svelte

Commit Graph

Author	SHA1	Message	Date
github-actions[bot]	a9f48540e2	Version Packages (#18389 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.56.3 ### Patch Changes - fix: ignore errors that occur in destroyed effects ([#18384](https://github.com/sveltejs/svelte/pull/18384)) - fix: type BigInts in `$state.snapshot(...)` return values ([#18388](https://github.com/sveltejs/svelte/pull/18388)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	1 month ago
sijie-Z	71a6515bd6	fix: check boundary exists before calling error handler in async derived (#18384 ) fixes #18383 I traced the issue to `packages/svelte/src/internal/client/error-handling.js`, specifically the `invoke_error_boundary` function. The problem is at line 56 where `effect.b.error(error)` is called without checking if `effect.b` exists. What happens is: when an async `$derived` rejects inside a `<svelte:boundary>`, the error is handled correctly the first time. But if the boundary is destroyed before the rejection fully settles (e.g. component unmounts), a subsequent settle tries to call `effect.b.error()` on a destroyed boundary where `effect.b` is `null`, causing a `TypeError`. The fix adds a null check for `effect.b` before calling `error()`. If the boundary has been destroyed, we skip it and continue bubbling up to the parent boundary. This way the error still gets handled properly instead of crashing. This could also be tested by creating a component with an async `$derived` that rejects after the component unmounts, but I wanted to get the fix up first for review. --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	1 month ago
sijie-Z	3d83c9abe6	fix: add bigint to Primitive type for $state.snapshot (#18388 ) Fixes #18385 ## Problem `$state.snapshot` infers BigInt properties as `never` because `bigint` is missing from the `Primitive` type definition. BigInt is a valid JavaScript primitive and is supported by `structuredClone`. ## Solution Added `bigint` to the `Primitive` type in both `packages/svelte/src/ambient.d.ts` and `packages/svelte/types/index.d.ts`. ## Before ```ts const object = $state({ number: 1n }); const snapshot = $state.snapshot(object); // snapshot.number is inferred as never ❌ After const object = $state({ number: 1n }); const snapshot = $state.snapshot(object); // snapshot.number is correctly inferred as bigint ✅ Tests and linting - [x] This is a type-only change, no runtime behavior affected --------- Co-authored-by: Rich Harris <hello@rich-harris.dev>	1 month ago
github-actions[bot]	51baf1c1af	Version Packages (#18357 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.56.2 ### Patch Changes - fix: properly track effect end node for async sibling component ([#18371](https://github.com/sveltejs/svelte/pull/18371)) - fix: prevent false-positive reactivity loss warning ([#18373](https://github.com/sveltejs/svelte/pull/18373)) - chore: bump esrap dependency ([#18372](https://github.com/sveltejs/svelte/pull/18372)) - fix: ignore declaration tags for animation directive ([#18366](https://github.com/sveltejs/svelte/pull/18366)) - fix: reject pending async deriveds on discard ([#18308](https://github.com/sveltejs/svelte/pull/18308)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	1 month ago
Simon H	3d5c4ab620	fix: prevent false-positive reactivity loss warning (#18373 ) By checking that current/previous batch are null we filter out false positives. `reactivity_loss_tracker` is only reset after a microtask, so if a flush happens before that, we get warnings for things we shouldn't warn on. Fixes #18370 --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	1 month ago
Simon H	bdb1a0f847	fix: ensure async block assigns correct nodes to effect (#18371 ) If a block has a sole component child, we apply an optimization to not need a template. But if that sole child is wrapped in `$.async`, it can happens that the block's effect is assigned the wrong end node. In the reproduction this happens because we have two components inside a Child which is rendered only after an async block resolves. In `$.append` we have logic to not reassign nodes when the active effect didn't already run, which it has by the time we come across it (because the async work had to resolve first; we added this in https://github.com/sveltejs/svelte/pull/17120 to prevent the opposite, nodes being "rewinded" to an earlier position) and so the second sibling component's `$.append` will not set its end node to the effect. As a result the end node is wrong (too early). To fix this we assign the nodes in `$.async`. We could also use `compareDocumentPosition` in `$.append` to only ever go forward, but that feels a bit heavier performance-wise. --------- Co-authored-by: paoloricciuti <ricciutipaolo@gmail.com> Co-authored-by: Rich Harris <rich.harris@vercel.com>	1 month ago
