Update xpath dependency (#507)

vendor/github.com/antchfx/htmlquery/.travis.yml

@@ -1,9 +1,9 @@
 language: go
 
 go:
-  - 1.6
-  - 1.7
-  - 1.8
+  - 1.9.x
+  - 1.12.x
+  - 1.13.x
 
 install:
   - go get golang.org/x/net/html/charset

vendor/github.com/antchfx/htmlquery/README.md

@@ -10,7 +10,7 @@ Overview
 
 `htmlquery` is an XPath query package for HTML, lets you extract data or evaluate from HTML documents by an XPath expression.
 
-`htmlquery` build-in the query object caching feature based on [LRU](https://godoc.org/github.com/golang/groupcache/lru), this feature will caching the recently used XPATH query string. enable caching can avoid re-compile XPath expression each query. 
+`htmlquery` built-in the query object caching feature based on [LRU](https://godoc.org/github.com/golang/groupcache/lru), this feature will caching the recently used XPATH query string. Enable query caching can avoid re-compile XPath expression each query. 
 
 Installation
 ====
@@ -101,7 +101,17 @@ Yes, you can. We offer the `QuerySelector` and `QuerySelectorAll` methods, It wi
 
 Cache a query expression object(or reused) will avoid re-compile XPath query expression, improve your query performance.
 
