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Author	SHA1	Message	Date
Ivan	5edd8b0602	fix: chain preprocessor sourcemaps with an empty sources[0] (#18518) ... ## Summary Fixes #18491 — the compiler discards an upstream plugin's sourcemap when it's generated without a `source` option (e.g. `new MagicString(code).generateMap()`), producing wrong devtools/stack-trace positions. ### Root cause `compile()` already supports composing an incoming sourcemap into its output via `options.sourcemap` (`merge_with_preprocessor_map` → `apply_preprocessor_sourcemap` → `combine_sourcemaps` in `packages/svelte/src/compiler/utils/mapped_code.js`). This is the same mechanism `preprocess()` uses internally, and it's the documented contract for tools that transform a `.svelte` file before compiling it (see `CompileOptions.sourcemap`'s doc comment). `combine_sourcemaps` composes maps by matching `sourcefile === filename` (the basename of the file being compiled). A sourcemap produced by `new MagicString(code).generateMap()` **without** a `source` option — which is exactly what the reporter's Vite plugin does — has `sources: ['']`. That empty string never equals `filename`, so `remapping()` treats the node as a leaf (the "original" file) instead of a branch to keep chaining through, and the whole incoming map is silently dropped. The result: every position that flows through that segment resolves to `{ source: null, line: null, column: null }`, which is what produces the wrong/missing devtools mapping described in the issue. Vite itself already has to handle this exact ambiguity: in `pluginContainer.ts`'s `_getCombinedSourcemap`, an empty `sources[0]` from a MagicString-based transform is patched to refer to the file being transformed before Vite uses it internally. This PR applies the same normalization on svelte's side, so the contract holds regardless of whether the caller happens to pass a `source` option to `generateMap()`. ### Fix In `apply_preprocessor_sourcemap`, normalize an incoming map's `sources: ['']` (or `[null]`/`[undefined]`) to `[filename]` before calling `combine_sourcemaps`, so the chain-matching step can actually find it.	9 hours ago
Paolo Ricciuti	41642b70ee	fix: avoid declaration tag warning in event handlers (#18500) ... Closes #18493 Co-authored-by: justjavac <justjavac@gmail.com>	18 hours ago
Paolo Ricciuti	8fb7ceeba5	fix: don't treat declaration tags as parts inside each blocks (#18507) ... Closes #18506 Declaration tags in the scope of an each block were considered "parts" and transformed to use their value instead of the signal itself. We can safely check on the `kind` of the binding since a `kind` of `state`, `state_raw` or `derived` in the each scope needs to be a declaration tag (and it's a stable reference so we can use them directly)	4 days ago
Paolo Ricciuti	b1cadd1eae	chore: drop dead code that make TSGO fail (#18496)	1 week ago
Paolo Ricciuti	b9e03714eb	fix: correctly transform declaration tags during SSR (#18492) ... Closes #18490	1 week ago
github-actions[bot]	eae50dfd1c	Version Packages (#18435) ... 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@5.56.4 ### Patch Changes - fix: include wrapping parentheses in `{@const}` declarator `end` position ([#18436](https://github.com/sveltejs/svelte/pull/18436)) - fix: always unset reactivity context after restoring it ([#18453](https://github.com/sveltejs/svelte/pull/18453)) - fix: don't notify `searchParams` subscribers when the URL changes without affecting the search string ([#18425](https://github.com/sveltejs/svelte/pull/18425)) - fix: strip `?` from optional parameters in `<script lang="ts">` so generated JavaScript is valid ([#18448](https://github.com/sveltejs/svelte/pull/18448)) Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>	2 weeks ago
Simon H	36ae0622a8	fix: always unset reactivity context after restoring it (#18453) ... When calling `save`, we restore the context after the promise resolves. But we do not unset it after the subsequent synchronous execution. That means that until `unset_context` runs in `async_derived` we will not have the correct (nulled) context. That causes problems if the `save` isn't the last promise contributing to the `async_derived`, because it means the context is not properly unset until the promise _after_ the `save` within the `async_derived` settles. This can cause all sorts of mixups, including a wrong mutation error. fixes #18441	3 weeks ago
