397 lines
10 KiB
TypeScript
397 lines
10 KiB
TypeScript
/**
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* @license
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* Copyright 2023 Google Inc.
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* SPDX-License-Identifier: Apache-2.0
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*/
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declare global {
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interface SymbolConstructor {
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/**
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* A method that is used to release resources held by an object. Called by
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* the semantics of the `using` statement.
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*/
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readonly dispose: unique symbol;
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/**
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* A method that is used to asynchronously release resources held by an
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* object. Called by the semantics of the `await using` statement.
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*/
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readonly asyncDispose: unique symbol;
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}
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interface Disposable {
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[Symbol.dispose](): void;
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}
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interface AsyncDisposable {
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[Symbol.asyncDispose](): PromiseLike<void>;
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}
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}
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(Symbol as any).dispose ??= Symbol('dispose');
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(Symbol as any).asyncDispose ??= Symbol('asyncDispose');
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/**
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* @internal
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*/
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export const disposeSymbol: typeof Symbol.dispose = Symbol.dispose;
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/**
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* @internal
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*/
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export const asyncDisposeSymbol: typeof Symbol.asyncDispose =
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Symbol.asyncDispose;
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/**
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* @internal
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*/
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export class DisposableStackPolyfill {
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#disposed = false;
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#stack: Disposable[] = [];
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/**
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* Returns a value indicating whether the stack has been disposed.
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*/
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get disposed(): boolean {
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return this.#disposed;
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}
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/**
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* Alias for `[Symbol.dispose]()`.
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*/
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dispose(): void {
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this[disposeSymbol]();
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}
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/**
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* Adds a disposable resource to the top of stack, returning the resource.
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* Has no effect if provided `null` or `undefined`.
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*
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* @param value - A `Disposable` object, `null`, or `undefined`.
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* `null` and `undefined` will not be added, but will be returned.
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* @returns The provided `value`.
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*/
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use<T extends Disposable | null | undefined>(value: T): T {
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if (value && typeof value[disposeSymbol] === 'function') {
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this.#stack.push(value);
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}
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return value;
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}
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/**
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* Adds a non-disposable resource and a disposal callback to the top of the stack.
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*
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* @param value - A resource to be disposed.
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* @param onDispose - A callback invoked to dispose the provided value.
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* Will be invoked with `value` as the first parameter.
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* @returns The provided `value`.
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*/
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adopt<T>(value: T, onDispose: (value: T) => void): T {
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this.#stack.push({
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[disposeSymbol]() {
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onDispose(value);
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},
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});
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return value;
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}
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/**
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* Add a disposal callback to the top of the stack to be invoked when stack is disposed.
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* @param onDispose - A callback to invoke when this object is disposed.
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*/
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defer(onDispose: () => void): void {
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this.#stack.push({
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[disposeSymbol]() {
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onDispose();
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},
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});
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}
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/**
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* Move all resources out of this stack and into a new `DisposableStack`, and
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* marks this stack as disposed.
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* @returns The new `DisposableStack`.
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*
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* @example
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*
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* ```ts
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* class C {
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* #res1: Disposable;
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* #res2: Disposable;
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* #disposables: DisposableStack;
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* constructor() {
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* // stack will be disposed when exiting constructor for any reason
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* using stack = new DisposableStack();
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*
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* // get first resource
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* this.#res1 = stack.use(getResource1());
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*
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* // get second resource. If this fails, both `stack` and `#res1` will be disposed.
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* this.#res2 = stack.use(getResource2());
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*
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* // all operations succeeded, move resources out of `stack` so that
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* // they aren't disposed when constructor exits
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* this.#disposables = stack.move();
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* }
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*
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* [disposeSymbol]() {
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* this.#disposables.dispose();
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* }
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* }
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* ```
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*/
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move(): DisposableStackPolyfill {
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if (this.#disposed) {
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throw new ReferenceError('A disposed stack can not use anything new');
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}
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const stack = new DisposableStackPolyfill();
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stack.#stack = this.#stack;
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this.#stack = [];
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this.#disposed = true;
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return stack;
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}
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/**
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* Disposes each resource in the stack in last-in-first-out (LIFO) manner.
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*/
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[disposeSymbol](): void {
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if (this.#disposed) {
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return;
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}
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this.#disposed = true;
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const errors: unknown[] = [];
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for (const resource of this.#stack.reverse()) {
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try {
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resource[disposeSymbol]();
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} catch (e) {
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errors.push(e);
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}
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}
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if (errors.length === 1) {
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throw errors[0];
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} else if (errors.length > 1) {
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let suppressed = null;
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for (const error of errors) {
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if (suppressed === null) {
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suppressed = error;
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} else {
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suppressed = new SuppressedErrorPolyfill(error, suppressed);
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}
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}
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throw suppressed;
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}
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}
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readonly [Symbol.toStringTag] = 'DisposableStack';
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}
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/**
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* @internal
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*/
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export const DisposableStack: typeof DisposableStackPolyfill =
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(globalThis.DisposableStack as any) ?? DisposableStackPolyfill;
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/**
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* @internal
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*/
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export class AsyncDisposableStackPolyfill {
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#disposed = false;
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#stack: AsyncDisposable[] = [];
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/**
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* Returns a value indicating whether the stack has been disposed.