-#### Disable caching feature
+#### XPath query object cache performance
+
+```
+goos: windows
+goarch: amd64
+pkg: github.com/antchfx/htmlquery
+BenchmarkSelectorCache-4                20000000                55.2 ns/op
+BenchmarkDisableSelectorCache-4           500000              3162 ns/op
+```
+
+#### How to disable caching?
 
 ```
 htmlquery.DisableSelectorCache = true

vendor/github.com/antchfx/htmlquery/cache.go

@@ -3,9 +3,8 @@ package htmlquery
 import (
 	"sync"
 
-	"github.com/golang/groupcache/lru"
-
 	"github.com/antchfx/xpath"
+	"github.com/golang/groupcache/lru"
 )
 
 // DisableSelectorCache will disable caching for the query selector if value is true.
@@ -16,8 +15,9 @@ var DisableSelectorCache = false
 var SelectorCacheMaxEntries = 50
 
 var (
-	cacheOnce sync.Once
-	cache     *lru.Cache
+	cacheOnce  sync.Once
+	cache      *lru.Cache
+	cacheMutex sync.Mutex
 )
 
 func getQuery(expr string) (*xpath.Expr, error) {
@@ -25,8 +25,10 @@ func getQuery(expr string) (*xpath.Expr, error) {
 		return xpath.Compile(expr)
 	}
 	cacheOnce.Do(func() {
-		cache = lru.New(50)
+		cache = lru.New(SelectorCacheMaxEntries)
 	})
+	cacheMutex.Lock()
+	defer cacheMutex.Unlock()
 	if v, ok := cache.Get(expr); ok {
 		return v.(*xpath.Expr), nil
 	}

vendor/github.com/antchfx/htmlquery/go.mod

@@ -0,0 +1,9 @@
+module github.com/antchfx/htmlquery
+
+go 1.14
+
+require (
+	github.com/antchfx/xpath v1.1.6
+	github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e
+	golang.org/x/net v0.0.0-20200421231249-e086a090c8fd
+)

vendor/github.com/antchfx/htmlquery/go.sum

@@ -0,0 +1,11 @@
+github.com/antchfx/xpath v1.1.6 h1:6sVh6hB5T6phw1pFpHRQ+C4bd8sNI+O58flqtg7h0R0=
+github.com/antchfx/xpath v1.1.6/go.mod h1:Yee4kTMuNiPYJ7nSNorELQMr1J33uOpXDMByNYhvtNk=
+github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e h1:1r7pUrabqp18hOBcwBwiTsbnFeTZHV9eER/QT5JVZxY=
+github.com/golang/groupcache v0.0.0-20200121045136-8c9f03a8e57e/go.mod h1:cIg4eruTrX1D+g88fzRXU5OdNfaM+9IcxsU14FzY7Hc=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/net v0.0.0-20200421231249-e086a090c8fd h1:QPwSajcTUrFriMF1nJ3XzgoqakqQEsnZf9LdXdi2nkI=
+golang.org/x/net v0.0.0-20200421231249-e086a090c8fd/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

vendor/github.com/antchfx/xpath/README.md

@@ -144,6 +144,8 @@ Supported Features
 `not()`| ✓ |
 `number()`| ✓ |
 `position()`| ✓ |
+`replace()`| ✓ |
+`reverse()`| ✓ |
 `round()`| ✓ |
 `starts-with()`| ✓ |
 `string()`| ✓ |

vendor/github.com/antchfx/xpath/build.go

@@ -77,7 +77,18 @@ func (b *builder) processAxisNode(root *axisNode) (query, error) {
 				} else {
 					qyGrandInput = &contextQuery{}
 				}
-				qyOutput = &descendantQuery{Input: qyGrandInput, Predicate: predicate, Self: true}
+				// fix #20: https://github.com/antchfx/htmlquery/issues/20
+				filter := func(n NodeNavigator) bool {
+					v := predicate(n)
+					switch root.Prop {
+					case "text":
+						v = v && n.NodeType() == TextNode
+					case "comment":
+						v = v && n.NodeType() == CommentNode
+					}
+					return v
+				}
+				qyOutput = &descendantQuery{Input: qyGrandInput, Predicate: filter, Self: true}
 				return qyOutput, nil
 			}
 		}
@@ -243,6 +254,25 @@ func (b *builder) processFunctionNode(root *functionNode) (query, error) {
 			return nil, err
 		}
 		qyOutput = &functionQuery{Input: argQuery, Func: normalizespaceFunc}
+	case "replace":
+		//replace( string , string, string )
+		if len(root.Args) != 3 {
+			return nil, errors.New("xpath: replace function must have three parameters")
+		}
+		var (
+			arg1, arg2, arg3 query
+			err              error
+		)
+		if arg1, err = b.processNode(root.Args[0]); err != nil {
+			return nil, err
+		}
+		if arg2, err = b.processNode(root.Args[1]); err != nil {
+			return nil, err
+		}
+		if arg3, err = b.processNode(root.Args[2]); err != nil {
+			return nil, err
+		}
+		qyOutput = &functionQuery{Input: b.firstInput, Func: replaceFunc(arg1, arg2, arg3)}
 	case "translate":
 		//translate( string , string, string )
 		if len(root.Args) != 3 {
