← full-stack-fastapi-template / frontend/src/client/core/CancelablePromise.ts
| 1 | export class CancelError extends Error { |
| 2 | constructor(message: string) { |
| 3 | super(message); |
| 4 | this.name = 'CancelError'; |
| 5 | } |
| 6 | |
| 7 | public get isCancelled(): boolean { |
| 8 | return true; |
| 9 | } |
| 10 | } |
| 11 | |
| 12 | export interface OnCancel { |
| 13 | readonly isResolved: boolean; |
| 14 | readonly isRejected: boolean; |
| 15 | readonly isCancelled: boolean; |
| 16 | |
| 17 | (cancelHandler: () => void): void; |
| 18 | } |
| 19 | |
| 20 | export class CancelablePromise<T> implements Promise<T> { |
| 21 | private _isResolved: boolean; |
| 22 | private _isRejected: boolean; |
| 23 | private _isCancelled: boolean; |
| 24 | readonly cancelHandlers: (() => void)[]; |
| 25 | readonly promise: Promise<T>; |
| 26 | private _resolve?: (value: T | PromiseLike<T>) => void; |
| 27 | private _reject?: (reason?: unknown) => void; |
| 28 | |
| 29 | constructor( |
| 30 | executor: ( |
| 31 | resolve: (value: T | PromiseLike<T>) => void, |
| 32 | reject: (reason?: unknown) => void, |
| 33 | onCancel: OnCancel |
| 34 | ) => void |
| 35 | ) { |
| 36 | this._isResolved = false; |
| 37 | this._isRejected = false; |
| 38 | this._isCancelled = false; |
| 39 | this.cancelHandlers = []; |
| 40 | this.promise = new Promise<T>((resolve, reject) => { |
| 41 | this._resolve = resolve; |
| 42 | this._reject = reject; |
| 43 | |
| 44 | const onResolve = (value: T | PromiseLike<T>): void => { |
| 45 | if (this._isResolved || this._isRejected || this._isCancelled) { |
| 46 | return; |
| 47 | } |
| 48 | this._isResolved = true; |
| 49 | if (this._resolve) this._resolve(value); |
| 50 | }; |
| 51 | |
| 52 | const onReject = (reason?: unknown): void => { |
| 53 | if (this._isResolved || this._isRejected || this._isCancelled) { |
| 54 | return; |
| 55 | } |
| 56 | this._isRejected = true; |
| 57 | if (this._reject) this._reject(reason); |
| 58 | }; |
| 59 | |
| 60 | const onCancel = (cancelHandler: () => void): void => { |
| 61 | if (this._isResolved || this._isRejected || this._isCancelled) { |
| 62 | return; |
| 63 | } |
| 64 | this.cancelHandlers.push(cancelHandler); |
| 65 | }; |
| 66 | |
| 67 | Object.defineProperty(onCancel, 'isResolved', { |
| 68 | get: (): boolean => this._isResolved, |
| 69 | }); |
| 70 | |
| 71 | Object.defineProperty(onCancel, 'isRejected', { |
| 72 | get: (): boolean => this._isRejected, |
| 73 | }); |
| 74 | |
| 75 | Object.defineProperty(onCancel, 'isCancelled', { |
| 76 | get: (): boolean => this._isCancelled, |
| 77 | }); |
| 78 | |
| 79 | return executor(onResolve, onReject, onCancel as OnCancel); |
| 80 | }); |
| 81 | } |
| 82 | |
| 83 | get [Symbol.toStringTag]() { |
| 84 | return "Cancellable Promise"; |
| 85 | } |
| 86 | |
| 87 | public then<TResult1 = T, TResult2 = never>( |
| 88 | onFulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null, |
| 89 | onRejected?: ((reason: unknown) => TResult2 | PromiseLike<TResult2>) | null |
| 90 | ): Promise<TResult1 | TResult2> { |
| 91 | return this.promise.then(onFulfilled, onRejected); |
| 92 | } |
| 93 | |
| 94 | public catch<TResult = never>( |
| 95 | onRejected?: ((reason: unknown) => TResult | PromiseLike<TResult>) | null |
| 96 | ): Promise<T | TResult> { |
| 97 | return this.promise.catch(onRejected); |
| 98 | } |
| 99 | |
| 100 | public finally(onFinally?: (() => void) | null): Promise<T> { |
| 101 | return this.promise.finally(onFinally); |
| 102 | } |
| 103 | |
| 104 | public cancel(): void { |
| 105 | if (this._isResolved || this._isRejected || this._isCancelled) { |
| 106 | return; |
| 107 | } |
| 108 | this._isCancelled = true; |
| 109 | if (this.cancelHandlers.length) { |
| 110 | try { |
| 111 | for (const cancelHandler of this.cancelHandlers) { |
| 112 | cancelHandler(); |
| 113 | } |
| 114 | } catch (error) { |
| 115 | console.warn('Cancellation threw an error', error); |
| 116 | return; |
| 117 | } |
| 118 | } |
| 119 | this.cancelHandlers.length = 0; |
| 120 | if (this._reject) this._reject(new CancelError('Request aborted')); |
| 121 | } |
| 122 | |
| 123 | public get isCancelled(): boolean { |
| 124 | return this._isCancelled; |
| 125 | } |
| 126 | } |