Merge pull request #115 from PuerkitoBio/i114

Treat invalid selector strings as a Matcher that doesn't match anything

.travis.yml

@@ -4,4 +4,7 @@ go:
     - 1.1
     - 1.2
     - 1.3
+    - 1.4
+    - 1.5
+    - 1.6
     - tip

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2012-2014, Martin Angers & Contributors
+Copyright (c) 2012-2016, Martin Angers & Contributors
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

README.md

@@ -1,8 +1,4 @@
-# goquery - a little like that j-thing, only in Go
-
-[![build status](https://secure.travis-ci.org/PuerkitoBio/goquery.png)](http://travis-ci.org/PuerkitoBio/goquery)
-
-[![GoDoc](https://godoc.org/github.com/PuerkitoBio/goquery?status.png)](http://godoc.org/github.com/PuerkitoBio/goquery)
+# goquery - a little like that j-thing, only in Go [![build status](https://secure.travis-ci.org/PuerkitoBio/goquery.png)](http://travis-ci.org/PuerkitoBio/goquery) [![GoDoc](https://godoc.org/github.com/PuerkitoBio/goquery?status.png)](http://godoc.org/github.com/PuerkitoBio/goquery)
 
 goquery brings a syntax and a set of features similar to [jQuery][] to the [Go language][go]. It is based on Go's [net/html package][html] and the CSS Selector library [cascadia][]. Since the net/html parser returns nodes, and not a full-featured DOM tree, jQuery's stateful manipulation functions (like height(), css(), detach()) have been left off.
 
@@ -30,6 +26,7 @@ Please note that because of the net/html dependency, goquery requires Go1.1+.
 
 **Note that goquery's API is now stable, and will not break.**
 
+*    **2016-06-15** : Invalid selector strings internally compile to a `Matcher` implementation that never matches any node (instead of a panic). So for example, `doc.Find("~")` returns an empty `*Selection` object.
 *    **2016-02-02** : Add `NodeName` utility function similar to the DOM's `nodeName` property. It returns the tag name of the first element in a selection, and other relevant values of non-element nodes (see godoc for details). Add `OuterHtml` utility function similar to the DOM's `outerHTML` property (named `OuterHtml` in small caps for consistency with the existing `Html` method on the `Selection`).
 *    **2015-04-20** : Add `AttrOr` helper method to return the attribute's value or a default value if absent. Thanks to [piotrkowalczuk][piotr].
 *    **2015-02-04** : Add more manipulation functions - Prepend* - thanks again to [Andrew Stone][thatguystone].
@@ -61,7 +58,12 @@ Utility functions that are not in jQuery but are useful in Go are implemented as
 
 The complete [godoc reference documentation can be found here][doc].
 
-Please note that Cascadia's selectors do not necessarily match all supported selectors of jQuery (Sizzle). See the [cascadia project][cascadia] for details.
+Please note that Cascadia's selectors do not necessarily match all supported selectors of jQuery (Sizzle). See the [cascadia project][cascadia] for details. Invalid selector strings compile to a `Matcher` that fails to match any node. Behaviour of the various functions that take a selector string as argument follows from that fact, e.g. (where `~` is an invalid selector string):
+
+* `Find("~")` returns an empty selection because the selector string doesn't match anything.
+* `Add("~")` returns a new selection that holds the same nodes as the original selection, because it didn't add any node (selector string didn't match anything).
+* `ParentsFiltered("~")` returns an empty selection because the selector string doesn't match anything.
+* `ParentsUntil("~")` returns all parents of the selection because the selector string didn't match any element to stop before the top element.
 
 ## Examples
 

array_test.go

@@ -14,6 +14,11 @@ func TestFirstEmpty(t *testing.T) {
 	assertLength(t, sel.Nodes, 0)
 }
 
+func TestFirstInvalid(t *testing.T) {
+	sel := Doc().Find("").First()
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestFirstRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-content")
 	sel2 := sel.First().End()
@@ -36,6 +41,11 @@ func TestLastEmpty(t *testing.T) {
 	assertLength(t, sel.Nodes, 0)
 }
 
+func TestLastInvalid(t *testing.T) {
+	sel := Doc().Find("").Last()
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestLastRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-content")
 	sel2 := sel.Last().End()
@@ -63,6 +73,11 @@ func TestEqEmpty(t *testing.T) {
 	assertLength(t, sel.Nodes, 0)
 }
 
