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store.ts
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store.ts
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import type { Atom, WritableAtom } from './atom'
import {
cancelSuspensePromise,
createSuspensePromise,
isEqualSuspensePromise,
isSuspensePromise,
isSuspensePromiseAlreadyCancelled,
} from './suspensePromise'
import type { SuspensePromise } from './suspensePromise'
type Awaited<T> = T extends Promise<infer V> ? Awaited<V> : T
type AnyAtomValue = unknown
type AnyAtom = Atom<AnyAtomValue>
type AnyWritableAtom = WritableAtom<AnyAtomValue, unknown, void | Promise<void>>
type OnUnmount = () => void
type WriteGetter = Parameters<WritableAtom<AnyAtomValue, unknown>['write']>[0]
type Setter = Parameters<WritableAtom<AnyAtomValue, unknown>['write']>[1]
const hasInitialValue = <T extends Atom<AnyAtomValue>>(
atom: T
): atom is T & (T extends Atom<infer Value> ? { init: Value } : never) =>
'init' in atom
type ReadError = unknown
type Revision = number
type InvalidatedRevision = number
type ReadDependencies = Map<AnyAtom, Revision>
/**
* Immutable atom state, tracked for both mounted and unmounted atoms in a store.
* @private This is for internal use and not considered part of the public API.
*/
export type AtomState<Value = AnyAtomValue> = {
/**
* Counts number of times atom has actually changed or recomputed.
*/
r: Revision
/**
* Marks the revision of this atom when a transitive dependency was invalidated.
* Mounted atoms are considered invalidated when `r === i`.
*/
i?: InvalidatedRevision
/**
* Maps from a dependency to the dependency's revision when it was last read.
* We can skip recomputation of an atom by comparing the ReadDependencies revision
* of each dependency to that dependencies's current revision.
*/
d: ReadDependencies
} & ({ e: ReadError } | { p: SuspensePromise } | { v: Awaited<Value> })
/**
* Represents a version of a store. A version contains a state for every atom
* read during the version's lifetime.
*
* In concurrent React rendering, state can "branch" during transitions: the
* current state may continue to be rendered while a new state is being built
* concurrently. We key our atom state containers by this global version to
* represent the state for each diverging branch.
*
* While a new version is being built, we read atom previous state from the
* previous version.
*/
export type VersionObject = {
/**
* "p"arent version.
*
* Once a version is committed completely, the `p` property is deleted so the
* child version is independent, and the parent version can be garbage
* collected.
*
* See [Provider] for more details on version data flow.
*/
p?: VersionObject
}
type Listeners = Set<(version?: VersionObject) => void>
type Dependents = Set<AnyAtom>
/**
* State tracked for mounted atoms. An atom is considered "mounted" if it has a
* subscriber, or is a transitive dependency of another atom that has a
* subscriber.
*
* The mounted state of an atom is freed once it is no longer mounted.
*/
type Mounted = {
/** The list of subscriber functions. */
l: Listeners
/** Atoms that depend on *this* atom. Used to fan out invalidation. */
t: Dependents
/** Function to run when the atom is unmounted. */
u?: OnUnmount
}
// for debugging purpose only
type StateListener = () => void
type MountedAtoms = Set<AnyAtom>
// store methods (not for public API)
/**
* Read an atom's [AtomState], an internal data structure that is not considered
* part of the public API. See [useAtom] for more details.
*
* Derived atom states may be recomputed if they are invalidated and any of
* their transitive dependencies have changed.
*/
export const READ_ATOM = 'r'
/**
* Invoke an atom's [WritableAtom.write] method with an update value.
* That `write` method may set one or more atoms.
* The default `write` method of primitive atoms just sets the atom itself to
* the update value.
*/
export const WRITE_ATOM = 'w'
/**
* Commit pending writes to an atom.
* (The current implementation commits pending writes to all atoms; this is subject to change.)