Simon H	e4bfc5f45a	chore: bump esrap dependency (#18372 ) Avoid installing the broken 2.2.10 version Closes #18369	1 month ago
Simon H	1b4c43b8e5	fix: ignore declaration tags for animation directive (#18366 ) Fixes #18365	2 months ago
Simon H	a81f96549d	fix: reject pending async deriveds on discard (#18308 ) The rejects all async deriveds of a batch as `OBSOLETE`, so they don't hang around and bail early without triggering the batch. If we don't do this, an async derived can trigger the already done batch, which schedules an effect that is never flushed. Because it is never flushed the branches it touched on its way up are never cleared, and so anything else in that subtree is now unreactive.	2 months ago
github-actions[bot]	3ef761b87b	Version Packages (#18346 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.56.1 ### Patch Changes - fix: error at compile time on duplicate snippet/declaration tag definitions ([#18351](https://github.com/sveltejs/svelte/pull/18351)) - fix: parse declaration tag contents more robustly ([#18353](https://github.com/sveltejs/svelte/pull/18353)) - fix: correctly transform references to earlier declarators in a declaration tag (e.g. `{let a = $state(0), b = $derived(a * 2)}`) ([#18348](https://github.com/sveltejs/svelte/pull/18348)) - fix: avoid spurious `state_referenced_locally` warnings for `$derived` declarations in declaration tags ([#18348](https://github.com/sveltejs/svelte/pull/18348)) - fix: tolerate whitespace before `let`/`const` in declaration tags ([#18348](https://github.com/sveltejs/svelte/pull/18348)) - fix: prevent infinite loop when a tag's expression ends with a trailing `/` at the end of the input ([#18350](https://github.com/sveltejs/svelte/pull/18350)) - fix: more robust parsing of declaration tags with regards to `type` ([#18330](https://github.com/sveltejs/svelte/pull/18330)) - fix: preserve newlines in spread input values when the `type` attribute is applied after `value` ([#18345](https://github.com/sveltejs/svelte/pull/18345)) - fix: update `SvelteURLSearchParams` when setting duplicate keys to the same joined value ([#18336](https://github.com/sveltejs/svelte/pull/18336)) - fix: check references for blockers on server, too ([#18352](https://github.com/sveltejs/svelte/pull/18352)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	2 months ago
Simon H	5b8db1be35	fix: error at compile time on duplicate snippet/declaration tag definitions (#18351 )	2 months ago
Simon H	56013a2c01	fix: check references for blockers on server, too (#18352 ) We forgot the server in #18309 Fixes #18344	2 months ago
hjaber	2afb895ffa	fix: parse declaration tags with a division operator in the initializer (#18353 ) Mimic what `parseExpressionAt` does --------- Co-authored-by: hjaber <hjaber@users.noreply.github.com> Co-authored-by: Simon Holthausen <simon.holthausen@vercel.com>	2 months ago
Yuichiro Yamashita	b471c15e61	fix: don't hang on a tag whose expression ends with a trailing slash (#18350 ) close https://github.com/sveltejs/svelte/issues/18349	2 months ago
Yuichiro Yamashita	c74f44fff9	fix: don't mistake `type` identifier expressions for TS `type` declarations in tags (#18330 ) Detect TypeScript `type` declarations by actually parsing instead of by character-class blacklists, so that expressions like `{type === 'all' ? a : b}` or `{type instanceof Foo}` aren't misclassified as malformed declarations. Closes #18328 --------- Co-authored-by: Simon Holthausen <simon.holthausen@vercel.com> Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>	2 months ago
Rich Harris	b76b937e00	fix: various declaration tag bugs (#18348 ) closes #18334	2 months ago