+func TestEqInvalid(t *testing.T) {
+	sel := Doc().Find("").Eq(0)
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestEqInvalidPositive(t *testing.T) {
 	sel := Doc().Find(".pvk-content").Eq(3)
 	assertLength(t, sel.Nodes, 0)
@@ -85,6 +100,16 @@ func TestSlice(t *testing.T) {
 	assertLength(t, sel.Nodes, 2)
 }
 
+func TestSliceEmpty(t *testing.T) {
+	defer assertPanic(t)
+	Doc().Find("x").Slice(0, 2)
+}
+
+func TestSliceInvalid(t *testing.T) {
+	defer assertPanic(t)
+	Doc().Find("").Slice(0, 2)
+}
+
 func TestSliceOutOfBounds(t *testing.T) {
 	defer assertPanic(t)
 	Doc().Find(".pvk-content").Slice(2, 12)
@@ -157,6 +182,13 @@ func TestIndexSelector(t *testing.T) {
 	}
 }
 
+func TestIndexSelectorInvalid(t *testing.T) {
+	sel := Doc().Find(".hero-unit")
+	if i := sel.IndexSelector(""); i != -1 {
+		t.Errorf("Expected index of -1, got %v.", i)
+	}
+}
+
 func TestIndexOfNode(t *testing.T) {
 	sel := Doc().Find("div.pvk-gutter")
 	if i := sel.IndexOfNode(sel.Nodes[1]); i != 1 {

doc.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2012-2014, Martin Angers & Contributors
+// Copyright (c) 2012-2016, Martin Angers & Contributors
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without modification,

expand.go

@@ -1,16 +1,13 @@
 package goquery
 
-import (
-	"github.com/andybalholm/cascadia"
-	"golang.org/x/net/html"
-)
+import "golang.org/x/net/html"
 
 // Add adds the selector string's matching nodes to those in the current
 // selection and returns a new Selection object.
 // The selector string is run in the context of the document of the current
 // Selection object.
 func (s *Selection) Add(selector string) *Selection {
-	return s.AddNodes(findWithMatcher([]*html.Node{s.document.rootNode}, cascadia.MustCompile(selector))...)
+	return s.AddNodes(findWithMatcher([]*html.Node{s.document.rootNode}, compileMatcher(selector))...)
 }
 
 // AddMatcher adds the matcher's matching nodes to those in the current

expand_test.go

@@ -9,6 +9,16 @@ func TestAdd(t *testing.T) {
 	assertLength(t, sel.Nodes, 19)
 }
 
+func TestAddInvalid(t *testing.T) {
+	sel1 := Doc().Find("div.row-fluid")
+	sel2 := sel1.Add("")
+	assertLength(t, sel1.Nodes, 9)
+	assertLength(t, sel2.Nodes, 9)
+	if sel1 == sel2 {
+		t.Errorf("selections should not be the same")
+	}
+}
+
 func TestAddRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-content")
 	sel2 := sel.Add("a").End()

filter.go

@@ -1,19 +1,16 @@
 package goquery
 
-import (
-	"github.com/andybalholm/cascadia"
-	"golang.org/x/net/html"
-)
+import "golang.org/x/net/html"
 
 // Filter reduces the set of matched elements to those that match the selector string.
 // It returns a new Selection object for this subset of matching elements.
 func (s *Selection) Filter(selector string) *Selection {
-	return s.FilterMatcher(cascadia.MustCompile(selector))
+	return s.FilterMatcher(compileMatcher(selector))
 }
 
 // FilterMatcher reduces the set of matched elements to those that match
-// the given matcher.
-// It returns a new Selection object for this subset of matching elements.
+// the given matcher. It returns a new Selection object for this subset
+// of matching elements.
 func (s *Selection) FilterMatcher(m Matcher) *Selection {
 	return pushStack(s, winnow(s, m, true))
 }
@@ -21,7 +18,7 @@ func (s *Selection) FilterMatcher(m Matcher) *Selection {
 // Not removes elements from the Selection that match the selector string.
 // It returns a new Selection object with the matching elements removed.
 func (s *Selection) Not(selector string) *Selection {
-	return s.NotMatcher(cascadia.MustCompile(selector))
+	return s.NotMatcher(compileMatcher(selector))
 }
 
 // NotMatcher removes elements from the Selection that match the given matcher.

filter_test.go

@@ -14,6 +14,11 @@ func TestFilterNone(t *testing.T) {
 	assertLength(t, sel.Nodes, 0)
 }
 
