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chore: simplify batch logic a bit more #16845

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Merged
merged 5 commits into from
Sep 25, 2025
Merged

chore: simplify batch logic a bit more #16845

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64a2c83
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Rich-Harris Sep 25, 2025
e46a428
remove unnecessary flushSync
Rich-Harris Sep 25, 2025
5c1cc0f
simplify
Rich-Harris Sep 25, 2025
493e2f4
merge
Rich-Harris Sep 25, 2025
2f575a5
Merge branch 'simplify-batch' into simplify-batch-more
Rich-Harris Sep 25, 2025
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4 changes: 2 additions & 2 deletions packages/svelte/src/internal/client/dom/blocks/await.js
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ import {
set_dev_current_component_function,
set_dev_stack
} from '../../context.js';
import { flushSync } from '../../reactivity/batch.js';
import { flushSync, is_flushing_sync } from '../../reactivity/batch.js';

const PENDING = 0;
const THEN = 1;
Expand Down Expand Up @@ -126,7 +126,7 @@ export function await_block(node, get_input, pending_fn, then_fn, catch_fn) {

// without this, the DOM does not update until two ticks after the promise
// resolves, which is unexpected behaviour (and somewhat irksome to test)
flushSync();
if (!is_flushing_sync) flushSync();
}
}
}
Expand Down
6 changes: 1 addition & 5 deletions packages/svelte/src/internal/client/dom/task.js
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Expand Up @@ -10,10 +10,6 @@ function run_micro_tasks() {
run_all(tasks);
}

export function has_pending_tasks() {
return micro_tasks.length > 0;
}

/**
* @param {() => void} fn
*/
Expand All @@ -40,7 +36,7 @@ export function queue_micro_task(fn) {
* Synchronously run any queued tasks.
*/
export function flush_tasks() {
if (micro_tasks.length > 0) {
while (micro_tasks.length > 0) {
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@elliott-with-the-longest-name-on-github elliott-with-the-longest-name-on-github Sep 25, 2025

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terrifying change 😆

run_micro_tasks();
}
}
23 changes: 12 additions & 11 deletions packages/svelte/src/internal/client/reactivity/batch.js
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Expand Up @@ -23,7 +23,7 @@ import {
update_effect
} from '../runtime.js';
import * as e from '../errors.js';
import { flush_tasks, has_pending_tasks, queue_micro_task } from '../dom/task.js';
import { flush_tasks, queue_micro_task } from '../dom/task.js';
import { DEV } from 'esm-env';
import { invoke_error_boundary } from '../error-handling.js';
import { old_values } from './sources.js';
Expand Down Expand Up @@ -355,20 +355,18 @@ export class Batch {
}

flush() {
this.activate();

if (queued_root_effects.length > 0) {
this.activate();
flush_effects();

if (current_batch !== null && current_batch !== this) {
// this can happen if a new batch was created during `flush_effects()`
return;
}
} else if (this.#pending === 0) {
this.#commit();
}

if (current_batch !== null && current_batch !== this) {
// this can happen if a `flushSync` occurred during `flush_effects()`,
// which is permitted in legacy mode despite being a terrible idea
return;
}

this.deactivate();
}

Expand Down Expand Up @@ -468,14 +466,17 @@ export function flushSync(fn) {
var result;

if (fn) {
flush_effects();
if (current_batch !== null) {
flush_effects();
}

result = fn();
}

while (true) {
flush_tasks();

if (queued_root_effects.length === 0 && !has_pending_tasks()) {
if (queued_root_effects.length === 0) {
current_batch?.flush();

// we need to check again, in case we just updated an `$effect.pending()`
Expand Down
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