jyc.dev	a6985bcd24	fix: strip `?` from optional parameters in svelte lang ts (#18448) ... In `esrap@2.2.12` we fixed the missing `?` in ts files https://github.com/sveltejs/esrap/pull/139 It's good for `ts`, but bad for svelte compiler that was not removing it as it was a esrap issue not printing it :/ This issue came: https://github.com/sveltejs/esrap/issues/141 This PR is fixing the issue in the compiler stripping the `?`	3 weeks ago
Yuichiro Yamashita	c4daa490bb	fix: include wrapping parentheses in `{@const}` declarator end (#18436) ... `{@const x = (a)}` (and any `{@const}` whose initializer is wrapped in parentheses, e.g. `(a = b)`, `({ ... })`) produced a `VariableDeclarator` whose `end` fell before the closing `)`. `read_expression` strips the wrapping parens from the returned node but advances the parser past them, so `init.end` excludes the `)` while the parser position does not. Use the parser position for the declarator `end` instead. Fixes source slices / tooling that rely on the node range (the range previously yielded invalid, unbalanced source). <img width="2064" height="1746" alt="image" src="https://github.com/user-attachments/assets/64153ee5-d543-442d-8018-d3668acfd7a7" /> ### 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 - [ ] Run the tests with `pnpm test` and lint the project with `pnpm lint`	4 weeks ago
Nic Polumeyv	0510174bc0	fix: make `SvelteURLSearchParams` notifications accurate (#18425) ... `SvelteURLSearchParams` has two notification bugs that surface through `SvelteURL`. The first is over-notification. Setting `url.href` always rebuilds the params and bumps their version signal, even when the search string didn't change at all. Effects that read `size` (or any params method) re-run on every unrelated `href` write, which is #17218, where it caused infinite effect loops in a router. The fix is a guard in the internal replace path that bails out when the incoming params serialize identically to the current ones. The second is under-notification, and it's sneakier. Every read method tracks the version signal, `get`, `getAll`, `has`, `keys`, `values`, `entries`, `toString`, `size`, the iterator... except `forEach`, which was never overridden. The inherited platform method reads the internal list directly and subscribes to nothing, so a template that renders params via `forEach` never updates: ```js $effect(() => { url.searchParams.forEach((value, key) => entries.push(`${key}=${value}`)); // never re-runs }); ``` We found this one in the wild while making `page.url` a `SvelteURL` in sveltejs/kit#16031. Kit's own test suite renders query params with `forEach`, and the coarse object-identity signal that previously masked the gap went away, leaving stale UI after client-side navigations. The fix is the same one-line tracking pattern every other read method already uses. Fixes #17218 --- - [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`	4 weeks ago
dependabot[bot]	8ea3ee8c62	chore(deps-dev): bump esbuild from 0.25.11 to 0.28.1 (#18427) ... Bumps [esbuild](https://github.com/evanw/esbuild) from 0.25.11 to 0.28.1. <details> <summary>Release notes</summary> <p><em>Sourced from <a href="https://github.com/evanw/esbuild/releases">esbuild's releases</a>.</em></p> <blockquote> <h2>v0.28.1</h2> <ul> <li> <p>Disallow <code>\</code> in local development server HTTP requests (<a href="https://github.com/evanw/esbuild/security/advisories/GHSA-g7r4-m6w7-qqqr">GHSA-g7r4-m6w7-qqqr</a>)</p> <p>This release fixes a security issue where HTTP requests to esbuild's local development server could traverse outside of the serve directory on Windows using a <code>\</code> backslash character. It happened due to the use of Go's <code>path.Clean()</code> function, which only handles Unix-style <code>/</code> characters. HTTP requests with paths containing <code>\</code> are no longer allowed.</p> <p>Thanks to <a href="https://github.com/dellalibera"><code>@​dellalibera</code></a> for reporting this issue.</p> </li> <li> <p>Add integrity checks to the Deno API (<a href="https://github.com/evanw/esbuild/security/advisories/GHSA-gv7w-rqvm-qjhr">GHSA-gv7w-rqvm-qjhr</a>)</p> <p>The previous release of esbuild added integrity checks to esbuild's npm install script. This release also adds integrity checks to esbuild's Deno install script. Now esbuild's Deno API will also fail with an error if the downloaded esbuild binary contains something other than the expected content.