120 lines
3.1 KiB
JavaScript
120 lines
3.1 KiB
JavaScript
import {AbortError} from "../utils/error.js";
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import {BaseObservable} from "./BaseObservable.js";
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// like an EventEmitter, but doesn't have an event type
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export class BaseObservableValue extends BaseObservable {
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emit(argument) {
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for (const h of this._handlers) {
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h(argument);
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}
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}
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}
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class WaitForHandle {
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constructor(observable, predicate) {
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this._promise = new Promise((resolve, reject) => {
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this._reject = reject;
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this._subscription = observable.subscribe(v => {
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if (predicate(v)) {
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this._reject = null;
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resolve(v);
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this.dispose();
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}
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});
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});
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}
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get promise() {
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return this._promise;
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}
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dispose() {
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if (this._subscription) {
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this._subscription();
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this._subscription = null;
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}
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if (this._reject) {
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this._reject(new AbortError());
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this._reject = null;
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}
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}
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}
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class ResolvedWaitForHandle {
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constructor(promise) {
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this.promise = promise;
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}
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dispose() {}
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}
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export class ObservableValue extends BaseObservableValue {
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constructor(initialValue) {
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super();
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this._value = initialValue;
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}
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get() {
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return this._value;
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}
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set(value) {
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if (value !== this._value) {
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this._value = value;
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this.emit(this._value);
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}
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}
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waitFor(predicate) {
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if (predicate(this.get())) {
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return new ResolvedWaitForHandle(Promise.resolve(this.get()));
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} else {
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return new WaitForHandle(this, predicate);
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}
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}
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}
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export function tests() {
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return {
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"set emits an update": assert => {
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const a = new ObservableValue();
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let fired = false;
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const subscription = a.subscribe(v => {
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fired = true;
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assert.strictEqual(v, 5);
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});
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a.set(5);
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assert(fired);
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subscription();
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},
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"set doesn't emit if value hasn't changed": assert => {
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const a = new ObservableValue(5);
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let fired = false;
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const subscription = a.subscribe(() => {
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fired = true;
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});
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a.set(5);
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a.set(5);
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assert(!fired);
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subscription();
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},
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"waitFor promise resolves on matching update": async assert => {
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const a = new ObservableValue(5);
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const handle = a.waitFor(v => v === 6);
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Promise.resolve().then(() => {
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a.set(6);
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});
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await handle.promise;
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assert.strictEqual(a.get(), 6);
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},
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"waitFor promise rejects when disposed": async assert => {
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const a = new ObservableValue();
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const handle = a.waitFor(() => false);
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Promise.resolve().then(() => {
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handle.dispose();
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});
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await assert.rejects(handle.promise, AbortError);
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},
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}
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}
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