diff --git a/.changeset/common-ways-deny.md b/.changeset/common-ways-deny.md
new file mode 100644
index 0000000000..75e9375965
--- /dev/null
+++ b/.changeset/common-ways-deny.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: don't (re)connect deriveds when read inside branch/root effects
diff --git a/.changeset/curly-wasps-hide.md b/.changeset/curly-wasps-hide.md
new file mode 100644
index 0000000000..7e55d77ba0
--- /dev/null
+++ b/.changeset/curly-wasps-hide.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: skip unnecessary derived effect in earlier batch
diff --git a/.changeset/dull-oranges-fry.md b/.changeset/dull-oranges-fry.md
new file mode 100644
index 0000000000..0efcc6fa2d
--- /dev/null
+++ b/.changeset/dull-oranges-fry.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: avoid declaration tag warning in event handlers
diff --git a/.changeset/shiny-keys-dance.md b/.changeset/shiny-keys-dance.md
new file mode 100644
index 0000000000..20cf754212
--- /dev/null
+++ b/.changeset/shiny-keys-dance.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: transform computed keys in keyed `{#each}` destructuring patterns
diff --git a/.changeset/tame-donkeys-jump.md b/.changeset/tame-donkeys-jump.md
new file mode 100644
index 0000000000..aae38910db
--- /dev/null
+++ b/.changeset/tame-donkeys-jump.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: chain preprocessor sourcemaps with an empty `sources[0]` instead of dropping them
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_broad_block.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_broad_block.bench.js
new file mode 100644
index 0000000000..e8451ec3fa
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_broad_block.bench.js
@@ -0,0 +1,47 @@
+import assert from 'node:assert';
+import * as $ from 'svelte/internal/client';
+import { block } from '../../../../packages/svelte/src/internal/client/reactivity/effects.js';
+
+// Like `kairo_broad`, but each derived is also read by a block effect, as
+// happens with e.g. `{#if derived}` in a component. Measures our #traverse perf better.
+export default () => {
+ let head = $.state(0);
+ let last = head;
+ let counter = 0;
+
+ const destroy = $.effect_root(() => {
+ for (let i = 0; i < 50; i++) {
+ let current = $.derived(() => {
+ return $.get(head) + i;
+ });
+ let current2 = $.derived(() => {
+ return $.get(current) + 1;
+ });
+ block(() => {
+ $.get(current2);
+ });
+ $.render_effect(() => {
+ $.get(current2);
+ counter++;
+ });
+ last = current2;
+ }
+ });
+
+ return {
+ destroy,
+ run() {
+ $.flush(() => {
+ $.set(head, 1);
+ });
+ counter = 0;
+ for (let i = 0; i < 50; i++) {
+ $.flush(() => {
+ $.set(head, i);
+ });
+ assert.equal($.get(last), i + 50);
+ }
+ assert.equal(counter, 50 * 50);
+ }
+ };
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_deep_block.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_deep_block.bench.js
new file mode 100644
index 0000000000..a8d9fa8c35
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_deep_block.bench.js
@@ -0,0 +1,48 @@
+import assert from 'node:assert';
+import * as $ from 'svelte/internal/client';
+import { block } from '../../../../packages/svelte/src/internal/client/reactivity/effects.js';
+
+let len = 50;
+const iter = 50;
+
+// Like `kairo_deep`, but the derived chain is also read by a block effect, as
+// happens with e.g. `{#if derived}` in a component. Measures our #traverse perf better.
