New: no-global-assign rule (fixes #6585)

conf/eslint.json

@@ -41,6 +41,7 @@
         "no-fallthrough": "error",
         "no-floating-decimal": "off",
         "no-func-assign": "error",
+        "no-global-assign": "off",
         "no-implicit-coercion": "off",
         "no-implicit-globals": "off",
         "no-implied-eval": "off",

docs/rules/no-extend-native.md

@@ -1,5 +1,7 @@
 # Disallow Extending of Native Objects (no-extend-native)
 
+This rule was **deprecated** in ESLint v3.2.0 and replaced by the [no-global-assign](no-global-assign.md) rule.
+
 In JavaScript, you can extend any object, including builtin or "native" objects. Sometimes people change the behavior of these native objects in ways that break the assumptions made about them in other parts of the code.
 
 For example here we are overriding a builtin method that will then affect all Objects, even other builtins.
@@ -72,4 +74,4 @@ You may want to disable this rule when working with polyfills that try to patch
 
 ## Related Rules
 
-* [no-native-reassign](no-native-reassign.md)
+* [no-global-assign](no-global-assign.md)

docs/rules/no-global-assign.md

@@ -0,0 +1,89 @@
+# Disallow assignment to native objects or read-only global variables (no-global-assign)
+
+JavaScript environments contain a number of built-in global variables, such as `window` in browsers and `process` in Node.js. In almost all cases, you don't want to assign a value to these global variables as doing so could result in losing access to important functionality. For example, you probably don't want to do this in browser code:
+
+```js
+window = {};
+```
+
+While examples such as `window` are obvious, there are often hundreds of built-in global objects provided by JavaScript environments. It can be hard to know if you're assigning to a global variable or not.
+
+## Rule Details
+
+This rule disallows modifications to read-only global variables.
+
+ESLint has the capability to configure global variables as read-only.
+
+* [Specifying Environments](../user-guide/configuring#specifying-environments)
+* [Specifying Globals](../user-guide/configuring#specifying-globals)
+
+Examples of **incorrect** code for this rule:
+
+```js
+/*eslint no-global-assign: "error"*/
+
+Object = null
+undefined = 1
+```
+
+```js
+/*eslint no-global-assign: "error"*/
+/*eslint-env browser*/
+
+window = {}
+length = 1
+top = 1
+```
+
+```js
+/*eslint no-global-assign: "error"*/
+/*globals a:false*/
+
+a = 1
+```
+
+Examples of **correct** code for this rule:
+
+```js
+/*eslint no-global-assign: "error"*/
+
+a = 1
+var b = 1
+b = 2
+```
+
+```js
+/*eslint no-global-assign: "error"*/
+/*eslint-env browser*/
+
+onload = function() {}
+```
+
+```js
+/*eslint no-global-assign: "error"*/
+/*globals a:true*/
+
+a = 1
+```
+
+## Options
+
+This rule accepts an `exceptions` option, which can be used to specify a list of builtins for which reassignments will be allowed:
+
+```json
+{
+    "rules": {
+        "no-global-assign": ["error", {"exceptions": ["Object"]}]
+    }
+}
+```
+
+## When Not To Use It
+
+If you are trying to override one of the native objects.
+
+## Related Rules
+
+* [no-extend-native](no-extend-native.md)
+* [no-redeclare](no-redeclare.md)
+* [no-shadow](no-shadow.md)

docs/user-guide/configuring.md

@@ -227,7 +227,7 @@ And in YAML:
 
 These examples allow `var1` to be overwritten in your code, but disallow it for `var2`.
 
-**Note:** Enable the [no-native-reassign](../rules/no-native-reassign.md) rule to disallow modifications to read-only global variables in your code.
+**Note:** Enable the [no-global-assign](../rules/no-global-assign.md) rule to disallow modifications to read-only global variables in your code.
 
 ## Configuring Plugins
 

lib/rules/no-extend-native.js

@@ -1,6 +1,7 @@
 /**
  * @fileoverview Rule to flag adding properties to native object's prototypes.
  * @author David Nelson
+ * @deprecated in ESLint v3.2.0
  */
 
 "use strict";

