Update: Add support for parens on left side for-loops (fixes: #8393)

lib/rules/no-extra-parens.js

@@ -255,6 +255,23 @@ module.exports = {
                 !astUtils.canTokensBeAdjacent(tokenBeforeLeftParen, firstToken);
         }
 
+        /**
+         * Determines whether a node should be followed by an additional space when removing parens
+         * @param {ASTNode} node node to evaluate; must be surrounded by parentheses
+         * @returns {boolean} `true` if a space should be inserted after the node
+         * @private
+         */
+        function requiresTrailingSpace(node) {
+            const nextTwoTokens = sourceCode.getTokensAfter(node, { count: 2 });
+            const rightParenToken = nextTwoTokens[0];
+            const tokenAfterRightParen = nextTwoTokens[1];
+            const tokenBeforeRightParen = sourceCode.getLastToken(node);
+
+            return rightParenToken && tokenAfterRightParen &&
+                !sourceCode.isSpaceBetweenTokens(rightParenToken, tokenAfterRightParen) &&
+                !astUtils.canTokensBeAdjacent(tokenBeforeRightParen, tokenAfterRightParen);
+        }
+
         /**
          * Report the node
          * @param {ASTNode} node node to evaluate
@@ -279,7 +296,7 @@ module.exports = {
                     return fixer.replaceTextRange([
                         leftParenToken.range[0],
                         rightParenToken.range[1]
-                    ], (requiresLeadingSpace(node) ? " " : "") + parenthesizedSource);
+                    ], (requiresLeadingSpace(node) ? " " : "") + parenthesizedSource + (requiresTrailingSpace(node) ? " " : ""));
                 }
             });
         }
@@ -488,12 +505,18 @@ module.exports = {
                 if (hasExcessParens(node.right)) {
                     report(node.right);
                 }
+                if (hasExcessParens(node.left)) {
+                    report(node.left);
+                }
             },
 
             ForOfStatement(node) {
                 if (hasExcessParens(node.right)) {
                     report(node.right);
                 }
+                if (hasExcessParens(node.left)) {
+                    report(node.left);
+                }
             },
 
             ForStatement(node) {

tests/lib/rules/no-extra-parens.js

@@ -41,7 +41,6 @@ function invalid(code, output, type, line, config) {
     if (line) {
         result.errors[0].line = line;
     }
-
     return result;
 }
 
@@ -996,6 +995,27 @@ ruleTester.run("no-extra-parens", rule, {
             1,
             { parserOptions: { ecmaVersion: 2015 } }
         ),
+        invalid(
+            "for ((foo) of bar);",
+            "for (foo of bar);",
+            "Identifier",
+            1,
+            { parserOptions: { ecmaVersion: 2015 } }
+        ),
+        invalid(
+            "for ((foo)in bar);",
+            "for (foo in bar);",
+            "Identifier",
+            1,
+            { parserOptions: { ecmaVersion: 2015 } }
+        ),
+        invalid(
+            "for ((foo['bar'])of baz);",
+            "for (foo['bar']of baz);",
+            "MemberExpression",
+            1,
+            { parserOptions: { ecmaVersion: 2015 } }
+        ),
         invalid(
             "() => (({ foo: 1 }).foo)",
             "() => ({ foo: 1 }).foo",