</p> <p>Note that esbuild's Deno API installs from <code>registry.npmjs.org</code> by default, but allows the <code>NPM_CONFIG_REGISTRY</code> environment variable to override this with a custom package registry. This change means that the esbuild executable served by <code>NPM_CONFIG_REGISTRY</code> must now match the expected content.</p> <p>Thanks to <a href="https://github.com/sondt99"><code>@​sondt99</code></a> for reporting this issue.</p> </li> <li> <p>Avoid inlining <code>using</code> and <code>await using</code> declarations (<a href="https://redirect.github.com/evanw/esbuild/issues/4482">#4482</a>)</p> <p>Previously esbuild's minifier sometimes incorrectly inlined <code>using</code> and <code>await using</code> declarations into subsequent uses of that declaration, which then fails to dispose of the resource correctly. This bug happened because inlining was done for <code>let</code> and <code>const</code> declarations by avoiding doing it for <code>var</code> declarations, which no longer worked when more declaration types were added. Here's an example:</p> <pre lang="js"><code>// Original code { using x = new Resource() x.activate() } <p>// Old output (with --minify)<br /> new Resource().activate();</p> <p>// New output (with --minify)<br /> {using e=new Resource;e.activate()}<br /> </code></pre></p> </li> <li> <p>Fix module evaluation when an error is thrown (<a href="https://redirect.github.com/evanw/esbuild/issues/4461">#4461</a>, <a href="https://redirect.github.com/evanw/esbuild/pull/4467">#4467</a>)</p> <p>If an error is thrown during module evaluation, esbuild previously didn't preserve the state of the module for subsequent module references. This was observable if <code>import()</code> or <code>require()</code> is used to import a module multiple times. The thrown error is supposed to be thrown by every call to <code>import()</code> or <code>require()</code>, not just the first. With this release, esbuild will now throw the same error every time you call <code>import()</code> or <code>require()</code> on a module that throws during its evaluation.</p> </li> <li> <p>Fix some edge cases around the <code>new</code> operator (<a href="https://redirect.github.com/evanw/esbuild/issues/4477">#4477</a>)</p> <p>Previously esbuild incorrectly printed certain edge cases involving complex expressions inside the target of a <code>new</code> expression (specifically an optional chain and/or a tagged template literal). The generated code for the <code>new</code> target was not correctly wrapped with parentheses, and either contained a syntax error or had different semantics. These edge cases have been fixed so that they now correctly wrap the <code>new</code> target in parentheses. Here is an example of some affected code:</p> <pre lang="js"><code>// Original code new (foo()`bar`)() new (foo()?.bar)() <p>// Old output<br /> new foo()<code>bar</code>();<br /> new (foo())?.bar();</p> <p></code></pre></p> </li> </ul> <!-- raw HTML omitted --> </blockquote> <p>... (truncated)</p> </details> <details> <summary>Changelog</summary> <p><em>Sourced from <a href="https://github.com/evanw/esbuild/blob/main/CHANGELOG-2025.md">esbuild's changelog</a>.</em></p> <blockquote> <h1>Changelog: 2025</h1> <p>This changelog documents all esbuild versions published in the year 2025 (versions 0.25.0 through 0.27.2).</p> <h2>0.27.2</h2> <ul> <li> <p>Allow import path specifiers starting with <code>#/</code> (<a href="https://redirect.github.com/evanw/esbuild/pull/4361">#4361</a>)</p> <p>Previously the specification for <code>package.json</code> disallowed import path specifiers starting with <code>#/</code>, but this restriction <a href="https://redirect.github.com/nodejs/node/pull/60864">has recently been relaxed</a> and support for it is being added across the JavaScript ecosystem. One use case is using it for a wildcard pattern such as mapping <code>#/*</code> to <code>./src/*</code> (previously you had to use another character such as <code>#_*</code> instead, which was more confusing). There is some more context in <a href="https://redirect.github.com/nodejs/node/issues/49182">nodejs/node#49182</a>.