remove unecessary rerender

add support for non-promise values

Author: Josef Blake

.babelrc renamed to __tests__/.babelrc

@@ -19,22 +19,22 @@ afterEach(() => {
   ReactDOM.unmountComponentAtNode(mountNode);
 });
 
-test("renders", () => {
+test("renders (default)", () => {
   expect(() => mount(<Async />)).not.toThrowError();
 });
 
-test("throws error if not passed a promise", () => {
+test("supports non-promise values", () => {
   const onError = jest.fn();
 
-  [1, {}, [], null].forEach(notPromise => {
+  [1, {}, [], undefined, null].forEach(notPromise => {
     mount(
       <ErrorBoundary onError={onError}>
         <Async await={notPromise} />
       </ErrorBoundary>
     );
   });
 
-  expect(onError).toHaveBeenCalledTimes(4);
+  expect(onError).toHaveBeenCalledTimes(0);
 });
 
 test("resolves promise", async () => {

__tests__/Async.js

@@ -1,8 +1,18 @@
 import React from "react";
 
+const isPromise = promise => promise && typeof promise.then === "function";
+
 const cache = new WeakMap();
 
 const getCachedState = promise => {
+  if (!isPromise(promise)) {
+    return {
+      status: 1,
+      value: promise,
+      error: undefined
+    };
+  }
+
   if (!cache.has(promise)) {
     const result = {
       status: 0,
@@ -43,10 +53,12 @@ class Async extends React.Component {
       subscribed = false;
     };
 
-    this.props.await.then(
-      () => subscribed && this.componentWillMount(),
-      () => subscribed && this.componentWillMount()
-    );
+    if (this.state.status === 0) {
+      this.props.await.then(
+        () => subscribed && this.componentWillMount(),
+        () => subscribed && this.componentWillMount()
+      );
+    }
   }
 
   componentDidUpdate(prevProps) {
@@ -73,7 +85,6 @@ class Async extends React.Component {
 }
 
 Async.defaultProps = {
-  await: Promise.resolve(),
   children: () => null
 };