Stream file does not seem to work.

Describe the bug

Unable to return a fs.createReadStream from an endpoint. There are plenty of examples for fetching a file from URL, and sending as stream, but sometimes a log file or file located on machine needs to be sent.

Reproduction

When attempting to return a fs.createReadStream via endpoint like so:

readStream = await fs.createReadStream(file) 
                     return {
                         
                         body:readStream,
                         headers: responseHeaders
                         };

an error results:

Node streams are no longer supported — use a ReadableStream instead
Error: Node streams are no longer supported — use a ReadableStream instead

These issues below relate in they attempt to stream or talk about documentation for examples missing, but do not talk about an opened file and how to actually send the file via a stream, for example a giant 1GB file: https://github.com/sveltejs/kit/issues/5344 https://github.com/sveltejs/kit/issues/5412 https://stackoverflow.com/questions/72894078/sveltekit-node-streams-are-no-longer-supported

Logs

Postman call to endpoint results in error above.

System Info

Chrome
Node v18.2.0
		"@sveltejs/adapter-auto": "next",
		"@sveltejs/kit": "next",
		"autoprefixer": "^10.4.7",
		"eslint": "^8.16.0",
		"eslint-config-prettier": "^8.3.0",
		"eslint-plugin-svelte3": "^4.0.0",
		"postcss": "^8.4.14",
		"prettier": "^2.6.2",
		"prettier-plugin-svelte": "^2.7.0",
		"svelte": "^3.44.0",
		"svelte-preprocess": "^4.10.7",
		"tailwindcss": "^3.1.6",
		"vite": "^3.0.0"
	},

Severity

annoyance

Additional Information

Maybe there is an alternative way to do this. But I don’t see any examples how to natively pipe this to a response in Sveltekit like you would in Express I returned a readableStream but the response is essentially the stream and not the contents

[half-metal]

Yes! @repsac-by that works, thanks for showing how to do the return with Readable.toWeb Looking through the web stream standard @Conduitry, I’m not sure how anyone is to figure out that toWeb would ever solve anything

Many parts of the Node documentation on streams is confusing. Would be nice if they did a section on “modern” way to use streams and for the various common use cases. Their examples are limited, and a bit all over the place.

@AliBasicCoder yes that looks like it would work too, and that is what I was doing, except I was confused how you open a file that is stored locally, and then send that without more code. I’m still not sure where on the readableToReadStream you pull in that fs opened file, but I’ll play around with that eventually. For now, the solution from @repsac-by will work for what I need.

[AliBasicCoder]

you just have to use web stream not node’s

here is code that will help you (remove type antotions if you aren’t using TS)

// converts web stream to node
export function readStreamToReadable(readStream: ReadableStream) {
  const result = new Readable({ read() {} });
  const reader = readStream.getReader();
  function push() {
    reader.read().then(({ done, value }) => {
      if (done) {
        return result.push(null);
      }
      result.push(value);
      push();
    });
  }
  push();
  return result;
}

// converts node stream to web
export function readableToReadStream(
  readable: Readable
): ReadableStream<Uint8Array> {
  return new ReadableStream({
    start(controller) {
      readable.addListener("data", (chunk: Buffer) => {
        controller.enqueue(new Uint8Array(chunk));
      });
      readable.addListener("end", () => {
        controller.close();
      });
      readable.addListener("error", (err) => {
        controller.error(err);
      });
    },
  });
}