Add environment support to client

[CalsRanna]

This is the code in client.dart:

Future<ServerConnection> connectStdioServer(
    String command,
    List<String> arguments, {
    Sink<String>? protocolLogSink,
  }) async {
    final process = await Process.start(command, arguments);
    process.stderr
        .transform(utf8.decoder)
        .transform(const LineSplitter())
        .listen((line) {
          stderr.writeln('[StdErr from server $command]: $line');
        });
    final channel = StreamChannel.withCloseGuarantee(
          process.stdout,
          process.stdin,
        )
        .transform(StreamChannelTransformer.fromCodec(utf8))
        .transformStream(const LineSplitter())
        .transformSink(
          StreamSinkTransformer.fromHandlers(
            handleData: (data, sink) {
              sink.add('$data\n');
            },
          ),
        );
    final connection = connectServer(channel, protocolLogSink: protocolLogSink);
    unawaited(connection.done.then((_) => process.kill()));
    return connection;
  }

As we can see, the Process.start supportsMap<String, String>? environment, but MCPClient DOES NOT expose it. So why the environment is not supported in Client?

And the temp way to solve this is you define a new function in extension on MCPClient, and copy the code up here and add environment support yourself with importing async and stream channel packages.

[jakemac53]

Sure, this seems like something we can add. I kind of wish we had just taken a Process as an argument so we didn't have to duplicate all of these parameters, but it's probably not worth doing a breaking change for that.

[jakemac53]

We would accept a PR for this if you want to provide one, otherwise we can probably get to it in a little bit.

[jakemac53]

Actually, we are doing a breaking change release anyways so I think I am going to roll this into that, and change connectStdioServer to take a stdin sink and stdout stream, which will allow us to drop the dart:io dependency as well, making this package runnable on the web.