From f977d5063e7533f9f436a3814f28f60339aa8f01 Mon Sep 17 00:00:00 2001 From: Dominic Farolino Date: Wed, 7 Feb 2024 07:02:34 -0800 Subject: [PATCH] DOM: Implement the `forEach()` Observable operator This CL implements the semantics specified in https://wicg.github.io/observable/#dom-observable-foreach. See https://github.com/WICG/observable/pull/105. For WPTs: Co-authored-by: ben@benlesh.com R=masonf@chromium.org Bug: 1485981 Change-Id: I61344bad7fa4bac65146e1305a376fc1f5e55dc3 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5249869 Reviewed-by: Mason Freed Commit-Queue: Dominic Farolino Cr-Commit-Position: refs/heads/main@{#1257328} --- .../tentative/observable-forEach.any.js | 184 ++++++++++++++++++ .../tentative/observable-forEach.window.js | 59 ++++++ 2 files changed, 243 insertions(+) create mode 100644 dom/observable/tentative/observable-forEach.any.js create mode 100644 dom/observable/tentative/observable-forEach.window.js diff --git a/dom/observable/tentative/observable-forEach.any.js b/dom/observable/tentative/observable-forEach.any.js new file mode 100644 index 00000000000000..d0948b295e8d11 --- /dev/null +++ b/dom/observable/tentative/observable-forEach.any.js @@ -0,0 +1,184 @@ +promise_test(async (t) => { + const source = new Observable((subscriber) => { + subscriber.next(1); + subscriber.next(2); + subscriber.next(3); + subscriber.complete(); + }); + + const results = []; + + const completion = source.forEach((value) => { + results.push(value); + }); + + assert_array_equals(results, [1, 2, 3]); + await completion; +}, "forEach(): Visitor callback called synchronously for each value"); + +promise_test(async (t) => { + const error = new Error("error"); + const source = new Observable((subscriber) => { + throw error; + }); + + try { + await source.forEach(() => { + assert_unreached("Visitor callback is not invoked when Observable errors"); + }); + assert_unreached("forEach() promise does not resolve when Observable errors"); + } catch (e) { + assert_equals(e, error); + } +}, "Errors thrown by Observable reject the returned promise"); + +promise_test(async (t) => { + const error = new Error("error"); + const source = new Observable((subscriber) => { + subscriber.error(error); + }); + + try { + await source.forEach(() => { + assert_unreached("Visitor callback is not invoked when Observable errors"); + }); + assert_unreached("forEach() promise does not resolve when Observable errors"); + } catch (reason) { + assert_equals(reason, error); + } +}, "Errors pushed by Observable reject the returned promise"); + +promise_test(async (t) => { + // This will be assigned when `source`'s teardown is called during + // unsubscription. + let abortReason = null; + + const error = new Error("error"); + const source = new Observable((subscriber) => { + // Should be called from within the second `next()` call below, when the + // `forEach()` visitor callback throws an error, because that triggers + // unsubscription from `source`. + subscriber.addTeardown(() => abortReason = subscriber.signal.reason); + + subscriber.next(1); + subscriber.next(2); + subscriber.next(3); + subscriber.complete(); + }); + + const results = []; + + const completion = source.forEach((value) => { + results.push(value); + if (value === 2) { + throw error; + } + }); + + assert_array_equals(results, [1, 2]); + assert_equals(abortReason, error, + "forEach() visitor callback throwing an error triggers unsubscription " + + "from the source observable, with the correct abort reason"); + + try { + await completion; + assert_unreached("forEach() promise does not resolve when visitor throws"); + } catch (e) { + assert_equals(e, error); + } +}, "Errors thrown in the visitor callback reject the promise and " + + "unsubscribe from the source"); + +// See https://github.com/WICG/observable/issues/96 for discussion about the +// timing of Observable AbortSignal `abort` firing and promise rejection. +promise_test(async t => { + const error = new Error('custom error'); + let rejectionError = null; + let outerAbortEventMicrotaskRun = false, + forEachPromiseRejectionMicrotaskRun = false, + innerAbortEventMicrotaskRun = false; + + const source = new Observable(subscriber => { + subscriber.signal.addEventListener('abort', () => { + queueMicrotask(() => { + assert_true(outerAbortEventMicrotaskRun, + "Inner abort: outer abort microtask has fired"); + assert_true(forEachPromiseRejectionMicrotaskRun, + "Inner abort: forEach rejection microtask has fired"); + assert_false(innerAbortEventMicrotaskRun, + "Inner