@@ -272,27 +302,27 @@ func (b *builder) processFunctionNode(root *functionNode) (query, error) {
 		}
 		qyOutput = &functionQuery{Input: argQuery, Func: notFunc}
 	case "name", "local-name", "namespace-uri":
-		inp := b.firstInput
 		if len(root.Args) > 1 {
 			return nil, fmt.Errorf("xpath: %s function must have at most one parameter", root.FuncName)
 		}
+		var (
+			arg query
+			err error
+		)
 		if len(root.Args) == 1 {
-			argQuery, err := b.processNode(root.Args[0])
+			arg, err = b.processNode(root.Args[0])
 			if err != nil {
 				return nil, err
 			}
-			inp = argQuery
 		}
-		f := &functionQuery{Input: inp}
 		switch root.FuncName {
 		case "name":
-			f.Func = nameFunc
+			qyOutput = &functionQuery{Input: b.firstInput, Func: nameFunc(arg)}
 		case "local-name":
-			f.Func = localNameFunc
+			qyOutput = &functionQuery{Input: b.firstInput, Func: localNameFunc(arg)}
 		case "namespace-uri":
-			f.Func = namespaceFunc
+			qyOutput = &functionQuery{Input: b.firstInput, Func: namespaceFunc(arg)}
 		}
-		qyOutput = f
 	case "true", "false":
 		val := root.FuncName == "true"
 		qyOutput = &functionQuery{
@@ -379,6 +409,15 @@ func (b *builder) processFunctionNode(root *functionNode) (query, error) {
 			args = append(args, q)
 		}
 		qyOutput = &functionQuery{Input: b.firstInput, Func: concatFunc(args...)}
+	case "reverse":
+		if len(root.Args) == 0 {
+			return nil, fmt.Errorf("xpath: reverse(node-sets) function must with have parameters node-sets")
+		}
+		argQuery, err := b.processNode(root.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		qyOutput = &transformFunctionQuery{Input: argQuery, Func: reverseFunc}
 	default:
 		return nil, fmt.Errorf("not yet support this function %s()", root.FuncName)
 	}

vendor/github.com/antchfx/xpath/func.go

@@ -134,42 +134,64 @@ func roundFunc(q query, t iterator) interface{} {
 }
 
 // nameFunc is a XPath functions name([node-set]).
-func nameFunc(q query, t iterator) interface{} {
-	v := q.Select(t)
-	if v == nil {
-		return ""
+func nameFunc(arg query) func(query, iterator) interface{} {
+	return func(q query, t iterator) interface{} {
+		var v NodeNavigator
+		if arg == nil {
+			v = t.Current()
+		} else {
+			v = arg.Select(t)
+			if v == nil {
+				return ""
+			}
+		}
+		ns := v.Prefix()
+		if ns == "" {
+			return v.LocalName()
+		}
+		return ns + ":" + v.LocalName()
 	}
-	ns := v.Prefix()
-	if ns == "" {
-		return v.LocalName()
-	}
-	return ns + ":" + v.LocalName()
 }
 
 // localNameFunc is a XPath functions local-name([node-set]).
-func localNameFunc(q query, t iterator) interface{} {
-	v := q.Select(t)
-	if v == nil {
-		return ""
+func localNameFunc(arg query) func(query, iterator) interface{} {
+	return func(q query, t iterator) interface{} {
+		var v NodeNavigator
+		if arg == nil {
+			v = t.Current()
+		} else {
+			v = arg.Select(t)
+			if v == nil {
+				return ""
+			}
+		}
+		return v.LocalName()
 	}
-	return v.LocalName()
 }
 
 // namespaceFunc is a XPath functions namespace-uri([node-set]).
-func namespaceFunc(q query, t iterator) interface{} {
-	v := q.Select(t)
-	if v == nil {
-		return ""
+func namespaceFunc(arg query) func(query, iterator) interface{} {
+	return func(q query, t iterator) interface{} {
+		var v NodeNavigator
+		if arg == nil {
+			v = t.Current()
+		} else {
+			// Get the first node in the node-set if specified.
+			v = arg.Select(t)
+			if v == nil {
+				return ""
+			}
+		}
+		// fix about namespace-uri() bug: https://github.com/antchfx/xmlquery/issues/22
+		// TODO: In the next version, add NamespaceURL() to the NodeNavigator interface.
+		type namespaceURL interface {
+			NamespaceURL() string
+		}
+		if f, ok := v.(namespaceURL); ok {
+			return f.NamespaceURL()
+		}
+		return v.Prefix()
 	}
-	// fix about namespace-uri() bug: https://github.com/antchfx/xmlquery/issues/22
-	// TODO: In the next version, add NamespaceURL() to the NodeNavigator interface.
-	type namespaceURL interface {
-		NamespaceURL() string
-	}
-	if f, ok := v.(namespaceURL); ok {
-		return f.NamespaceURL()
-	}
-	return v.Prefix()
 }
 
 func asBool(t iterator, v interface{}) bool {
