Warning about components implementing shouldComponentUpdate()

instead of throwing an error.

index.js

@@ -4,8 +4,11 @@
  */
 'use strict';
 
+var warning = require('fbjs/lib/warning');
 var shallowEqual = require('fbjs/lib/shallowEqual');
 
+
+
 /**
  * Tells if a component should update given it's next props
  * and state.
@@ -18,18 +21,22 @@ function shouldComponentUpdate(nextProps, nextState) {
 }
 
 /**
- * Get a text description of the component that can be used to identify it
- * in error messages.
+ * Returns a text description of the component that can be
+ * used to identify it in error messages.
  *
- * Adapted from: https://github.com/facebook/react/blob/v15.4.0-rc.3/src/renderers/shared/stack/reconciler/ReactCompositeComponent.js#L1143
- * @return {string} The name or "a component".
+ * @see https://github.com/facebook/react/blob/v15.4.0-rc.3/src/renderers/shared/stack/reconciler/ReactCompositeComponent.js#L1143
+ * @param {function} component The component.
+ * @return {string} The name of the component.
  */
 function getComponentName(component) {
   var constructor = component.prototype && component.prototype.constructor;
+
   return (
-    component.displayName || (constructor && constructor.displayName) ||
-    component.name || (constructor && constructor.name) ||
-    "a component"
+    component.displayName
+    || (constructor && constructor.displayName)
+    || component.name
+    || (constructor && constructor.name)
+    || 'a component'
   );
 }
 
@@ -40,10 +47,16 @@ function getComponentName(component) {
  */
 function pureRenderDecorator(component) {
   if (component.prototype.shouldComponentUpdate !== undefined) {
-    var componentName = getComponentName(component);
-    throw new Error("Cannot add a pure render decorator to " + componentName
-      + ", because it already implements `shouldComponentUpdate()`.")
+    // We're not using the condition mecanism of warning()
+    // here to avoid useless calls to getComponentName().
+    warning(
+      false,
+      'Cannot decorate `%s` with @pureRenderDecorator, '
+      + 'because it already implements `shouldComponentUpdate().',
+      getComponentName(component)
+    )
   }
+
   component.prototype.shouldComponentUpdate = shouldComponentUpdate;
   return component;
 }