+func TestFilterInvalid(t *testing.T) {
+	sel := Doc().Find(".span12").Filter("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestFilterRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-content")
 	sel2 := sel.Filter(".alert").End()
@@ -74,6 +79,11 @@ func TestNot(t *testing.T) {
 	assertLength(t, sel.Nodes, 1)
 }
 
+func TestNotInvalid(t *testing.T) {
+	sel := Doc().Find(".span12").Not("")
+	assertLength(t, sel.Nodes, 2)
+}
+
 func TestNotRollback(t *testing.T) {
 	sel := Doc().Find(".span12")
 	sel2 := sel.Not(".alert").End()
@@ -145,6 +155,11 @@ func TestHas(t *testing.T) {
 	// Has() returns the high-level .container-fluid div, and the one that is the immediate parent of center-content
 }
 
+func TestHasInvalid(t *testing.T) {
+	sel := Doc().Find(".container-fluid").Has("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestHasRollback(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.Has(".center-content").End()

manipulation.go

@@ -3,7 +3,6 @@ package goquery
 import (
 	"strings"
 
-	"github.com/andybalholm/cascadia"
 	"golang.org/x/net/html"
 )
 
@@ -15,7 +14,7 @@ import (
 //
 // This follows the same rules as Selection.Append.
 func (s *Selection) After(selector string) *Selection {
-	return s.AfterMatcher(cascadia.MustCompile(selector))
+	return s.AfterMatcher(compileMatcher(selector))
 }
 
 // AfterMatcher applies the matcher from the root document and inserts the matched elements
@@ -66,7 +65,7 @@ func (s *Selection) AfterNodes(ns ...*html.Node) *Selection {
 // appended to all target locations except the last one, which will be moved
 // as noted in (2).
 func (s *Selection) Append(selector string) *Selection {
-	return s.AppendMatcher(cascadia.MustCompile(selector))
+	return s.AppendMatcher(compileMatcher(selector))
 }
 
 // AppendMatcher appends the elements specified by the matcher to the end of each element
@@ -103,7 +102,7 @@ func (s *Selection) AppendNodes(ns ...*html.Node) *Selection {
 //
 // This follows the same rules as Selection.Append.
 func (s *Selection) Before(selector string) *Selection {
-	return s.BeforeMatcher(cascadia.MustCompile(selector))
+	return s.BeforeMatcher(compileMatcher(selector))
 }
 
 // BeforeMatcher inserts the matched elements before each element in the set of matched elements.
@@ -165,7 +164,7 @@ func (s *Selection) Empty() *Selection {
 // Prepend prepends the elements specified by the selector to each element in
 // the set of matched elements, following the same rules as Append.
 func (s *Selection) Prepend(selector string) *Selection {
-	return s.PrependMatcher(cascadia.MustCompile(selector))
+	return s.PrependMatcher(compileMatcher(selector))
 }
 
 // PrependMatcher prepends the elements specified by the matcher to each
@@ -216,7 +215,7 @@ func (s *Selection) Remove() *Selection {
 // RemoveFiltered removes the set of matched elements by selector.
 // It returns the Selection of removed nodes.
 func (s *Selection) RemoveFiltered(selector string) *Selection {
-	return s.RemoveMatcher(cascadia.MustCompile(selector))
+	return s.RemoveMatcher(compileMatcher(selector))
 }
 
 // RemoveMatcher removes the set of matched elements.
@@ -231,7 +230,7 @@ func (s *Selection) RemoveMatcher(m Matcher) *Selection {
 //
 // This follows the same rules as Selection.Append.
 func (s *Selection) ReplaceWith(selector string) *Selection {
-	return s.ReplaceWithMatcher(cascadia.MustCompile(selector))
+	return s.ReplaceWithMatcher(compileMatcher(selector))
 }
 
 // ReplaceWithMatcher replaces each element in the set of matched elements with
@@ -293,7 +292,7 @@ func (s *Selection) Unwrap() *Selection {
 //
 // It returns the original set of elements.
 func (s *Selection) Wrap(selector string) *Selection {
-	return s.WrapMatcher(cascadia.MustCompile(selector))
+	return s.WrapMatcher(compileMatcher(selector))
 }
 
 // WrapMatcher wraps each element in the set of matched elements inside the
@@ -345,7 +344,7 @@ func (s *Selection) wrapNodes(ns ...*html.Node) *Selection {
 //
 // It returns the original set of elements.
 func (s *Selection) WrapAll(selector string) *Selection {
-	return s.WrapAllMatcher(cascadia.MustCompile(selector))
+	return s.WrapAllMatcher(compileMatcher(selector))
 }
 
