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feature: transaction api chore: transaction guards * we don't allow cells, used in transaction to be mutated outside transaction once it's alive * we don't allow cells, mutated during transaction (outside transaction) to be used in transaction + apply comments + + +
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,151 @@ | ||
| import type { Signal } from "signal-polyfill"; | ||
|
|
||
| type Mutation = () => void; | ||
|
|
||
| let activeTransaction: Transaction | null = null; | ||
| const activeTransactions: Transaction[] = []; | ||
| const createdTransactions: Set<Transaction> = new Set(); | ||
| export function popActiveTransaction(): void { | ||
| activeTransactions.pop(); | ||
| activeTransaction = activeTransactions[activeTransactions.length - 1] || null; | ||
| } | ||
| export function pushActiveTransaction(transaction: Transaction): void { | ||
| activeTransactions.push(transaction); | ||
| activeTransaction = transaction; | ||
| } | ||
|
|
||
| export function signalTransactionSetter( | ||
| signal: Signal.State<any>, | ||
| value: any, | ||
| ): void { | ||
| if (activeTransaction) { | ||
| const { cellState, usedCells, seenCells } = activeTransaction; | ||
| if (!cellState.has(signal)) { | ||
| usedCells.add(signal); | ||
| } | ||
| seenCells.add(signal); | ||
| cellState.set(signal, value); | ||
| } else { | ||
| signal.set(value); | ||
| } | ||
| } | ||
| export function signalTransactionGetter(signal: Signal.State<any>): any { | ||
| if (activeTransaction) { | ||
| const { cellState, usedCells } = activeTransaction; | ||
| if (usedCells.has(signal)) { | ||
| return cellState.get(signal); | ||
| } | ||
| } | ||
| return signal.get(); | ||
| } | ||
|
|
||
| export class Transaction { | ||
| constructor(fn?: Mutation) { | ||
| if (fn) { | ||
| this.execute(fn); | ||
| } | ||
| } | ||
| cellState: WeakMap<Signal.State<any>, unknown> = new WeakMap(); | ||
| usedCells: Set<Signal.State<any>> = new Set(); | ||
| seenCells: WeakSet<Signal.State<any>> = new WeakSet(); | ||
| prevSeenCells: Set<WeakSet<Signal.State<any>>> = new Set(); | ||
| execute(fn: Mutation): void { | ||
| createdTransactions.add(this); | ||
| try { | ||
| pushActiveTransaction(this); | ||
| fn(); | ||
| } finally { | ||
| popActiveTransaction(); | ||
| } | ||
| } | ||
| ensureSafeToCommit() { | ||
| this.usedCells.forEach((signal) => { | ||
| for (const prevSeen of this.prevSeenCells) { | ||
| if (prevSeen.has(signal)) { | ||
| throw new Error("Transaction conflict"); | ||
| } | ||
| } | ||
| }); | ||
| } | ||
| commit(fn?: Mutation): void { | ||
| if (fn) { | ||
| this.execute(fn); | ||
| } | ||
| this.ensureSafeToCommit(); | ||
| const parentTransaction = | ||
| activeTransactions[activeTransactions.length - 1] || null; | ||
| if (parentTransaction) { | ||
| const { usedCells, cellState } = parentTransaction; | ||
| this.usedCells.forEach((signal) => { | ||
| usedCells.add(signal); | ||
| cellState.set(signal, this.cellState.get(signal)); | ||
| }); | ||
| } else { | ||
| this.usedCells.forEach((signal) => { | ||
| signal.set(this.cellState.get(signal)); | ||
| }); | ||
| } | ||
| for (const t of createdTransactions) { | ||
| if (t !== this && !activeTransactions.includes(t)) { | ||
| t.prevSeenCells.add(t.seenCells); | ||
| } | ||
| } | ||
| this.cleanup(); | ||
| } | ||
| rollback(): void { | ||
| this.cleanup(); | ||
| } | ||
| cleanup(): void { | ||
| createdTransactions.delete(this); | ||
| this.cellState = new WeakMap(); | ||
| this.usedCells = new Set(); | ||
| this.seenCells = new WeakSet(); | ||
| this.prevSeenCells = new Set(); | ||
| } | ||
| follow(promise: Promise<any>): Promise<any> { | ||
| return promise | ||
| .then((result) => { | ||
| this.commit(); | ||
| return result; | ||
| }) | ||
| .catch((error) => { | ||
| this.rollback(); | ||
| return Promise.reject(error); | ||
| }); | ||
| } | ||
| } | ||
|
|
||
| /* Usage sample: | ||
| Let's say we managing add user form, we have input with user name and list of users. | ||
| We have a state object that holds the user name and list of users. | ||
| class App { | ||
| @signal userName = ''; | ||
| @signal users = []; | ||
| async addUser() { | ||
| const addUserTransaction = new Transaction(); | ||
| // optimistic update | ||
| addUserTransaction.execute(() => { | ||
| this.users = [...this.users, this.userName]; | ||
| this.userName = ''; | ||
| }); | ||
| fetch('/api/add-user', { | ||
| method: 'POST', | ||
| body: JSON.stringify({ userName: this.userName }), | ||
| )).then(async (req) => { | ||
| const serverUsers = await req.json(); | ||
| // commit the transaction | ||
| addUserTransaction.commit(() => { | ||
| this.users = serverUsers; | ||
| }); | ||
| }).catch(() => { | ||
| // rollback the transaction | ||
| addUserTransaction.rollback(); | ||
| }); | ||
| } | ||
| } | ||
| */ |
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