jdoughty04	378bb25097	fix: set input type before spread value (#18345 ) ### Before submitting the PR, please make sure you do the following - [x] It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs - [x] Prefix your PR title with `feat:`, `fix:`, `chore:`, or `docs:`. - [x] This message body should clearly illustrate what problems it solves. - [x] Ideally, include a test that fails without this PR but passes with it. - [x] If this PR changes code within `packages/svelte/src`, add a changeset (`npx changeset`). ### Tests and linting - [x] Run the tests with `pnpm test` and lint the project with `pnpm lint` Fixes #18332. When spread props put `value` before a later `type="hidden"` on an `<input>`, `set_attributes` currently writes the value while the element is still a text input. Browsers sanitize text input values by removing newlines, so the hidden input permanently loses them before `type` is applied. This sets an input's `type` first whenever the same spread update also includes `value` or `__value`, so the existing value handling runs with the final input type. The new runtime-browser sample covers both the problematic spread-first order and the already-working type-first order. Validation: - `corepack pnpm lint` - `CI=1 corepack pnpm test` - `corepack pnpm vitest run packages/svelte/tests/runtime-browser/test.ts -t input-type-before-value-spread` --------- Co-authored-by: Rich Harris <rich.harris@vercel.com> Co-authored-by: Rich Harris <hello@rich-harris.dev>	2 months ago
jiyujie2006	2f6307af65	Fix searchParams.set duplicate updates (#18336 ) ## Summary - detect `SvelteURLSearchParams#set` changes by comparing duplicate value lists instead of joined strings - update reactive subscribers when duplicate params collapse to a single value with the same concatenated text - cover both `SvelteURLSearchParams` and `SvelteURL.searchParams` synchronization ## Tests - pnpm exec vitest run packages/svelte/src/reactivity/url-search-params.test.ts -t "URLSearchParams.set updates when duplicate values collapse to the same joined string" - pnpm exec vitest run packages/svelte/src/reactivity/url-search-params.test.ts packages/svelte/src/reactivity/url.test.ts --------- Co-authored-by: Rich Harris <hello@rich-harris.dev>	2 months ago
github-actions[bot]	70afafe18e	Version Packages (#18315 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.56.0 ### Minor Changes - feat: allow declarations in the template ([#18282](https://github.com/sveltejs/svelte/pull/18282)) ### Patch Changes - perf: use `createElement` instead of `createElementNS` for HTML elements ([#18262](https://github.com/sveltejs/svelte/pull/18262)) - perf: store `current_sources` as a `Set` for O(1) membership checks ([#18278](https://github.com/sveltejs/svelte/pull/18278)) - perf: deduplicate identical hoisted templates within a component ([#18320](https://github.com/sveltejs/svelte/pull/18320)) - perf: hoist `rest_props` exclude list as a module-scope `Set` ([#18252](https://github.com/sveltejs/svelte/pull/18252)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	2 months ago
Mathias Picker	2fae91af6d	perf: deduplicate identical hoisted templates within a component (#18320 ) Byte-identical templates hoisted from different fragments, elements, or branches now share a single `$.from_html` factory instead of each emitting its own module-scope variable - this shrinks generated output and avoids redundant runtime template parsing. Dedup is keyed on `(content, flags)` and is skipped in dev mode (templates there are wrapped in `$.add_locations`, which embeds per-call-site info). ### Before submitting the PR, please make sure you do the following - [ ] It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs - [x] Prefix your PR title with `feat:`, `fix:`, `chore:`, or `docs:`. - [x] This message body should clearly illustrate what problems it solves. - [x] Ideally, include a test that fails without this PR but passes with it. - [x] If this PR changes code within `packages/svelte/src`, add a changeset (`npx changeset`). ### Tests and linting - [x] Run the tests with `pnpm test` and lint the project with `pnpm lint` --------- Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Co-authored-by: Rich Harris <rich.harris@vercel.com>	2 months ago
Mathias Picker	a40c745fd9	perf: hoist rest_props exclude list as a module-scope Set (#18252 ) The compiler emitted an inline string array as the second argument to `$.rest_props(...)`, and the runtime did a linear `Array.prototype.includes` on it on every property access via the rest-props Proxy. The exclude list only depends on the component definition, not on the instance, so it can be hoisted to module scope and shared by every instance. Switching it to a `Set` at the same time makes each lookup O(1). For a component like `<Button ...rest />` rendered N times, this turns one per-instance allocation (plus a linear search on every rest-prop access) into one module-scope allocation plus O(1) lookups. The legacy `$$restProps` path is unchanged — it mutates the exclude list in its `deleteProperty` trap, so it can't share a hoisted Set across instances. --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	2 months ago
