getFunction method

XPathFunctionItem getFunction(XmlName name, [ int? arity ])

Looks up an XPath function with the given name and optional arity.

Implementation

XPathFunctionItem getFunction(XmlName name, [int? arity]) {
  if (name.prefix != null && name.namespaceUri == null) {
    throw XPathEvaluationException(
      XPathErrorCode.XPST0081,
      'Cannot expand namespace prefix: ${name.prefix}',
    );
  }
  final function = functions[name];
  if (function != null) {
    if (arity != null && function is XPathOverloadedFunction) {
      final specific = function.getForArity(arity);
      if (specific != null) return specific;
      throw XPathEvaluationException(
        XPathErrorCode.XPST0017,
        'Function "$name" does not support arity $arity',
      );
    }
    if (arity != null && !function.isVariadic && function.arity != arity) {
      throw XPathEvaluationException(
        XPathErrorCode.XPST0017,
        'Function "$name" does not support arity $arity',
      );
    }
    if (arity != null && function.isVariadic && arity < function.arity) {
      throw XPathEvaluationException(
        XPathErrorCode.XPST0017,
        'Function "$name" expects at least ${function.arity} arguments, but got $arity',
      );
    }
    return function;
  }
  throw XPathEvaluationException(
    XPathErrorCode.XPST0017,
    'Unknown function: $name',
  );
}