Fix ignorePureComponents when using class expressions.

lib/rules/prefer-stateless-function.js

@@ -296,16 +296,19 @@ module.exports = {
       });
     }
 
-    return {
-      ClassDeclaration: function (node) {
-        if (ignorePureComponents && utils.isPureComponent(node)) {
-          markSCUAsDeclared(node);
-        }
+    function visitClass(node) {
+      if (ignorePureComponents && utils.isPureComponent(node)) {
+        markSCUAsDeclared(node);
+      }
 
-        if (node.decorators && node.decorators.length) {
-          markDecoratorsAsUsed(node);
-        }
-      },
+      if (node.decorators && node.decorators.length) {
+        markDecoratorsAsUsed(node);
+      }
+    }
+
+    return {
+      ClassDeclaration: visitClass,
+      ClassExpression: visitClass,
 
       // Mark `this` destructuring as a usage of `this`
       VariableDeclarator: function(node) {
@@ -401,7 +404,6 @@ module.exports = {
           if (list[component].hasSCU && list[component].usePropsOrContext) {
             continue;
           }
-
           context.report({
             node: list[component].node,
             message: 'Component should be written as a pure function'

tests/lib/rules/prefer-stateless-function.js

@@ -64,6 +64,19 @@ ruleTester.run('prefer-stateless-function', rule, {
       options: [{
         ignorePureComponents: true
       }]
+    }, {
+      // Extends from PureComponent in an expression context.
+      code: [
+        'const Foo = class extends React.PureComponent {',
+        '  render() {',
+        '    return <div>{this.props.foo}</div>;',
+        '  }',
+        '};'
+      ].join('\n'),
+      parserOptions: parserOptions,
+      options: [{
+        ignorePureComponents: true
+      }]
     }, {
       // Has a lifecyle method
       code: [