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*/
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get disposed(): boolean {
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return this.#disposed;
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}
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/**
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* Alias for `[Symbol.asyncDispose]()`.
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*/
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async disposeAsync(): Promise<void> {
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await this[asyncDisposeSymbol]();
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}
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/**
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* Adds a AsyncDisposable resource to the top of stack, returning the resource.
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* Has no effect if provided `null` or `undefined`.
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*
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* @param value - A `AsyncDisposable` object, `null`, or `undefined`.
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* `null` and `undefined` will not be added, but will be returned.
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* @returns The provided `value`.
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*/
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use<T extends AsyncDisposable | Disposable | null | undefined>(value: T): T {
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if (value) {
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const asyncDispose = (value as AsyncDisposable)[asyncDisposeSymbol];
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const dispose = (value as Disposable)[disposeSymbol];
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if (typeof asyncDispose === 'function') {
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this.#stack.push(value as AsyncDisposable);
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} else if (typeof dispose === 'function') {
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this.#stack.push({
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[asyncDisposeSymbol]: async () => {
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(value as Disposable)[disposeSymbol]();
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},
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});
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}
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}
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return value;
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}
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/**
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* Adds a non-disposable resource and a disposal callback to the top of the stack.
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*
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* @param value - A resource to be disposed.
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* @param onDispose - A callback invoked to dispose the provided value.
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* Will be invoked with `value` as the first parameter.
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* @returns The provided `value`.
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*/
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adopt<T>(value: T, onDispose: (value: T) => Promise<void>): T {
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this.#stack.push({
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[asyncDisposeSymbol]() {
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return onDispose(value);
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},
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});
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return value;
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}
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/**
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* Add a disposal callback to the top of the stack to be invoked when stack is disposed.
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* @param onDispose - A callback to invoke when this object is disposed.
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*/
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defer(onDispose: () => Promise<void>): void {
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this.#stack.push({
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[asyncDisposeSymbol]() {
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return onDispose();
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},
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});
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}
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/**
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* Move all resources out of this stack and into a new `DisposableStack`, and
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* marks this stack as disposed.
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* @returns The new `AsyncDisposableStack`.
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*
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* @example
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*
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* ```ts
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* class C {
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* #res1: Disposable;
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* #res2: Disposable;
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* #disposables: DisposableStack;
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* constructor() {
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* // stack will be disposed when exiting constructor for any reason
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* using stack = new DisposableStack();
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*
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* // get first resource
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* this.#res1 = stack.use(getResource1());
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*
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* // get second resource. If this fails, both `stack` and `#res1` will be disposed.
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* this.#res2 = stack.use(getResource2());
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*
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* // all operations succeeded, move resources out of `stack` so that
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* // they aren't disposed when constructor exits
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* this.#disposables = stack.move();
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* }
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*
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* [disposeSymbol]() {
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* this.#disposables.dispose();
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* }
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* }
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* ```
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*/
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move(): AsyncDisposableStackPolyfill {
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if (this.#disposed) {
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throw new ReferenceError('A disposed stack can not use anything new');
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}
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const stack = new AsyncDisposableStackPolyfill();
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stack.#stack = this.#stack;
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this.#stack = [];
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this.#disposed = true;
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return stack;
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}
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/**
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* Disposes each resource in the stack in last-in-first-out (LIFO) manner.
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*/
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async [asyncDisposeSymbol](): Promise<void> {
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if (this.#disposed) {
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return;
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}
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this.#disposed = true;
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const errors: unknown[] = [];
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for (const resource of this.#stack.reverse()) {
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try {
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await resource[asyncDisposeSymbol]();
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} catch (e) {
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errors.push(e);
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}
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}
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if (errors.length === 1) {
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throw errors[0];
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} else if (errors.length > 1) {
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let suppressed = null;
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for (const error of errors) {
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if (suppressed === null) {
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suppressed = error;
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} else {
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suppressed = new SuppressedErrorPolyfill(error, suppressed);
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}
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}
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throw suppressed;
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}
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}
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readonly [Symbol.toStringTag] = 'AsyncDisposableStack';
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}
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/**
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* @internal
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*/
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export const AsyncDisposableStack: typeof AsyncDisposableStackPolyfill =
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(globalThis.AsyncDisposableStack as any) ?? AsyncDisposableStackPolyfill;
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/**
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* @internal
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* Represents an error that occurs when multiple errors are thrown during
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* the disposal of resources. This class encapsulates the primary error and
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* any suppressed errors that occurred subsequently.
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*/
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class SuppressedErrorPolyfill extends Error {
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#error: unknown;
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#suppressed: unknown;
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constructor(
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error: unknown,
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suppressed: unknown,
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message = 'An error was suppressed during disposal',
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) {
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super(message);
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this.name = 'SuppressedError';
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this.#error = error;
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this.#suppressed = suppressed;
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}
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/**
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* The primary error that occurred during disposal.
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*/
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get error(): unknown {
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return this.#error;
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}
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/**
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* The suppressed error i.e. the error that was suppressed
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* because it occurred later in the flow after the original error.
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*/
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get suppressed(): unknown {
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return this.#suppressed;
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}
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}
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/**
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* @internal
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*/
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export const SuppressedError: typeof SuppressedErrorPolyfill =
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(globalThis.SuppressedError as any) ?? SuppressedErrorPolyfill;
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