@@ -240,7 +262,7 @@ func startwithFunc(arg1, arg2 query) func(query, iterator) interface{} {
 			m, n string
 			ok   bool
 		)
-		switch typ := arg1.Evaluate(t).(type) {
+		switch typ := functionArgs(arg1).Evaluate(t).(type) {
 		case string:
 			m = typ
 		case query:
@@ -252,7 +274,7 @@ func startwithFunc(arg1, arg2 query) func(query, iterator) interface{} {
 		default:
 			panic(errors.New("starts-with() function argument type must be string"))
 		}
-		n, ok = arg2.Evaluate(t).(string)
+		n, ok = functionArgs(arg2).Evaluate(t).(string)
 		if !ok {
 			panic(errors.New("starts-with() function argument type must be string"))
 		}
@@ -267,7 +289,7 @@ func endwithFunc(arg1, arg2 query) func(query, iterator) interface{} {
 			m, n string
 			ok   bool
 		)
-		switch typ := arg1.Evaluate(t).(type) {
+		switch typ := functionArgs(arg1).Evaluate(t).(type) {
 		case string:
 			m = typ
 		case query:
@@ -279,7 +301,7 @@ func endwithFunc(arg1, arg2 query) func(query, iterator) interface{} {
 		default:
 			panic(errors.New("ends-with() function argument type must be string"))
 		}
-		n, ok = arg2.Evaluate(t).(string)
+		n, ok = functionArgs(arg2).Evaluate(t).(string)
 		if !ok {
 			panic(errors.New("ends-with() function argument type must be string"))
 		}
@@ -294,8 +316,7 @@ func containsFunc(arg1, arg2 query) func(query, iterator) interface{} {
 			m, n string
 			ok   bool
 		)
-
-		switch typ := arg1.Evaluate(t).(type) {
+		switch typ := functionArgs(arg1).Evaluate(t).(type) {
 		case string:
 			m = typ
 		case query:
@@ -308,7 +329,7 @@ func containsFunc(arg1, arg2 query) func(query, iterator) interface{} {
 			panic(errors.New("contains() function argument type must be string"))
 		}
 
-		n, ok = arg2.Evaluate(t).(string)
+		n, ok = functionArgs(arg2).Evaluate(t).(string)
 		if !ok {
 			panic(errors.New("contains() function argument type must be string"))
 		}
@@ -345,7 +366,7 @@ func normalizespaceFunc(q query, t iterator) interface{} {
 func substringFunc(arg1, arg2, arg3 query) func(query, iterator) interface{} {
 	return func(q query, t iterator) interface{} {
 		var m string
-		switch typ := arg1.Evaluate(t).(type) {
+		switch typ := functionArgs(arg1).Evaluate(t).(type) {
 		case string:
 			m = typ
 		case query:
@@ -359,14 +380,14 @@ func substringFunc(arg1, arg2, arg3 query) func(query, iterator) interface{} {
 		var start, length float64
 		var ok bool
 
-		if start, ok = arg2.Evaluate(t).(float64); !ok {
+		if start, ok = functionArgs(arg2).Evaluate(t).(float64); !ok {
 			panic(errors.New("substring() function first argument type must be int"))
 		} else if start < 1 {
 			panic(errors.New("substring() function first argument type must be >= 1"))
 		}
 		start--
 		if arg3 != nil {
-			if length, ok = arg3.Evaluate(t).(float64); !ok {
+			if length, ok = functionArgs(arg3).Evaluate(t).(float64); !ok {
 				panic(errors.New("substring() function second argument type must be int"))
 			}
 		}
@@ -384,7 +405,7 @@ func substringFunc(arg1, arg2, arg3 query) func(query, iterator) interface{} {
 func substringIndFunc(arg1, arg2 query, after bool) func(query, iterator) interface{} {
 	return func(q query, t iterator) interface{} {
 		var str string
-		switch v := arg1.Evaluate(t).(type) {
+		switch v := functionArgs(arg1).Evaluate(t).(type) {
 		case string:
 			str = v
 		case query:
@@ -395,7 +416,7 @@ func substringIndFunc(arg1, arg2 query, after bool) func(query, iterator) interf
 			str = node.Value()
 		}
 		var word string
-		switch v := arg2.Evaluate(t).(type) {
+		switch v := functionArgs(arg2).Evaluate(t).(type) {
 		case string:
 			word = v
 		case query:
@@ -424,7 +445,7 @@ func substringIndFunc(arg1, arg2 query, after bool) func(query, iterator) interf
 // equal to the number of characters in a given string.
 func stringLengthFunc(arg1 query) func(query, iterator) interface{} {
 	return func(q query, t iterator) interface{} {
-		switch v := arg1.Evaluate(t).(type) {
+		switch v := functionArgs(arg1).Evaluate(t).(type) {
 		case string:
 			return float64(len(v))