Simon H	59d3a36f82	feat: allow declarations in the template (#18282 ) Allows `{let/const ...}` declarations in all places (and more) where we already allow `{@const ...}` (which will eventually get deprecated in favor of this new feature). Closes: #16490 Companion PRs: - https://github.com/sveltejs/language-tools/pull/3033 - https://github.com/sveltejs/prettier-plugin-svelte/pull/533 - https://github.com/sveltejs/eslint-plugin-svelte/pull/1533 - https://github.com/sveltejs/svelte-eslint-parser/pull/891 --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	2 months ago
Mathias Picker	a9916053d9	perf: use createElement instead of createElementNS for HTML elements (#18262 ) ## Summary The current wrapper always calls `document.createElementNS(namespace ?? NAMESPACE_HTML, tag, options)` — even for HTML elements (the >99% case), and even when `options` would be `undefined`. Two effects compound: 1. Route HTML elements through `createElement` — Blink has a fast path that skips the namespace lookup `createElementNS` always performs. 2. Omit the trailing `undefined` argument — V8/Blink take a slower path for `createElementNS(ns, tag, undefined)` (and `createElement(tag, undefined)`) than for the bare 2-arg form. This applies symmetrically to the SVG/MathML branch, where the wrapper now also avoids the `undefined` 3rd arg. The wrapper dispatches to the fastest call shape for every input — `{HTML, non-HTML}` × `{with is, without is}` × no `undefined` ever. ## Affects Every place Svelte constructs a DOM element internally: `<svelte:element>`, `run_scripts`, the per-component `<style>` injector, the `{@html}` wrapper, and the `<template>` element used to clone string templates. ## Numbers Measured in headless Chromium (Chromium 145) using the browser bench harness from #18261, 2–3 runs, median. Lower per-call is better; higher hz is better. ### Raw call shapes (what each shape costs in the browser) \| \| hz \| per-call \| \| ------------------------------------------- \| -------: \| -------: \| \| `createElement(tag)` \| ~1,210k \| ~0.83 µs \| \| `createElement(tag, undefined)` \| ~901k \| ~1.11 µs \| \| `createElementNS(NS_HTML, tag)` \| ~913k \| ~1.10 µs \| \| `createElementNS(NS_HTML, tag, undefined)` \| ~630k \| ~1.59 µs \| \| `createElement(tag, { is })` \| ~484k \| ~2.07 µs \| \| `createElementNS(SVG_NS, tag)` \| ~333k \| ~3.01 µs \| \| `createElementNS(SVG_NS, tag, undefined)` \| ~303k \| ~3.30 µs \| \| `createElementNS(SVG_NS, tag, { is })` \| ~245k \| ~4.08 µs \| Two stable effects fall out: - Trailing `undefined` is consistently slower than the bare form — ~26% on `createElement`, ~31% on `createElementNS` (HTML), ~10% on `createElementNS` (SVG). - `createElement` skips a namespace lookup that `createElementNS` always performs — ~32% delta for equal-shape calls (`createElement(tag)` vs `createElementNS(NS_HTML, tag)`). ### Per-case impact of this PR \| Case (namespace, `is`) \| Old wrapper call \| Old hz \| New wrapper call \| New hz \| Speedup \| \| ----------------------------- \| --------------------------------------------- \| --------: \| ------------------------------ \| --------: \| ------: \| \| HTML, no `is` (dominant path) \| `createElementNS(NS_HTML, tag, undefined)` \| ~630k \| `createElement(tag)` \| ~1,210k \| ~92% (1.92×) \| \| HTML, with `is` \| `createElementNS(NS_HTML, tag, { is })` \| (slow) \| `createElement(tag, { is })` \| ~484k \| similar to above (just the NS-skip) \| \| SVG/MathML, no `is` \| `createElementNS(ns, tag, undefined)` \| ~303k \| `createElementNS(ns, tag)` \| ~333k \| ~10% \| \| SVG/MathML, with `is` \| `createElementNS(ns, tag, { is })` \| ~245k \| same \| ~245k \| no change \| No measurable change in JSDOM (both shapes route through the same JS implementation there). The headline gain — ~92% on the dominant HTML-no-`is` path — combines both effects roughly equally: dropping the `undefined` (~46%) and switching to `createElement` (~32%). Wrapper-vs-raw was also verified: the new wrapper measured to within ±2% of raw `document.createElement(tag)` for the HTML-no-`is` case, so the function-call indirection adds no measurable overhead. See #18261 for the benchmark and methodology. ## Test plan - [x] All 5881 runtime tests still pass (runtime-runes + runtime-legacy) - [x] `<svelte:element xmlns={null}>` correctly falls back to HTML (covered by existing `dynamic-element-dynamic-namespace` test) - [x] SVG/MathML namespaces still go through `createElementNS` - [x] Custom-element `is` option still honoured on both branches 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>	2 months ago