*/
export const COMMIT_ATOM = 'c'
/**
* Add a subscriber function to an atom. Returns a function that removes the
* subscriber.
*
* The subscriber is called in two cases:
*
* - For writable atoms, the subscriber is called whenever the atom is directly
* changed by `atom.write`.
* - For derived atoms, the subscriber is called whenever the atom is
* *invalidated* (i.e. when it's possibly transitive dependencies change or
* become invalidated), **not** when the actual Value of the atom changes.
* Derived atoms are only recomputed on read.
*/
export const SUBSCRIBE_ATOM = 's'
/**
* Bulk-apply new values to atoms.
*/
export const RESTORE_ATOMS = 'h'
// store dev methods (these are tentative and subject to change)
export const DEV_SUBSCRIBE_STATE = 'n'
export const DEV_GET_MOUNTED_ATOMS = 'l'
export const DEV_GET_ATOM_STATE = 'a'
export const DEV_GET_MOUNTED = 'm'
/**
* Create a new store. Each store is an independent, isolated universe of atom
* states.
*
* Jotai atoms are not themselves state containers. When you read or write an
* atom, that state is stored in a store. You can think of a Store like a
* multi-layered map from atoms to states, like this:
*
* ```
* // Conceptually, a Store is a map from atoms to states.
* // The real type is a bit different.
* type Store = Map<VersionObject, Map<Atom, AtomState>>
* ```
*
* @param initialValues An iterable where item is a pair of [an atom, its
* initial value]. Use to set initial state of writable atoms; useful for
* testing.
*
* @returns A store.
*/
export const createStore = (
initialValues?: Iterable<readonly [AnyAtom, AnyAtomValue]>
) => {
const committedAtomStateMap = new WeakMap<AnyAtom, AtomState>()
const mountedMap = new WeakMap<AnyAtom, Mounted>()
const pendingMap = new Map<
AnyAtom,
AtomState /* prevAtomState */ | undefined
>()
let stateListeners: Set<StateListener>
let mountedAtoms: MountedAtoms
if (__DEV__) {
stateListeners = new Set()
mountedAtoms = new Set()
}
if (initialValues) {
for (const [atom, value] of initialValues) {
const atomState: AtomState = { v: value, r: 0, d: new Map() }
if (__DEV__) {
Object.freeze(atomState)
if (!hasInitialValue(atom)) {
console.warn(
'Found initial value for derived atom which can cause unexpected behavior',
atom
)
}
}
committedAtomStateMap.set(atom, atomState)
}
}
type SuspensePromiseCache = Map<VersionObject | undefined, SuspensePromise>
const suspensePromiseCacheMap = new WeakMap<AnyAtom, SuspensePromiseCache>()
const addSuspensePromiseToCache = (
version: VersionObject | undefined,
atom: AnyAtom,
suspensePromise: SuspensePromise
): void => {
let cache = suspensePromiseCacheMap.get(atom)
if (!cache) {
cache = new Map()
suspensePromiseCacheMap.set(atom, cache)
}
suspensePromise.then(() => {
if ((cache as SuspensePromiseCache).get(version) === suspensePromise) {
;(cache as SuspensePromiseCache).delete(version)
if (!(cache as SuspensePromiseCache).size) {
suspensePromiseCacheMap.delete(atom)
}
}
})
cache.set(version, suspensePromise)
}
const cancelAllSuspensePromiseInCache = (
atom: AnyAtom
): Set<VersionObject | undefined> => {
const versionSet = new Set<VersionObject | undefined>()
const cache = suspensePromiseCacheMap.get(atom)
if (cache) {
suspensePromiseCacheMap.delete(atom)
cache.forEach((suspensePromise, version) => {
cancelSuspensePromise(suspensePromise)
versionSet.add(version)
})
}
return versionSet
}
const versionedAtomStateMapMap = new WeakMap<
VersionObject,
Map<AnyAtom, AtomState>
>()
const getVersionedAtomStateMap = (version: VersionObject) => {
let versionedAtomStateMap = versionedAtomStateMapMap.get(version)
if (!versionedAtomStateMap) {
