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Merged
merged 3 commits into from
May 13, 2025
Merged

Add some flags to example, fix version issue #127

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c9e9b13
Add Schema validation
gspencergoog May 13, 2025
80f677d
Add log, address comments
gspencergoog May 13, 2025
5405a0e
Add server name to log messages, flush messages
gspencergoog May 13, 2025
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3 changes: 3 additions & 0 deletions pkgs/dart_mcp/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,9 @@
- Update file system example to support relative paths.
- Fix a bug in notification handling where leaving off the parameters caused a
type exception.
- Added `--help`, `--log`, and `--model` flags to the workflow example.
- Fixed a bug where the examples would only connect to a server with the latest
protocol version.

## 0.2.0

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8 changes: 5 additions & 3 deletions pkgs/dart_mcp/example/client.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -24,10 +24,12 @@ void main() async {
),
);
print('initialized: $initializeResult');
if (initializeResult.protocolVersion != ProtocolVersion.latestSupported) {
if (!initializeResult.protocolVersion!.isSupported) {
throw StateError(
'Protocol version mismatch, expected ${ProtocolVersion.latestSupported}, '
'got ${initializeResult.protocolVersion}',
'Protocol version mismatch, expected a version between '
'${ProtocolVersion.oldestSupported} and '
'${ProtocolVersion.latestSupported}, but received '
'${initializeResult.protocolVersion}',
);
}

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97 changes: 83 additions & 14 deletions pkgs/dart_mcp/example/workflow_client.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,14 @@ import 'package:cli_util/cli_logging.dart';
import 'package:dart_mcp/client.dart';
import 'package:google_generative_ai/google_generative_ai.dart' as gemini;

/// The list of Gemini models that are accepted as a "--model" argument.
/// Defaults to the first one in the list.
const List<String> allowedGeminiModels = [
'gemini-2.5-pro-exp-03-25',
'gemini-2.0-flash',
'gemini-2.5-flash-preview-04-17',
];

void main(List<String> args) {
final geminiApiKey = Platform.environment['GEMINI_API_KEY'];
if (geminiApiKey == null) {
Expand All @@ -23,21 +31,28 @@ void main(List<String> args) {
}

final parsedArgs = argParser.parse(args);
if (parsedArgs.wasParsed('help')) {
print(argParser.usage);
exit(0);
}
final serverCommands = parsedArgs['server'] as List<String>;
final logger = Logger.standard();
final logFilePath = parsedArgs.option('log');
runZonedGuarded(
() {
WorkflowClient(
serverCommands,
geminiApiKey: geminiApiKey,
verbose: parsedArgs.flag('verbose'),
dtdUri: parsedArgs.option('dtd'),
model: parsedArgs.option('model')!,
persona: parsedArgs.flag('dash') ? _dashPersona : null,
logger: logger,
logFile: logFilePath != null ? File(logFilePath) : null,
);
},
(e, s) {
logger.stderr('$e\n$s\n');
(exception, stack) {
logger.stderr('$exception\n$stack\n');
},
);
}
Expand All @@ -54,28 +69,38 @@ final argParser =
abbr: 'v',
help: 'Enables verbose logging for logs from servers.',
)
..addOption(
'log',
abbr: 'l',
help:
'If specified, will create the given log file and log server '
'traffic and diagnostic messages.',
)
..addFlag('dash', help: 'Use the Dash mascot persona.', defaultsTo: false)
..addOption(
'dtd',
help: 'Pass the DTD URI to use for this workflow session.',
);
)
..addOption(
'model',
defaultsTo: allowedGeminiModels.first,
allowed: allowedGeminiModels,
help: 'Pass the name of the model to use to run inferences.',
)
..addFlag('help', abbr: 'h', help: 'Print the usage for this command.');

final class WorkflowClient extends MCPClient with RootsSupport {
final Logger logger;
int totalInputTokens = 0;
int totalOutputTokens = 0;