Mathias Picker	67090e8ee8	perf: store current_sources as Set for O(1) membership checks (#18278 ) `current_sources` tracks the sources created within the active reaction so that reading or writing them during that same reaction doesn't trigger a re-run. It was an `Array` checked with `Array.prototype.includes.call(...)` in three hot places: the `state_unsafe_mutation` guard, `set()`'s destruction check, and `schedule_possible_effect_self_invalidation`. --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	2 months ago
github-actions[bot]	0bb715d3cf	Version Packages (#18255 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.55.10 ### Patch Changes - fix: unlink errored and otherwise finished batch ([#18264](https://github.com/sveltejs/svelte/pull/18264)) - perf: walk composedPath() directly in delegated event propagation ([#18268](https://github.com/sveltejs/svelte/pull/18268)) - fix: transfer effects when merging batches ([#18254](https://github.com/sveltejs/svelte/pull/18254)) - fix: allow `$derived(await ...)` in disconnected effect roots ([#18273](https://github.com/sveltejs/svelte/pull/18273)) - fix: remove temporary raw-text hydration markers ([#18269](https://github.com/sveltejs/svelte/pull/18269)) - fix: propagate async `@const` blockers through closure references so template expressions like `{(() => host)()}` correctly wait for the awaited value ([#18309](https://github.com/sveltejs/svelte/pull/18309)) - fix: properly unlink batches ([#18298](https://github.com/sveltejs/svelte/pull/18298)) - fix: settle discarded batch ([#18290](https://github.com/sveltejs/svelte/pull/18290)) - fix: declare `let:` directives before `{@const}` declarations on slotted elements ([#18271](https://github.com/sveltejs/svelte/pull/18271)) - fix: resume outro-ed branches if they were kept around ([#18291](https://github.com/sveltejs/svelte/pull/18291)) - fix: avoid waterfall-warning when async resolves to same value ([#18297](https://github.com/sveltejs/svelte/pull/18297)) - fix: correctly coordinate component-level effects inside async blocks ([#18260](https://github.com/sveltejs/svelte/pull/18260)) - fix: make unnecessary commit work less likely ([#18263](https://github.com/sveltejs/svelte/pull/18263)) - chore: add tag name to `a11y_click_events_have_key_events` warning ([#18272](https://github.com/sveltejs/svelte/pull/18272)) - fix: catch rejected promises while merging/committing ([#18266](https://github.com/sveltejs/svelte/pull/18266)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	2 months ago
Elliott Johnson	e705369dee	fix: propagate async @const blockers through closure references (#18309 ) Right now, if you have the following: ```svelte {@const data = await foo} <p>{(() => data)()}<p> ``` It will blow up during CSR, because it tries to read `data` before it exists. The solution to this is to consider references inside closures as blockers for those closures. This _does_ mean we'll overblock in some circumstances, such as: ```svelte {@const data = await foo} <button onclick={() => data}>foo<button> ``` But I wonder if that's actually incorrect? If the user were to click `onclick` before `data` is ready, it would blow up. --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	2 months ago
Rich Harris	ec08dbc7ee	fix: only unlink batch if we're done with it (#18298 ) alternative to #18296 — no need to make batches relinkable if we only unlink them when we're fully done with them	2 months ago
Simon H	c01e598fff	fix: avoid waterfall-warning when async resolves to same value (#18297 )	2 months ago
Rich Harris	070a0c4f77	Revert "perf: use Set instead of Array for constant lookups in utils.js" (#18294 ) Reverts sveltejs/svelte#18250	2 months ago
Simon H	60eaa92b0b	fix: resume outro-ed branches if they were kept around (#18291 ) If a branch is removed from the visible dom, it may be kept around because a subsequent batch will intro it again. If we don't resume the effects it will stay inert and therefore not react to updates anymore	2 months ago
Simon H	871e590c59	fix: settle discarded batch (#18290 ) Without this the promise would never resolve	2 months ago
