+            line: 1,
+            column: 11,
+            type: "ArrowFunctionExpression",
+            messageId: "expectedParens",
+            endLine: 1,
+            endColumn: 12
+        }]
     }
+
 ];
 
 ruleTester.run("arrow-parens", rule, {