 // WrapAllMatcher wraps a single HTML structure, matched by the given Matcher,
@@ -415,7 +414,7 @@ func (s *Selection) WrapAllNode(n *html.Node) *Selection {
 //
 // It returns the original set of elements.
 func (s *Selection) WrapInner(selector string) *Selection {
-	return s.WrapInnerMatcher(cascadia.MustCompile(selector))
+	return s.WrapInnerMatcher(compileMatcher(selector))
 }
 
 // WrapInnerMatcher wraps an HTML structure, matched by the given selector,

query.go

@@ -1,15 +1,12 @@
 package goquery
 
-import (
-	"github.com/andybalholm/cascadia"
-	"golang.org/x/net/html"
-)
+import "golang.org/x/net/html"
 
 // Is checks the current matched set of elements against a selector and
 // returns true if at least one of these elements matches.
 func (s *Selection) Is(selector string) bool {
 	if len(s.Nodes) > 0 {
-		return s.IsMatcher(cascadia.MustCompile(selector))
+		return s.IsMatcher(compileMatcher(selector))
 	}
 
 	return false

query_test.go

@@ -11,6 +11,13 @@ func TestIs(t *testing.T) {
 	}
 }
 
+func TestIsInvalid(t *testing.T) {
+	sel := Doc().Find(".footer p:nth-child(1)")
+	if sel.Is("") {
+		t.Error("Is should not succeed with invalid selector string")
+	}
+}
+
 func TestIsPositional(t *testing.T) {
 	sel := Doc().Find(".footer p:nth-child(2)")
 	if !sel.Is("p:nth-child(2)") {

traversal.go

@@ -1,9 +1,6 @@
 package goquery
 
-import (
-	"github.com/andybalholm/cascadia"
-	"golang.org/x/net/html"
-)
+import "golang.org/x/net/html"
 
 type siblingType int
 
@@ -24,7 +21,7 @@ const (
 // elements, filtered by a selector. It returns a new Selection object
 // containing these matched elements.
 func (s *Selection) Find(selector string) *Selection {
-	return pushStack(s, findWithMatcher(s.Nodes, cascadia.MustCompile(selector)))
+	return pushStack(s, findWithMatcher(s.Nodes, compileMatcher(selector)))
 }
 
 // FindMatcher gets the descendants of each element in the current set of matched
@@ -93,7 +90,7 @@ func (s *Selection) Children() *Selection {
 // filtered by the specified selector. It returns a new
 // Selection object containing these elements.
 func (s *Selection) ChildrenFiltered(selector string) *Selection {
-	return filterAndPush(s, getChildrenNodes(s.Nodes, siblingAll), cascadia.MustCompile(selector))
+	return filterAndPush(s, getChildrenNodes(s.Nodes, siblingAll), compileMatcher(selector))
 }
 
 // ChildrenMatcher gets the child elements of each element in the Selection,
@@ -112,7 +109,7 @@ func (s *Selection) Parent() *Selection {
 // ParentFiltered gets the parent of each element in the Selection filtered by a
 // selector. It returns a new Selection object containing the matched elements.
 func (s *Selection) ParentFiltered(selector string) *Selection {
-	return filterAndPush(s, getParentNodes(s.Nodes), cascadia.MustCompile(selector))
+	return filterAndPush(s, getParentNodes(s.Nodes), compileMatcher(selector))
 }
 
 // ParentMatcher gets the parent of each element in the Selection filtered by a
@@ -124,7 +121,7 @@ func (s *Selection) ParentMatcher(m Matcher) *Selection {
 // Closest gets the first element that matches the selector by testing the
 // element itself and traversing up through its ancestors in the DOM tree.
 func (s *Selection) Closest(selector string) *Selection {
-	cs := cascadia.MustCompile(selector)
+	cs := compileMatcher(selector)
 	return s.ClosestMatcher(cs)
 }
 
@@ -177,7 +174,7 @@ func (s *Selection) Parents() *Selection {
 // ParentsFiltered gets the ancestors of each element in the current
 // Selection. It returns a new Selection object with the matched elements.
 func (s *Selection) ParentsFiltered(selector string) *Selection {
-	return filterAndPush(s, getParentsNodes(s.Nodes, nil, nil), cascadia.MustCompile(selector))
+	return filterAndPush(s, getParentsNodes(s.Nodes, nil, nil), compileMatcher(selector))
 }
 
