Add no-will-update-set-state rule

README.md

@@ -102,6 +102,7 @@ Finally, enable all of the rules that you would like to use.  Use [our preset](#
 * [react/no-unescaped-entities](docs/rules/no-unescaped-entities.md): Prevent invalid characters from appearing in markup
 * [react/no-unknown-property](docs/rules/no-unknown-property.md): Prevent usage of unknown DOM property (fixable)
 * [react/no-unused-prop-types](docs/rules/no-unused-prop-types.md): Prevent definitions of unused prop types
+* [react/no-will-update-set-state](docs/rules/no-will-update-set-state.md): Prevent usage of `setState` in `componentWillUpdate`
 * [react/prefer-es6-class](docs/rules/prefer-es6-class.md): Enforce ES5 or ES6 class for React Components
 * [react/prefer-stateless-function](docs/rules/prefer-stateless-function.md): Enforce stateless React Components to be written as a pure function
 * [react/prop-types](docs/rules/prop-types.md): Prevent missing props validation in a React component definition

docs/rules/no-will-update-set-state.md

@@ -0,0 +1,90 @@
+# Prevent usage of setState in componentWillUpdate (no-will-update-set-state)
+
+Updating the state during the componentWillUpdate step can lead to indeterminate component state and is not allowed.
+
+## Rule Details
+
+The following patterns are considered warnings:
+
+```jsx
+var Hello = React.createClass({
+  componentWillUpdate: function() {
+     this.setState({
+        name: this.props.name.toUpperCase()
+      });
+    },
+  render: function() {
+    return <div>Hello {this.state.name}</div>;
+  }
+});
+```
+
+The following patterns are not considered warnings:
+
+```jsx
+var Hello = React.createClass({
+  componentWillUpdate: function() {
+    this.props.prepareHandler();
+  },
+  render: function() {
+    return <div>Hello {this.props.name}</div>;
+  }
+});
+```
+
+```jsx
+var Hello = React.createClass({
+  componentWillUpdate: function() {
+    this.prepareHandler(function callback(newName) {
+      this.setState({
+        name: newName
+      });
+    });
+  },
+  render: function() {
+    return <div>Hello {this.props.name}</div>;
+  }
+});
+```
+
+## Rule Options
+
+```js
+...
+"no-will-update-set-state": [<enabled>, <mode>]
+...
+```
+
+### `disallow-in-func` mode
+
+By default this rule forbids any call to `this.setState` in `componentWillUpdate` outside of functions. The `disallow-in-func` mode makes this rule more strict by disallowing calls to `this.setState` even within functions.
+
+The following patterns are considered warnings:
+
+```jsx
+var Hello = React.createClass({
+  componentDidUpdate: function() {
+     this.setState({
+        name: this.props.name.toUpperCase()
+      });
+    },
+  render: function() {
+    return <div>Hello {this.state.name}</div>;
+  }
+});
+```
+
+```jsx
+var Hello = React.createClass({
+  componentDidUpdate: function() {
+    this.prepareHandler(function callback(newName) {
+      this.setState({
+        name: newName
+      });
+    });
+  },
+  render: function() {
+    return <div>Hello {this.state.name}</div>;
+  }
+});
+```

index.js

@@ -20,6 +20,7 @@ var allRules = {
   'no-did-update-set-state': require('./lib/rules/no-did-update-set-state'),
   'no-render-return-value': require('./lib/rules/no-render-return-value'),
   'no-unescaped-entities': require('./lib/rules/no-unescaped-entities'),
+  'no-will-update-set-state': require('./lib/rules/no-will-update-set-state'),
   'react-in-jsx-scope': require('./lib/rules/react-in-jsx-scope'),
   'jsx-uses-vars': require('./lib/rules/jsx-uses-vars'),
   'jsx-handler-names': require('./lib/rules/jsx-handler-names'),

lib/rules/no-will-update-set-state.js

@@ -0,0 +1,66 @@
+/**
+ * @fileoverview Prevent usage of setState in componentWillUpdate
+ * @author Yannick Croissant
+ */
+'use strict';
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: 'Prevent usage of setState in componentWillUpdate',
+      category: 'Best Practices',
+      recommended: false
+    },
+
+    schema: [{
+      enum: ['disallow-in-func']
+    }]
+  },
+
+  create: function(context) {
+
+    var mode = context.options[0] || 'allow-in-func';
+
+    // --------------------------------------------------------------------------
+    // Public
+    // --------------------------------------------------------------------------
+
+    return {
+
+      CallExpression: function(node) {
+        var callee = node.callee;
+        if (
+          callee.type !== 'MemberExpression' ||
+          callee.object.type !== 'ThisExpression' ||
+          callee.property.name !== 'setState'
+        ) {
+          return;
+        }
+        var ancestors = context.getAncestors(callee).reverse();
+        var depth = 0;
+        for (var i = 0, j = ancestors.length; i < j; i++) {
+          if (/Function(Expression|Declaration)$/.test(ancestors[i].type)) {
+            depth++;
+          }
+          if (
+            (ancestors[i].type !== 'Property' && ancestors[i].type !== 'MethodDefinition') ||
+            ancestors[i].key.name !== 'componentWillUpdate' ||
+            (mode !== 'disallow-in-func' && depth > 1)
+          ) {
+            continue;
+          }
+          context.report({
+            node: callee,
+            message: 'Do not use setState in componentWillUpdate'
+          });
+          break;
+        }
+      }
+    };
+
+  }
+};