Add 'persist' option to Pending helper so it can also show while loading for the first time.

Author: ghengeveld

README.md

@@ -268,7 +268,8 @@ Renders only while the deferred promise is still pending (not yet run).
 
 #### Props
 
-- `children` {Function|Node} Function which receives props object or React node
+- `persist` {boolean} Show until we have data, even while loading or when an error occurred. By default it hides as soon as the promise starts loading.
+- `children` {Function|Node} Function which receives props object or React node.
 
 #### Examples
 
@@ -281,7 +282,17 @@ Renders only while the deferred promise is still pending (not yet run).
 ```
 
 ```js
-<Async.Pending>{({ run }) => <button onClick={run}>Run</button>}</Async.Pending>
+<Async.Pending persist>
+  {({ error, isLoading, run }) => (
+    <div>
+      <p>This text is only rendered while the promise has not resolved yet.</p>
+      <button onClick={run} disabled={!isLoading}>
+        Run
+      </button>
+      {error && <p>{error.message}</p>}
+    </div>
+  )}
+</Async.Pending>
 ```
 
 ## Acknowledgements

src/index.js

@@ -113,12 +113,15 @@ export const createInstance = (defaultProps = {}) => {
   /**
    * Renders only when deferred promise is pending (not yet run).
    *
+   * @prop {boolean} persist Show until we have data, even while loading or when an error occurred
    * @prop {Function|Node} children Function (passing error and props) or React node
    */
-  Async.Pending = ({ children }) => (
+  Async.Pending = ({ children, persist }) => (
     <Consumer>
       {props => {
-        if (props.isLoading || props.data || props.error) return null
+        if (props.data !== undefined) return null
+        if (!persist && props.isLoading) return null
+        if (!persist && props.error !== undefined) return null
         return typeof children === "function" ? children(props) : children || null
       }}
     </Consumer>