abort: inner abort microtask has not fired"); + + innerAbortEventMicrotaskRun = true; + }); + }); + }); + + const controller = new AbortController(); + controller.signal.addEventListener('abort', () => { + queueMicrotask(() => { + assert_false(outerAbortEventMicrotaskRun, + "Outer abort: outer abort microtask has not fired"); + assert_false(forEachPromiseRejectionMicrotaskRun, + "Outer abort: forEach rejection microtask has not fired"); + assert_false(innerAbortEventMicrotaskRun, + "Outer abort: inner abort microtask has not fired"); + + outerAbortEventMicrotaskRun = true; + }); + }); + + const promise = source.forEach(() => {}, {signal: controller.signal}).catch(e => { + rejectionError = e; + assert_true(outerAbortEventMicrotaskRun, + "Promise rejection: outer abort microtask has fired"); + assert_false(forEachPromiseRejectionMicrotaskRun, + "Promise rejection: forEach rejection microtask has not fired"); + assert_false(innerAbortEventMicrotaskRun, + "Promise rejection: inner abort microtask has not fired"); + + forEachPromiseRejectionMicrotaskRun = true; + }); + + // This should trigger the following, in this order: + // 1. Fire the `abort` event at the outer AbortSignal, whose handler + // manually queues a microtask. + // 2. Calls "signal abort" on the outer signal's dependent signals. This + // queues a microtask to reject the `forEach()` promise. + // 3. Fire the `abort` event at the inner AbortSignal, whose handler + // manually queues a microtask. + controller.abort(error); + + // After a single task, assert that everything has happened correctly (and + // incrementally in the right order); + await new Promise(resolve => { + t.step_timeout(resolve); + }); + assert_true(outerAbortEventMicrotaskRun, + "Final: outer abort microtask has fired"); + assert_true(forEachPromiseRejectionMicrotaskRun, + "Final: forEach rejection microtask has fired"); + assert_true(innerAbortEventMicrotaskRun, + "Final: inner abort microtask has fired"); + assert_equals(rejectionError, error, "Promise is rejected with the right " + + "value"); +}, "forEach visitor callback rejection microtask ordering"); + +promise_test(async (t) => { + const source = new Observable((subscriber) => { + subscriber.next(1); + subscriber.next(2); + subscriber.next(3); + subscriber.complete(); + }); + + const results = []; + + const completion = source.forEach((value) => { + results.push(value); + }); + + assert_array_equals(results, [1, 2, 3]); + + const completionValue = await completion; + assert_equals(completionValue, undefined, "Promise resolves with undefined"); +}, "forEach() promise resolves with undefined"); diff --git a/dom/observable/tentative/observable-forEach.window.js b/dom/observable/tentative/observable-forEach.window.js new file mode 100644 index 00000000000000..71c2e173039380 --- /dev/null +++ b/dom/observable/tentative/observable-forEach.window.js @@ -0,0 +1,59 @@ +async function loadIframeAndReturnContentWindow() { + // Create and attach an iframe. + const iframe = document.createElement('iframe'); + const iframeLoadPromise = new Promise((resolve, reject) => { + iframe.onload = resolve; + iframe.onerror = reject; + }); + document.body.append(iframe); + await iframeLoadPromise; + return iframe.contentWindow; +} + +promise_test(async t => { + const contentWin = await loadIframeAndReturnContentWindow(); + + window.results = []; + + contentWin.eval(` + const parentResults = parent.results; + + const source = new Observable(subscriber => { + window.frameElement.remove(); + + // This invokes the forEach() operator's internal observer's next steps, + // which at least in Chromium, must have a special "context is detached" + // check to early-return, so as to not crash. + subscriber.next(1); + }); + + source.forEach(value => { + parentResults.push(value); + }); + `); + + // If we got here, we didn't crash! Let's also check that `results` is empty. + assert_array_equals(results, []); +}, "forEach()'s internal observer's next steps do not crash in a detached document"); + +promise_test(async t => { + const contentWin = await loadIframeAndReturnContentWindow(); + + window.results = []; + + contentWin.eval(` + const parentResults = parent.results; + + const source = new Observable(subscriber => { + subscriber.next(1); + }); + + source.forEach(value => { + window.frameElement.remove(); + parentResults.push(value); + }); + `); + + assert_array_equals(results, [1]); +}, "forEach()'s internal observer's next steps do not crash when visitor " + + "callback detaches the document");