versionedAtomStateMap = new Map()
versionedAtomStateMapMap.set(version, versionedAtomStateMap)
}
return versionedAtomStateMap
}
const getAtomState = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>
): AtomState<Value> | undefined => {
if (version) {
const versionedAtomStateMap = getVersionedAtomStateMap(version)
let atomState = versionedAtomStateMap.get(atom) as
| AtomState<Value>
| undefined
if (!atomState) {
atomState = getAtomState(version.p, atom)
if (atomState) {
if ('p' in atomState) {
atomState.p.then(() => versionedAtomStateMap.delete(atom))
}
versionedAtomStateMap.set(atom, atomState)
}
}
return atomState
}
return committedAtomStateMap.get(atom) as AtomState<Value> | undefined
}
const setAtomState = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>,
atomState: AtomState<Value>
): void => {
if (__DEV__) {
Object.freeze(atomState)
}
if (version) {
const versionedAtomStateMap = getVersionedAtomStateMap(version)
versionedAtomStateMap.set(atom, atomState)
} else {
const prevAtomState = committedAtomStateMap.get(atom)
committedAtomStateMap.set(atom, atomState)
if (!pendingMap.has(atom)) {
pendingMap.set(atom, prevAtomState)
}
}
}
const createReadDependencies = (
version: VersionObject | undefined,
prevReadDependencies: ReadDependencies = new Map(),
dependencies?: Set<AnyAtom>
): ReadDependencies => {
if (!dependencies) {
return prevReadDependencies
}
const readDependencies: ReadDependencies = new Map()
let changed = false
dependencies.forEach((atom) => {
const revision = getAtomState(version, atom)?.r || 0
readDependencies.set(atom, revision)
if (prevReadDependencies.get(atom) !== revision) {
changed = true
}
})
if (prevReadDependencies.size === readDependencies.size && !changed) {
return prevReadDependencies
}
return readDependencies
}
const setAtomValue = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>,
value: Awaited<Value>,
dependencies?: Set<AnyAtom>,
suspensePromise?: SuspensePromise
): AtomState<Value> => {
const atomState = getAtomState(version, atom)
if (atomState) {
if (
suspensePromise &&
(!('p' in atomState) ||
!isEqualSuspensePromise(atomState.p, suspensePromise))
) {
// newer async read is running, not updating
return atomState
}
if ('p' in atomState) {
cancelSuspensePromise(atomState.p)
}
}
const nextAtomState: AtomState<Value> = {
v: value,
r: atomState?.r || 0,
d: createReadDependencies(version, atomState?.d, dependencies),
}
if (
!atomState ||
!('v' in atomState) || // new value, or
!Object.is(atomState.v, value) // different value
) {
++nextAtomState.r // increment revision
if (nextAtomState.d.has(atom)) {
nextAtomState.d = new Map(nextAtomState.d).set(atom, nextAtomState.r)
}
} else if (
nextAtomState.d !== atomState.d &&
(nextAtomState.d.size !== atomState.d.size ||
!Array.from(nextAtomState.d.keys()).every((a) => atomState.d.has(a)))
) {
// value is not changed, but dependencies are changed
// we should schdule a flush in async
// FIXME any better way? https://github.com/pmndrs/jotai/issues/947
Promise.resolve().then(() => {
flushPending(version)
})
}
setAtomState(version, atom, nextAtomState)
return nextAtomState
}
const setAtomReadError = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>,
error: ReadError,
dependencies?: Set<AnyAtom>,
suspensePromise?: SuspensePromise
): AtomState<Value> => {
const atomState = getAtomState(version, atom)
if (atomState) {
if (
suspensePromise &&
(!('p' in atomState) ||
!isEqualSuspensePromise(atomState.p, suspensePromise))
) {
// newer async read is running, not updating
return atomState
}
if ('p' in atomState) {
cancelSuspensePromise(atomState.p)
}
}
