fix(cloudflare): strip return statements from frontmatter in esbuild scan plugin

[rururux]

fixes: #15518

Changes

In the previous implementation of the Cloudflare Workers integration, the following error occurred when esbuild attempted to scan dependencies by loading the code:

✘ [ERROR] Top-level return cannot be used inside an ECMAScript module

This pull request addresses this issue with the following changes:

• Modified esbuild input: Before passing code to esbuild, return statements are now replaced with throw . This logic is based on the implementation found in vite-plugin-astro/compile.ts. To ensure source maps remain accurate, the replacement includes padding to maintain the original character count.
• Added comments explaining potential errors that might arise from this change in specific edge cases.

Testing

• Verified that the Top-level return cannot be ... error no longer occurs.
• Added a test case to ensure that the replacement logic does not break the syntax (which would previously trigger a Failed to run dependency scan ... error).

Docs

N/A

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[Princesseuh]

Looks great, awesome work!

[rururux]

Thank you so much! 🥳

[eighty4]

Would this also present with astro-check warnings on return Astro.redirect in Frontmatter? I'm seeing UNUSED_IMPORT_EXAMPLE is declared but its value is never read warnings when importing utils to use with Astro.redirect.

[Princesseuh]

No, that's unrelated to this.

[eighty4]

@Princesseuh I understand that the esbuild plugin in the cloudflare adapter throwing an error doesn't cause the warnings in astro-check, but it does seem like it's the same problem presenting in different areas of the Astro ecosystem.

Doing this in frontmatter that is handled in middleware seems to be a workaround for the astro-check warnings on top level return statement:

if (condition)
    throw SomeHttpResponse()