mirror of https://github.com/sveltejs/svelte
fix: leave stale promises to wait for a later resolution, instead of rejecting (#18180)
This incorporates some of the fixes and insights from #18177, but gets rid of the `skip` logic. Instead, we differentiate between _stale_ and _obsolete_ promises. A promise is stale if it has been overtaken by a subsequent update, and was rejected with `STALE_REACTION`: ```ts async function search(query: string) { return fetch(`/search?q=${query}`, { signal: getAbortSignal() }).then((r) => r.json()); } ``` In this case, if we start typing `pot`, and then finish typing `potato`, the first promise will eventually resolve with the results for `/search?q=potato`, instead of the batch entering a weird limbo/zombie state. A promise is obsolete if it belongs to a now-destroyed effect, meaning that toggling `show` doesn't result in an accumulation of never-resolving batches: ```svelte {#if show} {await neverResolves()} {/if} ``` Fixes part of https://github.com/sveltejs/kit/issues/15431 --------- Co-authored-by: Simon Holthausen <simon.holthausen@vercel.com> Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>pull/18186/head
Rich Harris
4 months ago
committed by
GitHub
parent
4d2b6c61e0
commit
908c9d0312
@ -0,0 +1,5 @@
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---
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'svelte': patch
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---
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fix: leave stale promises to wait for a later resolution, instead of rejecting
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@ -0,0 +1,30 @@
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import { tick } from 'svelte';
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import { test } from '../../test';
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export default test({
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async test({ assert, target }) {
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await tick();
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const [increment, shift, middle] = target.querySelectorAll('button');
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const [div] = target.querySelectorAll('div');
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increment.click();
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await tick();
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increment.click();
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await tick();
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increment.click();
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await tick();
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middle.click(); // resolve the second increment which will make the if block go away and the first batch discarded
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await tick();
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assert.htmlEqual(div.innerHTML, '2 2');
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shift.click();
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await tick();
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shift.click();
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await tick();
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shift.click();
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await tick();
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shift.click();
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await tick();
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assert.htmlEqual(div.innerHTML, '3 3');
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}
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});
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<script>
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let a = $state(0);
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const deferred = [];
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function delay(value) {
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if (!value) return value;
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return new Promise((resolve) => deferred.push(() => resolve(value)));
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}
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</script>
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<div>
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{a} {await delay(a)}
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{#if a < 2}
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{await delay(a)}
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{/if}
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</div>
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<button onclick={() => {a++;}}>a++</button>
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<button onclick={() => deferred.shift()?.()}>shift</button>
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<button onclick={() => deferred[2]()}>middle</button>
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import { tick } from 'svelte';
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import { test } from '../../test';
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export default test({
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async test({ assert, target }) {
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await tick();
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const [increment, hide, pop] = target.querySelectorAll('button');
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increment.click();
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await tick();
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pop.click();
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await tick();
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hide.click(); // hides the if block, which cancels the pending async inside, which means the batch can complete
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await tick();
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assert.htmlEqual(
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target.innerHTML,
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`<button>increment</button> <button>hide</button> <button>pop</button> 1`
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);
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pop.click();
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await tick();
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assert.htmlEqual(
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target.innerHTML,
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`<button>increment</button> <button>hide</button> <button>pop</button> 1`
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);
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}
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});
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<script>
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let show = $state(true);
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let count = $state(0);
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const queue = [];
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function push(value) {
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if (!value) return value;
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return new Promise(r => queue.push(() => r(value)));
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}
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</script>
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<button onclick={() => count += 1}>increment</button>
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<button onclick={() => show = false}>hide</button>
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<!-- pop() so that the outer one resolves first, not the one inside the if block -->
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<button onclick={() => queue.pop()?.()}>pop</button>
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{await push(count)}
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{#if show}
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{await push(count)}
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{/if}
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@ -0,0 +1,33 @@
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import { tick } from 'svelte';
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import { test } from '../../test';
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export default test({
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async test({ assert, target }) {
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await tick();
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const [increment, shift] = target.querySelectorAll('button');
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increment.click();
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await tick();
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increment.click();
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await tick();
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assert.htmlEqual(
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target.innerHTML,
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`<button>3</button><button>shift</button><p>1 = 1</p><p>fizz: true</p><p>buzz: true</p>`
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);
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shift.click();
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await tick();
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assert.htmlEqual(
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target.innerHTML,
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`<button>3</button><button>shift</button><p>1 = 1</p><p>fizz: true</p><p>buzz: true</p>`
