fix(frontmatter): preserve strings and comments when replacing top-le…

[web-dev0521]

Changes

• Fixes a regex bug where return was incorrectly rewritten inside string literals, template literals, and comments during esbuild's dep-scan / frontmatter error-check phase
• Replaces the two-pass \breturn\b regex with a single-pass state-machine regex that skips over all string/comment tokens before rewriting bare return statements
• Fixes the primary report case: gen.return(value) → was producing gen.throw (value) (syntax error); now preserved correctly
• Extracts a shared replaceTopLevelReturns() helper into utils.ts to deduplicate logic between the cloudflare esbuild plugin and compile.ts

Affected files:

• packages/integrations/cloudflare/src/esbuild-plugin-astro-frontmatter.ts
• packages/astro/src/vite-plugin-astro/utils.ts
• packages/astro/src/vite-plugin-astro/compile.ts

Closes #16551

Testing

The fix is a pure regex change with no new dependencies. Verified manually against the cases from the issue:

Input	Before	After
gen.return(val)	gen.throw (val) ← syntax error	unchanged ✓
"return value"	"throw value"	unchanged ✓
// return foo	// throw foo	unchanged ✓
`return ${x}`	`throw ${x}`	unchanged ✓
return foo	return foo	throw foo ✓
return;	return;	throw 0; ✓

No new tests added — the two affected code paths are internal-only (esbuild dep scan and compile-error enhancement), exercised by the existing integration test suite.

Docs

No user-facing behavior change — this only affects internal dep scanning and error reporting during compilation. No docs update needed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 34a064c

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

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[web-dev0521]

Hello, @matthewp!
Happy Friday!
This is my first contribution for Astro Repository.
Could you please review my PR?
Thanks.

[codspeed-hq]

Merging this PR will improve performance by 11.21%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
✅ 17 untouched benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	Build: hybrid site (static + server)	8.9 s	8 s	+11.21%

---

_{Comparing web-dev0521:fix/frontmatter-return-regex-16551 (34a064c) with main (1e70d18)¹}

Footnotes

1. No successful run was found on main (4b2a2ef) during the generation of this report, so 1e70d18 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[matthewp]

@web-dev0521 code looks good, just need a changeset. pnpm run changeset. Follow this guide: https://contribute.docs.astro.build/docs-for-code-changes/changesets/

[web-dev0521]

Hi, @matthewp !
Thank you for the review. I’ve added the changeset.
Could you please take a look and let me know if the description reads well, or if you’d like me to adjust the wording?

[matthewp]

Thanks, looks good! Tests are currently failing on main, once i fix that i'll update this and merge it.

[matthewp]

it should be fixed now. i'll merge when it passes.

[web-dev0521]

Thanks.