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use-swr.ts
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// TODO: use @ts-expect-error
import {
useCallback,
useContext,
useState,
useRef,
useMemo,
useDebugValue
} from 'react'
import defaultConfig, { cache } from './config'
import { IS_SERVER, rAF, useIsomorphicLayoutEffect } from './env'
import SWRConfigContext from './swr-config-context'
import {
Action,
Broadcaster,
Fetcher,
Key,
Mutator,
SWRResponse,
RevalidatorOptions,
Trigger,
Updater,
SWRConfiguration
} from './types'
type Revalidator = (...args: any[]) => void
// global state managers
const CONCURRENT_PROMISES: Record<string, any> = {}
const CONCURRENT_PROMISES_TS: Record<string, number> = {}
const FOCUS_REVALIDATORS: Record<string, Revalidator[]> = {}
const RECONNECT_REVALIDATORS: Record<string, Revalidator[]> = {}
const CACHE_REVALIDATORS: Record<string, Updater[]> = {}
const MUTATION_TS: Record<string, number> = {}
const MUTATION_END_TS: Record<string, number> = {}
// generate strictly increasing timestamps
const now = (() => {
let ts = 0
return () => ++ts
})()
// setup DOM events listeners for `focus` and `reconnect` actions
if (!IS_SERVER) {
const revalidate = (revalidators: Record<string, Revalidator[]>) => {
if (!defaultConfig.isDocumentVisible() || !defaultConfig.isOnline()) return
for (const key in revalidators) {
if (revalidators[key][0]) revalidators[key][0]()
}
}
if (typeof defaultConfig.registerOnFocus === 'function') {
defaultConfig.registerOnFocus(() => revalidate(FOCUS_REVALIDATORS))
}
if (typeof defaultConfig.registerOnReconnect === 'function') {
defaultConfig.registerOnReconnect(() => revalidate(RECONNECT_REVALIDATORS))
}
}
const trigger: Trigger = (_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, 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,
currentIsValidating,
i > 0
)
)
}
// return new updated value
return Promise.all(promises).then(() => cache.get(key))
}
return Promise.resolve(cache.get(key))
}
const broadcastState: Broadcaster = (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, isValidating)
}
}
}
const mutate: Mutator = async (_key, _data, shouldRevalidate = true) => {
const [key, , keyErr] = cache.serializeKey(_key)
if (!key) return
// if there is no new data to update, let's just revalidate the key
if (typeof _data === 'undefined') return trigger(_key, shouldRevalidate)
// update global timestamps
MUTATION_TS[key] = now() - 1
MUTATION_END_TS[key] = 0
// track timestamps before await asynchronously
const beforeMutationTs = MUTATION_TS[key]
const beforeConcurrentPromisesTs = CONCURRENT_PROMISES_TS[key]
let data: any, error: unknown
let isAsyncMutation = false
if (_data && typeof _data === 'function') {
// `_data` is a function, call it passing current cache value
try {
_data = _data(cache.get(key))
} catch (err) {
// if `_data` function throws an error synchronously, it shouldn't be cached
_data = undefined
error = err
}
}
if (_data && typeof _data.then === 'function') {
// `_data` is a promise
isAsyncMutation = true
try {
data = await _data
} catch (err) {
error = err
}
} else {
data = _data
}
const shouldAbort = (): boolean | void => {
// check if other mutations have occurred since we've started this mutation
if (
beforeMutationTs !== MUTATION_TS[key] ||
beforeConcurrentPromisesTs !== CONCURRENT_PROMISES_TS[key]
) {
if (error) throw error
return true
}
}
// if there's a race we don't update cache or broadcast change, just return the data
if (shouldAbort()) return data
if (typeof data !== 'undefined') {
// update cached data
cache.set(key, data)
}