+export default () => {
+ let head = $.state(0);
+ let current = head;
+ for (let i = 0; i < len; i++) {
+ let c = current;
+ current = $.derived(() => {
+ return $.get(c) + 1;
+ });
+ }
+ let counter = 0;
+
+ const destroy = $.effect_root(() => {
+ block(() => {
+ $.get(current);
+ });
+
+ $.render_effect(() => {
+ $.get(current);
+ counter++;
+ });
+ });
+
+ return {
+ destroy,
+ run() {
+ $.flush(() => {
+ $.set(head, 1);
+ });
+ counter = 0;
+ for (let i = 0; i < iter; i++) {
+ $.flush(() => {
+ $.set(head, i);
+ });
+ assert.equal($.get(current), len + i);
+ }
+ assert.equal(counter, iter);
+ }
+ };
+};
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/function.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/function.js
index 7bdb2243f2..6b3d227eca 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/function.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/function.js
@@ -18,7 +18,9 @@ export function visit_function(node, context) {
context.next({
...context.state,
- function_depth: context.state.function_depth + 1,
+ // we generally want to use scope.function_depth unless we specifically increased
+ // that in state.function_depth (e.g. a derived)
+ function_depth: Math.max(context.state.scope.function_depth, context.state.function_depth) + 1,
expression: null
});
}
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js
index a1371b516a..b33eddd461 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js
@@ -294,7 +294,10 @@ export function EachBlock(node, context) {
let key_function = b.id('$.index');
if (node.metadata.keyed) {
- const pattern = /** @type {Pattern} */ (node.context); // can only be keyed when a context is provided
+ // can only be keyed when a context is provided
+ const pattern = /** @type {Pattern} */ (
+ context.visit(/** @type {Pattern} */ (node.context), key_state)
+ );
const expression = /** @type {Expression} */ (
context.visit(/** @type {Expression} */ (node.key), key_state)
);
diff --git a/packages/svelte/src/compiler/utils/mapped_code.js b/packages/svelte/src/compiler/utils/mapped_code.js
index 7686ba59c6..635743c0c4 100644
--- a/packages/svelte/src/compiler/utils/mapped_code.js
+++ b/packages/svelte/src/compiler/utils/mapped_code.js
@@ -311,6 +311,13 @@ function apply_preprocessor_sourcemap(filename, svelte_map, preprocessor_map_inp
typeof preprocessor_map_input === 'string'
? JSON.parse(preprocessor_map_input)
: preprocessor_map_input;
+ // A preprocessor map with a missing/empty `sources[0]` (e.g. from a MagicString transform
+ // created without a `source` option) can't be matched against `filename` during combination,
+ // which silently drops the chain instead of erroring. Normalize it to `filename` first, the
+ // same way Vite treats an empty `sources[0]` as referring to the file being transformed.
+ if (preprocessor_map.sources?.length === 1 && !preprocessor_map.sources[0]) {
+ preprocessor_map.sources = [filename];
+ }
const result_map = combine_sourcemaps(filename, [svelte_map, preprocessor_map]);
// Svelte expects a SourceMap which includes toUrl and toString. Instead of wrapping our output in a class,
// we just tack on the extra properties.
diff --git a/packages/svelte/src/internal/client/reactivity/batch.js b/packages/svelte/src/internal/client/reactivity/batch.js
index 7d14b80519..5becae2dc9 100644
--- a/packages/svelte/src/internal/client/reactivity/batch.js
+++ b/packages/svelte/src/internal/client/reactivity/batch.js
@@ -530,6 +530,12 @@ export class Batch {
const mark = (value) => {
var reactions = value.reactions;
if (reactions === null) return;
+ // skip if value is derived and is neither dirty nor maybe dirty. transitive
+ // deriveds (a derived depending on another derived) are only MAYBE_DIRTY, so
+ // we must continue traversing them to reach the effects that depend on them
+ if ((value.f & DERIVED) !== 0 && (value.f & (DIRTY | MAYBE_DIRTY)) === 0) {
+ return;
+ }
for (const reaction of reactions) {
var flags = reaction.f;
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 45171ca4a7..32222dfb52 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -62,6 +62,9 @@ import { set_signal_status, update_derived_status } from './reactivity/status.js
import * as w from './warnings.js';
import { push_renderer } from './custom-renderer/state.js';
+/**
+ * True if updating in an effect context that is reactive (i.e. not branch/root effects)
+ */
let is_updating_effect = false;
export let is_destroying_effect = false;
@@ -445,7 +448,7 @@ export function update_effect(effect) {
var was_updating_effect = is_updating_effect;
active_effect = effect;
- is_updating_effect = true;
+ is_updating_effect = (flags & (BRANCH_EFFECT | ROOT_EFFECT)) === 0; // Branch/root effects are not reactive contexts
var pop_renderer = push_renderer(effect.r);
diff --git a/packages/svelte/tests/runtime-runes/samples/async-batch-derived/_config.js b/packages/svelte/tests/runtime-runes/samples/async-batch-derived/_config.js
new file mode 100644
index 0000000000..d5286d9d95
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-batch-derived/_config.js
@@ -0,0 +1,28 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+ async test({ assert, target }) {
+ const [increment, pop] = target.querySelectorAll('button');
+
+ increment.click();
+ await tick();
+ assert.htmlEqual(
+ target.innerHTML,
+ ` Loading...
`
+ );
+ increment.click();
+ await tick();
+ assert.htmlEqual(
+ target.innerHTML,
+ ` Loading...
`
+ );
+ pop.click();
+ await tick();
+ assert.htmlEqual(target.innerHTML, ` 2 2 1`);
+
+ pop.click();
+ await tick();
+ assert.htmlEqual(target.innerHTML, ` 2 2 1`);
+ }
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-batch-derived/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-batch-derived/main.svelte
new file mode 100644
index 0000000000..af7f0f468c
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-batch-derived/main.svelte
@@ -0,0 +1,29 @@
+
+
+
+
+{#snippet defaultPending()}
+ Loading...