const nextAtomState: AtomState<Value> = {
e: error, // set read error
r: atomState?.r || 0,
d: createReadDependencies(version, atomState?.d, dependencies),
}
setAtomState(version, atom, nextAtomState)
return nextAtomState
}
const setAtomSuspensePromise = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>,
suspensePromise: SuspensePromise,
dependencies?: Set<AnyAtom>
): AtomState<Value> => {
const atomState = getAtomState(version, atom)
if (atomState && 'p' in atomState) {
if (isEqualSuspensePromise(atomState.p, suspensePromise)) {
// the same promise, not updating
return atomState
}
cancelSuspensePromise(atomState.p)
}
addSuspensePromiseToCache(version, atom, suspensePromise)
const nextAtomState: AtomState<Value> = {
p: suspensePromise,
r: atomState?.r || 0,
d: createReadDependencies(version, atomState?.d, dependencies),
}
setAtomState(version, atom, nextAtomState)
return nextAtomState
}
const setAtomPromiseOrValue = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>,
promiseOrValue: Value,
dependencies?: Set<AnyAtom>
): AtomState<Value> => {
if (promiseOrValue instanceof Promise) {
const suspensePromise = createSuspensePromise(
promiseOrValue
.then((value: Awaited<Value>) => {
setAtomValue(version, atom, value, dependencies, suspensePromise)
})
.catch((e) => {
if (e instanceof Promise) {
if (isSuspensePromise(e)) {
// schedule another read later
// FIXME not 100% confident with this code
return e.then(() => {
readAtomState(version, atom, true)
})
}
return e
}
setAtomReadError(version, atom, e, dependencies, suspensePromise)
})
)
return setAtomSuspensePromise(
version,
atom,
suspensePromise,
dependencies
)
}
return setAtomValue(
version,
atom,
promiseOrValue as Awaited<Value>,
dependencies
)
}
const setAtomInvalidated = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>
): void => {
const atomState = getAtomState(version, atom)
if (atomState) {
const nextAtomState: AtomState<Value> = {
...atomState, // copy everything
i: atomState.r, // set invalidated revision
}
setAtomState(version, atom, nextAtomState)
} else if (__DEV__) {
console.warn('[Bug] could not invalidate non existing atom', atom)
}
}
const readAtomState = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>,
force?: boolean
): AtomState<Value> => {
if (!force) {
// See if we can skip recomputing this atom.
const atomState = getAtomState(version, atom)
if (atomState) {
// First, check if we already have suspending promise
if (
atomState.r !== atomState.i && // revision is not invalidated
'p' in atomState &&
!isSuspensePromiseAlreadyCancelled(atomState.p)
) {
return atomState
}
// Second, ensure that each atom we depend on is up to date.
// Recursive calls to `readAtomState(version, a)` will recompute `a` if
// it's out of date thus increment its revision number if it changes.
atomState.d.forEach((_, a) => {
if (a !== atom) {
if (!mountedMap.has(a)) {
// Dependency is new or unmounted.
// Invalidation doesn't touch unmounted atoms, so we need to recurse
// into this dependency in case it needs to update.
readAtomState(version, a)
} else {
// Dependency is mounted.
const aState = getAtomState(version, a)
if (
aState &&
aState.r === aState.i // revision is invalidated
) {
readAtomState(version, a)
}
}
}
})
// If a dependency's revision changed since this atom was last computed,
// then we're out of date and need to recompute.
if (
Array.from(atomState.d).every(([a, r]) => {
const aState = getAtomState(version, a)
return (
aState &&
'v' in aState && // has value
aState.r === r // revision is equal to the last one
)
})
) {
return atomState
}
}
}
// Compute a new state for this atom.
