void handler()

in frontend_server_common/lib/src/frontend_server_client.dart [63:146]
72 lines of code
16 McCabe index (conditional complexity)

  void handler(String message) {
    if (message.startsWith('Observatory listening')) {
      stderr.writeln(message);
      return;
    }
    if (message.startsWith('Observatory server failed')) {
      throw Exception(message);
    }
    if (_badState) {
      return;
    }
    var kResultPrefix = 'result ';
    if (boundaryKey == null && message.startsWith(kResultPrefix)) {
      boundaryKey = message.substring(kResultPrefix.length);
      return;
    }
    // Invalid state, see commented issue below for more information.
    // NB: both the completeError and _badState flags are required to avoid
    // filling the console with exceptions.
    if (boundaryKey == null) {
      // Throwing a synchronous exception via throwToolExit will fail to cancel
      // the stream. Instead use completeError so that the error is returned
      // from the awaited future that the compiler consumers are expecting.
      compilerOutput.completeError(
          'Frontend server tests encountered an internal problem. '
          'This can be caused by printing to stdout into the stream that is '
          'used for communication between frontend server (in sdk) or '
          'frontend server client (in dwds tests).'
          '\n\n'
          'Additional debugging information:\n'
          '  StdoutState: $state\n'
          '  compilerMessageReceived: $compilerMessageReceived\n'
          '  message: $message\n'
          '  _expectSources: $_expectSources\n'
          '  sources: $sources\n');
      // There are several event turns before the tool actually exits from a
      // tool exception. Normally, the stream should be cancelled to prevent
      // more events from entering the bad state, but because the error
      // is coming from handler itself, there is no clean way to pipe this
      // through. Instead, we set a flag to prevent more messages from
      // registering.
      _badState = true;
      return;
    }
    if (message.startsWith(boundaryKey)) {
      if (_expectSources) {
        if (state == StdoutState.collectDiagnostic) {
          state = StdoutState.collectDependencies;
          return;
        }
      }
      if (message.length <= boundaryKey.length) {
        compilerOutput.complete(null);
        return;
      }
      var spaceDelimiter = message.lastIndexOf(' ');
      compilerOutput.complete(CompilerOutput(
          message.substring(boundaryKey.length + 1, spaceDelimiter),
          int.parse(message.substring(spaceDelimiter + 1).trim()),
          sources));
      return;
    }
    if (state == StdoutState.collectDiagnostic) {
      if (!_suppressCompilerMessages) {
        if (compilerMessageReceived == false) {
          consumer('\nCompiler message:');
          compilerMessageReceived = true;
        }
        consumer(message);
      }
    } else {
      assert(state == StdoutState.collectDependencies);
      switch (message[0]) {
        case '+':
          sources.add(Uri.parse(message.substring(1)));
          break;
        case '-':
          sources.remove(Uri.parse(message.substring(1)));
          break;
        default:
          _logger.warning('Unexpected prefix for $message uri - ignoring');
      }
    }
  }