// always update or reset the error
cache.set(keyErr, error)
// reset the timestamp to mark the mutation has ended
MUTATION_END_TS[key] = now() - 1
if (!isAsyncMutation) {
// we skip broadcasting if there's another mutation happened synchronously
if (shouldAbort()) return data
}
// enter the revalidation stage
// update existing SWR Hooks' state
const updaters = CACHE_REVALIDATORS[key]
if (updaters) {
const promises = []
for (let i = 0; i < updaters.length; ++i) {
promises.push(
updaters[i](!!shouldRevalidate, data, error, undefined, i > 0)
)
}
// return new updated value
return Promise.all(promises).then(() => {
if (error) throw error
return cache.get(key)
})
}
// throw error or return data to be used by caller of mutate
if (error) throw error
return data
}
function useSWR<Data = any, Error = any>(
...args:
| readonly [Key]
| readonly [Key, Fetcher<Data> | null]
| readonly [Key, SWRConfiguration<Data, Error> | undefined]
| readonly [
Key,
Fetcher<Data> | null,
SWRConfiguration<Data, Error> | undefined
]
): SWRResponse<Data, Error> {
const _key = args[0]
const config = Object.assign(
{},
defaultConfig,
useContext(SWRConfigContext),
args.length > 2
? args[2]
: args.length === 2 && typeof args[1] === 'object'
? args[1]
: {}
)
// in typescript args.length > 2 is not same as args.lenth === 3
// we do a safe type assertion here
// args.length === 3
const fn = (args.length > 2
? args[1]
: args.length === 2 && typeof args[1] === 'function'
? args[1]
: /**
pass fn as null will disable revalidate
https://paco.sh/blog/shared-hook-state-with-swr
*/
args[1] === null
? args[1]
: config.fetcher) as Fetcher<Data> | null
// we assume `key` as the identifier of the request
// `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, keyValidating] = cache.serializeKey(_key)
const configRef = useRef(config)
useIsomorphicLayoutEffect(() => {
configRef.current = config
})
const willRevalidateOnMount = () => {
return (
config.revalidateOnMount ||
(!config.initialData && config.revalidateOnMount === undefined)
)
}
const resolveData = () => {
const cachedData = cache.get(key)
return typeof cachedData === 'undefined' ? config.initialData : cachedData
}
const resolveIsValidating = () => {
return !!cache.get(keyValidating) || (key && willRevalidateOnMount())
}
const initialData = resolveData()
const initialError = cache.get(keyErr)
const initialIsValidating = resolveIsValidating()
// if a state is accessed (data, error or isValidating),
// we add the state to dependencies so if the state is
// updated in the future, we can trigger a rerender
const stateDependencies = useRef({
data: false,
error: false,
isValidating: false
})
const stateRef = useRef({
data: initialData,
error: initialError,
isValidating: initialIsValidating
})
// display the data label in the React DevTools next to SWR hooks
useDebugValue(stateRef.current.data)
const rerender = useState<unknown>({})[1]
let dispatch = useCallback(
(payload: Action<Data, Error>) => {
let shouldUpdateState = false
for (let k in payload) {
// @ts-ignore
if (stateRef.current[k] === payload[k]) {
continue
}
// @ts-ignore
stateRef.current[k] = payload[k]
// @ts-ignore
if (stateDependencies.current[k]) {
shouldUpdateState = true
}
}
if (shouldUpdateState) {
// if component is unmounted, should skip rerender
// if component is not mounted, should skip rerender
if (unmountedRef.current || !initialMountedRef.current) return
rerender({})
}
},
// config.suspense isn't allowed to change during the lifecycle
// eslint-disable-next-line react-hooks/exhaustive-deps
[]
)
// error ref inside revalidate (is last request errored?)
