prevent more overfiring

packages/svelte/src/internal/client/reactivity/batch.js

@@ -1291,6 +1291,7 @@ export function eager(fn) {
 	let parent = active_reaction;
 
 	let version = version_map.get(parent) ?? source(0);
+	version.f |= EAGER_EFFECT;
 	version_map.set(parent, version);
 
 	if (DEV) {
@@ -1308,12 +1309,15 @@ export function eager(fn) {
 			// the first time this runs, we create an eager effect
 			// that will run eagerly whenever the expression changes
 			var previous_batch_values = batch_values;
+			var previous_stale_sources = stale_sources;
 
 			try {
 				batch_values = null;
+				stale_sources = null;
 				value = fn();
 			} finally {
 				batch_values = previous_batch_values;
+				stale_sources = previous_stale_sources;
 			}
 
 			return;

packages/svelte/src/internal/client/reactivity/sources.js

@@ -354,14 +354,15 @@ export function increment(source) {
  * Make `reaction` re-run in the current batch. For a derived this means dirtying
  * its reactions, as if the derived's value had changed.
  * @param {Reaction} reaction
+ * @param {number} status
  */
-export function invalidate(reaction) {
-	set_signal_status(reaction, DIRTY);
+export function invalidate(reaction, status) {
+	set_signal_status(reaction, status);
 
 	if ((reaction.f & DERIVED) !== 0) {
 		seen = null;
 		count_deps = 0;
-		mark_reactions(/** @type {Derived} */ (reaction), DIRTY, null);
+		mark_reactions(/** @type {Derived} */ (reaction), status, null);
 		seen = null;
 	} else {
 		schedule_effect(/** @type {Effect} */ (reaction));

packages/svelte/src/internal/client/runtime.js

@@ -23,7 +23,8 @@ import {
 	ERROR_VALUE,
 	MANAGED_EFFECT,
 	REACTION_RAN,
-	ASYNC
+	ASYNC,
+	EAGER_EFFECT
 } from './constants.js';
 import { invalidate, old_values } from './reactivity/sources.js';
 import {
@@ -790,17 +791,20 @@ function get_batch_value(signal, first_time) {
 				batch.stale_readers.add(reader);
 
 				if (current.is_eager) {
-					// TODO only do this if we can see that the batch doesn't have this already scheduled in (maybe)dirty effects.
-					batch.oncommit(() => {
-						batch.stale_readers.delete(reader);
-						Batch.ensure();
-						invalidate(reader);
-					});
+					// Reactions of eager effects with at least one non-eager effect (which we know is true here due to the stale_sources check above)
+					// need to rerun because they could do something like `$state.eager(count) !== count`.
+					if (reader.deps?.some((dep) => dep.f & EAGER_EFFECT)) {
+						batch.oncommit(() => {
+							batch.stale_readers.delete(reader);
+							Batch.ensure();
+							invalidate(reader, DIRTY);
+						});
+					}
 				} else {
 					queue_micro_task(() => {
 						batch.stale_readers.delete(reader);
 						const b = batch.activate();
-						invalidate(reader);
+						invalidate(reader, MAYBE_DIRTY);
 						b.flush();
 					});
 				}

packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring-2/_config.js

@@ -0,0 +1,38 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		await tick();
+
+		const [increment_a, increment_a_b, shift_second, shift] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		increment_a.click();
+		await tick();
+		assert.deepEqual(logs, ['a_d: 1']);
+		logs.length = 0;
+
+		increment_a_b.click();
+		await tick();
+		assert.deepEqual(logs, ['a_d: 2', 'c: 1']);
+		logs.length = 0;
+
+		shift_second.click(); // a_d of second batch
+		await tick();
+		assert.deepEqual(logs, ['c: 3']);
+		logs.length = 0;
+
+		shift.click(); // a_d of first batch - should not rerun second batch
+		await tick();
+		assert.deepEqual(logs, ['c: 1']);
+		logs.length = 0;
+
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, '3');
+		assert.deepEqual(logs, []);
+	}
+});

packages/svelte/tests/runtime-runes/samples/async-derived-not-overfiring-2/main.svelte

@@ -0,0 +1,21 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+	let a_d = $derived(await delay(a, 'a_d'));
+	let c = $derived(await delay(a_d + b, 'c'));
+
+	function delay(value, source) {
+		if (!value) return value;
+		console.log(source + ': ' + value);
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+
+	let deferred = [];
+</script> 
+
+<button onclick={() => a++}>increment a</button>
+<button onclick={() => {a++; b++}}>increment a & b</button>
+<button onclick={() => deferred.splice(1,1)[0]?.()}>shift second</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+
+<p>{c}</p>

packages/svelte/tests/runtime-runes/samples/async-eager-block/_config.js

@@ -2,7 +2,7 @@ import { tick } from 'svelte';
 import { test } from '../../test';
 
 export default test({
-	async test({ assert, target }) {
+	async test({ assert, target, logs }) {
 		await tick();
 		const [increment, resolve] = target.querySelectorAll('button');
 
@@ -10,14 +10,15 @@ export default test({
 		await tick();
 		assert.htmlEqual(
 			target.innerHTML,
-			'<button>increment</button> <button>resolve</button> 0 <p>loading...</p>'
+			'<button>increment</button> <button>resolve</button> 0 <p>loading...</p> <p>1</p>' // <p>0</p> would also be ok here
 		);
 
 		resolve.click();
 		await tick();
 		assert.htmlEqual(
 			target.innerHTML,
-			'<button>increment</button> <button>resolve</button> 1 <p>1</p>'
+			'<button>increment</button> <button>resolve</button> 1 <p>1</p> <p>1</p>'
 		);
+		assert.deepEqual(logs, [0, 1]);
 	}
 });

packages/svelte/tests/runtime-runes/samples/async-eager-block/main.svelte

@@ -13,8 +13,13 @@
 <button onclick={() => queued.shift()?.()}>resolve</button>
 
 {await delay(count)}
+
 {#if $state.eager(count) !== count}
 	<p>loading...</p>
 {:else}
 	<p>{count}</p>
 {/if}
+
+{#if $state.eager(console.log(count) || count)}
+	<p>{count}</p>
+{/if}