Is it possible to return an arbitrary Response from a form action?

[simonsarris]

In an API GET I could write something to return an arbitrary Response, like:

// API endpoint to get some file and initiate user download
export const GET = async ({ cookies }) => {
  // ...

  const someFile = fs.readFileSync(`someFilePathOnDrive`);
  return new Response(someFile, {
    status: 200,
    headers: {
      'Content-type': 'multipart/form-data',
      'Content-Disposition': `attachment; filename=someFileName.someFileExtension`
    }
  });
};

And it will download that file for the user. This file is not serializable.

Is it not possible in SvelteKit to do the same thing with form actions? Perhaps I'm simply overlooking something, or not understanding a limitation.

[teemingc]

Sounds like it could work if you throw a redirect to the GET endpoint at the end of the form action. (haven't tested this).
https://kit.svelte.dev/docs/load#redirects

Or would it work by simply using the GET endpoint URL as the form action? Instead of using the POST method and sveltekit's form actions.

[benquan]

@simonsarris Did you find a solution for your problem? I am trying to return a csv from a form action call.

[stephane-vanraes]

No it is not possible, actions are designed to populate the form property of a page and therefore have to be fully serializable. A generic file, image or csv doesn't fall into that category. So the result from an action always has to be a simple object.

You will have to implement your form handling the "normal" way using an API endpoint as described here: https://kit.svelte.dev/docs/form-actions#alternatives

[simonsarris]

Yeah, I just ended up using an API endpoint.