Update: enforceForArrowConditionals to no-extra-parens (fixes #6196…

…) (#8439)
eslint · Jun 22, 2017 · 291a783 · 291a783
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diff --git a/docs/rules/no-extra-parens.md b/docs/rules/no-extra-parens.md
@@ -22,6 +22,7 @@ This rule has an object option for exceptions to the `"all"` option:
 * `"returnAssign": false` allows extra parentheses around assignments in `return` statements
 * `"nestedBinaryExpressions": false` allows extra parentheses in nested binary expressions
 * `"ignoreJSX": "none|all|multi-line|single-line"` allows extra parentheses around no/all/multi-line/single-line JSX components. Defaults to `none`.
+* `"enforceForArrowConditionals": false` allows extra parentheses around ternary expressions which are the body of an arrow function
 
 ### all
 
@@ -165,6 +166,17 @@ const Component = (<div />)
 const Component = (<div><p /></div>)
 ```
 
+### enforceForArrowConditionals
+
+Examples of **correct** code for this rule with the `"all"` and `{ "enforceForArrowConditionals": false }` options:
+
+```js
+/* eslint no-extra-parens: ["error", "all", { "enforceForArrowConditionals": 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"] },
+                                enforceForArrowConditionals: { type: "boolean" }
                             },
                             additionalProperties: false
                         }
@@ -67,6 +68,9 @@ 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 IGNORE_ARROW_CONDITIONALS = ALL_NODES && context.options[1] &&
+            context.options[1].enforceForArrowConditionals === false;
+
         const PRECEDENCE_OF_ASSIGNMENT_EXPR = precedence({ type: "AssignmentExpression" });
         const PRECEDENCE_OF_UPDATE_EXPR = precedence({ type: "UpdateExpression" });
 
@@ -448,6 +452,13 @@ module.exports = {
                     return;
                 }
 
+                if (node.body.type === "ConditionalExpression" &&
+                    IGNORE_ARROW_CONDITIONALS &&
+                    !isParenthesisedTwice(node.body)
+                ) {
+                    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
@@ -368,6 +368,10 @@ ruleTester.run("no-extra-parens", rule, {
             "/>)"
         ].join("\n"), options: ["all", { ignoreJSX: "multi-line" }] },
 
+        // ["all", { enforceForArrowConditionals: false }]
+        { code: "var a = b => 1 ? 2 : 3", options: ["all", { enforceForArrowConditionals: false }], parserOptions: { ecmaVersion: 6 } },
+        { code: "var a = (b) => (1 ? 2 : 3)", options: ["all", { enforceForArrowConditionals: false }], parserOptions: { ecmaVersion: 6 } },
+
         {
             code: "let a = [ ...b ]",
             parserOptions: { ecmaVersion: 2015 }
@@ -921,6 +925,32 @@ ruleTester.run("no-extra-parens", rule, {
             options: ["all", { ignoreJSX: "none" }]
         }),
 
+        // ["all", { enforceForArrowConditionals: true }]
+        {
+            code: "var a = (b) => (1 ? 2 : 3)",
+            parserOptions: { ecmaVersion: 6 },
+            options: ["all", { enforceForArrowConditionals: true }],
+            errors: [
+                {
+                    message: "Gratuitous parentheses around expression."
+                }
+            ],
+            output: "var a = (b) => 1 ? 2 : 3"
+        },
+
+        // ["all", { enforceForArrowConditionals: false }]
+        {
+            code: "var a = (b) => ((1 ? 2 : 3))",
+            parserOptions: { ecmaVersion: 6 },
+            options: ["all", { enforceForArrowConditionals: false }],
+            errors: [
+                {
+                    message: "Gratuitous parentheses around expression."
+                }
+            ],
+            output: "var a = (b) => (1 ? 2 : 3)"
+        },
+
         // https://github.com/eslint/eslint/issues/8175
         invalid(
             "let a = [...(b)]",