const dependencies = new Set<AnyAtom>()
try {
const promiseOrValue = atom.read(<V>(a: Atom<V>) => {
dependencies.add(a)
const aState =
(a as AnyAtom) === atom
? getAtomState(version, a)
: readAtomState(version, a)
if (aState) {
if ('e' in aState) {
throw aState.e // read error
}
if ('p' in aState) {
throw aState.p // suspense promise
}
return aState.v as Awaited<V> // value
}
if (hasInitialValue(a)) {
return a.init
}
// NOTE invalid derived atoms can reach here
throw new Error('no atom init')
})
return setAtomPromiseOrValue(version, atom, promiseOrValue, dependencies)
} catch (errorOrPromise) {
if (errorOrPromise instanceof Promise) {
const suspensePromise = createSuspensePromise(errorOrPromise)
return setAtomSuspensePromise(
version,
atom,
suspensePromise,
dependencies
)
}
return setAtomReadError(version, atom, errorOrPromise, dependencies)
}
}
const readAtom = <Value>(
readingAtom: Atom<Value>,
version?: VersionObject
): AtomState<Value> => {
const atomState = readAtomState(version, readingAtom)
return atomState
}
const addAtom = (addingAtom: AnyAtom): Mounted => {
let mounted = mountedMap.get(addingAtom)
if (!mounted) {
mounted = mountAtom(addingAtom)
}
return mounted
}
// FIXME doesn't work with mutually dependent atoms
const canUnmountAtom = (atom: AnyAtom, mounted: Mounted) =>
!mounted.l.size &&
(!mounted.t.size || (mounted.t.size === 1 && mounted.t.has(atom)))
const delAtom = (deletingAtom: AnyAtom): void => {
const mounted = mountedMap.get(deletingAtom)
if (mounted && canUnmountAtom(deletingAtom, mounted)) {
unmountAtom(deletingAtom)
}
}
const invalidateDependents = <Value>(
version: VersionObject | undefined,
atom: Atom<Value>
): void => {
const mounted = mountedMap.get(atom)
mounted?.t.forEach((dependent) => {
if (dependent !== atom) {
setAtomInvalidated(version, dependent)
invalidateDependents(version, dependent)
}
})
}
const writeAtomState = <Value, Update, Result extends void | Promise<void>>(
version: VersionObject | undefined,
atom: WritableAtom<Value, Update, Result>,
update: Update
): Result => {
let isSync = true
const writeGetter: WriteGetter = <V>(
a: Atom<V>,
options?: {
unstable_promise: boolean
}
) => {
const aState = readAtomState(version, a)
if ('e' in aState) {
throw aState.e // read error
}
if ('p' in aState) {
if (options?.unstable_promise) {
return aState.p.then(() =>
writeGetter(a as unknown as Atom<Promise<unknown>>, options as any)
) as Promise<Awaited<V>> // FIXME proper typing
}
if (__DEV__) {
console.info(
'Reading pending atom state in write operation. We throw a promise for now.',
a
)
}
throw aState.p // suspense promise
}
if ('v' in aState) {
return aState.v as Awaited<V> // value
}
if (__DEV__) {
console.warn(
'[Bug] no value found while reading atom in write operation. This is probably a bug.',
a
)
}
throw new Error('no value found')
}
const setter: Setter = <V, U, R extends void | Promise<void>>(
a: WritableAtom<V, U, R>,
v?: V
) => {
let promiseOrVoid: void | Promise<void>
if ((a as AnyWritableAtom) === atom) {
if (!hasInitialValue(a)) {
// NOTE technically possible but restricted as it may cause bugs
throw new Error('atom not writable')
}
const versionSet = cancelAllSuspensePromiseInCache(a)
versionSet.forEach((cancelledVersion) => {
if (cancelledVersion !== version) {
