feat(utils): atomFamily supports getParams and unstable_listen api

src/vanilla/utils/atomFamily.ts

@@ -1,11 +1,22 @@
 import type { Atom } from '../../vanilla.ts'
 
 type ShouldRemove<Param> = (createdAt: number, param: Param) => boolean
+type Cleanup = () => void
+type Callback<Param, AtomType> = (event: {
+  type: 'CREATE' | 'REMOVE'
+  param: Param
+  atom: AtomType
+}) => void
 
 export interface AtomFamily<Param, AtomType> {
   (param: Param): AtomType
+  getParams(): Iterable<Param>
   remove(param: Param): void
   setShouldRemove(shouldRemove: ShouldRemove<Param> | null): void
+  /**
+   * fires when a atom is created or removed
+   */
+  unstable_listen(callback: Callback<Param, AtomType>): Cleanup
 }
 
 export function atomFamily<Param, AtomType extends Atom<unknown>>(
@@ -20,6 +31,7 @@ export function atomFamily<Param, AtomType extends Atom<unknown>>(
   type CreatedAt = number // in milliseconds
   let shouldRemove: ShouldRemove<Param> | null = null
   const atoms: Map<Param, [AtomType, CreatedAt]> = new Map()
+  const listeners = new Set<Callback<Param, AtomType>>()
   const createAtom = (param: Param) => {
     let item: [AtomType, CreatedAt] | undefined
     if (areEqual === undefined) {
@@ -43,16 +55,40 @@ export function atomFamily<Param, AtomType extends Atom<unknown>>(
     }
 
     const newAtom = initializeAtom(param)
+    notifyListeners('CREATE', param, newAtom)
     atoms.set(param, [newAtom, Date.now()])
     return newAtom
   }
 
+  function notifyListeners(
+    type: 'CREATE' | 'REMOVE',
+    param: Param,
+    atom: AtomType,
+  ) {
+    for (const listener of listeners) {
+      listener({ type, param, atom })
+    }
+  }
+
+  createAtom.unstable_listen = (callback: Callback<Param, AtomType>) => {
+    listeners.add(callback)
+    return () => {
+      listeners.delete(callback)
+    }
+  }
+
+  createAtom.getParams = () => atoms.keys()
+
   createAtom.remove = (param: Param) => {
     if (areEqual === undefined) {
+      if (!atoms.has(param)) return
+      const [atom] = atoms.get(param)!
+      notifyListeners('REMOVE', param, atom)
       atoms.delete(param)
     } else {
-      for (const [key] of atoms) {
+      for (const [key, [atom]] of atoms) {
         if (areEqual(key, param)) {
+          notifyListeners('REMOVE', key, atom)
           atoms.delete(key)
           break
         }
@@ -63,8 +99,9 @@ export function atomFamily<Param, AtomType extends Atom<unknown>>(
   createAtom.setShouldRemove = (fn: ShouldRemove<Param> | null) => {
     shouldRemove = fn
     if (!shouldRemove) return
-    for (const [key, value] of atoms) {
-      if (shouldRemove(value[1], key)) {
+    for (const [key, [atom, createdAt]] of atoms) {
+      if (shouldRemove(createdAt, key)) {
+        notifyListeners('REMOVE', key, atom)
         atoms.delete(key)
       }
     }

tests/vanilla/utils/atomFamily.test.ts

@@ -0,0 +1,95 @@
+import { expect, it, vi } from 'vitest'
+import { atom, createStore } from 'jotai/vanilla'
+import type { Atom } from 'jotai/vanilla'
+import { atomFamily } from 'jotai/vanilla/utils'
+
+it('should create atoms with different params', () => {
+  const store = createStore()
+  const aFamily = atomFamily((param: number) => atom(param))
+
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(store.get(aFamily(2))).toEqual(2)
+})
+
+it('should remove atoms', () => {
+  const store = createStore()
+  const initializeAtom = vi.fn((param: number) => atom(param))
+  const aFamily = atomFamily(initializeAtom)
+
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(store.get(aFamily(2))).toEqual(2)
+  aFamily.remove(2)
+  initializeAtom.mockClear()
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(initializeAtom).toHaveBeenCalledTimes(0)
+  expect(store.get(aFamily(2))).toEqual(2)
+  expect(initializeAtom).toHaveBeenCalledTimes(1)
+})
+
+it('should remove atoms with custom comparator', () => {
+  const store = createStore()
+  const initializeAtom = vi.fn((param: number) => atom(param))
+  const aFamily = atomFamily(initializeAtom, (a, b) => a === b)
+
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(store.get(aFamily(2))).toEqual(2)
+  expect(store.get(aFamily(3))).toEqual(3)
+  aFamily.remove(2)
+  initializeAtom.mockClear()
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(initializeAtom).toHaveBeenCalledTimes(0)
+  expect(store.get(aFamily(2))).toEqual(2)
+  expect(initializeAtom).toHaveBeenCalledTimes(1)
+})
+
+it('should remove atoms with custom shouldRemove', () => {
+  const store = createStore()
+  const initializeAtom = vi.fn((param: number) => atom(param))
+  const aFamily = atomFamily<number, Atom<number>>(initializeAtom)
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(store.get(aFamily(2))).toEqual(2)
+  expect(store.get(aFamily(3))).toEqual(3)
+  aFamily.setShouldRemove((_createdAt, param) => param % 2 === 0)
+  initializeAtom.mockClear()
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(initializeAtom).toHaveBeenCalledTimes(0)
+  expect(store.get(aFamily(2))).toEqual(2)
+  expect(initializeAtom).toHaveBeenCalledTimes(1)
+  expect(store.get(aFamily(3))).toEqual(3)
+  expect(initializeAtom).toHaveBeenCalledTimes(1)
+})
+
+it('should notify listeners', () => {
+  const aFamily = atomFamily((param: number) => atom(param))
+  const listener = vi.fn(() => {})
+  type Event = { type: 'CREATE' | 'REMOVE'; param: number; atom: Atom<number> }
+  const unsubscribe = aFamily.unstable_listen(listener)
+  const atom1 = aFamily(1)
+  expect(listener).toHaveBeenCalledTimes(1)
+  const eventCreate = listener.mock.calls[0]?.at(0) as unknown as Event
+  if (!eventCreate) throw new Error('eventCreate is undefined')
+  expect(eventCreate.type).toEqual('CREATE')
+  expect(eventCreate.param).toEqual(1)
+  expect(eventCreate.atom).toEqual(atom1)
+  listener.mockClear()
+  aFamily.remove(1)
+  expect(listener).toHaveBeenCalledTimes(1)
+  const eventRemove = listener.mock.calls[0]?.at(0) as unknown as Event
+  expect(eventRemove.type).toEqual('REMOVE')
+  expect(eventRemove.param).toEqual(1)
+  expect(eventRemove.atom).toEqual(atom1)
+  unsubscribe()
+  listener.mockClear()
+  aFamily(2)
+  expect(listener).toHaveBeenCalledTimes(0)
+})
+
+it('should return all params', () => {
+  const store = createStore()
+  const aFamily = atomFamily((param: number) => atom(param))
+
+  expect(store.get(aFamily(1))).toEqual(1)
+  expect(store.get(aFamily(2))).toEqual(2)
+  expect(store.get(aFamily(3))).toEqual(3)
+  expect(Array.from(aFamily.getParams())).toEqual([1, 2, 3])
+})