Promote isValidating to the global level of data and error

.gitignore

@@ -7,5 +7,6 @@ esm
 .next
 .DS_Store
 .idea
+.vscode
 examples/**/yarn.lock
 package-lock.json

src/cache.ts

@@ -42,7 +42,7 @@ export default class Cache implements CacheInterface {
   }
 
   // TODO: introduce namespace for the cache
-  serializeKey(key: keyInterface): [string, any, string] {
+  serializeKey(key: keyInterface): [string, any, string, string] {
     let args = null
     if (typeof key === 'function') {
       try {
@@ -63,8 +63,9 @@ export default class Cache implements CacheInterface {
     }
 
     const errorKey = key ? 'err@' + key : ''
+    const isValidatingKey = key ? 'validating@' + key : ''
 
-    return [key, args, errorKey]
+    return [key, args, errorKey, isValidatingKey]
   }
 
   subscribe(listener: cacheListener) {

src/types.ts

@@ -71,7 +71,8 @@ export type mutateInterface<Data = any> = (
 export type broadcastStateInterface<Data = any, Error = any> = (
   key: string,
   data: Data,
-  error?: Error
+  error?: Error,
+  isValidating?: boolean
 ) => void
 export type responseInterface<Data, Error> = {
   data?: Data
@@ -127,7 +128,7 @@ export interface CacheInterface {
   has(key: keyInterface): boolean
   delete(key: keyInterface): void
   clear(): void
-  serializeKey(key: keyInterface): [string, any, string]
+  serializeKey(key: keyInterface): [string, any, string, string]
   subscribe(listener: cacheListener): () => void
 }
 

src/use-swr.ts

@@ -75,18 +75,25 @@ if (!IS_SERVER && window.addEventListener) {
 const trigger: triggerInterface = (_key, shouldRevalidate = true) => {
   // we are ignoring the second argument which correspond to the arguments
   // the fetcher will receive when key is an array
-  const [key, , keyErr] = cache.serializeKey(_key)
+  const [key, , keyErr, keyValidating] = cache.serializeKey(_key)
   if (!key) return Promise.resolve()
 
   const updaters = CACHE_REVALIDATORS[key]
 
   if (key && updaters) {
     const currentData = cache.get(key)
     const currentError = cache.get(keyErr)
+    const currentIsValidating = cache.get(keyValidating)
     const promises = []
     for (let i = 0; i < updaters.length; ++i) {
       promises.push(
-        updaters[i](shouldRevalidate, currentData, currentError, i > 0)
+        updaters[i](
+          shouldRevalidate,
+          currentData,
+          currentError,
+          currentIsValidating,
+          i > 0
+        )
       )
     }
     // return new updated value
@@ -95,11 +102,16 @@ const trigger: triggerInterface = (_key, shouldRevalidate = true) => {
   return Promise.resolve(cache.get(key))
 }
 
-const broadcastState: broadcastStateInterface = (key, data, error) => {
+const broadcastState: broadcastStateInterface = (
+  key,
+  data,
+  error,
+  isValidating
+) => {
   const updaters = CACHE_REVALIDATORS[key]
   if (key && updaters) {
     for (let i = 0; i < updaters.length; ++i) {
-      updaters[i](false, data, error)
+      updaters[i](false, data, error, isValidating)
     }
   }
 }
@@ -167,7 +179,9 @@ const mutate: mutateInterface = async (
   if (updaters) {
     const promises = []
     for (let i = 0; i < updaters.length; ++i) {
-      promises.push(updaters[i](!!shouldRevalidate, data, error, i > 0))
+      promises.push(
+        updaters[i](!!shouldRevalidate, data, error, undefined, i > 0)
+      )
     }
     // return new updated value
     return Promise.all(promises).then(() => {
@@ -216,7 +230,7 @@ function useSWR<Data = any, Error = any>(
   // `key` can change but `fn` shouldn't
   // (because `revalidate` only depends on `key`)
   // `keyErr` is the cache key for error objects
-  const [key, fnArgs, keyErr] = cache.serializeKey(_key)
+  const [key, fnArgs, keyErr, keyValidating] = cache.serializeKey(_key)
 
   config = Object.assign(
     {},
@@ -232,6 +246,7 @@ function useSWR<Data = any, Error = any>(
 
   const initialData = cache.get(key) || config.initialData
   const initialError = cache.get(keyErr)
+  const initialIsValidating = cache.get(keyValidating)
 