WorkflowClient(
this.serverCommands, {
required String geminiApiKey,
required String model,
required this.logger,
String? dtdUri,
this.verbose = false,
required this.logger,
String? persona,
File? logFile,
}) : model = gemini.GenerativeModel(
model: 'gemini-2.5-pro-preview-03-25',
// model: 'gemini-2.0-flash',
// model: 'gemini-2.5-flash-preview-04-17',
model: model,
apiKey: geminiApiKey,
systemInstruction: systemInstructions(persona: persona),
),
Expand All @@ -85,6 +110,7 @@ final class WorkflowClient extends MCPClient with RootsSupport {
super(
ClientImplementation(name: 'Gemini workflow client', version: '0.1.0'),
) {
logSink = _createLogSink(logFile);
addRoot(
Root(
uri: Directory.current.absolute.uri.toString(),
Expand All @@ -110,6 +136,10 @@ final class WorkflowClient extends MCPClient with RootsSupport {
_startChat();
}

final Logger logger;
Sink<String>? logSink;
int totalInputTokens = 0;
int totalOutputTokens = 0;
final StreamQueue<String> stdinQueue;
final List<String> serverCommands;
final List<ServerConnection> serverConnections = [];
Expand All @@ -118,6 +148,36 @@ final class WorkflowClient extends MCPClient with RootsSupport {
final gemini.GenerativeModel model;
final bool verbose;

Sink<String>? _createLogSink(File? logFile) {
if (logFile == null) {
return null;
}
Sink<String>? logSink;
logFile.createSync(recursive: true);
final fileByteSink = logFile.openWrite(
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Just to confirm, this will actually write the bytes to disk relatively quickly when we write to the sink? Do we need to call flush or anything?

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Hmm. It will be buffered by default, but I guess we do want it to be pretty up-to-date. I don't think I can turn off the buffering on the file descriptor. I added a call to flush each time something is added to the sink.

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When I did this previously I just did regular writes in append mode for each line that came in, instead of keeping it open like this. In theory this is better though, but we do want to actually see the logs.

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Flushing should do that, and this is only in the example.

I did look at doing the flush where we do the adding to the sink in the main package, but then we'd have to change the Sink<String> to an IOSink, since the base Sink doesn't have flush(), which would be a breaking change.

mode: FileMode.write,
encoding: utf8,
);
logSink = fileByteSink.transform<String>(
StreamSinkTransformer.fromHandlers(
handleData: (String data, EventSink<List<int>> innerSink) {
innerSink.add(utf8.encode(data));
},
handleError: (
Object error,
StackTrace stackTrace,
EventSink<List<int>> innerSink,
) {
innerSink.addError(error, stackTrace);
},
handleDone: (EventSink<List<int>> innerSink) {
innerSink.close();
},
),
);
return logSink;
}

void _startChat() async {
if (serverCommands.isNotEmpty) {
await _connectToServers();
Expand Down Expand Up @@ -317,6 +377,10 @@ final class WorkflowClient extends MCPClient with RootsSupport {
/// Invokes a function and adds the result as context to the chat history.
Future<void> _handleFunctionCall(gemini.FunctionCall functionCall) async {
chatHistory.add(gemini.Content.model([functionCall]));
logSink?.add(
'+++ Calling function ${functionCall.name} with args: '
'${functionCall.args}\n',
);
final connection = connectionForFunction[functionCall.name]!;
final result = await connection.callTool(
CallToolRequest(name: functionCall.name, arguments: functionCall.args),
Expand Down Expand Up @@ -349,7 +413,11 @@ final class WorkflowClient extends MCPClient with RootsSupport {
final parts = server.split(' ');
try {
serverConnections.add(
await connectStdioServer(parts.first, parts.skip(1).toList()),
await connectStdioServer(
parts.first,
parts.skip(1).toList(),
protocolLogSink: logSink,
),
);
} catch (e) {
logger.stderr('Failed to connect to server $server: $e');
Expand All @@ -370,10 +438,11 @@ final class WorkflowClient extends MCPClient with RootsSupport {
),
);
final serverName = connection.serverInfo?.name ?? 'server';
if (result.protocolVersion != ProtocolVersion.latestSupported) {
if (!result.protocolVersion!.isSupported) {
logger.stderr(
'Protocol version mismatch for $serverName, '
'expected ${ProtocolVersion.latestSupported}, got '
'expected a version between ${ProtocolVersion.oldestSupported} and '
'${ProtocolVersion.latestSupported}, but got '
'${result.protocolVersion}. Disconnecting.',
);
await connection.shutdown();
Expand Down
4 changes: 2 additions & 2 deletions pkgs/dart_mcp/lib/src/shared.dart
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Expand Up @@ -167,15 +167,15 @@ StreamChannel<String> _maybeForwardMessages(
.transformStream(
StreamTransformer.fromHandlers(
handleData: (data, sink) {
protocolLogSink.add('<<< $data');
protocolLogSink.add('<<< $data\n');
sink.add(data);
},
),
)
.transformSink(
StreamSinkTransformer.fromHandlers(
handleData: (data, sink) {
protocolLogSink.add('>>> $data');
protocolLogSink.add('>>> $data\n');
sink.add(data);
},
),
Expand Down