Mathias Picker	e6110d31c5	perf: use Set instead of Array for constant lookups in utils.js (#18250 ) Several constant lookup tables in `utils.js` were arrays searched with `Array.prototype.includes`, which is O(n). They're queried often — per attribute during attribute setup and SSR, per event during event delegation, and per identifier during compilation. Switching them to `Set` makes each lookup O(1) without changing any public behaviour.	2 months ago
Simon H	fe9ab936b6	fix: allow `$derived(await ...)` in disconnected effect roots (#18273 ) If `$effect.root` is created outside the component tree, the boundary property is null Fixes #18188	2 months ago
Karl Georgsen	f023e8d7c8	chore: add tag name to a11y_click_events_have_key_events warning (#18272 ) Ref: https://github.com/sveltejs/svelte/issues/15100 Adds the tag name to the `a11y_click_events_have_key_events` warning given when a non-interactive element has a click handler but no keyboard events. This already happens in `a11y_no_static_element_interactions`, and should probably happen in many more messages.	2 months ago
wheelman	bb69f9c44c	fix: declare `let:` directives before `{@const}` on slotted elements (#18271 ) Fixes #18119 (missed a spot in #16985)	2 months ago
Puneet Dixit	8b961be0b1	fix: remove raw-text hydration markers (#18269 ) Fixes #14413. This keeps the temporary raw-text hydration sentinel used by dynamic `<svelte:element>` from becoming part of the final DOM. Hydration still gets a marker to advance through for raw-text children, but the marker is removed after the child renderer runs, so `<style>` and `<script>` contents stay identical to SSR output. Tests: - `pnpm test hydration -t svelte-head-dynamic-style` - `pnpm test hydration` - `pnpm test runtime-runes -t svelte-element` - `pnpm lint` - `git diff --check` --------- Co-authored-by: Puneet Dixit <236133619+puneetdixit200@users.noreply.github.com> Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>	2 months ago
Mathias Picker	04d408b29d	perf: walk composedPath() directly in delegated event propagation (#18268 ) ## Summary The propagation walk in `handle_event_propagation` already calls `event.composedPath()` at the start to find the entry index, but then re-derives the same chain step-by-step via `current_target.assignedSlot \|\| current_target.parentNode \|\| .host`. Three property reads per iteration is measurable on the hot event path. Walk the captured `path` array by index instead. ## Notes on behavior `composedPath()` is the spec-compliant snapshot of the dispatch chain: - Same shadow-DOM crossings (slots and shadow roots are included for composed events). - Same `host` traversal (composed-path crosses shadow boundaries when appropriate). - Differs from the previous walk in one edge case: if a handler removes a parent mid-dispatch, the snapshot-based walk continues through the captured chain (matches native browser semantics — the previous `parentNode` walk would have stopped at a null parent). ## Performance Measured in real Chromium on a click through a 30-deep tree with five delegated handlers: ~245k hz → ~277k hz (~+13%, ~−12% per-event time). ## Test plan - [x] All 6006 runtime tests pass (runtime-runes + runtime-legacy + runtime-browser) - [x] Native shadow-DOM event tests (in runtime-browser) pass unchanged 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>	2 months ago
Simon H	078f901f61	fix: catch rejected promises while merging/committing (#18266 ) A committing/merging batch can have promises that were rejected (e.g. as obsolete). We gotta "forward" this rejection, too, instead of just the successful promise. At best it results in a uncaught rejection (`async-branch-merge-obsolete`), at worst it means error boundaries are not correctly displayed (`async-later-promise-fails-first`). Solves the reproduction in https://github.com/sveltejs/svelte/issues/18221#issuecomment-4507803845	2 months ago
Simon H	a6002b587c	fix: unlink errored and otherwise finished batch (#18264 ) This fixes the issue in https://github.com/sveltejs/svelte/issues/18221#issuecomment-4497918414 where an error can create follup-up invariant errors. The batch errors, has no chance to run otherwise (no more pending work) and is therefore "dead". That means we need to unlink it otherwise it's becoming a "zombie" and hangs around, causing unnecessary and potentially buggy (as seen in the reproduction) merge/commit work. I was not able to reduce the reproduction down to a test case that fails without the fix, but it does make a related error test from #17888 work more correctly.	2 months ago
