Add support for custom non-html route encoding

[altano]

Changes

See #4545 for further discussion of the issue, but the summary is that currently non-html routes have their buffers encoded as utf-8 when being written to disk during an SSG build, which works for some streams but not others. The main use case that isn't working is a PNG file route. The binary stream gets mangled by encoding as utf-8, destroying the PNG image. By allowing a binary encoding, the PNG image is written to disk correctly instead.

NOTE: By causing the API surface of endpoints (which return Response) and ssg routes (which return this custom object) we're making the life of whoever tackles withastro/docs#760 a little harder.

Testing

I have added a placeholder.png.ts route to the examples/non-html-routes example project. This route was previously broken (since there was no way to specify a binary encoding) but now works perfectly. Just run pnpm build in this example dir and observe that the dist/placeholder.png file is valid and can be previewed.

Docs

I've submitted a PR to update the docs: withastro/docs#1434

Alternative

Let the body be string | Buffer instead of string. When writing a Buffer, fs.writeFile ignores the encoding option.

Why I chose current implementation instead: the ergonomics of allowing both string and Buffer might be easier on the user, but we shouldn't force people to create a Buffer (if they don't already have one) to override the encoding.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0e49bf2

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

This PR includes changesets to release 14 packages

Name	Type
astro	Minor
@e2e/astro-component	Patch
@e2e/error-react-spectrum	Patch
@e2e/error-sass	Patch
@e2e/errors	Patch
@e2e/hydration-race	Patch
@e2e/lit-component	Patch
@e2e/preact-component	Patch
@e2e/react-component	Patch
@e2e/solid-component	Patch
@e2e/solid-recurse	Patch
@e2e/svelte-component	Patch
@e2e/e2e-tailwindcss	Patch
@e2e/ts-resolution	Patch

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[matthewp]

Thanks! Change looks good overall. Instead of having an example which I don't think people would use, could you move that code into a test at packages/astro/test/fixtures/?

[altano]

Code updated:

• example removed
• test added (both .json and .png pages)
• object spread replaced with explicit assignment

[matthewp]

@altano thank you! Everything looks good, this will be merged when we are ready to do our next minor release.