void visitFormalParameterList()

in lib/src/source_visitor.dart [1511:1606]
60 lines of code
14 McCabe index (conditional complexity)

  void visitFormalParameterList(FormalParameterList node,
      {bool nestExpression = true}) {
    // Corner case: empty parameter lists.
    if (node.parameters.isEmpty) {
      token(node.leftParenthesis);

      // If there is a comment, do allow splitting before it.
      if (node.rightParenthesis.precedingComments != null) soloZeroSplit();

      token(node.rightParenthesis);
      return;
    }

    // If the parameter list has a trailing comma, format it like a collection
    // literal where each parameter goes on its own line, they are indented +2,
    // and the ")" ends up on its own line.
    if (hasCommaAfter(node.parameters.last)) {
      _visitTrailingCommaParameterList(node);
      return;
    }

    var requiredParams = node.parameters
        .where((param) => param is! DefaultFormalParameter)
        .toList();
    var optionalParams =
        node.parameters.whereType<DefaultFormalParameter>().toList();

    if (nestExpression) builder.nestExpression();
    token(node.leftParenthesis);

    _metadataRules.add(MetadataRule());

    PositionalRule? rule;
    if (requiredParams.isNotEmpty) {
      rule = PositionalRule(null, 0, 0);
      _metadataRules.last.bindPositionalRule(rule);

      builder.startRule(rule);
      if (_isInLambda(node)) {
        // Don't allow splitting before the first argument (i.e. right after
        // the bare "(" in a lambda. Instead, just stuff a null chunk in there
        // to avoid confusing the arg rule.
        rule.beforeArgument(null);
      } else {
        // Split before the first argument.
        rule.beforeArgument(zeroSplit());
      }

      builder.startSpan();

      for (var param in requiredParams) {
        visit(param);
        _writeCommaAfter(param);

        if (param != requiredParams.last) rule.beforeArgument(split());
      }

      builder.endSpan();
      builder.endRule();
    }

    if (optionalParams.isNotEmpty) {
      var namedRule = NamedRule(null, 0, 0);
      if (rule != null) rule.setNamedArgsRule(namedRule);

      _metadataRules.last.bindNamedRule(namedRule);

      builder.startRule(namedRule);

      // Make sure multi-line default values are indented.
      builder.startBlockArgumentNesting();

      namedRule.beforeArgument(builder.split(space: requiredParams.isNotEmpty));

      // "[" or "{" for optional parameters.
      token(node.leftDelimiter);

      for (var param in optionalParams) {
        visit(param);
        _writeCommaAfter(param);

        if (param != optionalParams.last) namedRule.beforeArgument(split());
      }

      builder.endBlockArgumentNesting();
      builder.endRule();

      // "]" or "}" for optional parameters.
      token(node.rightDelimiter);
    }

    _metadataRules.removeLast();

    token(node.rightParenthesis);
    if (nestExpression) builder.unnest();
  }