Simon H	4656e6895d	fix: make unnecessary commit work less likely (#18263 ) While looking at https://github.com/sveltejs/svelte/issues/18221#issuecomment-4497918414 and trying to understand how the invariant can happen I noticed that we are not correctly filtering during commit. - we were not ignoring deriveds - we were not comparing the correct values (checking `source.v` instead of the saved value) and not checking if their "is a derived" state differs I'm not able to come up with a test where something fails without these (possibly because it's more about an optimization to do less reruns and not about correctness) fixes, but they do make sense.	2 months ago
Simon H	91a42e2ed6	fix: correctly coordinate component-level effects inside async blocks (#18260 ) While looking at the reproduction in https://github.com/sveltejs/svelte/issues/18221#issuecomment-4497918414 I immediately got greeted with a runtime error when running it in the playground (weirdly not in the Stackblitz version). The error was that a component expected a binding to be set in onMount, but the timing of onMount was wrong. Turns out it's because our logic to determine whether or not to defer top level effects is flawed. `REACTION_RAN`, which was used previously, is already set if the initialized component is inside an async block. We instead check for `component_context.i` which is set to `true` on `pop()`.	2 months ago
Simon H	65283bc13a	fix: transfer effects when merging batches (#18254 ) An effect could be gated behind a branch. If we don't defer + transfer them upon merge, the branch would still be marked clean but the effect behind it is dirty but no longer reachable. It's not reachable via mark either because that one only concerns itself with block/async effects, and the branch gating the effect is not guaranteed to be touched by that. Fixes #18249 Little sad side-effect: Since we cannot reliably know _before_ traversal if we have no blocking pending work left (the traversal could mark an if block falsy which contains the last blocker), we gotta undo a performance optimization.	2 months ago
github-actions[bot]	b65a3f3fc5	Version Packages (#18240 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.55.9 ### Patch Changes - fix: don't unset batch when calling `{#await ...}` promise ([#18243](https://github.com/sveltejs/svelte/pull/18243)) - fix: promise-ify `{#await await ...}` expressions on the server and correctly hydrate them on the client ([#18243](https://github.com/sveltejs/svelte/pull/18243)) - fix: deduplicate dependencies that are added outside the init/update cycle ([#18243](https://github.com/sveltejs/svelte/pull/18243)) - fix: avoid false-positive batch invariant error ([#18246](https://github.com/sveltejs/svelte/pull/18246)) - fix: inline primitive constants in attribute values during SSR ([#18232](https://github.com/sveltejs/svelte/pull/18232)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	2 months ago
Simon H	d654db83ef	fix: avoid false-positive batch invariant error (#18246 ) Thanks to https://github.com/sveltejs/svelte/issues/17940#issuecomment-4480016550 I was finally able to isolate and reproduce a false-positive invariant error. I had a hunch this could happen and this shows it. Essentially, you can end up in situations where two batches are scheduled to run in the same microtask queue flush, and if the first rebases the second the invariant will throw, which is wrong. We can avoid this by checking if a decrement is queued.	2 months ago
Simon H	000c594e05	fix: `{#await await ...}` and async dependencies fixes (#18243 ) This started out as an investigation to get rid of the runtime code for `{#await ...}` that deactivated a batch prior to reading the promise function. That can result in a new batch being created if the promise invocation happens to write a source. Through that I discovered two other bugs: 1. The way we handle `{#await await ...}` was flawed around SSR/hydration: On the server it would await the expression (which it should not; `{#await await ...}` is kind of a weird special case here) and during hydration it did not produce matching nodes, leading to hydration fails. 2. When reading a dependency after an await expression which we add to the current reaction, we did not deduplicate those reads. That can lead to duplicate dependencies, which in turn can lead to bugs when `remove_reaction` later runs. Conside this: You have `deps = [count, unrelated, count]`. Now you do `remove_reactions(deps, 1)`, i.e. "remove all reactions after the first one". That means the "disconnect these from each other" logic runs for `count`, too, because it's also in the third position, but that is wrong because it is also in the first position, i.e. the connection should be kept. --------- Co-authored-by: Rich Harris <rich.harris@vercel.com>	2 months ago
