Fix: one-var allows uninitialized vars in ForIn/ForOf (fixes #5744) (#…

…6272)
eslint · Jun 5, 2016 · 316a507 · 316a507
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diff --git a/docs/rules/one-var.md b/docs/rules/one-var.md
@@ -203,6 +203,8 @@ function foo() {
 
 When configured with an object as the first option, you can individually control how `var`, `let`, and `const` are handled, or alternatively how `uninitialized` and `initialized` variables are handled (which if used will override `var`, `let`, and `const`).
 
+**Note:** A variable declared in a for-in or for-of loop will not be flagged with the option `{ uninitialized: "always" }`, as this value is determined by the loop.
+
 The following patterns are not considered problems:
 
 ```js
@@ -234,6 +236,16 @@ function foo() {
     var foo = true;
     var bar = false;
 }
+
+let x, y;
+for (let z of foo) {
+    doSomething(z);
+}
+
+let x, y, z;
+for (z of foo) {
+    doSomething(z);
+}
 ```
 
 If you are configuring the rule with an object, by default, if you didn't specify declaration type it will not be checked. So the following pattern is not considered a warning when options are set to: `{ var: "always", let: "always" }`

diff --git a/lib/rules/one-var.js b/lib/rules/one-var.js
@@ -286,6 +286,9 @@ module.exports = {
                             context.report(node, "Combine this with the previous '" + type + "' statement with initialized variables.");
                         }
                         if (options[type].uninitialized === MODE_ALWAYS) {
+                            if (node.parent.left === node && (node.parent.type === "ForInStatement" || node.parent.type === "ForOfStatement")) {
+                                return;
+                            }
                             context.report(node, "Combine this with the previous '" + type + "' statement with uninitialized variables.");
                         }
                     }

diff --git a/tests/lib/rules/one-var.js b/tests/lib/rules/one-var.js
@@ -188,6 +188,56 @@ ruleTester.run("one-var", rule, {
             code: "for (let x in foo) {}; for (let y in foo) {}",
             parserOptions: { ecmaVersion: 6 },
             options: [{ uninitialized: "always" }]
+        },
+        {
+            code: "var x; for (var y in foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x, y; for (y in foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x, y; for (var z in foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x; for (var y in foo) {var bar = y; for (var z in bar) {}}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var a = 1; var b = 2; var x, y; for (var z in foo) {var baz = z; for (var d in baz) {}}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x; for (var y of foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x, y; for (y of foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x, y; for (var z of foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var x; for (var y of foo) {var bar = y; for (var z of bar) {}}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
+        },
+        {
+            code: "var a = 1; var b = 2; var x, y; for (var z of foo) {var baz = z; for (var d of baz) {}}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }]
         }
     ],
     invalid: [
@@ -482,6 +532,72 @@ ruleTester.run("one-var", rule, {
                 line: 1,
                 column: 10
             } ]
+        },
+        {
+            code: "var x = 1, y = 2; for (var z in foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }],
+            errors: [{
+                message: "Split initialized 'var' declarations into multiple statements.",
+                type: "VariableDeclaration",
+                line: 1,
+                column: 1
+            }]
+        },
+        {
+            code: "var x = 1, y = 2; for (var z of foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }],
+            errors: [{
+                message: "Split initialized 'var' declarations into multiple statements.",
+                type: "VariableDeclaration",
+                line: 1,
+                column: 1
+            }]
+        },
+        {
+            code: "var x; var y; for (var z in foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }],
+            errors: [{
+                message: "Combine this with the previous 'var' statement with uninitialized variables.",
+                type: "VariableDeclaration",
+                line: 1,
+                column: 8
+            }]
+        },
+        {
+            code: "var x; var y; for (var z of foo) {}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }],
+            errors: [{
+                message: "Combine this with the previous 'var' statement with uninitialized variables.",
+                type: "VariableDeclaration",
+                line: 1,
+                column: 8
+            }]
+        },
+        {
+            code: "var x; for (var y in foo) {var bar = y; var a; for (var z of bar) {}}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }],
+            errors: [{
+                message: "Combine this with the previous 'var' statement with uninitialized variables.",
+                type: "VariableDeclaration",
+                line: 1,
+                column: 41
+            }]
+        },
+        {
+            code: "var a = 1; var b = 2; var x, y; for (var z of foo) {var c = 3, baz = z; for (var d in baz) {}}",
+            parserOptions: { ecmaVersion: 6 },
+            options: [{ initialized: "never", uninitialized: "always" }],
+            errors: [{
+                message: "Split initialized 'var' declarations into multiple statements.",
+                type: "VariableDeclaration",
+                line: 1,
+                column: 53
+            }]
         }
     ]
 });