Handle UpdateExpressions in no-direct-mutation-state

This rule should also catch increment & decrement operators.

Author: zpao

lib/rules/no-direct-mutation-state.js

@@ -45,6 +45,36 @@ module.exports = {
       }
     }
 
+    /**
+     * Walks throughs the MemberExpression to the top-most property.
+     * @param {Object} node The node to process
+     * @returns {Object} The outer-most MemberExpression
+     */
+    function getOuterMemberExpression(node) {
+      while (node.object && node.object.property) {
+        node = node.object;
+      }
+      return node;
+    }
+
+    /**
+     * Determine if this MemberExpression is for `this.state`
+     * @param {Object} node The node to process
+     * @returns {Boolean}
+     */
+    function isStateMemberExpression(node) {
+      return node.object.type === 'ThisExpression' && node.property.name === 'state';
+    }
+
+    /**
+     * Determine if we should currently ignore assignments in this component.
+     * @param {?Object} component The component to process
+     * @returns {Boolean} True if we should skip assignment checks.
+     */
+    function shouldIgnoreComponent(component) {
+      return !component || (component.inConstructor && !component.inCallExpression);
+    }
+
     // --------------------------------------------------------------------------
     // Public
     // --------------------------------------------------------------------------
@@ -64,19 +94,12 @@ module.exports = {
       },
 
       AssignmentExpression(node) {
-        let item;
         const component = components.get(utils.getParentComponent());
-        if (!component || (component.inConstructor && !component.inCallExpression) || !node.left || !node.left.object) {
+        if (shouldIgnoreComponent(component) || !node.left || !node.left.object) {
           return;
         }
-        item = node.left;
-        while (item.object && item.object.property) {
-          item = item.object;
-        }
-        if (
-          item.object.type === 'ThisExpression' &&
-          item.property.name === 'state'
-        ) {
+        const item = getOuterMemberExpression(node.left);
+        if (isStateMemberExpression(item)) {
           const mutations = (component && component.mutations) || [];
           mutations.push(node.left.object);
           components.set(node, {
@@ -86,6 +109,22 @@ module.exports = {
         }
       },
 
+      UpdateExpression(node) {
+        const component = components.get(utils.getParentComponent());
+        if (shouldIgnoreComponent(component) || node.argument.type !== 'MemberExpression') {
+          return;
+        }
+        const item = getOuterMemberExpression(node.argument);
+        if (isStateMemberExpression(item)) {
+          const mutations = (component && component.mutations) || [];
+          mutations.push(item);
+          components.set(node, {
+            mutateSetState: true,
+            mutations
+          });
+        }
+      },
+
       'CallExpression:exit': function(node) {
         components.set(node, {
           inCallExpression: false

tests/lib/rules/no-direct-mutation-state.js

@@ -69,6 +69,14 @@ ruleTester.run('no-direct-mutation-state', rule, {
       '  }',
       '}'
     ].join('\n')
+  }, {
+    code: [
+      'class Hello extends React.Component {',
+      '  constructor() {',
+      '    this.state.foo = 1;',
+      '  }',
+      '}'
+    ].join('\n')
   }, {
     code: `
       class OneComponent extends Component {
@@ -97,6 +105,18 @@ ruleTester.run('no-direct-mutation-state', rule, {
     errors: [{
       message: 'Do not mutate state directly. Use setState().'
     }]
+  }, {
+    code: [
+      'var Hello = createReactClass({',
+      '  render: function() {',
+      '    this.state.foo++;',
+      '    return <div>Hello {this.props.name}</div>;',
+      '  }',
+      '});'
+    ].join('\n'),
+    errors: [{
+      message: 'Do not mutate state directly. Use setState().'
+    }]
   }, {
     code: [
       'var Hello = createReactClass({',