Unable to send request with bodyBytes set when using streamRequests

[TheOneWithTheBraid]

When trying to send a request with Request.bodyBytes set, I realized the request is given a conversion error as body rather than the actually provided body.

Minimal sample to reproduce :

import 'dart:convert';

import 'package:fetch_client/fetch_client.dart';
import 'package:http/http.dart';

Future<void> main() async {
  final client = FetchClient(
    mode: RequestMode.cors,
    credentials: RequestCredentials.omit,
    cache: RequestCache.noStore,
    referrerPolicy: RequestReferrerPolicy.strictOriginWhenCrossOrigin,
    streamRequests: true,
  );

  final request = Request(
    'POST',
    Uri.parse('https://example.com'),
  );

  request.headers['content-type'] = 'application/json';
  request.bodyBytes = utf8.encode(jsonEncode({'test': 'foo'}));
  final response = await client.send(request);
  final responseBody = await response.stream.toBytes();

  final responseString = utf8.decode(responseBody);
  print(responseString);
}

When inspecting the request in the dev tools of my browser, the request body shows as :

[object ReadableStream]

Rather than the expected

{"test":"foo"}

I'd expect a fallback on non-streamed requests if the browser does not support them.

Environment:

Firefox 139.0.1 on Linux

[Zekfad]

This works as intended since you've explicitly opted in request streaming.

I believe checking for specific browser is out of scope of this module, I can add feature check and throw UnsupportedError, but you still will need to do check compatibility, since you're only supposed to catch exceptions and not errors.

It's possible to implement feature check via fetch_api, use canStreamRequests function.

The problem is that if I introduce fallback, many people will think that request streaming works until it blows up (mostly due to memory usage for collecting stream) and ask why request streaming is not working when it's enabled. I think it will create more harm than good.

One option is to expose canStreamRequests in fetch_client as well, but I'm not sure where to put it.

I'm open for suggestions.