enhance: Immediately fetch polling subscriptions

docs/api/PollingSubscription.md

@@ -7,10 +7,18 @@ hide_title: true
 # PollingSubscription implements [Subscription](./SubscriptionManager.md)
 
 Will dispatch a `fetch` action at the minimum interval of all subscriptions to this
-resource. Pauses when offline. Immediately fetches when online status returns.
+resource.
+
+- Pauses when offline.
+- Immediately fetches when online status returns.
+- Immediately fetches any new subscriptions.
 
 ```tsx
-import { SubscriptionManager, PollingSubscription, CacheProvider } from 'rest-hooks';
+import {
+  SubscriptionManager,
+  PollingSubscription,
+  CacheProvider,
+} from 'rest-hooks';
 import ReactDOM from 'react-dom';
 
 const subscriptionManager = new SubscriptionManager(PollingSubscription);
@@ -19,7 +27,7 @@ ReactDOM.render(
   <CacheProvider subscriptionManager={subscriptionManager}>
     <App />
   </CacheProvider>,
-  document.body
+  document.body,
 );
 ```
 

packages/rest-hooks/src/state/PollingSubscription.ts

@@ -31,6 +31,7 @@ export default class PollingSubscription implements Subscription {
     this.url = url;
     this.frequencyHistogram.set(this.frequency, 1);
     this.dispatch = dispatch;
+    if (isOnline()) this.update();
     this.run();
   }
 

packages/rest-hooks/src/state/__tests__/pollingSubscription.ts

@@ -47,11 +47,12 @@ describe('PollingSubscription', () => {
     ).toThrow();
   });
 
-  it('should not call immediately', () => {
-    expect(dispatch.mock.calls.length).toBe(0);
+  it('should call immediately', () => {
+    expect(dispatch.mock.calls.length).toBe(1);
   });
 
   it('should call after period', () => {
+    dispatch.mockReset();
     jest.advanceTimersByTime(5000);
     expect(dispatch.mock.calls.length).toBe(1);
     expect(dispatch.mock.calls[0]).toMatchSnapshot();

website/versioned_docs/version-4.0/api/PollingSubscription.md

@@ -0,0 +1,42 @@
+---
+title: PollingSubscription implements Subscription
+sidebar_label: PollingSubscription
+hide_title: true
+id: version-4.0-PollingSubscription
+original_id: PollingSubscription
+---
+
+# PollingSubscription implements [Subscription](./SubscriptionManager.md)
+
+Will dispatch a `fetch` action at the minimum interval of all subscriptions to this
+resource.
+
+- Pauses when offline.
+- Immediately fetches when online status returns.
+- Immediately fetches any new subscriptions.
+
+```tsx
+import {
+  SubscriptionManager,
+  PollingSubscription,
+  CacheProvider,
+} from 'rest-hooks';
+import ReactDOM from 'react-dom';
+
+const subscriptionManager = new SubscriptionManager(PollingSubscription);
+
+ReactDOM.render(
+  <CacheProvider subscriptionManager={subscriptionManager}>
+    <App />
+  </CacheProvider>,
+  document.body,
+);
+```
+
+## Dispatched Actions
+
+- 'rest-hooks/fetch'
+
+> #### Note:
+>
+> This is already used by `CacheProvider` by default.