feat: Add populateCache option to mutate

src/index.ts

@@ -21,6 +21,7 @@ export {
   BareFetcher,
   Fetcher,
   MutatorCallback,
+  MutatorOptions,
   Middleware,
   Arguments
 } from './types'

src/types.ts

@@ -142,13 +142,19 @@ export type MutatorCallback<Data = any> = (
   currentValue?: Data
 ) => Promise<undefined | Data> | undefined | Data
 
+export type MutatorOptions = {
+  revalidate?: boolean
+  populateCache?: boolean
+}
+
 export type Broadcaster<Data = any, Error = any> = (
   cache: Cache<Data>,
   key: string,
   data: Data,
   error?: Error,
   isValidating?: boolean,
-  shouldRevalidate?: boolean
+  revalidate?: boolean,
+  populateCache?: boolean
 ) => Promise<Data>
 
 export type State<Data, Error> = {
@@ -161,27 +167,27 @@ export type Mutator<Data = any> = (
   cache: Cache,
   key: Key,
   data?: Data | Promise<Data> | MutatorCallback<Data>,
-  shouldRevalidate?: boolean
+  opts?: boolean | MutatorOptions
 ) => Promise<Data | undefined>
 
 export interface ScopedMutator<Data = any> {
   /** This is used for bound mutator */
   (
     key: Key,
     data?: Data | Promise<Data> | MutatorCallback<Data>,
-    shouldRevalidate?: boolean
+    opts?: boolean | MutatorOptions
   ): Promise<Data | undefined>
   /** This is used for global mutator */
   <T = any>(
     key: Key,
     data?: T | Promise<T> | MutatorCallback<T>,
-    shouldRevalidate?: boolean
+    opts?: boolean | MutatorOptions
   ): Promise<T | undefined>
 }
 
 export type KeyedMutator<Data> = (
   data?: Data | Promise<Data> | MutatorCallback<Data>,
-  shouldRevalidate?: boolean
+  opts?: boolean | MutatorOptions
 ) => Promise<Data | undefined>
 
 // Public types

src/utils/broadcast-state.ts

@@ -8,7 +8,8 @@ export const broadcastState: Broadcaster = (
   data,
   error,
   isValidating,
-  revalidate
+  revalidate,
+  populateCache = true
 ) => {
   const [
     EVENT_REVALIDATORS,
@@ -21,9 +22,11 @@ export const broadcastState: Broadcaster = (
   const revalidators = EVENT_REVALIDATORS[key]
   const updaters = STATE_UPDATERS[key] || []
 
-  // Always update states of all hooks.
-  for (let i = 0; i < updaters.length; ++i) {
-    updaters[i](data, error, isValidating)
+  // Cache was populated, update states of all hooks.
+  if (populateCache && updaters) {
+    for (let i = 0; i < updaters.length; ++i) {
+      updaters[i](data, error, isValidating)
+    }
   }
 
   // If we also need to revalidate, only do it for the first hook.

src/utils/mutate.ts

@@ -4,20 +4,26 @@ import { SWRGlobalState, GlobalState } from './global-state'
 import { broadcastState } from './broadcast-state'
 import { getTimestamp } from './timestamp'
 
-import { Key, Cache, MutatorCallback } from '../types'
+import { Key, Cache, MutatorCallback, MutatorOptions } from '../types'
 
 export const internalMutate = async <Data>(
   ...args: [
     Cache,
     Key,
     undefined | Data | Promise<Data | undefined> | MutatorCallback<Data>,
-    undefined | boolean
+    undefined | boolean | MutatorOptions
   ]
 ) => {
-  const [cache, _key] = args
+  const [cache, _key, _data, _opts] = args
+
+  // When passing as a boolean, it's explicitily used to disable/enable
+  // revalidation.
+  const options =
+    typeof _opts === 'boolean' ? { revalidate: _opts } : _opts || {}
+
   // Fallback to `true` if it's not explicitly set to `false`
-  const revalidate = args[3] !== false
-  let _data = args[2]
+  const revalidate = options.revalidate !== false
+  const populateCache = options.populateCache !== false
 
   // Serilaize key
   const [key, , keyErr] = serialize(_key)
@@ -36,31 +42,33 @@ export const internalMutate = async <Data>(
       cache.get(key),
       cache.get(keyErr),
       UNDEFINED,
-      revalidate
+      revalidate,
+      populateCache
     )
   }
 
-  let data: any, error: unknown
+  let data: any = _data
+  let error: unknown
 
   // Update global timestamps.
   const beforeMutationTs = (MUTATION_TS[key] = getTimestamp())
   MUTATION_END_TS[key] = 0
 
-  if (isFunction(_data)) {
-    // `_data` is a function, call it passing current cache value.
+  if (isFunction(data)) {
+    // `data` is a function, call it passing current cache value.
     try {
-      _data = (_data as MutatorCallback<Data>)(cache.get(key))
+      data = (data as MutatorCallback<Data>)(cache.get(key))
     } catch (err) {
       // If it throws an error synchronously, we shouldn't update the cache.
       error = err
     }
   }
 
-  // `_data` is a promise/thenable, resolve the final data first.
-  if (_data && isFunction((_data as Promise<Data>).then)) {
+  // `data` is a promise/thenable, resolve the final data first.
+  if (data && isFunction((data as Promise<Data>).then)) {
     // This means that the mutation is async, we need to check timestamps to
     // avoid race conditions.
-    data = await (_data as Promise<Data>).catch(err => {
+    data = await (data as Promise<Data>).catch(err => {
       error = err
     })
 
@@ -71,16 +79,16 @@ export const internalMutate = async <Data>(
       if (error) throw error
       return data
     }
-  } else {
-    data = _data
   }
 
-  // Only update cached data if there's no error. Data can be `undefined` here.
-  if (!error) {
-    cache.set(key, data)
+  if (populateCache) {
+    if (!error) {
+      // Only update cached data if there's no error. Data can be `undefined` here.
+      cache.set(key, data)
+    }
+    // Always update or reset the error.
+    cache.set(keyErr, error)
   }
-  // Always update or reset the error.
-  cache.set(keyErr, error)
 
   // Reset the timestamp to mark the mutation has ended.
   MUTATION_END_TS[key] = getTimestamp()
@@ -92,10 +100,11 @@ export const internalMutate = async <Data>(
     data,
     error,
     UNDEFINED,
-    revalidate
+    revalidate,
+    populateCache
   )
 
   // Throw error or return data
   if (error) throw error
-  return res
+  return populateCache ? res : data
 }

test/use-swr-local-mutation.test.tsx

@@ -982,4 +982,33 @@ describe('useSWR - local mutation', () => {
     await sleep(300)
     await screen.findByText('success')
   })
+
+  it('should not update the cache when `populateCache` is disabled', async () => {
+    const key = createKey()
+    function Page() {
+      const { data, mutate } = useSWR(key, () => 'foo')
+      return (
+        <>
+          <div>data: {String(data)}</div>
+          <button
+            onClick={() =>
+              mutate('bar', {
+                revalidate: false,
+                populateCache: false
+              })
+            }
+          >
+            mutate
+          </button>
+        </>
+      )
+    }
+
+    renderWithConfig(<Page />)
+    await screen.findByText('data: foo')
+
+    fireEvent.click(screen.getByText('mutate'))
+    await sleep(30)
+    await screen.findByText('data: foo')
+  })
 })