 // ParentsMatcher gets the ancestors of each element in the current
@@ -190,7 +187,7 @@ func (s *Selection) ParentsMatcher(m Matcher) *Selection {
 // not including the element matched by the selector. It returns a new Selection
 // object containing the matched elements.
 func (s *Selection) ParentsUntil(selector string) *Selection {
-	return pushStack(s, getParentsNodes(s.Nodes, cascadia.MustCompile(selector), nil))
+	return pushStack(s, getParentsNodes(s.Nodes, compileMatcher(selector), nil))
 }
 
 // ParentsUntilMatcher gets the ancestors of each element in the Selection, up to but
@@ -221,7 +218,7 @@ func (s *Selection) ParentsUntilNodes(nodes ...*html.Node) *Selection {
 // results based on a selector string. It returns a new Selection
 // object containing the matched elements.
 func (s *Selection) ParentsFilteredUntil(filterSelector, untilSelector string) *Selection {
-	return filterAndPush(s, getParentsNodes(s.Nodes, cascadia.MustCompile(untilSelector), nil), cascadia.MustCompile(filterSelector))
+	return filterAndPush(s, getParentsNodes(s.Nodes, compileMatcher(untilSelector), nil), compileMatcher(filterSelector))
 }
 
 // ParentsFilteredUntilMatcher is like ParentsUntilMatcher, with the option to filter the
@@ -234,7 +231,7 @@ func (s *Selection) ParentsFilteredUntilMatcher(filter, until Matcher) *Selectio
 // option to filter the results based on a selector string. It returns a new
 // Selection object containing the matched elements.
 func (s *Selection) ParentsFilteredUntilSelection(filterSelector string, sel *Selection) *Selection {
-	return s.ParentsMatcherUntilSelection(cascadia.MustCompile(filterSelector), sel)
+	return s.ParentsMatcherUntilSelection(compileMatcher(filterSelector), sel)
 }
 
 // ParentsMatcherUntilSelection is like ParentsUntilSelection, with the
@@ -251,7 +248,7 @@ func (s *Selection) ParentsMatcherUntilSelection(filter Matcher, sel *Selection)
 // option to filter the results based on a selector string. It returns a new
 // Selection object containing the matched elements.
 func (s *Selection) ParentsFilteredUntilNodes(filterSelector string, nodes ...*html.Node) *Selection {
-	return filterAndPush(s, getParentsNodes(s.Nodes, nil, nodes), cascadia.MustCompile(filterSelector))
+	return filterAndPush(s, getParentsNodes(s.Nodes, nil, nodes), compileMatcher(filterSelector))
 }
 
 // ParentsMatcherUntilNodes is like ParentsUntilNodes, with the
@@ -271,7 +268,7 @@ func (s *Selection) Siblings() *Selection {
 // filtered by a selector. It returns a new Selection object containing the
 // matched elements.
 func (s *Selection) SiblingsFiltered(selector string) *Selection {
-	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingAll, nil, nil), cascadia.MustCompile(selector))
+	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingAll, nil, nil), compileMatcher(selector))
 }
 
 // SiblingsMatcher gets the siblings of each element in the Selection
@@ -291,7 +288,7 @@ func (s *Selection) Next() *Selection {
 // Selection filtered by a selector. It returns a new Selection object
 // containing the matched elements.
 func (s *Selection) NextFiltered(selector string) *Selection {
-	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingNext, nil, nil), cascadia.MustCompile(selector))
+	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingNext, nil, nil), compileMatcher(selector))
 }
 
 // NextMatcher gets the immediately following sibling of each element in the
@@ -311,7 +308,7 @@ func (s *Selection) NextAll() *Selection {
 // Selection filtered by a selector. It returns a new Selection object
 // containing the matched elements.
 func (s *Selection) NextAllFiltered(selector string) *Selection {
-	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingNextAll, nil, nil), cascadia.MustCompile(selector))
+	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingNextAll, nil, nil), compileMatcher(selector))
 }
 
 // NextAllMatcher gets all the following siblings of each element in the
@@ -331,7 +328,7 @@ func (s *Selection) Prev() *Selection {
 // Selection filtered by a selector. It returns a new Selection object
 // containing the matched elements.
 func (s *Selection) PrevFiltered(selector string) *Selection {
-	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingPrev, nil, nil), cascadia.MustCompile(selector))
+	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingPrev, nil, nil), compileMatcher(selector))
 }
 
 // PrevMatcher gets the immediately preceding sibling of each element in the
@@ -351,7 +348,7 @@ func (s *Selection) PrevAll() *Selection {
 // Selection filtered by a selector. It returns a new Selection object
 // containing the matched elements.
 func (s *Selection) PrevAllFiltered(selector string) *Selection {
-	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingPrevAll, nil, nil), cascadia.MustCompile(selector))
+	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingPrevAll, nil, nil), compileMatcher(selector))
 }
 
