Make Netlify adapter actually append redirects

[hippotastic]

Changes

The previous code in the astro:build:done hook called fs.existsSync(_redirects) to check if the redirects target file already exists, before deciding to either call appendFile or writeFile. Unfortunately, _redirects is not the file name/URL, but the contents, so this check always failed. The code therefore always used writeFile, effectively overwriting any existing contents of the _redirects file.

My code eliminates this check and always uses appendFile, which will automatically create the file if it doesn't exist yet (as per the Node.js docs).

If you put your own custom redirects in a /public/_redirects file, they will get copied to the build output directory and Astro will now add its own redirects to the end instead of always overwriting the file.

Testing

The new code was tested locally on Windows 10 by building an example site using the fixed Netlify adapter, both with and without an existing /public/_redirects file.

I also ran pnpm run test --filter @astrojs/netlify without any errors.

Docs

This is just a fix, so no documentation is needed per se. It however allows the use case outlined above (putting custom redirects in a /public/_redirects file), which wasn't possible before due to the buggy check. Adding custom redirects could optionally be documented as an advanced usage scenario.

[changeset-bot]

🦋 Changeset detected

Latest commit: b4b99dd

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

This PR includes changesets to release 1 package

Name	Type
@astrojs/netlify	Patch

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[FredKSchott]

LGTM!