Class PromiseChain

src/platform/common/utils/async.ts:155–189

 * Provides the ability to chain promises.
 */
export class PromiseChain {
    private currentPromise: Promise<void | undefined> = Promise.resolve(undefined);
    /**
     * Chain the provided promise after all previous promises have successfully completed.
     * If the previously chained promises have failed, then this call will fail.
     */
    public async chain<T>(promise: () => Promise<T>): Promise<T> {
        const deferred = createDeferred<T>();
        const previousPromise = this.currentPromise;
        this.currentPromise = this.currentPromise.then(async () => {
            try {
                const result = await promise();
                deferred.resolve(result);
            } catch (ex) {
                deferred.reject(ex);
                throw ex;
            }
        });
        // Wait for previous promises to complete.
        await previousPromise;
        return deferred.promise;
    }
    /**
     * Chain the provided promise after all previous promises have completed (ignoring errors in previous promises).
     */
    public chainFinally<T>(promise: () => Promise<T>): Promise<T> {
        const deferred = createDeferred<T>();
        this.currentPromise = this.currentPromise.finally(() =>
            promise()
                .then((result) => deferred.resolve(result))
                .catch((ex) => deferred.reject(ex))
        );
        return deferred.promise;
    }
}

export interface ITask<T> {
    (): T;