const unmountedRef = useRef(false)
const keyRef = useRef(key)
// check if component is mounted in suspense mode
const initialMountedRef = useRef(false)
// do unmount check for callbacks
const eventsCallback = useCallback(
(event, ...params) => {
if (unmountedRef.current) return
if (!initialMountedRef.current) return
if (key !== keyRef.current) return
// @ts-ignore
configRef.current[event](...params)
},
[key]
)
const boundMutate: SWRResponse<Data, Error>['mutate'] = useCallback(
(data, shouldRevalidate) => {
return mutate(keyRef.current, data, shouldRevalidate)
},
[]
)
const addRevalidator = (
revalidators: Record<string, Revalidator[]>,
callback: Revalidator
) => {
if (!revalidators[key]) {
revalidators[key] = [callback]
} else {
revalidators[key].push(callback)
}
return () => {
const keyedRevalidators = revalidators[key]
const index = keyedRevalidators.indexOf(callback)
if (index >= 0) {
// O(1): faster than splice
keyedRevalidators[index] =
keyedRevalidators[keyedRevalidators.length - 1]
keyedRevalidators.pop()
}
}
}
// start a revalidation
const revalidate = useCallback(
async (revalidateOpts: RevalidatorOptions = {}): Promise<boolean> => {
if (!key || !fn) return false
if (unmountedRef.current) return false
if (configRef.current.isPaused()) return false
const { retryCount = 0, dedupe = false } = revalidateOpts
let loading = true
let shouldDeduping =
typeof CONCURRENT_PROMISES[key] !== 'undefined' && dedupe
// start fetching
try {
dispatch({
isValidating: true
})
cache.set(keyValidating, true)
if (!shouldDeduping) {
// also update other hooks
broadcastState(
key,
stateRef.current.data,
stateRef.current.error,
true
)
}
let newData
let startAt
if (shouldDeduping) {
// there's already an ongoing request,
// this one needs to be deduplicated.
startAt = CONCURRENT_PROMISES_TS[key]
newData = await CONCURRENT_PROMISES[key]
} else {
// if no cache being rendered currently (it shows a blank page),
// we trigger the loading slow event.
if (config.loadingTimeout && !cache.get(key)) {
setTimeout(() => {
if (loading) eventsCallback('onLoadingSlow', key, config)
}, config.loadingTimeout)
}
if (fnArgs !== null) {
CONCURRENT_PROMISES[key] = fn(...fnArgs)
} else {
CONCURRENT_PROMISES[key] = fn(key)
}
CONCURRENT_PROMISES_TS[key] = startAt = now()
newData = await CONCURRENT_PROMISES[key]
setTimeout(() => {
delete CONCURRENT_PROMISES[key]
delete CONCURRENT_PROMISES_TS[key]
}, config.dedupingInterval)
// trigger the success event,
// only do this for the original request.
eventsCallback('onSuccess', newData, key, config)
}
// if there're other ongoing request(s), started after the current one,
// we need to ignore the current one to avoid possible race conditions:
// req1------------------>res1 (current one)
// req2---------------->res2
// the request that fired later will always be kept.
if (CONCURRENT_PROMISES_TS[key] > startAt) {
return false
}
// if there're other mutations(s), overlapped with the current revalidation:
// case 1:
// req------------------>res
// mutate------>end
// case 2:
// req------------>res
// mutate------>end
// case 3:
// req------------------>res
// mutate-------...---------->
// we have to ignore the revalidation result (res) because it's no longer fresh.
// meanwhile, a new revalidation should be triggered when the mutation ends.
