Add response cancellation function

[glanium]

I mean Response cancellation than Request cancellation. i.e. After received response, I wanna cancel response.

following is usecase

    final response = await c.send(request);
    if (response.contentLength != null && response.contentLength! > 100 * 1024 * 1024) { // <-- Big data then cancel
      final subscription = response.stream.listen((value) {});
      await subscription.cancel();
    }

In dart' stream, Stream can be cacelled by invoking subscription's cancel method. Then StreamController will be notifed of cancel.

As long as i look at current crotnet_http implementaion, cancel request is ignored completely.

https://github.com/dart-lang/http/blob/c114aa06c510a28e942e9158711ed052b492c980/pkgs/cronet_http/lib/src/cronet_client.dart#L144C1-L152C26

  // The order of callbacks generated by Cronet is documented here:
  // https://developer.android.com/guide/topics/connectivity/cronet/lifecycle
  return jb.UrlRequestCallbackProxy_UrlRequestCallbackInterface.implement(
      jb.$UrlRequestCallbackProxy_UrlRequestCallbackInterfaceImpl(
    onResponseStarted: (urlRequest, responseInfo) {
      responseStream = StreamController(onCancel: () {  urlRequest.cancel();  }); // <---- Cancel?
      final responseHeaders =
          _cronetToClientHeaders(responseInfo.getAllHeaders());
      int? contentLength;

Add onCancel callback to StreamController then handle cancel request.

This applies to cupertino_http package if it support cancel.

HTTP2 supports multiplexing, and can force the stream to be closed by sending frame RST_STREAM

In case of HTTP1, Cancel causes connection close?

thx.

[glanium]

following might be safer implementation.

jb.UrlRequestCallbackProxy_UrlRequestCallbackInterface _urlRequestCallbacks(
    BaseRequest request, Completer<StreamedResponse> responseCompleter) {
  StreamController<List<int>>? responseStream;
  JByteBuffer? jByteBuffer;
  var numRedirects = 0;
  var cancelled;  // <-- flag

  // The order of callbacks generated by Cronet is documented here:
  // https://developer.android.com/guide/topics/connectivity/cronet/lifecycle
  return jb.UrlRequestCallbackProxy_UrlRequestCallbackInterface.implement(
      jb.$UrlRequestCallbackProxy_UrlRequestCallbackInterfaceImpl(
    onResponseStarted: (urlRequest, responseInfo) {
      responseStream = StreamController(onCancel: () => cancelled = true);  // <--- set flag
      final responseHeaders =
          _cronetToClientHeaders(responseInfo.getAllHeaders());
      int? contentLength;


      switch (responseHeaders['content-length']) {
        case final contentLengthHeader?
            when !_digitRegex.hasMatch(contentLengthHeader):
          responseCompleter.completeError(ClientException(
            'Invalid content-length header [$contentLengthHeader].',
            request.url,
          ));
          urlRequest.cancel();
          return;
        case final contentLengthHeader?:
          contentLength = int.parse(contentLengthHeader);
      }
      responseCompleter.complete(StreamedResponse(
        responseStream!.stream,
        responseInfo.getHttpStatusCode(),
        contentLength: contentLength,
        reasonPhrase: responseInfo
            .getHttpStatusText()
            .toDartString(releaseOriginal: true),
        request: request,
        isRedirect: false,
        headers: responseHeaders,
      ));


      jByteBuffer = JByteBuffer.allocateDirect(_bufferSize);
      urlRequest.read(jByteBuffer!);
    },
    onRedirectReceived: (urlRequest, responseInfo, newLocationUrl) {
      if (!request.followRedirects) {
        urlRequest.cancel();
        responseCompleter.complete(StreamedResponse(
            const Stream.empty(), // Cronet provides no body for redirects.
            responseInfo.getHttpStatusCode(),
            contentLength: 0,
            reasonPhrase: responseInfo
                .getHttpStatusText()
                .toDartString(releaseOriginal: true),
            request: request,
            isRedirect: true,
            headers: _cronetToClientHeaders(responseInfo.getAllHeaders())));
        return;
      }
      ++numRedirects;
      if (numRedirects <= request.maxRedirects) {
        urlRequest.followRedirect();
      } else {
        urlRequest.cancel();
        responseCompleter.completeError(
            ClientException('Redirect limit exceeded', request.url));
      }
    },
    onReadCompleted: (urlRequest, responseInfo, byteBuffer) {
     if (cancelled) {  
       urlRequest.cancel();                          // <-- cancel and cleanup here
       //responseStream!.sink.close();   
       byteBuffer.release();
     } else {
        byteBuffer.flip();
        responseStream!
            .add(jByteBuffer!.asUint8List().sublist(0, byteBuffer.remaining));
        byteBuffer.clear();
        urlRequest.read(byteBuffer);
      }
    },

[mohsinnaqvi606]

Any update on this? This functionality is still missing.