Sean Kenneth Doherty	a5df6616ea	fix: avoid unnecessary stringify in server attributes (#18232 ) ### Before submitting the PR, please make sure you do the following - [x] It's really useful if your PR references an issue where it is discussed ahead of time. Fixes #10031. - [x] Prefix your PR title with `feat:`, `fix:`, `chore:`, or `docs:`. - [x] This message body should clearly illustrate what problems it solves. - [x] Ideally, include a test that fails without this PR but passes with it. - [x] If this PR changes code within `packages/svelte/src`, add a changeset (`npx changeset`). ### What this changes Server attribute template generation currently wraps each dynamic expression in `$.stringify`, even when the compiler can prove the expression is a string or a known constant. This reuses the existing scope evaluation metadata so server output can avoid `$.stringify` for proven string/constant chunks while keeping it for possibly nullish unknown values. The updated snapshot covers a mixed attribute with a known string, mutable state, `null`, numeric/undefined constants, a known string-producing `typeof`, and an unknown prop value. ### Tests and linting - [x] `pnpm test snapshot -t nullish-coallescence-omittance` - [x] `pnpm test snapshot` - [x] `pnpm --filter svelte check` - [x] `pnpm lint` - [x] `pnpm prettier --check .changeset/slow-bikes-serve.md` --------- Co-authored-by: Rich Harris <hello@rich-harris.dev>	2 months ago
github-actions[bot]	f9440dc3ed	Version Packages (#18239 ) This PR was opened by the [Changesets release](https://github.com/changesets/action) GitHub action. When you're ready to do a release, you can merge this and the packages will be published to npm automatically. If you're not ready to do a release yet, that's fine, whenever you add more changesets to main, this PR will be updated. # Releases ## svelte@5.55.8 ### Patch Changes - fix(print): handle `svelte:body` and fix keyframe percentage double-printing ([#18234](https://github.com/sveltejs/svelte/pull/18234)) - fix: execute uninitialized derived even if it's destroyed ([#18228](https://github.com/sveltejs/svelte/pull/18228)) - fix: use named symbols everywhere ([#18238](https://github.com/sveltejs/svelte/pull/18238)) - fix: don't run teardown effects when deriveds are unfreezed ([#18227](https://github.com/sveltejs/svelte/pull/18227)) - fix: unset context synchronously in `run` ([#18236](https://github.com/sveltejs/svelte/pull/18236)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	2 months ago
OfirHaf	ca3f35bf7d	fix(print): handle svelte:body and fix keyframe percentage double-printing (#18234 ) Fixes #18206 and fixes #18207 — both are printer bugs in `packages/svelte/src/compiler/print/index.js`. ## Changes ### Fix 1: `svelte:body` crashes the printer (#18206) `SvelteBody` was missing from the visitor map, causing a crash with `Error: Not implemented: SvelteBody`. Added the handler (same one-liner pattern as `SvelteDocument`, `SvelteHead`, etc.) and added `SvelteBody` to the `is_block_element` check so whitespace is handled consistently. ### Fix 2: Keyframe percent stops print as `0%%` (#18207) `Percentage.value` already includes the `%` sign (captured by `/\d+(\.\d+)?%/y`), but the printer was writing `` `${node.value}%` `` — appending a second `%`. Changed to `context.write(node.value)` to match the `Nth` printer pattern directly above it. Also updated the existing `style` snapshot which had `50%%` (the bug was silently baked in), and added dedicated test samples for both fixes.	2 months ago
Rich Harris	2bc3592eb1	fix: use named symbols everywhere (#18238 ) This isn't _really_ a fix since these should never surface to the user, but it's useful for debugging when they do, as in https://github.com/sveltejs/kit/pull/15779. Instead of seeing `Symbol()` we see e.g. `Symbol(uninitialized)` which makes it easier to understand where a bug is coming from.	2 months ago
Simon H	dc1f037fa6	fix: don't run teardown effects when deriveds are unfreezed (#18227 ) The logic was flawed - a teardown effect only has a teardown function but not `fn` property, but unfreeze thought that everything with a `teardown` needs to be unfreezed Helps with #18221 (though likely doesn't fix it completely, at least not the more general `batch.#roots`problems)	2 months ago

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