setAtomPromiseOrValue(cancelledVersion, a, v)
}
})
setAtomPromiseOrValue(version, a, v)
invalidateDependents(version, a)
} else {
promiseOrVoid = writeAtomState(version, a as AnyWritableAtom, v)
}
if (!isSync) {
flushPending(version)
}
return promiseOrVoid
}
const promiseOrVoid = atom.write(writeGetter, setter, update)
isSync = false
version = undefined
return promiseOrVoid
}
const writeAtom = <Value, Update, Result extends void | Promise<void>>(
writingAtom: WritableAtom<Value, Update, Result>,
update: Update,
version?: VersionObject
): Result => {
const promiseOrVoid = writeAtomState(version, writingAtom, update)
flushPending(version)
return promiseOrVoid
}
const isActuallyWritableAtom = (atom: AnyAtom): atom is AnyWritableAtom =>
!!(atom as AnyWritableAtom).write
const mountAtom = <Value>(
atom: Atom<Value>,
initialDependent?: AnyAtom
): Mounted => {
// mount self
const mounted: Mounted = {
t: new Set(initialDependent && [initialDependent]),
l: new Set(),
}
mountedMap.set(atom, mounted)
if (__DEV__) {
mountedAtoms.add(atom)
}
// mount read dependencies before onMount
const atomState = readAtomState(undefined, atom)
atomState.d.forEach((_, a) => {
const aMounted = mountedMap.get(a)
if (aMounted) {
aMounted.t.add(atom) // add dependent
} else {
if (a !== atom) {
mountAtom(a, atom)
}
}
})
// onMount
if (isActuallyWritableAtom(atom) && atom.onMount) {
const setAtom = (update: unknown) => writeAtom(atom, update)
const onUnmount = atom.onMount(setAtom)
if (onUnmount) {
mounted.u = onUnmount
}
}
return mounted
}
const unmountAtom = <Value>(atom: Atom<Value>): void => {
// unmount self
const onUnmount = mountedMap.get(atom)?.u
if (onUnmount) {
onUnmount()
}
mountedMap.delete(atom)
if (__DEV__) {
mountedAtoms.delete(atom)
}
// unmount read dependencies afterward
const atomState = getAtomState(undefined, atom)
if (atomState) {
atomState.d.forEach((_, a) => {
if (a !== atom) {
const mounted = mountedMap.get(a)
if (mounted) {
mounted.t.delete(atom)
if (canUnmountAtom(a, mounted)) {
unmountAtom(a)
}
}
}
})
} else if (__DEV__) {
console.warn('[Bug] could not find atom state to unmount', atom)
}
}
const mountDependencies = <Value>(
atom: Atom<Value>,
atomState: AtomState<Value>,
prevReadDependencies?: ReadDependencies
): void => {
const dependencies = new Set(atomState.d.keys())
prevReadDependencies?.forEach((_, a) => {
if (dependencies.has(a)) {
// not changed
dependencies.delete(a)
return
}
const mounted = mountedMap.get(a)
if (mounted) {
mounted.t.delete(atom) // delete from dependents
if (canUnmountAtom(a, mounted)) {
unmountAtom(a)
}
}
})
dependencies.forEach((a) => {
const mounted = mountedMap.get(a)
if (mounted) {
mounted.t.add(atom) // add to dependents
} else if (mountedMap.has(atom)) {
// we mount dependencies only when atom is already mounted
// Note: we should revisit this when you find other issues
// https://github.com/pmndrs/jotai/issues/942
mountAtom(a, atom)
}
})
}
const flushPending = (version: VersionObject | undefined): void => {
if (version) {
const versionedAtomStateMap = getVersionedAtomStateMap(version)
versionedAtomStateMap.forEach((atomState, atom) => {
if (atomState !== committedAtomStateMap.get(atom)) {
const mounted = mountedMap.get(atom)
mounted?.l.forEach((listener) => listener(version))
}
})
return
}
