add cacheQuery to fix last() not working on subgroup. #76, #78

build.go

@@ -521,6 +521,9 @@ func (b *builder) processNode(root node) (q query, err error) {
 			return
 		}
 		q = &groupQuery{Input: q}
+		// fix https://github.com/antchfx/xpath/issues/76
+		q = &cacheQuery{Input: q}
+		b.firstInput = q
 	}
 	return
 }

func.go

@@ -53,6 +53,14 @@ func positionFunc(q query, t iterator) interface{} {
 
 // lastFunc is a XPath Node Set functions last().
 func lastFunc(q query, t iterator) interface{} {
+	//
+	type Counter interface {
+		count() int
+	}
+	if p, ok := q.(Counter); ok {
+		return float64(p.count())
+	}
+
 	var (
 		count = 0
 		node  = t.Current().Copy()
@@ -158,7 +166,8 @@ func nameFunc(arg query) func(query, iterator) interface{} {
 		if arg == nil {
 			v = t.Current()
 		} else {
-			v = arg.Clone().Select(t)
+			arg.Reset()
+			v = arg.Select(t)
 			if v == nil {
 				return ""
 			}
@@ -178,7 +187,8 @@ func localNameFunc(arg query) func(query, iterator) interface{} {
 		if arg == nil {
 			v = t.Current()
 		} else {
-			v = arg.Clone().Select(t)
+			arg.Reset()
+			v = arg.Select(t)
 			if v == nil {
 				return ""
 			}
@@ -195,7 +205,8 @@ func namespaceFunc(arg query) func(query, iterator) interface{} {
 			v = t.Current()
 		} else {
 			// Get the first node in the node-set if specified.
-			v = arg.Clone().Select(t)
+			arg.Reset()
+			v = arg.Select(t)
 			if v == nil {
 				return ""
 			}
@@ -592,7 +603,8 @@ func functionArgs(q query) query {
 	if _, ok := q.(*functionQuery); ok {
 		return q
 	}
-	return q.Clone()
+	q.Reset()
+	return q
 }
 
 func reverseFunc(q query, t iterator) func() NodeNavigator {

func_test.go

@@ -8,8 +8,7 @@ func (t testQuery) Select(_ iterator) NodeNavigator {
 	panic("implement me")
 }
 
-func (t testQuery) Clone() query {
-	return t
+func (t testQuery) Reset() {
 }
 
 func (t testQuery) Evaluate(_ iterator) interface{} {