feature: provide config.isIdle indicating idle state and stop revalid…

…ation (#845)

* feature: ignore revalidations when config.isIdle() is truthy

* add test

* rename to isPaused(), ignore errors in catch

src/config.ts

@@ -70,7 +70,8 @@ const defaultConfig: ConfigInterface = {
 
   fetcher: webPreset.fetcher,
   isOnline: webPreset.isOnline,
-  isDocumentVisible: webPreset.isDocumentVisible
+  isDocumentVisible: webPreset.isDocumentVisible,
+  isPaused: () => false
 }
 
 export { cache }

src/types.ts

@@ -22,6 +22,7 @@ export interface ConfigInterface<
 
   isOnline?: () => boolean
   isDocumentVisible?: () => boolean
+  isPaused?: () => boolean
   onLoadingSlow?: (key: string, config: ConfigInterface<Data, Error>) => void
   onSuccess?: (
     data: Data,

src/use-swr.ts

@@ -376,6 +376,7 @@ function useSWR<Data = any, Error = any>(
     ): Promise<boolean> => {
       if (!key || !fn) return false
       if (unmountedRef.current) return false
+      if (config.isPaused()) return false
       revalidateOpts = Object.assign({ dedupe: false }, revalidateOpts)
 
       let loading = true
@@ -499,6 +500,13 @@ function useSWR<Data = any, Error = any>(
         delete CONCURRENT_PROMISES[key]
         delete CONCURRENT_PROMISES_TS[key]
 
+        if (config.isPaused()) {
+          dispatch({
+            isValidating: false
+          })
+          return false
+        }
+
         cache.set(keyErr, err)
 
         // get a new error

test/use-swr.test.tsx

@@ -1875,15 +1875,15 @@ describe('useSWR - local mutation', () => {
   })
 })
 
-describe('useSWR - context configs', () => {
+describe('useSWR - configs', () => {
   afterEach(cleanup)
 
   it('should read the config fallback from the context', async () => {
     let value = 0
     const fetcher = () => value++
 
     function Section() {
-      const { data } = useSWR('dynamic-10')
+      const { data } = useSWR('config-0')
       return <div>data: {data}</div>
     }
     function Page() {
@@ -1905,6 +1905,48 @@ describe('useSWR - context configs', () => {
     await act(() => new Promise(res => setTimeout(res, 110))) // update
     expect(container.firstChild.textContent).toMatchInlineSnapshot(`"data: 1"`)
   })
+
+  it('should stop revalidations when config.isPaused returns true', async () => {
+    const key = 'config-1'
+    let value = 0
+    let isSwrPaused = false
+    const fetcher = () => {
+      if (value === 2) throw new Error()
+      return value++
+    }
+
+    function Page() {
+      // config provider
+      const { mutate: boundMutate, data } = useSWR(key, fetcher, {
+        revalidateOnMount: true,
+        isPaused() {
+          return isSwrPaused
+        }
+      })
+
+      useEffect(() => {
+        // revalidate on mount and turn to idle
+        isSwrPaused = true
+      }, [])
+
+      return <div onClick={() => boundMutate()}>data: {data}</div>
+    }
+    const { container } = render(<Page />)
+
+    await waitForDomChange({ container })
+    expect(container.firstChild.textContent).toMatchInlineSnapshot(`"data: 0"`)
+    await act(async () => await 0)
+    expect(container.firstChild.textContent).toMatchInlineSnapshot(`"data: 0"`)
+    fireEvent.click(container.firstElementChild)
+    await act(async () => await 0)
+    expect(container.firstChild.textContent).toMatchInlineSnapshot(`"data: 0"`)
+    isSwrPaused = true
+    fireEvent.click(container.firstElementChild)
+    isSwrPaused = false
+    await act(async () => await 0)
+    // await act(() => {return new Promise(res => setTimeout(res, 50))})
+    expect(container.firstChild.textContent).toMatchInlineSnapshot(`"data: 0"`)
+  })
 })
 
 describe('useSWR - suspense', () => {