src/vs/base/test/common/virtualScheduling/runWithFakedTimers.ts
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/*---------------------------------------------------------------------------------------------
processor.ts ×17
* Copyright (c) Microsoft Corporation. All rights reserved.
* Licensed under the MIT License. See License.txt in the project root for license information.
*--------------------------------------------------------------------------------------------*/
import { CancellationTokenSource } from '../../../common/cancellation.js';
import { drainMicrotasksEmbedding } from './embedding.js';
import { pushGlobalTimeApi } from './globalTimeApi.js';
import { realTimeApi } from './timeApi.js';
import { untilToken, VirtualTimeProcessor } from './processor.js';
import { createRecordingRealTimeApi, RecordedTimerEvent } from './recordingTimeApi.js';
import { VirtualClock } from './virtualClock.js';
import { createVirtualTimeApi } from './virtualTimeApi.js';
export interface RunWithFakedTimersOptions {
readonly startTime?: number;
/** Default `true`. Set `false` to bypass virtual time entirely (for
* cases where the same test is parameterised over real/virtual time). */
readonly useFakeTimers?: boolean;
/** No effect in the new processor; accepted for legacy compatibility.
* The drain-microtasks embedding picks the fastest available macrotask
* primitive automatically. */
readonly useSetImmediate?: boolean;
/** Maximum number of virtual events the run is allowed to execute
* before being rejected. Default 100. */
readonly maxTaskCount?: number;
/**
* If set, called once `fn` resolves with the recorded timer events.
* In virtual mode the events come from the {@link VirtualTimeProcessor}'s
* own history; in real mode a recording wrapper around the host time
* API is installed for the duration of `fn`. Useful for swimlane
* diagnostics.
*/
readonly onHistory?: (history: readonly RecordedTimerEvent[]) => void;
}
/**
* Run `fn` with a virtual clock installed as the global time API.
*
* After `fn` resolves, the virtual queue is drained (so any timers `fn`
* scheduled and `await`ed for, transitively, complete deterministically).
* If `fn` throws, the queue is *not* drained — the original error is
* re-thrown immediately.
*/
options: RunWithFakedTimersOptions,
fn: () => Promise<T>,
): Promise<T> {
const useFakeTimers = options.useFakeTimers !== false;
if (!useFakeTimers) {
const history: RecordedTimerEvent[] = [];
const restore = pushGlobalTimeApi(createRecordingRealTimeApi(history));
try {
return await fn();
} finally {
restore.dispose();
options.onHistory(history);
}
const virtualApi = createVirtualTimeApi(clock);
const restoreGlobals = pushGlobalTimeApi(virtualApi);
const processor = new VirtualTimeProcessor(
clock,
drainMicrotasksEmbedding(realTimeApi),
realTimeApi,
{ defaultMaxEvents: options.maxTaskCount ?? 100 },
);
const cts = new CancellationTokenSource();
const runPromise = processor.run({ until: untilToken(cts.token) });
let didThrow = true;
let result: T;
try {
result = await fn();
} finally {
// Stop intercepting real-time scheduling before draining: any tasks
// scheduled during the drain itself must not land back in the
// virtual queue.
restoreGlobals.dispose();
cts.cancel();
try {
if (!didThrow) {
await runPromise;
} else {
// Avoid an unhandled rejection in case disposal rejects the
// run.
runPromise.catch(() => { /* swallowed: fn() already failed */ });
}
cts.dispose();
options.onHistory?.(processor.history);
processor.dispose();
}
}
return result;
}