 // PrevAllMatcher gets all the preceding siblings of each element in the
@@ -366,7 +363,7 @@ func (s *Selection) PrevAllMatcher(m Matcher) *Selection {
 // object containing the matched elements.
 func (s *Selection) NextUntil(selector string) *Selection {
 	return pushStack(s, getSiblingNodes(s.Nodes, siblingNextUntil,
-		cascadia.MustCompile(selector), nil))
+		compileMatcher(selector), nil))
 }
 
 // NextUntilMatcher gets all following siblings of each element up to but not
@@ -400,7 +397,7 @@ func (s *Selection) NextUntilNodes(nodes ...*html.Node) *Selection {
 // object containing the matched elements.
 func (s *Selection) PrevUntil(selector string) *Selection {
 	return pushStack(s, getSiblingNodes(s.Nodes, siblingPrevUntil,
-		cascadia.MustCompile(selector), nil))
+		compileMatcher(selector), nil))
 }
 
 // PrevUntilMatcher gets all preceding siblings of each element up to but not
@@ -434,7 +431,7 @@ func (s *Selection) PrevUntilNodes(nodes ...*html.Node) *Selection {
 // It returns a new Selection object containing the matched elements.
 func (s *Selection) NextFilteredUntil(filterSelector, untilSelector string) *Selection {
 	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingNextUntil,
-		cascadia.MustCompile(untilSelector), nil), cascadia.MustCompile(filterSelector))
+		compileMatcher(untilSelector), nil), compileMatcher(filterSelector))
 }
 
 // NextFilteredUntilMatcher is like NextUntilMatcher, with the option to filter
@@ -449,7 +446,7 @@ func (s *Selection) NextFilteredUntilMatcher(filter, until Matcher) *Selection {
 // option to filter the results based on a selector string. It returns a new
 // Selection object containing the matched elements.
 func (s *Selection) NextFilteredUntilSelection(filterSelector string, sel *Selection) *Selection {
-	return s.NextMatcherUntilSelection(cascadia.MustCompile(filterSelector), sel)
+	return s.NextMatcherUntilSelection(compileMatcher(filterSelector), sel)
 }
 
 // NextMatcherUntilSelection is like NextUntilSelection, with the
@@ -467,7 +464,7 @@ func (s *Selection) NextMatcherUntilSelection(filter Matcher, sel *Selection) *S
 // Selection object containing the matched elements.
 func (s *Selection) NextFilteredUntilNodes(filterSelector string, nodes ...*html.Node) *Selection {
 	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingNextUntil,
-		nil, nodes), cascadia.MustCompile(filterSelector))
+		nil, nodes), compileMatcher(filterSelector))
 }
 
 // NextMatcherUntilNodes is like NextUntilNodes, with the
@@ -483,7 +480,7 @@ func (s *Selection) NextMatcherUntilNodes(filter Matcher, nodes ...*html.Node) *
 // It returns a new Selection object containing the matched elements.
 func (s *Selection) PrevFilteredUntil(filterSelector, untilSelector string) *Selection {
 	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingPrevUntil,
-		cascadia.MustCompile(untilSelector), nil), cascadia.MustCompile(filterSelector))
+		compileMatcher(untilSelector), nil), compileMatcher(filterSelector))
 }
 
 // PrevFilteredUntilMatcher is like PrevUntilMatcher, with the option to filter
@@ -498,7 +495,7 @@ func (s *Selection) PrevFilteredUntilMatcher(filter, until Matcher) *Selection {
 // option to filter the results based on a selector string. It returns a new
 // Selection object containing the matched elements.
 func (s *Selection) PrevFilteredUntilSelection(filterSelector string, sel *Selection) *Selection {
-	return s.PrevMatcherUntilSelection(cascadia.MustCompile(filterSelector), sel)
+	return s.PrevMatcherUntilSelection(compileMatcher(filterSelector), sel)
 }
 
 // PrevMatcherUntilSelection is like PrevUntilSelection, with the
@@ -516,7 +513,7 @@ func (s *Selection) PrevMatcherUntilSelection(filter Matcher, sel *Selection) *S
 // Selection object containing the matched elements.
 func (s *Selection) PrevFilteredUntilNodes(filterSelector string, nodes ...*html.Node) *Selection {
 	return filterAndPush(s, getSiblingNodes(s.Nodes, siblingPrevUntil,
-		nil, nodes), cascadia.MustCompile(filterSelector))
+		nil, nodes), compileMatcher(filterSelector))
 }
 