if (
MUTATION_TS[key] &&
// case 1
(startAt <= MUTATION_TS[key] ||
// case 2
startAt <= MUTATION_END_TS[key] ||
// case 3
MUTATION_END_TS[key] === 0)
) {
dispatch({ isValidating: false })
return false
}
cache.set(keyErr, undefined)
cache.set(keyValidating, false)
// new state for the reducer
const newState: Action<Data, Error> = {
isValidating: false
}
if (typeof stateRef.current.error !== 'undefined') {
// we don't have an error
newState.error = undefined
}
if (!config.compare(stateRef.current.data, newData)) {
// deep compare to avoid extra re-render
// data changed
newState.data = newData
}
if (!config.compare(cache.get(key), newData)) {
cache.set(key, newData)
}
// merge the new state
dispatch(newState)
if (!shouldDeduping) {
// also update other hooks
broadcastState(key, newData, newState.error, false)
}
} catch (err) {
delete CONCURRENT_PROMISES[key]
delete CONCURRENT_PROMISES_TS[key]
if (configRef.current.isPaused()) {
dispatch({
isValidating: false
})
return false
}
cache.set(keyErr, err)
// get a new error
// don't use deep equal for errors
if (stateRef.current.error !== err) {
// we keep the stale data
dispatch({
isValidating: false,
error: err
})
if (!shouldDeduping) {
// also broadcast to update other hooks
broadcastState(key, undefined, err, false)
}
}
// events and retry
eventsCallback('onError', err, key, config)
if (config.shouldRetryOnError) {
// when retrying, we always enable deduping
eventsCallback('onErrorRetry', err, key, config, revalidate, {
retryCount: retryCount + 1,
dedupe: true
})
}
}
loading = false
return true
},
// dispatch is immutable, and `eventsCallback`, `fnArgs`, `keyErr`, and `keyValidating` are based on `key`,
// so we can them from the deps array.
//
// FIXME:
// `fn` and `config` might be changed during the lifecycle,
// but they might be changed every render like this.
// useSWR('key', () => fetch('/api/'), { suspense: true })
// So we omit the values from the deps array
// even though it might cause unexpected behaviors.
// eslint-disable-next-line react-hooks/exhaustive-deps
[key]
)
// mounted (client side rendering)
useIsomorphicLayoutEffect(() => {
if (!key) return undefined
// after `key` updates, we need to mark it as mounted
unmountedRef.current = false
const isUpdating = initialMountedRef.current
initialMountedRef.current = true
// after the component is mounted (hydrated),
// we need to update the data from the cache
// and trigger a revalidation
const currentHookData = stateRef.current.data
const latestKeyedData = resolveData()
// update the state if the key changed (not the inital render) or cache updated
keyRef.current = key
if (!config.compare(currentHookData, latestKeyedData)) {
dispatch({ data: latestKeyedData })
}
// revalidate with deduping
const softRevalidate = () => revalidate({ dedupe: true })
// trigger a revalidation
if (isUpdating || willRevalidateOnMount()) {
if (typeof latestKeyedData !== 'undefined' && !IS_SERVER) {
// delay revalidate if there's cache
// to not block the rendering
// @ts-ignore it's safe to use requestAnimationFrame in browser
rAF(softRevalidate)
} else {
softRevalidate()
}
}
let pending = false
const onFocus = () => {
if (pending || !configRef.current.revalidateOnFocus) return
pending = true
softRevalidate()
setTimeout(
() => (pending = false),
configRef.current.focusThrottleInterval
)
}
const onReconnect = () => {
if (configRef.current.revalidateOnReconnect) {
softRevalidate()
}
}
// register global cache update listener
const onUpdate: Updater<Data, Error> = (
shouldRevalidate = true,
updatedData,
updatedError,
updatedIsValidating,
dedupe = true
) => {
// update hook state
const newState: Action<Data, Error> = {}
let needUpdate = false
if (
typeof updatedData !== 'undefined' &&
!config.compare(stateRef.current.data, updatedData)
) {
newState.data = updatedData
needUpdate = true
}
// always update error
// because it can be `undefined`
if (stateRef.current.error !== updatedError) {
newState.error = updatedError
needUpdate = true
}
if (
typeof updatedIsValidating !== 'undefined' &&
stateRef.current.isValidating !== updatedIsValidating
) {
newState.isValidating = updatedIsValidating
needUpdate = true
}
if (needUpdate) {
dispatch(newState)
}
if (shouldRevalidate) {
if (dedupe) {
return softRevalidate()
