filter method

@override List<TreeReference> filter(DataInstance sourceInstance, TreeReference nodeset, XPathExpression predicate, List<TreeReference> children, EvaluationContext context, List<TreeReference> next(),)

The children of nodeset that pass predicate, or the result of next (the rest of the chain) when this strategy doesn't apply.

Implementation

@override
List<TreeReference> filter(
  DataInstance sourceInstance,
  TreeReference nodeset,
  XPathExpression predicate,
  List<TreeReference> children,
  EvaluationContext context,
  List<TreeReference> Function() next,
) {
  if (sourceInstance.instanceId == null) return next();
  final candidate = CompareToNodeExpression.parse(predicate);
  if (candidate != null) {
    return _cached(
      _key(sourceInstance, nodeset, predicate, context, candidate),
      next,
    );
  }
  if (predicate is XPathBoolExpr) {
    final candidateA = CompareToNodeExpression.parse(predicate.a);
    final candidateB = CompareToNodeExpression.parse(predicate.b);
    if (candidateA != null && candidateB != null) {
      final key =
          'XPathBoolExpr:${predicate.op}'
          '${_key(sourceInstance, nodeset, predicate.a, context, candidateA)}'
          '${_key(sourceInstance, nodeset, predicate.b, context, candidateB)}';
      return _cached(key, next);
    }
  }
  return next();
}