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PoC for promises as first class async citizens with scheduled macrota… #1

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56 changes: 52 additions & 4 deletions lib/common/promise.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,13 @@
* Use of this source code is governed by an MIT-style license that can be
* found in the LICENSE file at https://angular.io/license
*/

function scheduleMacroTaskWithCurrentZone(
source: string, callback: Function, data: TaskData, customSchedule: (task: Task) => void,
customCancel: (task: Task) => void): MacroTask {
return Zone.current.scheduleMacroTask(source, callback, data, customSchedule, customCancel);
}

interface Promise<T> {
finally<U>(onFinally?: () => U | PromiseLike<U>): Promise<T>;
}
Expand Down Expand Up @@ -94,6 +101,38 @@ Zone.__load_patch('ZoneAwarePromise', (global: any, Zone: ZoneType, api: _ZonePr
const REJECTED = false;
const REJECTED_NO_CATCH = 0;

const PROMISECONSTRUCT_SOURCE = 'Promise.constructor';

interface PromiseTaskData extends TaskData {
promise: ZoneAwarePromise<any>;
}

function placeholderCallback() {}

function scheduleTask(task: Task) {
return task;
}

function clearTask(task: Task) {
}

function makeTaskAwareResolver(promise: ZoneAwarePromise<any>, state: boolean): (value: any) => void {
return (v) => {
try {
resolvePromise(promise, state, v);
} catch (err) {
resolvePromise(promise, false, err);
}
// Do not return value or you will break the Promise spec.
const task: Task = (promise as any)['MACROTASK'];
if (task && task.state === 'scheduled') {
task.invoke();
} else if(task) {
task.cancelScheduleRequest();
}
};
}

function makeResolver(promise: ZoneAwarePromise<any>, state: boolean): (value: any) => void {
return (v) => {
try {
Expand Down Expand Up @@ -339,10 +378,19 @@ Zone.__load_patch('ZoneAwarePromise', (global: any, Zone: ZoneType, api: _ZonePr
}
(promise as any)[symbolState] = UNRESOLVED;
(promise as any)[symbolValue] = []; // queue;
try {
executor && executor(makeResolver(promise, RESOLVED), makeResolver(promise, REJECTED));
} catch (error) {
resolvePromise(promise, false, error);

const options: PromiseTaskData = {promise: promise};

if(executor) {
const task = scheduleMacroTaskWithCurrentZone(PROMISECONSTRUCT_SOURCE, placeholderCallback, options, scheduleTask, clearTask);
(promise as any)['MACROTASK'] = task;

try {
executor(makeTaskAwareResolver(promise, RESOLVED), makeTaskAwareResolver(promise, REJECTED));
} catch (error) {
resolvePromise(promise, false, error);
task.cancelScheduleRequest();
}
}
}

Expand Down