Astro hybrid output response headers

[friedemannsommer]

Is it the expected behavior of Astro's hybrid output to ignore the headers set in the Response object?

Suppose the following page exists:

export const prerender = true

export async function GET(): Promise<Response> {
    return new Response('Hello World!', {
        status: 200,
        headers: {
            'content-type': 'text/plain; charset=utf-8'
        }
    })
}

My assumption would be that Astro would create a file containing the actual response body
and either separately or as part of the response body store the associated headers.

In the generated output a file containing the "Hello World!" string exists in the client directory,
but when requesting the route via an HTTP client, it doesn't send the associated content-type header.

Astro manifest

This is a simplified and stripped down example containing only the "prerender" route:

{
    "adapterName": "@astrojs/node",
    "routes": [
        {
            "file": "prerender",
            "links": [],
            "scripts": [],
            "styles": [],
            "routeData": {
                "route": "/prerender",
                "isIndex": false,
                "type": "endpoint",
                "pattern": "^\\/prerender\\/?$",
                "segments": [
                    [
                        {
                            "content": "prerender",
                            "dynamic": false,
                            "spread": false
                        }
                    ]
                ],
                "params": [],
                "component": "src/pages/prerender.ts",
                "pathname": "/prerender",
                "prerender": true,
                "fallbackRoutes": [],
                "_meta": {
                    "trailingSlash": "ignore"
                }
            }
        }
    ],
    "base": "/",
    "trailingSlash": "ignore",
    "compressHTML": true,
    "componentMetadata": [],
    "renderers": [],
    "clientDirectives": [],
    "entryModules": {
        "/src/pages/prerender.ts": "chunks/prerender_CxqmRQwW.mjs"
    },
    "inlinedScripts": [],
    "assets": [
        "/prerender"
    ],
    "buildFormat": "directory",
    "checkOrigin": false,
    "rewritingEnabled": false,
    "experimentalEnvGetSecretEnabled": false
}

I have created a StackBlitz example that includes the relevant settings and files.
Please run the following commands in order (top to bottom):

1. npm run build
2. npm run preview
3. Request <preview URL>/prerender with any HTTP client
4. Note the abscene of the content-type: text/plain; charset=utf-8 header in the response

[delucis]

This is expected for prerendered routes. For anything that is pre-rendered Astro behaves essentially as a static site generator: it creates static HTML, CSS, etc. Deciding on MIME type headers etc. should then be done by whatever server ends up serving these static files. Usually this is done using a file extension — for example if you rename your example file to src/pages/prerender.txt.ts, it will generate a prerender.txt file and running npm run preview will show the correct Content-Type header.

[friedemannsommer]

Thanks, this clarified the behavior for me.