</p> <p>This change was contributed by <a href="https://github.com/hybrist"><code>@​hybrist</code></a>.</p> </li> <li> <p>Automatically add the <code>-webkit-mask</code> prefix (<a href="https://redirect.github.com/evanw/esbuild/issues/4357">#4357</a>, <a href="https://redirect.github.com/evanw/esbuild/issues/4358">#4358</a>)</p> <p>This release automatically adds the <code>-webkit-</code> vendor prefix for the <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties/mask"><code>mask</code></a> CSS shorthand property:</p> <pre lang="css"><code>/* Original code */ main { mask: url(x.png) center/5rem no-repeat } <p>/* Old output (with --target=chrome110) */<br /> main {<br /> mask: url(x.png) center/5rem no-repeat;<br /> }</p> <p>/* New output (with --target=chrome110) */<br /> main {<br /> -webkit-mask: url(x.png) center/5rem no-repeat;<br /> mask: url(x.png) center/5rem no-repeat;<br /> }<br /> </code></pre></p> <p>This change was contributed by <a href="https://github.com/BPJEnnova"><code>@​BPJEnnova</code></a>.</p> </li> <li> <p>Additional minification of <code>switch</code> statements (<a href="https://redirect.github.com/evanw/esbuild/issues/4176">#4176</a>, <a href="https://redirect.github.com/evanw/esbuild/issues/4359">#4359</a>)</p> <p>This release contains additional minification patterns for reducing <code>switch</code> statements. Here is an example:</p> <pre lang="js"><code>// Original code switch (x) { case 0: foo() break case 1: default: bar() } </code></pre> </li> </ul> <!-- raw HTML omitted --> </blockquote> <p>... (truncated)</p> </details> <details> <summary>Commits</summary> <ul> <li><a href="bb9db84c02"><code>bb9db84</code></a> publish 0.28.1 to npm</li> <li><a href="9ff053e53b"><code>9ff053e</code></a> security: add integrity checks to the Deno API</li> <li><a href="0a9bf2135b"><code>0a9bf21</code></a> enforce non-negative size in gzip parser</li> <li><a href="e2a1a71320"><code>e2a1a71</code></a> security: forbid <code>\\</code> in local dev server requests</li> <li><a href="83a2cbfc35"><code>83a2cbf</code></a> fix <a href="https://redirect.github.com/evanw/esbuild/issues/4482">#4482</a>: don't inline <code>using</code> declarations</li> <li><a href="308ad745d8"><code>308ad74</code></a> fix <a href="https://redirect.github.com/evanw/esbuild/issues/4471">#4471</a>: renaming of nested <code>var</code> declarations</li> <li><a href="f013f5f99a"><code>f013f5f</code></a> fix some typos</li> <li><a href="aafd6e48b1"><code>aafd6e4</code></a> chore: fix some minor issues in comments (<a href="https://redirect.github.com/evanw/esbuild/issues/4462">#4462</a>)</li> <li><a href="15300c30b5"><code>15300c3</code></a> follow up: cjs evaluation fixes</li> <li><a href="1bda0c31d7"><code>1bda0c3</code></a> fix <a href="https://redirect.github.com/evanw/esbuild/issues/4461">#4461</a>, fix <a href="https://redirect.github.com/evanw/esbuild/issues/4467">#4467</a>: esm evaluation fixes</li> <li>Additional commits viewable in <a href="https://github.com/evanw/esbuild/compare/v0.25.11...v0.28.1">compare view</a></li> </ul> </details> <details> <summary>Maintainer changes</summary> <p>This version was pushed to npm by <a href="https://www.npmjs.com/~GitHub%20Actions">GitHub Actions</a>, a new releaser for esbuild since your current version.</p> </details> <br /> [](https://docs.github.com/en/github/managing-security-vulnerabilities/about-dependabot-security-updates#about-compatibility-scores) Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting `@dependabot rebase`. [//]: # (dependabot-automerge-start) [//]: # (dependabot-automerge-end) --- <details> <summary>Dependabot commands and options</summary> <br /> You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot show <dependency name> ignore conditions` will show all of the ignore conditions of the specified dependency - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself) You can disable automated security fix PRs for this repo from the [Security Alerts page](https://github.com/sveltejs/svelte/network/alerts). </details> Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>	4 weeks ago
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
