ReadableStream, NodeJS.ReadableStream should be supported in response.body

[fixiabis]

Describe the bug

I want to send large files via stream, but not working, so:

I saw here, looks supported, response.body also could be NodeJS.ReadableStream:

kit/packages/kit/src/node.js

Lines 83 to 91 in 143d17f

	if (response.body instanceof Readable) {
	response.body.pipe(res);
	} else {
	if (response.body) {
	res.write(await response.arrayBuffer());
	}
	res.end();
	}

Then I checked implementation in kit/src/runtime/server/endpoint.js:

kit/packages/kit/src/runtime/server/endpoint.js

Lines 96 to 101 in 143d17f

	if (is_pojo(body) && (!type || type.startsWith('application/json'))) {
	headers.set('content-type', 'application/json; charset=utf-8');
	normalized_body = JSON.stringify(body);
	} else {
	normalized_body = /** @type {import('types').StrictBody} */ (body);
	}

And is_pojo in kit/src/runtime/server/utils.js:

kit/packages/kit/src/runtime/server/utils.js

Lines 36 to 51 in 143d17f

	export function is_pojo(body) {
	if (typeof body !== 'object') return false;
	if (body) {
	if (body instanceof Uint8Array) return false;
	// body could be a node Readable, but we don't want to import
	// node built-ins, so we use duck typing
	if (body._readableState && typeof body.pipe === 'function') return false;
	// similarly, it could be a web ReadableStream
	if (typeof ReadableStream !== 'undefined' && body instanceof ReadableStream) return false;
	}
	return true;
	}

Looks response.body could be NodeJS.ReadableStream or ReadableStream, but no, because:

kit/packages/kit/src/runtime/server/endpoint.js

Lines 87 to 91 in 143d17f

	if (!is_text(type) && !(body instanceof Uint8Array || is_string(body))) {
	return error(
	`${preface}: body must be an instance of string or Uint8Array if content-type is not a supported textual content-type`
	);
	}

There will throw an error preventing me from using it.

Additional type check added currently:

if (
	!is_text(type) &&
	!(
		body instanceof Uint8Array ||
		(typeof ReadableStream !== 'undefined' && body instanceof ReadableStream) ||
		(body !== null && body._readableState && typeof body.pipe === 'function') ||
		is_string(body)
	)
) {

Reproduction

// some endpoint script
export const get = (event) => {
  if (!permitted) {
    return { status: 403, body: 'You do not have permission to access the file.' };
  }

  const fileStream = fs.createReadStream(filePath);
  return { body: fileStream };
};

Logs

No response

System Info

Not important.

Severity

serious, but I can work around it

Additional Information

No response

[Conduitry]

This is a duplicate of #3419.