fix: no-unused-vars should be corrected in the logical assignment ope…

…rator Fixes #17299
eslint · Jun 29, 2023 · 9aff278 · 9aff278
1 parent c8b1f4d
commit 9aff278
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diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
@@ -448,6 +448,17 @@ module.exports = {
             );
         }
 
+        /**
+         * Checks whether a given operator is a logical assignment operator or not.
+         *
+         * Logical assignment operators are `&&=`, `||=`, and `??=`.
+         * @param {string} operator The operator to check.
+         * @returns {boolean} `true` if the operator is a logical assignment operator.
+         */
+        function isLogicalAssignmentOperator(operator) {
+            return /^(?:\?\?|&&|\|\|)=/u.test(operator);
+        }
+
         /**
          * Checks whether a given reference is a read to update itself or not.
          * @param {eslint-scope.Reference} ref A reference to check.
@@ -466,7 +477,8 @@ module.exports = {
                     (
                         parent.type === "AssignmentExpression" &&
                         parent.left === id &&
-                        isUnusedExpression(parent)
+                        isUnusedExpression(parent) &&
+                        !isLogicalAssignmentOperator(parent.operator)
                     ) ||
                     (
                         parent.type === "UpdateExpression" &&

diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
@@ -417,6 +417,20 @@ ruleTester.run("no-unused-vars", rule, {
         {
             code: "import.meta",
             parserOptions: { ecmaVersion: 2020, sourceType: "module" }
+        },
+
+        // https://github.com/eslint/eslint/issues/17299
+        {
+            code: "var a; a ||= 1;",
+            parserOptions: { ecmaVersion: 2021 }
+        },
+        {
+            code: "var a; a &&= 1;",
+            parserOptions: { ecmaVersion: 2021 }
+        },
+        {
+            code: "var a; a ??= 1;",
+            parserOptions: { ecmaVersion: 2021 }
         }
     ],
     invalid: [