Minh Lê	94bd27953e	docs: fix invalid `rows` CSS property in {#each} chess-board example (#18367) ... ## Problem The `{#each}` docs page has a runnable "chess board" example whose `<style>` block uses an invalid CSS property: ```css .chess-board { display: grid; grid-template-columns: repeat(8, 1fr); rows: repeat(8, 1fr); /* ← not a real CSS property */ ... } ``` There is no `rows` shorthand or longhand in CSS, so this line is silently dropped by every browser. The example clearly intends an 8×8 grid (note the matching `grid-template-columns` line directly above). ## Fix `rows` → `grid-template-rows`. One line, in `documentation/docs/03-template-syntax/03-each.md`. No prose changes.	1 month ago
Simon H	1b4c43b8e5	fix: ignore declaration tags for animation directive (#18366) ... Fixes #18365	1 month ago
Mathias Picker	85dcb91f7c	chore: upgrade to vitest v4 (#18265) ... ## Summary Bumps `vitest` and `@vitest/coverage-v8` from `^2.1.9` to `^4.1.7` (two major versions). Three small test-harness updates compensate for vitest 4 behavior changes; all 7569 tests still pass. - **`packages/svelte/tests/runtime-browser/test.ts`** — vitest 4 removed the deprecated `describe(name, fn, opts)` signature. Pass options as the second argument. - **`packages/svelte/tests/runtime-legacy/shared.ts`** — vitest 4's jsdom env binds `virtualConsole` to the original `globalThis.console` reference *before* vitest wraps the console, so inline-`<script>` logs and `jsdomError` events no longer reach per-test `console.{log,error}` overrides. Restore vitest 2's behavior by re-routing the virtual console through the live `console` in `beforeAll`. Also promote the window-error listener to a named function and remove it in `finally` — previously leaked listeners from earlier tests kept writing to module-level `unhandled_rejection`, polluting later tests. - **`vitest.config.js`** — bump `testTimeout` to 10s. The 5s default trips a handful of dev-mode tests that exercise `effect_update_depth_exceeded`, whose ~1000 Error-stack captures per flush are slower under vitest 4's deeper async stacks. ## Test plan - [x] `pnpm test` — 7569 passed, 63 skipped, 0 failed --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com> Co-authored-by: Rich Harris <rich.harris@vercel.com>	1 month 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.	1 month 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>	1 month ago
Simon H	5b8db1be35	fix: error at compile time on duplicate snippet/declaration tag definitions (#18351)	1 month ago
Simon H	56013a2c01	fix: check references for blockers on server, too (#18352) ... We forgot the server in #18309 Fixes #18344	1 month 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>	1 month 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	1 month 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>	1 month ago
Rich Harris	b76b937e00	fix: various declaration tag bugs (#18348) ... closes #18334	1 month 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>	1 month 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>	1 month ago
ottomated	11985c020f	docs: desloppify browser support page (#18333) ... The text in https://svelte.dev/docs/svelte/browser-support is quite redundant and has a lot of AI smell. I did my best to make it more concise and remove some slop comments in the generation script. Requires a companion PR in svelte.dev: https://github.com/sveltejs/svelte.dev/pull/2013 <img width="620" height="809" alt="image" src="https://github.com/user-attachments/assets/7be9d5ff-1623-4897-a2d4-9a601b20f54d" /> ### 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. - [ ] 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: Rich Harris <rich.harris@vercel.com>	1 month ago
Rich Harris	05a3bce6bb	chore: minor tidy-ups (#18326) ... some more stuff extracted from #18035	1 month ago
Rich Harris	e027d8bf22	chore: annotate `each_array` return value (#18325) ... tiny self-mergeable change extracted from #18035 — just turns `each_array` from a `Derived<any[]>` to a `Derived<V[]>`	1 month 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>	1 month ago
Rich Harris	6d26dce265	allow class/function expressions in tags (#18324) ... We shouldn't error on encountering `class` and `function`, because they are treated as expressions rather than declarations	1 month ago
7nik	6a955758a6	docs: mention since version of delcaration tags (#18322)	1 month 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>	1 month 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>	1 month ago
