Add jsx-boolean-value rule (fixes #11)

Author: yannickcr

README.md

@@ -43,6 +43,7 @@ Finally, enable all of the rules that you would like to use.
 {
   "rules": {
     "react/display-name": 1,
+    "react/jsx-boolean-value": 1,
     "react/jsx-quotes": 1,
     "react/jsx-no-undef": 1,
     "react/jsx-sort-props": 1,
@@ -63,6 +64,7 @@ Finally, enable all of the rules that you would like to use.
 # List of supported rules
 
 * [display-name](docs/rules/display-name.md): Prevent missing displayName in a React component definition
+* [jsx-boolean-value](docs/rules/jsx-boolean-value.md): Enforce boolean attributes notation in JSX
 * [jsx-quotes](docs/rules/jsx-quotes.md): Enforce quote style for JSX attributes
 * [jsx-no-undef](docs/rules/jsx-no-undef.md): Disallow undeclared variables in JSX
 * [jsx-sort-props](docs/rules/jsx-sort-props.md): Enforce props alphabetical sorting

docs/rules/jsx-boolean-value.md

@@ -0,0 +1,35 @@
+# Enforce boolean attributes notation in JSX (jsx-boolean-value)
+
+In JSX when using a boolean attribute you can set the attribute value to `true` or omit the value. This rule will enforce one or the other to keep consistency in your code.
+
+## Rule Details
+
+This rule takes one argument. If it is `"always"` then it warns whenever an attribute is missing it's value. If `"never"` then it warns if an attribute has a `true` value. The default value of this option is `"never"`.
+
+The following patterns are considered warnings when configured `"never"`:
+
+```js
+var Hello = <Hello personal={true} />;
+```
+
+The following patterns are not considered warnings when configured `"never"`:
+
+```js
+var Hello = <Hello personal />;
+```
+
+The following patterns are considered warnings when configured `"always"`:
+
+```js
+var Hello = <Hello personal />;
+```
+
+The following patterns are not considered warnings when configured `"always"`:
+
+```js
+var Hello = <Hello personal={true} />;
+```
+
+## When Not To Use It
+
+If you do not want to enforce any style for boolean attributes, then you can disable this rule.

index.js

@@ -15,7 +15,8 @@ module.exports = {
     'jsx-no-undef': require('./lib/rules/jsx-no-undef'),
     'jsx-quotes': require('./lib/rules/jsx-quotes'),
     'no-unknown-property': require('./lib/rules/no-unknown-property'),
-    'jsx-sort-props': require('./lib/rules/jsx-sort-props')
+    'jsx-sort-props': require('./lib/rules/jsx-sort-props'),
+    'jsx-boolean-value': require('./lib/rules/jsx-boolean-value')
   },
   rulesConfig: {
     'jsx-uses-react': 0,
@@ -31,6 +32,7 @@ module.exports = {
     'jsx-no-undef': 0,
     'jsx-quotes': 0,
     'no-unknown-property': 0,
-    'jsx-sort-props': 0
+    'jsx-sort-props': 0,
+    'jsx-boolean-value': 0
   }
 };

lib/rules/jsx-boolean-value.js

@@ -0,0 +1,36 @@
+/**
+ * @fileoverview Enforce boolean attributes notation in JSX
+ * @author Yannick Croissant
+ */
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = function(context) {
+
+  var configuration = context.options[0] || {};
+
+  var NEVER_MESSAGE = 'Value must be omitted for boolean attributes';
+  var ALWAYS_MESSAGE = 'Value must be set for boolean attributes';
+
+  return {
+    JSXAttribute: function(node) {
+      switch (configuration) {
+        case 'always':
+          if (node.value === null) {
+            context.report(node, ALWAYS_MESSAGE);
+          }
+          break;
+        case 'never':
+          if (node.value && node.value.type === 'JSXExpressionContainer' && node.value.expression.value === true) {
+            context.report(node, NEVER_MESSAGE);
+          }
+          break;
+        default:
+          break;
+      }
+    }
+  };
+};

tests/lib/rules/jsx-boolean-value.js

@@ -0,0 +1,30 @@
+/**
+ * @fileoverview Enforce boolean attributes notation in JSX
+ * @author Yannick Croissant
+ */
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+var eslint = require('eslint').linter;
+var ESLintTester = require('eslint-tester');
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+var eslintTester = new ESLintTester(eslint);
+eslintTester.addRuleTest('lib/rules/jsx-boolean-value', {
+    valid: [
+        {code: '<App foo />;', args: [1, 'never'], ecmaFeatures: {jsx: true}},
+        {code: '<App foo={true} />;', args: [1, 'always'], ecmaFeatures: {jsx: true}}
+    ],
+    invalid: [
+        {code: '<App foo={true} />;', args: [1, 'never'],
+         errors: [{message: 'Value must be omitted for boolean attributes'}], ecmaFeatures: {jsx: true}},
+        {code: '<App foo />;', args: [1, 'always'],
+         errors: [{message: 'Value must be set for boolean attributes'}], ecmaFeatures: {jsx: true}}
+    ]
+});