+{/snippet}
+
+{#if count > 0}
+
+ {await push(count)} {count} {other}
+
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/Child.svelte b/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/Child.svelte
new file mode 100644
index 0000000000..35544d0a55
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/Child.svelte
@@ -0,0 +1,7 @@
+
+
+{#each options as { [labelKey]: label, [valueKey]: value } (value)}
+ {label}: {value}
+{/each}
diff --git a/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/_config.js b/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/_config.js
new file mode 100644
index 0000000000..8a8789d712
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/_config.js
@@ -0,0 +1,29 @@
+import { flushSync } from 'svelte';
+import { ok, test } from '../../test';
+
+// https://github.com/sveltejs/svelte/issues/18519
+export default test({
+ html: `
+
+ 1: a1
+ 2: a2
+ 3: a3
+ `,
+
+ test({ assert, target }) {
+ const btn = target.querySelector('button');
+ ok(btn);
+
+ flushSync(() => btn.click());
+
+ assert.htmlEqual(
+ target.innerHTML,
+ `
+
+ 3: a3
+ 2: a2
+ 1: a1
+ `
+ );
+ }
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/main.svelte b/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/main.svelte
new file mode 100644
index 0000000000..6885a6918e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/each-keyed-computed-destructuring-key/main.svelte
@@ -0,0 +1,12 @@
+
+
+
+
diff --git a/packages/svelte/tests/signals/test.ts b/packages/svelte/tests/signals/test.ts
index 927ce2e665..07f79bd395 100644
--- a/packages/svelte/tests/signals/test.ts
+++ b/packages/svelte/tests/signals/test.ts
@@ -1503,4 +1503,22 @@ describe('signals', () => {
assert.deepEqual(log, ['inner destroyed', 'inner destroyed']);
};
});
+
+ test('derived read in an untracked context should not leak in deps reactions', () => {
+ return () => {
+ let s = state('hello');
+ let a = derived(() => $.get(s));
+ let b = derived(() => $.get(a));
+
+ let destroy = effect_root(() => {
+ $.get(b);
+ });
+
+ destroy();
+
+ // a was spuriously added to s.reactions via is_updating_effect
+ // even though the entire derived chain was read in an untracked context
+ assert.equal(s.reactions, null);
+ };
+ });
});
diff --git a/packages/svelte/tests/sourcemaps/samples/sourcemap-empty-source/_config.js b/packages/svelte/tests/sourcemaps/samples/sourcemap-empty-source/_config.js
new file mode 100644
index 0000000000..43a2a4c16a
--- /dev/null
+++ b/packages/svelte/tests/sourcemaps/samples/sourcemap-empty-source/_config.js
@@ -0,0 +1,29 @@
+import * as fs from 'node:fs';
+import MagicString from 'magic-string';
+import { test } from '../../test';
+
+// Simulates a bundler plugin (e.g. a Vite plugin using `magic-string`) that transforms
+// the Svelte source *before* it reaches `compile()`, and hands its own sourcemap to
+// `compileOptions.sourcemap` — the documented way to let svelte chain an upstream map
+// into its own output map. Crucially, the upstream map is generated *without* a `source`
+// option, exactly like `new MagicString(code).generateMap()` — this yields a sourcemap
+// whose `sources` is `['']`, which previously broke the chain entirely (see #18491)
+// instead of being treated as "this file", causing every mapping through it to resolve
+// to `{ source: null, line: null, column: null }`.
+const input = fs.readFileSync(new URL('./input.svelte', import.meta.url), 'utf-8');
+const src = new MagicString(input);
+src.overwrite(
+ src.original.indexOf('count * 2'),
+ src.original.indexOf('count * 2') + 'count * 2'.length,
+ 'count * 2',
+ {
+ storeName: false
+ }
+);
+
+export default test({
+ compileOptions: {
+ sourcemap: src.generateMap({ hires: true })
+ },
+ client: [{ str: 'let doubled' }]
+});
diff --git a/packages/svelte/tests/sourcemaps/samples/sourcemap-empty-source/input.svelte b/packages/svelte/tests/sourcemaps/samples/sourcemap-empty-source/input.svelte
new file mode 100644
index 0000000000..b4e0b50bdb
--- /dev/null
+++ b/packages/svelte/tests/sourcemaps/samples/sourcemap-empty-source/input.svelte
@@ -0,0 +1,6 @@
+
+
+
diff --git a/packages/svelte/tests/validator/samples/declaration-tag-state-referenced-locally/input.svelte b/packages/svelte/tests/validator/samples/declaration-tag-state-referenced-locally/input.svelte
index 90cc208e72..f422be9622 100644
--- a/packages/svelte/tests/validator/samples/declaration-tag-state-referenced-locally/input.svelte
+++ b/packages/svelte/tests/validator/samples/declaration-tag-state-referenced-locally/input.svelte
@@ -7,3 +7,7 @@
{let e = $state(0), f = e}
{a}{b}{c}{d}{e}{f}
+
+
\ No newline at end of file