Simon H	980c7e2321	fix: don't error on `{type}` in declaration tags (#18321) ... The `\b` in the regex matched on `}`, too, so you would get a very confusing "invalid declaration tag" error on `{type}`. Match on whitespace instead (because that's what has to come afterwards) --------- Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com> Co-authored-by: Vercel <vercel[bot]@users.noreply.github.com> Co-authored-by: Rich-Harris <hello@rich-harris.dev>	1 month ago
Rich Harris	5300843e86	chore: bump playwright (#18319) ... hopefully this will fix the CI timeouts	1 month 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>	1 month ago
Rich Harris	656dae6780	chore: try and discourage slop, even a tiny bit (#18293) ... i don't know how to stem the flood of slop PRs but maybe this will help a tiny bit --------- Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>	1 month ago
Rich Harris	3fad9cf838	chore: fix browser-support regression check (#18316) ... vercel bot caught this in the release PR https://github.com/sveltejs/svelte/pull/18315#pullrequestreview-4383622174	1 month ago
Rich Harris	a9e82dd388	chore: remove `on_fork_commit` (#18318) ... Simon thinks it was because he thought that committing the fork != committing the batch, and that this could result in an error boundary showing up too late. But that's not the case	1 month 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>	1 month ago
Mathias Picker	27e74c4df7	docs: add auto-generated browser support page (#18276) ... ## Summary Adds a [Browser support](https://github.com/MathiasWP/svelte/blob/document-pipeline-draft/documentation/docs/07-misc/05-browser-support.md) page listing the minimum browser versions Svelte's runtime and compiler output require. The page (headline floor + per-feature requirements) is auto-generated by `packages/svelte/scripts/generate-browser-support.js`, which scans the code Svelte actually ships against the [web-features](https://github.com/web-platform-dx/web-features) Baseline dataset and resolves results to concrete browser versions via [baseline-browser-mapping](https://github.com/web-platform-dx/baseline-browser-mapping). CI fails if a PR moves the floor without regenerating the page. For 5.55.9 the floor is **Baseline 2020**: Chrome/Edge 87, Firefox 83, Safari 14. ## How it works 1. **Headline floor.** Each runtime entry from `pkg.exports` is bundled with rollup using production conditions, then walked with TypeScript's compiler API + TypeChecker. The walker (`browser-support.detector.js`) flags any web-features ID the runtime references; the highest Baseline year among them is the floor. 2. **Per-feature requirements.** Every user-facing surface is enumerated programmatically — every `bind:*` from `binding_properties`, every public subpackage export discovered via `pkg.exports` + `import * as ns`, every rune from `RUNES`, and directives (`transition:` / `animate:` / `use:` / `@attach` / `{@html}` / custom elements). Each gets a fixture, compiled and bundled like user code, then scanned. A row appears only when the fixture's floor exceeds the runtime floor. 3. **Supplemental rules.** A handful of APIs `web-features` doesn't catalogue (`getComputedStyle(...).zoom`, `box: 'device-pixel-content-box'`) are detected with the same type-aware walker via a small `register_extra_rules` list with inline justifications. 4. **Ignore sets.** `SAFE_TO_IGNORE` covers dataset bugs and feature-detected APIs with graceful fallbacks. `BEHAVIORAL_IGNORE` hides APIs reached only via specific user code from the headline (they still surface as conditional rows); staleness-checked, so CI fails if an entry no longer exists in the runtime. Resolves #18198. Provides an answer to the long-standing #558. ## Test plan - [ ] \`pnpm --filter svelte generate:browser-support\` regenerates the page idempotently - [ ] CI fails when a code change bumps the floor without regenerating the page - [ ] Page renders correctly on svelte.dev 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com> Co-authored-by: Rich Harris <rich.harris@vercel.com>	1 month 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>	1 month 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>	1 month ago
Rich Harris	688671ec23	chore: fix printing in sandbox (#18311) ... when `PRINT` is true, the sandbox should write out the printed code. at present it doesn't do this if `AST` is not also true	1 month ago