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fix: skip block comments in read_value to prevent apostrophe parsing error#18153

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Rich-Harris merged 4 commits into
sveltejs:mainfrom
DORI2001:fix-css-comment-apostrophe
Apr 29, 2026
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fix: skip block comments in read_value to prevent apostrophe parsing error#18153
Rich-Harris merged 4 commits into
sveltejs:mainfrom
DORI2001:fix-css-comment-apostrophe

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Fixes #18134.

Problem

read_value() in packages/svelte/src/compiler/phases/1-parse/read/style.js has no logic to skip CSS block comments (/* ... */). When the parser encounters an apostrophe inside a comment, it sets quote_mark = "'" — treating it as the start of a string literal — then never finds a matching closing quote, and ultimately throws unexpected_eof at the end of the style block.

Minimal repro:

<style>
  /* it's a comment */
  .foo { color: red; }
</style>

Error: Unexpected end of input

Fix

Add a /* ... */ skip path inside the read_value loop, mirroring the same pattern already used in allow_comment_or_whitespace. When /* is detected outside a string or url context, the parser advances past the entire comment without adding its content to the value string.

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changeset-bot Bot commented Apr 29, 2026

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🦋 Changeset detected

Latest commit: a8e8106

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package
Name Type
svelte Patch

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@Rich-Harris

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/autofix

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thank you!

@Rich-Harris Rich-Harris merged commit 69b4c9f into sveltejs:main Apr 29, 2026
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@github-actions github-actions Bot mentioned this pull request Apr 29, 2026
Rich-Harris pushed a commit that referenced this pull request May 14, 2026
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@5.55.6

### Patch Changes

- fix: leave stale promises to wait for a later resolution, instead of
rejecting ([#18180](#18180))

- fix: keep dependencies of `$state.eager/pending`
([#18218](#18218))

- fix: reapply context after transforming error during SSR
([#18099](#18099))

- fix: don't rebase just-created batches
([#18117](#18117))

- chore: allow `null` for `pending` in typings
([#18201](#18201))

- fix: flush eager effects in production
([#18107](#18107))

- fix: rethrow error of failed iterable after calling `return()`
([#18169](#18169))

- fix: account for proxified instance when updating `bind:this`
([#18147](#18147))

- fix: ensure scheduled batch is flushed if not obsolete
([#18131](#18131))

- fix: resolve stale deriveds with latest value
([#18167](#18167))

- chore: remove unnecessary `increment_pending` calls
([#18183](#18183))

- fix: correctly compile component member expressions for SSR
([#18192](#18192))

- fix: reset `source.updated` stack traces after `flush`
([#18196](#18196))

- fix: replacing async 'blocking' strategy with 'merging'
([#18205](#18205))

- fix: allow `@debug` tags to reference awaited variables
([#18138](#18138))

- fix: re-run fallback props if dependencies update
([#18146](#18146))

- fix: abort running obsolete async branches
([#18118](#18118))

- fix: ignore comments when reading CSS values
([#18153](#18153))

- fix: wrap `Promise.all` in `save` during SSR
([#18178](#18178))

- fix: ignore false-positive errors of `$inspect` dependencies
([#18106](#18106))

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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Svelte CSS parser fails on apostrophe in CSS block comment with Unexpected end of input

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