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);
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shift.click();
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await tick();
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assert.htmlEqual(
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target.innerHTML,
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`<button>3</button><button>shift</button><p>3 = 3</p><p>fizz: true</p><p>buzz: false</p>`
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);
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}
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});
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@ -0,0 +1,44 @@
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<script>
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import { getAbortSignal } from 'svelte';
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const queue = [];
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let n = $state(1);
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let fizz = $state(true);
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let buzz = $state(true);
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function increment() {
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n++;
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fizz = n % 3 === 0;
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buzz = n % 5 === 0;
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}
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function push(value) {
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if (value === 1) return 1;
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const d = Promise.withResolvers();
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queue.push(() => d.resolve(value));
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const signal = getAbortSignal();
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signal.onabort = () => d.reject(signal.reason);
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return d.promise;
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}
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</script>
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<button onclick={increment}>
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{$state.eager(n)}
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</button>
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<button onclick={() => queue.shift()?.()}>shift</button>
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<p>{n} = {await push(n)}</p>
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{#if true}
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<p>fizz: {fizz}</p>
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{/if}
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{#if true}
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<p>buzz: {buzz}</p>
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{/if}
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@ -0,0 +1,34 @@
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import { tick } from 'svelte';
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import { test } from '../../test';
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export default test({
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async test({ assert, target }) {
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await tick();
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const [button1, button2, pop, shift] = target.querySelectorAll('button');
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const [p] = target.querySelectorAll('p');
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button1.click();
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await tick();
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button2.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
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shift.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
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pop.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
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pop.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `1 + 0 = 1 | 1 0`);
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shift.click();
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await tick();
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pop.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `1 + 2 = 3 | 1 1`);
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}
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});
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@ -0,0 +1,21 @@
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<script>
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const queue1 = [];
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const queue2 = [];
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let a = $state(0);
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let b = $state(0);
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let c = $state(0);
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let d = $state(0)
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function push(value, where = 1) {
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if (!value) return value;
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return new Promise(r => (where === 1 ? queue1 : queue2).push(() => r(value)));
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}
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</script>
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<button onclick={() => {a++;c++}}>a / c</button>
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<button onclick={() => {b+=2;d++}}>b / d</button>
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<button onclick={() => queue1.pop()?.()}>pop 1</button>
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<button onclick={() => queue2.shift()?.()}>shift 2</button>
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<p>{a} + {b} = {await push(a + b)} | {await push(c, 2)} {await push(d, 2)}</p>
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@ -0,0 +1,34 @@
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import { tick } from 'svelte';
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import { test } from '../../test';
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export default test({
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async test({ assert, target }) {
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await tick();
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const [button1, button2, shift_1, pop_1, shift_2] = target.querySelectorAll('button');
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const [p] = target.querySelectorAll('p');
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button1.click();
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await tick();
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button2.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
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pop_1.click();
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await tick();
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shift_2.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
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// Check that the first batch can still resolve before the second even if one of its async values
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// is already superseeded (but the subsequent batch as a whole is still pending).
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shift_1.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `1 + 0 = 1 | 1 0`);
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shift_1.click();
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await tick();
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shift_2.click();
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await tick();
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assert.htmlEqual(p.innerHTML, `1 + 2 = 3 | 1 1`);
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}
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});
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@ -0,0 +1,22 @@
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<script>
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const queue1 = [];
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const queue2 = [];
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let a = $state(0);
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let b = $state(0);
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let c = $state(0);
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let d = $state(0)
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function push(value, where = 1) {
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if (!value) return value;
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return new Promise(r => (where === 1 ? queue1 : queue2).push(() => r(value)));
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}
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</script>
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<button onclick={() => {a++;c++}}>a / c</button>
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<button onclick={() => {b+=2;d++}}>b / d</button>
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<button onclick={() => queue1.shift()?.()}>shift 1</button>
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<button onclick={() => queue1.pop()?.()}>pop 1</button>
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<button onclick={() => queue2.shift()?.()}>shift 2</button>
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<p>{a} + {b} = {await push(a + b)} | {await push(c, 2)} {await push(d, 2)}</p>
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