   // if a state is accessed (data, error or isValidating),
   // we add the state to dependencies so if the state is
@@ -244,7 +259,7 @@ function useSWR<Data = any, Error = any>(
   const stateRef = useRef({
     data: initialData,
     error: initialError,
-    isValidating: false
+    isValidating: initialIsValidating
   })
 
   const rerender = useState(null)[1]
@@ -321,6 +336,11 @@ function useSWR<Data = any, Error = any>(
         dispatch({
           isValidating: true
         })
+        cache.set(keyValidating, true)
+        if (!shouldDeduping) {
+          // also update other hooks
+          broadcastState(key, undefined, undefined, true)
+        }
 
         let newData
         let startAt
@@ -393,6 +413,7 @@ function useSWR<Data = any, Error = any>(
 
         cache.set(key, newData)
         cache.set(keyErr, undefined)
+        cache.set(keyValidating, false)
 
         // new state for the reducer
         const newState: actionType<Data, Error> = {
@@ -414,7 +435,7 @@ function useSWR<Data = any, Error = any>(
 
         if (!shouldDeduping) {
           // also update other hooks
-          broadcastState(key, newData, undefined)
+          broadcastState(key, newData, undefined, false)
         }
       } catch (err) {
         delete CONCURRENT_PROMISES[key]
@@ -433,7 +454,7 @@ function useSWR<Data = any, Error = any>(
 
           if (!shouldDeduping) {
             // also broadcast to update other hooks
-            broadcastState(key, undefined, err)
+            broadcastState(key, undefined, err, false)
           }
         }
 
@@ -518,6 +539,7 @@ function useSWR<Data = any, Error = any>(
       shouldRevalidate = true,
       updatedData,
       updatedError,
+      updatedIsValidating,
       dedupe = true
     ) => {
       // update hook state
@@ -539,6 +561,14 @@ function useSWR<Data = any, Error = any>(
         needUpdate = true
       }
 
+      if (
+        typeof updatedIsValidating !== 'undefined' &&
+        stateRef.current.isValidating !== updatedIsValidating
+      ) {
+        newState.isValidating = updatedIsValidating
+        needUpdate = true
+      }
+
       if (needUpdate) {
         dispatch(newState)
       }

test/use-swr.test.tsx

@@ -220,6 +220,50 @@ describe('useSWR', () => {
     expect(container.textContent).toMatchInlineSnapshot(`"err err err"`)
   })
 
+  it('should broadcast isValidating', async () => {
+    function useBroadcast3() {
+      const { isValidating, revalidate } = useSWR(
+        'broadcast-3',
+        () => new Promise(res => setTimeout(res, 100)),
+        {
+          // need to turn of deduping otherwise
+          // revalidating will be ignored
+          dedupingInterval: 10
+        }
+      )
+      return { isValidating, revalidate }
+    }
+    function Initiator() {
+      const { isValidating, revalidate } = useBroadcast3()
+      useEffect(() => {
+        const timeout = setTimeout(() => {
+          revalidate()
+        }, 200)
+        return () => clearTimeout(timeout)
+      }, [])
+      return <>{isValidating ? 'true' : 'false'}</>
+    }
+    function Consumer() {
+      const { isValidating } = useBroadcast3()
+      return <>{isValidating ? 'true' : 'false'}</>
+    }
+    function Page() {
+      return (
+        <>
+          <Initiator /> <Consumer /> <Consumer />
+        </>
+      )
+    }
+    const { container } = render(<Page />)
+    expect(container.textContent).toMatchInlineSnapshot(`"true true true"`)
+    await act(() => new Promise(res => setTimeout(res, 100)))
+    expect(container.textContent).toMatchInlineSnapshot(`"false false false"`)
+    await act(() => new Promise(res => setTimeout(res, 100)))
+    expect(container.textContent).toMatchInlineSnapshot(`"true true true"`)
+    await act(() => new Promise(res => setTimeout(res, 100)))
+    expect(container.textContent).toMatchInlineSnapshot(`"false false false"`)
+  })
+
   it('should accept object args', async () => {
     const obj = { v: 'hello' }
     const arr = ['world']