 		case query:
@@ -441,9 +462,9 @@ func stringLengthFunc(arg1 query) func(query, iterator) interface{} {
 // translateFunc is XPath functions translate() function returns a replaced string.
 func translateFunc(arg1, arg2, arg3 query) func(query, iterator) interface{} {
 	return func(q query, t iterator) interface{} {
-		str := asString(t, arg1.Evaluate(t))
-		src := asString(t, arg2.Evaluate(t))
-		dst := asString(t, arg3.Evaluate(t))
+		str := asString(t, functionArgs(arg1).Evaluate(t))
+		src := asString(t, functionArgs(arg2).Evaluate(t))
+		dst := asString(t, functionArgs(arg3).Evaluate(t))
 
 		var replace []string
 		for i, s := range src {
@@ -457,6 +478,17 @@ func translateFunc(arg1, arg2, arg3 query) func(query, iterator) interface{} {
 	}
 }
 
+// replaceFunc is XPath functions replace() function returns a replaced string.
+func replaceFunc(arg1, arg2, arg3 query) func(query, iterator) interface{} {
+	return func(q query, t iterator) interface{} {
+		str := asString(t, functionArgs(arg1).Evaluate(t))
+		src := asString(t, functionArgs(arg2).Evaluate(t))
+		dst := asString(t, functionArgs(arg3).Evaluate(t))
+
+		return strings.Replace(str, src, dst, -1)
+	}
+}
+
 // notFunc is XPATH functions not(expression) function operation.
 func notFunc(q query, t iterator) interface{} {
 	switch v := q.Evaluate(t).(type) {
@@ -477,6 +509,7 @@ func concatFunc(args ...query) func(query, iterator) interface{} {
 	return func(q query, t iterator) interface{} {
 		var a []string
 		for _, v := range args {
+			v = functionArgs(v)
 			switch v := v.Evaluate(t).(type) {
 			case string:
 				a = append(a, v)
@@ -490,3 +523,31 @@ func concatFunc(args ...query) func(query, iterator) interface{} {
 		return strings.Join(a, "")
 	}
 }
+
+// https://github.com/antchfx/xpath/issues/43
+func functionArgs(q query) query {
+	if _, ok := q.(*functionQuery); ok {
+		return q
+	}
+	return q.Clone()
+}
+
+func reverseFunc(q query, t iterator) func() NodeNavigator {
+	var list []NodeNavigator
+	for {
+		node := q.Select(t)
+		if node == nil {
+			break
+		}
+		list = append(list, node.Copy())
+	}
+	i := len(list)
+	return func() NodeNavigator {
+		if i <= 0 {
+			return nil
+		}
+		i--
+		node := list[i]
+		return node
+	}
+}

vendor/github.com/antchfx/xpath/operator.go

@@ -163,7 +163,17 @@ func cmpNodeSetString(t iterator, op string, m, n interface{}) bool {
 }
 
 func cmpNodeSetNodeSet(t iterator, op string, m, n interface{}) bool {
-	return false
+	a := m.(query)
+	b := n.(query)
+	x := a.Select(t)
+	if x == nil {
+		return false
+	}
+	y := b.Select(t)
+	if y == nil {
+		return false
+	}
+	return cmpStringStringF(op,x.Value(),y.Value())
 }
 
 func cmpStringNumeric(t iterator, op string, m, n interface{}) bool {

vendor/github.com/antchfx/xpath/query.go

@@ -227,6 +227,7 @@ func (c *childQuery) position() int {
 type descendantQuery struct {
 	iterator func() NodeNavigator
 	posit    int
+	level    int
 
 	Self      bool
 	Input     query
@@ -242,7 +243,7 @@ func (d *descendantQuery) Select(t iterator) NodeNavigator {
 				return nil
 			}
 			node = node.Copy()
-			level := 0
+			d.level = 0
 			positmap := make(map[int]int)
 			first := true
 			d.iterator = func() NodeNavigator {
@@ -250,30 +251,30 @@ func (d *descendantQuery) Select(t iterator) NodeNavigator {
 					first = false
 					if d.Predicate(node) {
 						d.posit = 1
-						positmap[level] = 1
+						positmap[d.level] = 1
 						return node
 					}
 				}
 
 				for {
 					if node.MoveToChild() {
-						level++
-						positmap[level] = 0
+						d.level = d.level + 1
+						positmap[d.level] = 0
 					} else {
 						for {
-							if level == 0 {
+							if d.level == 0 {
 								return nil
 							}
 							if node.MoveToNext() {
 								break
 							}
 							node.MoveToParent()
-							level--
+							d.level = d.level - 1
 						}
 					}
 					if d.Predicate(node) {
-						positmap[level]++
-						d.posit = positmap[level]
+						positmap[d.level]++
+						d.posit = positmap[d.level]
 						return node
 					}
 				}
