fix: Make no-unused-vars treat for..of loops same as for..in loops (#15868)

alexbassy · web-flow · commit f364d47013d1 · 2022-06-13T22:14:01.000+02:00
diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
@@ -484,12 +484,12 @@ module.exports = {
         }
 
         /**
-         * Determine if an identifier is used either in for-in loops.
+         * Determine if an identifier is used either in for-in or for-of loops.
          * @param {Reference} ref The reference to check.
          * @returns {boolean} whether reference is used in the for-in loops
          * @private
          */
-        function isForInRef(ref) {
+        function isForInOfRef(ref) {
             let target = ref.identifier.parent;
 
 
@@ -498,7 +498,7 @@ module.exports = {
                 target = target.parent.parent;
             }
 
-            if (target.type !== "ForInStatement") {
+            if (target.type !== "ForInStatement" && target.type !== "ForOfStatement") {
                 return false;
             }
 
@@ -531,7 +531,7 @@ module.exports = {
             let rhsNode = null;
 
             return variable.references.some(ref => {
-                if (isForInRef(ref)) {
+                if (isForInOfRef(ref)) {
                     return true;
                 }
 
diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
@@ -252,6 +252,15 @@ ruleTester.run("no-unused-vars", rule, {
         { code: "(function(obj) { for ( const name in obj ) { return true } })({})", parserOptions: { ecmaVersion: 6 } },
         { code: "(function(obj) { for ( const name in obj ) return true })({})", parserOptions: { ecmaVersion: 6 } },
 
+        // For-of loops
+        { code: "(function(iter) { let name; for ( name of iter ) return; })({});", parserOptions: { ecmaVersion: 6 } },
+        { code: "(function(iter) { let name; for ( name of iter ) { return; } })({});", parserOptions: { ecmaVersion: 6 } },
+        { code: "(function(iter) { for ( let name of iter ) { return true } })({})", parserOptions: { ecmaVersion: 6 } },
+        { code: "(function(iter) { for ( let name of iter ) return true })({})", parserOptions: { ecmaVersion: 6 } },
+
+        { code: "(function(iter) { for ( const name of iter ) { return true } })({})", parserOptions: { ecmaVersion: 6 } },
+        { code: "(function(iter) { for ( const name of iter ) return true })({})", parserOptions: { ecmaVersion: 6 } },
+
         // Sequence Expressions (See https://github.com/eslint/eslint/issues/14325)
         { code: "let x = 0; foo = (0, x++);", parserOptions: { ecmaVersion: 6 } },
         { code: "let x = 0; foo = (0, x += 1);", parserOptions: { ecmaVersion: 6 } },
@@ -704,6 +713,50 @@ ruleTester.run("no-unused-vars", rule, {
             }]
         },
 
+        // For-of loops
+        {
+            code: "(function(iter) { var name; for ( name of iter ) { i(); return; } })({});",
+            env: { es6: true },
+            errors: [{
+                line: 1,
+                column: 35,
+                messageId: "unusedVar",
+                data: {
+                    varName: "name",
+                    action: "assigned a value",
+                    additional: ""
+                }
+            }]
+        },
+        {
+            code: "(function(iter) { var name; for ( name of iter ) { } })({});",
+            env: { es6: true },
+            errors: [{
+                line: 1,
+                column: 35,
+                messageId: "unusedVar",
+                data: {
+                    varName: "name",
+                    action: "assigned a value",
+                    additional: ""
+                }
+            }]
+        },
+        {
+            code: "(function(iter) { for ( var name of iter ) { } })({});",
+            env: { es6: true },
+            errors: [{
+                line: 1,
+                column: 29,
+                messageId: "unusedVar",
+                data: {
+                    varName: "name",
+                    action: "assigned a value",
+                    additional: ""
+                }
+            }]
+        },
+
         // https://github.com/eslint/eslint/issues/3617
         {
             code: "\n/* global foobar, foo, bar */\nfoobar;",

Original file line number	Diff line number	Diff line change
`@@ -484,12 +484,12 @@ module.exports = {`
`484`	`484`	`}`
`485`	`485`
`486`	`486`	`/**`
`487`		`- * Determine if an identifier is used either in for-in loops.`
	`487`	`+ * Determine if an identifier is used either in for-in or for-of loops.`
`488`	`488`	`* @param {Reference} ref The reference to check.`
`489`	`489`	`* @returns {boolean} whether reference is used in the for-in loops`
`490`	`490`	`* @private`
`491`	`491`	`*/`
`492`		`- function isForInRef(ref) {`
	`492`	`+ function isForInOfRef(ref) {`
`493`	`493`	`let target = ref.identifier.parent;`
`494`	`494`
`495`	`495`
`@@ -498,7 +498,7 @@ module.exports = {`
`498`	`498`	`target = target.parent.parent;`
`499`	`499`	`}`
`500`	`500`
`501`		`- if (target.type !== "ForInStatement") {`
	`501`	`+ if (target.type !== "ForInStatement" && target.type !== "ForOfStatement") {`
`502`	`502`	`return false;`
`503`	`503`	`}`
`504`	`504`
`@@ -531,7 +531,7 @@ module.exports = {`
`531`	`531`	`let rhsNode = null;`
`532`	`532`
`533`	`533`	`return variable.references.some(ref => {`
`534`		`- if (isForInRef(ref)) {`
	`534`	`+ if (isForInOfRef(ref)) {`
`535`	`535`	`return true;`
`536`	`536`	`}`
`537`	`537`