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| class CancellablePromise { | |
| constructor(executorOrPromise) { | |
| let promise = executorOrPromise; | |
| if (!promise.then) promise = new Promise(executorOrPromise); | |
| this.cancelled = false; | |
| this._resolved = false; | |
| this._caught = false; | |
| this._thens = []; | |
| this._catches = []; | |
| this._queue = this._thens; | |
| this._result = null; | |
| this._process = result => { | |
| this._resolved = true; | |
| const then = this._queue.shift(); | |
| if (then) { | |
| try { | |
| this._result = then(result); | |
| } catch (x) { | |
| _catch(x); | |
| return; | |
| } | |
| if (this._result && this._result.then) { | |
| this._result = new CancellablePromise(this._result) | |
| .then(this._process) | |
| .catch(this._process); | |
| } else this._process(this._result); | |
| } | |
| }; | |
| const _then = result => this._process(result); | |
| const _catch = result => { | |
| this._caught = true; | |
| this._queue = this._catches; | |
| this._process(result); | |
| }; | |
| promise | |
| .then(_then) | |
| .catch(_catch); | |
| } | |
| cancel() { | |
| this.cancelled = true; | |
| this._queue = this._catches; | |
| this._resolved = true; | |
| this._caught = true; | |
| this._process({ cancelled: true }); | |
| } | |
| then(func) { | |
| this._thens.push(func); | |
| if (this._resolved && !this._caught) { | |
| this._process(this._result); | |
| } | |
| return this; | |
| } | |
| catch(func) { | |
| this._catches.push(func); | |
| if (this._resolved && this._caught) { | |
| this._process(this._result); | |
| } | |
| return this; | |
| } | |
| } |
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