 // PrevMatcherUntilNodes is like PrevUntilNodes, with the

traversal_test.go

@@ -21,9 +21,9 @@ func TestFindNotSelf(t *testing.T) {
 	assertLength(t, sel.Nodes, 0)
 }
 
-func TestFindInvalidSelector(t *testing.T) {
-	defer assertPanic(t)
-	Doc().Find(":+ ^")
+func TestFindInvalid(t *testing.T) {
+	sel := Doc().Find(":+ ^")
+	assertLength(t, sel.Nodes, 0)
 }
 
 func TestChainedFind(t *testing.T) {
@@ -31,6 +31,11 @@ func TestChainedFind(t *testing.T) {
 	assertLength(t, sel.Nodes, 4)
 }
 
+func TestChainedFindInvalid(t *testing.T) {
+	sel := Doc().Find("div.hero-unit").Find("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestChildren(t *testing.T) {
 	sel := Doc().Find(".pvk-content").Children()
 	assertLength(t, sel.Nodes, 5)
@@ -58,6 +63,11 @@ func TestChildrenFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 1)
 }
 
+func TestChildrenFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".pvk-content").ChildrenFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestChildrenFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-content")
 	sel2 := sel.ChildrenFiltered(".hero-unit").End()
@@ -69,6 +79,11 @@ func TestContentsFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 1)
 }
 
+func TestContentsFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".pvk-content").ContentsFiltered("~")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestContentsFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-content")
 	sel2 := sel.ContentsFiltered(".hero-unit").End()
@@ -102,6 +117,11 @@ func TestParentFiltered(t *testing.T) {
 	assertClass(t, sel, "hero-unit")
 }
 
+func TestParentFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".container-fluid").ParentFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestParentFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.ParentFiltered(".hero-unit").End()
@@ -130,6 +150,11 @@ func TestParentsFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 1)
 }
 
+func TestParentsFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".container-fluid").ParentsFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestParentsFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.ParentsFiltered("body").End()
@@ -141,6 +166,11 @@ func TestParentsUntil(t *testing.T) {
 	assertLength(t, sel.Nodes, 6)
 }
 
+func TestParentsUntilInvalid(t *testing.T) {
+	sel := Doc().Find(".container-fluid").ParentsUntil("")
+	assertLength(t, sel.Nodes, 8)
+}
+
 func TestParentsUntilRollback(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.ParentsUntil("body").End()
@@ -180,6 +210,11 @@ func TestParentsFilteredUntil(t *testing.T) {
 	assertLength(t, sel.Nodes, 2)
 }
 
+func TestParentsFilteredUntilInvalid(t *testing.T) {
+	sel := Doc().Find(".container-fluid").ParentsFilteredUntil("", "")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestParentsFilteredUntilRollback(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.ParentsFilteredUntil(".pvk-content", "body").End()
@@ -240,6 +275,11 @@ func TestSiblingsFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 3)
 }
 
+func TestSiblingsFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".pvk-gutter").SiblingsFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestSiblingsFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-gutter")
 	sel2 := sel.SiblingsFiltered(".pvk-content").End()
@@ -272,6 +312,11 @@ func TestNextFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 2)
 }
 
+func TestNextFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".container-fluid").NextFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestNextFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.NextFiltered("div").End()
@@ -310,6 +355,11 @@ func TestPrevFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 5)
 }
 
+func TestPrevFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".row-fluid").PrevFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestPrevFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".row-fluid")
 	sel2 := sel.PrevFiltered(".row-fluid").End()
@@ -342,6 +392,11 @@ func TestNextAllFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 2)
 }
 
+func TestNextAllFilteredInvalid(t *testing.T) {
+	sel := Doc().Find("#cf2 .row-fluid").NextAllFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestNextAllFilteredRollback(t *testing.T) {
 	sel := Doc().Find("#cf2 .row-fluid")
 	sel2 := sel.NextAllFiltered("[ng-cloak]").End()
@@ -380,6 +435,11 @@ func TestPrevAllFiltered(t *testing.T) {
 	assertLength(t, sel.Nodes, 3)
 }
 
+func TestPrevAllFilteredInvalid(t *testing.T) {
+	sel := Doc().Find(".pvk-gutter").PrevAllFiltered("")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestPrevAllFilteredRollback(t *testing.T) {
 	sel := Doc().Find(".pvk-gutter")
 	sel2 := sel.PrevAllFiltered(".pvk-content").End()
@@ -392,6 +452,11 @@ func TestNextUntil(t *testing.T) {
 	assertSelectionIs(t, sel, "h4")
 }
 