@@ -302,6 +303,10 @@ func (d *descendantQuery) position() int {
 	return d.posit
 }
 
+func (d *descendantQuery) depth() int {
+	return d.level
+}
+
 func (d *descendantQuery) Clone() query {
 	return &descendantQuery{Self: d.Self, Input: d.Input.Clone(), Predicate: d.Predicate}
 }
@@ -538,6 +543,7 @@ type filterQuery struct {
 	Input     query
 	Predicate query
 	posit     int
+	positmap  map[int]int
 }
 
 func (f *filterQuery) do(t iterator) bool {
@@ -563,7 +569,9 @@ func (f *filterQuery) position() int {
 }
 
 func (f *filterQuery) Select(t iterator) NodeNavigator {
-
+	if f.positmap == nil {
+		f.positmap = make(map[int]int)
+	}
 	for {
 
 		node := f.Input.Select(t)
@@ -574,10 +582,13 @@ func (f *filterQuery) Select(t iterator) NodeNavigator {
 
 		t.Current().MoveTo(node)
 		if f.do(t) {
-			f.posit++
+			// fix https://github.com/antchfx/htmlquery/issues/26
+			// Calculate and keep the each of matching node's position in the same depth.
+			level := getNodeDepth(f.Input)
+			f.positmap[level]++
+			f.posit = f.positmap[level]
 			return node
 		}
-		f.posit = 0
 	}
 }
 
@@ -590,8 +601,9 @@ func (f *filterQuery) Clone() query {
 	return &filterQuery{Input: f.Input.Clone(), Predicate: f.Predicate.Clone()}
 }
 
-// functionQuery is an XPath function that call a function to returns
-// value of current NodeNavigator node.
+// functionQuery is an XPath function that returns a computed value for
+// the Evaluate call of the current NodeNavigator node. Select call isn't
+// applicable for functionQuery.
 type functionQuery struct {
 	Input query                             // Node Set
 	Func  func(query, iterator) interface{} // The xpath function.
@@ -611,6 +623,34 @@ func (f *functionQuery) Clone() query {
 	return &functionQuery{Input: f.Input.Clone(), Func: f.Func}
 }
 
+// transformFunctionQuery diffs from functionQuery where the latter computes a scalar
+// value (number,string,boolean) for the current NodeNavigator node while the former
+// (transformFunctionQuery) performs a mapping or transform of the current NodeNavigator
+// and returns a new NodeNavigator. It is used for non-scalar XPath functions such as
+// reverse(), remove(), subsequence(), unordered(), etc.
+type transformFunctionQuery struct {
+	Input    query
+	Func     func(query, iterator) func() NodeNavigator
+	iterator func() NodeNavigator
+}
+
+func (f *transformFunctionQuery) Select(t iterator) NodeNavigator {
+	if f.iterator == nil {
+		f.iterator = f.Func(f.Input, t)
+	}
+	return f.iterator()
+}
+
+func (f *transformFunctionQuery) Evaluate(t iterator) interface{} {
+	f.Input.Evaluate(t)
+	f.iterator = nil
+	return f
+}
+
+func (f *transformFunctionQuery) Clone() query {
+	return &transformFunctionQuery{Input: f.Input.Clone(), Func: f.Func}
+}
+
 // constantQuery is an XPath constant operand.
 type constantQuery struct {
 	Val interface{}
@@ -827,8 +867,18 @@ func getHashCode(n NodeNavigator) uint64 {
 	switch n.NodeType() {
 	case AttributeNode, TextNode, CommentNode:
 		sb.WriteString(fmt.Sprintf("%s=%s", n.LocalName(), n.Value()))
-		if n.MoveToParent() {
-			sb.WriteString(n.LocalName())
+		// https://github.com/antchfx/htmlquery/issues/25
+		d := 1
+		for n.MoveToPrevious() {
+			d++
+		}
+		sb.WriteString(fmt.Sprintf("-%d", d))
+		for n.MoveToParent() {
+			d = 1
+			for n.MoveToPrevious() {
+				d++
+			}
+			sb.WriteString(fmt.Sprintf("-%d", d))
 		}
 	case ElementNode:
 		sb.WriteString(n.Prefix() + n.LocalName())
@@ -860,3 +910,13 @@ func getNodePosition(q query) int {
 	}
 	return 1
 }
+
+func getNodeDepth(q query) int {
+	type Depth interface {
+		depth() int
+	}
+	if count, ok := q.(Depth); ok {
+		return count.depth()
+	}
+	return 0
+}

vendor/github.com/antchfx/xpath/xpath.go

@@ -2,6 +2,7 @@ package xpath
 
 import (
 	"errors"
+	"fmt"
 )
 
 // NodeType represents a type of XPath node.
@@ -144,6 +145,9 @@ func Compile(expr string) (*Expr, error) {
 	if err != nil {
 		return nil, err
 	}
+	if qy == nil {
+		return nil, fmt.Errorf(fmt.Sprintf("undeclared variable in XPath expression: %s", expr))
+	}
 	return &Expr{s: expr, q: qy}, nil
 }