Update: Option to allow extra parens for cond assign (fixes #3317)

eslint · Jan 10, 2016 · 4182e65 · 4182e65
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diff --git a/docs/rules/no-extra-parens.md b/docs/rules/no-extra-parens.md
@@ -13,7 +13,15 @@ A few cases of redundant parentheses are always allowed:
 
 ### Options
 
-The default behavior of the rule is specified by `"all"` and it will report unnecessary parentheses around any expression. The following patterns are considered problems:
+This rule takes 1 argument, a string which must be one of the following:
+
+* `"all"` (default): it will report unnecessary parentheses around any expression.
+* `"all-except-cond-assign"`: extra parens are allowed for assignment in conditional statements.
+* `"functions"`: only function expressions will be checked for unnecessary parentheses.
+
+#### "all"
+
+The following patterns are considered problems:
 
 ```js
 /*eslint no-extra-parens: 2*/
@@ -41,7 +49,25 @@ The following patterns are not considered problems:
 (/^a$/).test(x);
 ```
 
-If the option is set to `"functions"`, only function expressions will be checked for unnecessary parentheses. The following patterns are considered problems:
+#### "all-except-cond-assign"
+
+The following patterns are not considered problems:
+
+```js
+/*eslint no-extra-parens: [2, "all-except-cond-assign"]*/
+
+while ((foo = bar())) {}
+
+if ((foo = bar())) {}
+
+do; while ((foo = bar()))
+
+for (;(a = b););
+```
+
+#### "functions"
+
+The following patterns are considered problems:
 
 ```js
 /*eslint no-extra-parens: [2, "functions"]*/

diff --git a/lib/rules/no-extra-parens.js b/lib/rules/no-extra-parens.js
@@ -13,6 +13,7 @@
 module.exports = function(context) {
 
     var ALL_NODES = context.options[0] !== "functions";
+    var EXCEPT_COND_ASSIGN = context.options[0] === "all-except-cond-assign";
     var sourceCode = context.getSourceCode();
 
     /**
@@ -343,7 +344,8 @@ module.exports = function(context) {
             }
         },
         "DoWhileStatement": function(node) {
-            if (hasDoubleExcessParens(node.test)) {
+            if (hasDoubleExcessParens(node.test) &&
+                    (!EXCEPT_COND_ASSIGN || node.test.type !== "AssignmentExpression")) {
                 report(node.test);
             }
         },
@@ -388,7 +390,8 @@ module.exports = function(context) {
                 report(node.init);
             }
 
-            if (node.test && hasExcessParens(node.test)) {
+            if (node.test && hasExcessParens(node.test) &&
+                    (!EXCEPT_COND_ASSIGN || node.test.type !== "AssignmentExpression")) {
                 report(node.test);
             }
 
@@ -397,7 +400,8 @@ module.exports = function(context) {
             }
         },
         "IfStatement": function(node) {
-            if (hasDoubleExcessParens(node.test)) {
+            if (hasDoubleExcessParens(node.test) &&
+                    (!EXCEPT_COND_ASSIGN || node.test.type !== "AssignmentExpression")) {
                 report(node.test);
             }
         },
@@ -483,7 +487,8 @@ module.exports = function(context) {
             }
         },
         "WhileStatement": function(node) {
-            if (hasDoubleExcessParens(node.test)) {
+            if (hasDoubleExcessParens(node.test) &&
+                    (!EXCEPT_COND_ASSIGN || node.test.type !== "AssignmentExpression")) {
                 report(node.test);
             }
         },
@@ -511,6 +516,6 @@ module.exports = function(context) {
 
 module.exports.schema = [
     {
-        "enum": ["all", "functions"]
+        "enum": ["all", "all-except-cond-assign", "functions"]
     }
 ];
diff --git a/tests/lib/rules/no-extra-parens.js b/tests/lib/rules/no-extra-parens.js
@@ -178,6 +178,12 @@ ruleTester.run("no-extra-parens", rule, {
         {code: "var a = (b = c)", options: ["functions"]},
         {code: "_ => (a = 0)", options: ["functions"], parserOptions: { ecmaVersion: 6 }},
 
+        // "all-except-cond-assign" enables extra parens around conditional assignments
+        {code: "while ((foo = bar())) {}", options: ["all-except-cond-assign"]},
+        {code: "if ((foo = bar())) {}", options: ["all-except-cond-assign"]},
+        {code: "do; while ((foo = bar()))", options: ["all-except-cond-assign"]},
+        {code: "for (;(a = b););", options: ["all-except-cond-assign"]},
+
         // https://github.com/eslint/eslint/issues/3653
         "(function(){}).foo(), 1, 2;",
         "(function(){}).foo++;",
@@ -304,6 +310,12 @@ ruleTester.run("no-extra-parens", rule, {
         invalid("(_ => 0), 0", "ArrowFunctionExpression", 1, {options: ["functions"], parserOptions: { ecmaVersion: 6 }}),
         invalid("a = (_ => 0)", "ArrowFunctionExpression", 1, {options: ["functions"], parserOptions: { ecmaVersion: 6 }}),
 
+
+        invalid("while ((foo = bar())) {}", "AssignmentExpression"),
+        invalid("if ((foo = bar())) {}", "AssignmentExpression"),
+        invalid("do; while ((foo = bar()))", "AssignmentExpression"),
+        invalid("for (;(a = b););", "AssignmentExpression"),
+
         // https://github.com/eslint/eslint/issues/3653
         invalid("((function(){})).foo();", "FunctionExpression"),
         invalid("((function(){}).foo());", "CallExpression"),