lib/rules/no-global-assign.js

@@ -0,0 +1,83 @@
+/**
+ * @fileoverview Rule to disallow assignments to native objects or read-only global variables
+ * @author Ilya Volodin
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        docs: {
+            description: "disallow assignments to native objects or read-only global variables",
+            category: "Best Practices",
+            recommended: true
+        },
+
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    exceptions: {
+                        type: "array",
+                        items: {type: "string"},
+                        uniqueItems: true
+                    }
+                },
+                additionalProperties: false
+            }
+        ]
+    },
+
+    create: function(context) {
+        var config = context.options[0];
+        var exceptions = (config && config.exceptions) || [];
+
+        /**
+         * Reports write references.
+         * @param {Reference} reference - A reference to check.
+         * @param {int} index - The index of the reference in the references.
+         * @param {Reference[]} references - The array that the reference belongs to.
+         * @returns {void}
+         */
+        function checkReference(reference, index, references) {
+            var identifier = reference.identifier;
+
+            if (reference.init === false &&
+                reference.isWrite() &&
+
+                // Destructuring assignments can have multiple default value,
+                // so possibly there are multiple writeable references for the same identifier.
+                (index === 0 || references[index - 1].identifier !== identifier)
+            ) {
+                context.report({
+                    node: identifier,
+                    message: "Read-only global '{{name}}' should not be modified.",
+                    data: identifier
+                });
+            }
+        }
+
+        /**
+         * Reports write references if a given variable is read-only builtin.
+         * @param {Variable} variable - A variable to check.
+         * @returns {void}
+         */
+        function checkVariable(variable) {
+            if (variable.writeable === false && exceptions.indexOf(variable.name) === -1) {
+                variable.references.forEach(checkReference);
+            }
+        }
+
+        return {
+            Program: function() {
+                var globalScope = context.getScope();
+
+                globalScope.variables.forEach(checkVariable);
+            }
+        };
+    }
+};

packages/eslint-config-eslint/default.yml

@@ -39,6 +39,7 @@ rules:
     no-extra-bind: "error"
     no-fallthrough: "error"
     no-floating-decimal: "error"
+    no-global-assign: "error"
     no-implied-eval: "error"
     no-invalid-this: "error"
     no-iterator: "error"
@@ -49,7 +50,7 @@ rules:
     no-mixed-spaces-and-tabs: ["error", false]
     no-multi-spaces: "error"
     no-multi-str: "error"
-    no-native-reassign: "error"
+    no-native-reassign: "off"
     no-nested-ternary: "error"
     no-new: "error"
     no-new-func: "error"

tests/lib/cli.js

@@ -472,7 +472,7 @@ describe("cli", function() {
     describe("when executing with global flag", function() {
         it("should default defined variables to read-only", function() {
             var filePath = getFixturePath("undef.js");
-            var exit = cli.execute("--global baz,bat --no-ignore --rule no-native-reassign:2 " + filePath);
+            var exit = cli.execute("--global baz,bat --no-ignore --rule no-global-assign:2 " + filePath);
 
             assert.isTrue(log.info.calledOnce);
             assert.equal(exit, 1);

tests/lib/rules/no-extend-native.js

@@ -1,6 +1,7 @@
 /**
  * @fileoverview Tests for no-extend-native rule.
  * @author David Nelson
+ * @deprecated in ESLint v3.2.0
  */
 
 "use strict";

tests/lib/rules/no-global-assign.js

@@ -0,0 +1,61 @@
+/**
+ * @fileoverview Tests for no-global-assign rule.
+ * @author Ilya Volodin
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+var rule = require("../../../lib/rules/no-global-assign"),
+    RuleTester = require("../../../lib/testers/rule-tester");
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+var ruleTester = new RuleTester();
+
+ruleTester.run("no-global-assign", rule, {
+    valid: [
+        "string = 'hello world';",
+        "var string;",
+        { code: "Object = 0;", options: [{exceptions: ["Object"]}] },
+        { code: "top = 0;" },
+        { code: "onload = 0;", env: {browser: true} },
+        { code: "require = 0;" },
+        { code: "a = 1", globals: {a: true}},
+        "/*global a:true*/ a = 1"
+    ],
+    invalid: [
+        { code: "String = 'hello world';", errors: [{ message: "Read-only global 'String' should not be modified.", type: "Identifier"}] },
+        { code: "String++;", errors: [{ message: "Read-only global 'String' should not be modified.", type: "Identifier"}] },
+        {
+            code: "({Object = 0, String = 0} = {});",
+            parserOptions: { ecmaVersion: 6 },
+            errors: [
+                {message: "Read-only global 'Object' should not be modified.", type: "Identifier"},
+                {message: "Read-only global 'String' should not be modified.", type: "Identifier"}
+            ]
+        },
+        {
+            code: "top = 0;",
+            env: {browser: true},
+            errors: [{ message: "Read-only global 'top' should not be modified.", type: "Identifier"}]
+        },
+        {
+            code: "require = 0;",
+            env: {node: true},
+            errors: [{ message: "Read-only global 'require' should not be modified.", type: "Identifier"}]
+        },
+
+        // Notifications of readonly are moved from no-undef: https://github.com/eslint/eslint/issues/4504
+        { code: "/*global b:false*/ function f() { b = 1; }", errors: [{ message: "Read-only global 'b' should not be modified.", type: "Identifier"}] },
+        { code: "function f() { b = 1; }", global: { b: false }, errors: [{ message: "Read-only global 'b' should not be modified.", type: "Identifier"}] },
+        { code: "/*global b:false*/ function f() { b++; }", errors: [{ message: "Read-only global 'b' should not be modified.", type: "Identifier"}] },
+        { code: "/*global b*/ b = 1;", errors: [{ message: "Read-only global 'b' should not be modified.", type: "Identifier"}] },
+        { code: "Array = 1;", errors: [{ message: "Read-only global 'Array' should not be modified.", type: "Identifier"}] }
+    ]
+});