while (pendingMap.size) {
const pending = Array.from(pendingMap)
pendingMap.clear()
pending.forEach(([atom, prevAtomState]) => {
const atomState = getAtomState(undefined, atom)
if (atomState && atomState.d !== prevAtomState?.d) {
mountDependencies(atom, atomState, prevAtomState?.d)
}
const mounted = mountedMap.get(atom)
mounted?.l.forEach((listener) => listener())
})
}
if (__DEV__) {
stateListeners.forEach((l) => l())
}
}
const commitVersionedAtomStateMap = (version: VersionObject) => {
const versionedAtomStateMap = getVersionedAtomStateMap(version)
versionedAtomStateMap.forEach((atomState, atom) => {
const prevAtomState = committedAtomStateMap.get(atom)
if (
atomState.r > (prevAtomState?.r || 0) ||
('v' in atomState &&
atomState.r === prevAtomState?.r &&
atomState.d !== prevAtomState?.d)
) {
committedAtomStateMap.set(atom, atomState)
if (atomState.d !== prevAtomState?.d) {
mountDependencies(atom, atomState, prevAtomState?.d)
}
}
})
}
const commitAtom = (_atom: AnyAtom | null, version?: VersionObject) => {
if (version) {
commitVersionedAtomStateMap(version)
}
flushPending(undefined)
}
const subscribeAtom = (
atom: AnyAtom,
callback: (version?: VersionObject) => void
) => {
const mounted = addAtom(atom)
const listeners = mounted.l
listeners.add(callback)
return () => {
listeners.delete(callback)
delAtom(atom)
}
}
const restoreAtoms = (
values: Iterable<readonly [AnyAtom, AnyAtomValue]>,
version?: VersionObject
): void => {
for (const [atom, value] of values) {
if (hasInitialValue(atom)) {
setAtomPromiseOrValue(version, atom, value)
invalidateDependents(version, atom)
}
}
flushPending(version)
}
if (__DEV__) {
return {
[READ_ATOM]: readAtom,
[WRITE_ATOM]: writeAtom,
[COMMIT_ATOM]: commitAtom,
[SUBSCRIBE_ATOM]: subscribeAtom,
[RESTORE_ATOMS]: restoreAtoms,
[DEV_SUBSCRIBE_STATE]: (l: StateListener) => {
stateListeners.add(l)
return () => {
stateListeners.delete(l)
}
},
[DEV_GET_MOUNTED_ATOMS]: () => mountedAtoms.values(),
[DEV_GET_ATOM_STATE]: (a: AnyAtom) => committedAtomStateMap.get(a),
[DEV_GET_MOUNTED]: (a: AnyAtom) => mountedMap.get(a),
}
}
return {
[READ_ATOM]: readAtom,
[WRITE_ATOM]: writeAtom,
[COMMIT_ATOM]: commitAtom,
[SUBSCRIBE_ATOM]: subscribeAtom,
[RESTORE_ATOMS]: restoreAtoms,
}
}
export type Store = ReturnType<typeof createStore>
export const createStoreForExport = (
initialValues?: Iterable<readonly [AnyAtom, AnyAtomValue]>
) => {
const store = createStore(initialValues)
const get = <Value>(atom: Atom<Value>) => {
const atomState = store[READ_ATOM](atom)
if ('e' in atomState) {
throw atomState.e // read error
}
if ('p' in atomState) {
return undefined // suspended
}
return atomState.v
}
const asyncGet = <Value>(atom: Atom<Value>) =>
new Promise<Awaited<Value>>((resolve, reject) => {
const atomState = store[READ_ATOM](atom)
if ('e' in atomState) {
reject(atomState.e) // read error
} else if ('p' in atomState) {
resolve(atomState.p.then(() => asyncGet(atom))) // retry later
} else {
resolve(atomState.v)
}
})
const set = <Value, Update, Result extends void | Promise<void>>(
atom: WritableAtom<Value, Update, Result>,
update: Update
) => store[WRITE_ATOM](atom, update)
const sub = (atom: AnyAtom, callback: () => void) =>
store[SUBSCRIBE_ATOM](atom, callback)
return {
get,
asyncGet,
set,
sub,
SECRET_INTERNAL_store: store,
}
}