} else {
return revalidate()
}
}
return false
}
const unsubFocus = addRevalidator(FOCUS_REVALIDATORS, onFocus)
const unsubReconnect = addRevalidator(RECONNECT_REVALIDATORS, onReconnect)
const unsubUpdate = addRevalidator(CACHE_REVALIDATORS, onUpdate)
return () => {
// cleanup
dispatch = () => null
// mark it as unmounted
unmountedRef.current = true
unsubFocus()
unsubReconnect()
unsubUpdate()
}
}, [key, revalidate])
useIsomorphicLayoutEffect(() => {
let timer: any = null
const tick = async () => {
if (
!stateRef.current.error &&
(configRef.current.refreshWhenHidden ||
configRef.current.isDocumentVisible()) &&
(configRef.current.refreshWhenOffline || configRef.current.isOnline())
) {
// only revalidate when the page is visible
// if API request errored, we stop polling in this round
// and let the error retry function handle it
await revalidate({ dedupe: true })
}
// Read the latest refreshInterval
if (configRef.current.refreshInterval && timer) {
timer = setTimeout(tick, configRef.current.refreshInterval)
}
}
if (configRef.current.refreshInterval) {
timer = setTimeout(tick, configRef.current.refreshInterval)
}
return () => {
if (timer) {
clearTimeout(timer)
timer = null
}
}
}, [
config.refreshInterval,
config.refreshWhenHidden,
config.refreshWhenOffline,
revalidate
])
// suspense
let latestData: Data | undefined
let latestError: unknown
if (config.suspense) {
// in suspense mode, we can't return empty state
// (it should be suspended)
// try to get data and error from cache
latestData = cache.get(key)
latestError = cache.get(keyErr)
if (typeof latestData === 'undefined') {
latestData = initialData
}
if (typeof latestError === 'undefined') {
latestError = initialError
}
if (
typeof latestData === 'undefined' &&
typeof latestError === 'undefined'
) {
// need to start the request if it hasn't
if (!CONCURRENT_PROMISES[key]) {
// trigger revalidate immediately
// to get the promise
// in this revalidate, should not rerender
revalidate()
}
if (
CONCURRENT_PROMISES[key] &&
typeof CONCURRENT_PROMISES[key].then === 'function'
) {
// if it is a promise
throw CONCURRENT_PROMISES[key]
}
// it's a value, return it directly (override)
latestData = CONCURRENT_PROMISES[key]
}
if (typeof latestData === 'undefined' && latestError) {
// in suspense mode, throw error if there's no content
throw latestError
}
}
// define returned state
// can be memorized since the state is a ref
const memoizedState = useMemo(() => {
// revalidate will be deprecated in the 1.x release
// because mutate() covers the same use case of revalidate().
// This remains only for backward compatibility
const state = { revalidate, mutate: boundMutate } as SWRResponse<
Data,
Error
>
Object.defineProperties(state, {
error: {
// `key` might be changed in the upcoming hook re-render,
// but the previous state will stay
// so we need to match the latest key and data (fallback to `initialData`)
get: function() {
stateDependencies.current.error = true
if (config.suspense) {
return latestError
}
return keyRef.current === key ? stateRef.current.error : initialError
},
enumerable: true
},
data: {
get: function() {
stateDependencies.current.data = true
if (config.suspense) {
return latestData
}
return keyRef.current === key ? stateRef.current.data : initialData
},
enumerable: true
},
isValidating: {
get: function() {
stateDependencies.current.isValidating = true
return key ? stateRef.current.isValidating : false
},
enumerable: true
}
})
return state
// `config.suspense` isn't allowed to change during the lifecycle.
// `boundMutate` is immutable, and the immutability of `revalidate` depends on `key`
// so we can omit them from the deps array,
// but we put it to enable react-hooks/exhaustive-deps rule.
// `initialData` and `initialError` are not initial values
// because they are changed during the lifecycle
// so we should add them in the deps array.
}, [
revalidate,
initialData,
initialError,
boundMutate,
key,
config.suspense,
latestError,
latestData
])
return memoizedState
}
Object.defineProperty(SWRConfigContext.Provider, 'default', {
value: defaultConfig
})
const SWRConfig = SWRConfigContext.Provider as typeof SWRConfigContext.Provider & {
default: SWRConfiguration
}
export { trigger, mutate, SWRConfig }
export default useSWR