Update: add confusingArrow to no-extra-parens (fixes eslint#6196)

Allows extra parentheses in arrow function syntax in places where it could be confused with a comparison operator.
alexander-akait · Apr 10, 2017 · 198ba8d · 198ba8d
1 parent 0c2a386
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diff --git a/docs/rules/no-extra-parens.md b/docs/rules/no-extra-parens.md
@@ -165,6 +165,17 @@ const Component = (<div />)
 const Component = (<div><p /></div>)
 ```
 
+### confusingArrow
+
+Examples of **correct** code for this rule with the `"all"` and `{ "confusingArrow": false }` options:
+
+```js
+/* eslint no-extra-parens: ["error", "all", { "confusingArrow": false }] */
+
+const b = a => 1 ? 2 : 3;
+const d = c => (1 ? 2 : 3);
+```
+
 ### functions
 
 Examples of **incorrect** code for this rule with the `"functions"` option:

diff --git a/lib/rules/no-extra-parens.js b/lib/rules/no-extra-parens.js
@@ -44,7 +44,8 @@ module.exports = {
                                 conditionalAssign: { type: "boolean" },
                                 nestedBinaryExpressions: { type: "boolean" },
                                 returnAssign: { type: "boolean" },
-                                ignoreJSX: { enum: ["none", "all", "single-line", "multi-line"] }
+                                ignoreJSX: { enum: ["none", "all", "single-line", "multi-line"] },
+                                confusingArrow: { type: "boolean" }
                             },
                             additionalProperties: false
                         }
@@ -67,6 +68,7 @@ module.exports = {
         const NESTED_BINARY = ALL_NODES && context.options[1] && context.options[1].nestedBinaryExpressions === false;
         const EXCEPT_RETURN_ASSIGN = ALL_NODES && context.options[1] && context.options[1].returnAssign === false;
         const IGNORE_JSX = ALL_NODES && context.options[1] && context.options[1].ignoreJSX;
+        const EXCEPT_CONFUSING_ARROW = ALL_NODES && context.options[1] && context.options[1].confusingArrow === false;
         const PRECEDENCE_OF_ASSIGNMENT_EXPR = precedence({ type: "AssignmentExpression" });
         const PRECEDENCE_OF_UPDATE_EXPR = precedence({ type: "UpdateExpression" });
 
@@ -431,6 +433,10 @@ module.exports = {
                     return;
                 }
 
+                if (node.body.type === "ConditionalExpression" && EXCEPT_CONFUSING_ARROW) {
+                    return;
+                }
+
                 if (node.body.type !== "BlockStatement") {
                     const firstBodyToken = sourceCode.getFirstToken(node.body, astUtils.isNotOpeningParenToken);
                     const tokenBeforeFirst = sourceCode.getTokenBefore(firstBodyToken);

diff --git a/tests/lib/rules/no-extra-parens.js b/tests/lib/rules/no-extra-parens.js
@@ -369,6 +369,10 @@ ruleTester.run("no-extra-parens", rule, {
             "/>)"
         ].join("\n"), options: ["all", { ignoreJSX: "multi-line" }] },
 
+        // ["all", { confusingArrow: false }]
+        { code: "var a = b => 1 ? 2 : 3", options: ["all", { confusingArrow: false }], parserOptions: { ecmaVersion: 6 } },
+        { code: "var a = (b) => (1 ? 2 : 3)", options: ["all", { confusingArrow: false }], parserOptions: { ecmaVersion: 6 } },
+
         {
             code: "let a = [ ...b ]",
             parserOptions: { ecmaVersion: 2015 }