+func TestNextUntilInvalid(t *testing.T) {
+	sel := Doc().Find(".alert a").NextUntil("")
+	assertLength(t, sel.Nodes, 2)
+}
+
 func TestNextUntil2(t *testing.T) {
 	sel := Doc().Find("#cf2-1").NextUntil("[ng-cloak]")
 	assertLength(t, sel.Nodes, 1)
@@ -446,6 +511,11 @@ func TestPrevUntil(t *testing.T) {
 	assertSelectionIs(t, sel, "h4")
 }
 
+func TestPrevUntilInvalid(t *testing.T) {
+	sel := Doc().Find(".alert p").PrevUntil("")
+	assertLength(t, sel.Nodes, 2)
+}
+
 func TestPrevUntil2(t *testing.T) {
 	sel := Doc().Find("[ng-cloak]").PrevUntil(":not([ng-cloak])")
 	assertLength(t, sel.Nodes, 1)
@@ -500,6 +570,11 @@ func TestNextFilteredUntil(t *testing.T) {
 	assertSelectionIs(t, sel, "#n3", "#n5", "#nf3", "#nf5")
 }
 
+func TestNextFilteredUntilInvalid(t *testing.T) {
+	sel := Doc2().Find(".two").NextFilteredUntil("", "")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestNextFilteredUntilRollback(t *testing.T) {
 	sel := Doc2().Find(".two")
 	sel2 := sel.NextFilteredUntil(".even", ".six").End()
@@ -542,6 +617,11 @@ func TestPrevFilteredUntil(t *testing.T) {
 	assertSelectionIs(t, sel, "#n4", "#n2", "#nf4", "#nf2")
 }
 
+func TestPrevFilteredUntilInvalid(t *testing.T) {
+	sel := Doc2().Find(".five").PrevFilteredUntil("", "")
+	assertLength(t, sel.Nodes, 0)
+}
+
 func TestPrevFilteredUntilRollback(t *testing.T) {
 	sel := Doc2().Find(".four")
 	sel2 := sel.PrevFilteredUntil(".odd", ".one").End()
@@ -598,6 +678,12 @@ func TestClosestNone(t *testing.T) {
 	assertLength(t, sel2.Nodes, 0)
 }
 
+func TestClosestInvalid(t *testing.T) {
+	sel := Doc().Find("h4")
+	sel2 := sel.Closest("")
+	assertLength(t, sel2.Nodes, 0)
+}
+
 func TestClosestMany(t *testing.T) {
 	sel := Doc().Find(".container-fluid")
 	sel2 := sel.Closest(".pvk-content")

type.go

@@ -6,6 +6,8 @@ import (
 	"net/http"
 	"net/url"
 
+	"github.com/andybalholm/cascadia"
+
 	"golang.org/x/net/html"
 )
 
@@ -113,3 +115,21 @@ type Matcher interface {
 	MatchAll(*html.Node) []*html.Node
 	Filter([]*html.Node) []*html.Node
 }
+
+// compileMatcher compiles the selector string s and returns
+// the corresponding Matcher. If s is an invalid selector string,
+// it returns a Matcher that fails all matches.
+func compileMatcher(s string) Matcher {
+	cs, err := cascadia.Compile(s)
+	if err != nil {
+		return invalidMatcher{}
+	}
+	return cs
+}
+
+// invalidMatcher is a Matcher that always fails to match.
+type invalidMatcher struct{}
+
+func (invalidMatcher) Match(n *html.Node) bool             { return false }
+func (invalidMatcher) MatchAll(n *html.Node) []*html.Node  { return nil }
+func (invalidMatcher) Filter(ns []*html.Node) []*html.Node { return nil }

type_test.go

@@ -108,6 +108,19 @@ func printSel(t *testing.T, sel *Selection) {
 	}
 }
 
+func shortPrintSel(t *testing.T, sel *Selection) {
+	sel.Each(func(i int, s *Selection) {
+		h, _ := OuterHtml(s)
+		if ix := strings.Index(h, "\n"); ix >= 0 {
+			h = h[:ix]
+		}
+		if len(h) > 100 {
+			h = h[:100]
+		}
+		fmt.Println(i, ">>> ", h)
+	})
+}
+
 func loadDoc(page string) *Document {
 	var f *os.File
 	var e error