path: add text filters

It is now possible to use a path filter like [text()='val'] to
select elements whose text matches a string.

2 files changed, 31 insertions, 2 deletions

diff --git a/path.go b/path.go
index 126eb15..f200332 100644
--- a/path.go
+++ b/path.go
@@ -25,7 +25,8 @@ only the following limited syntax is supported:
     [@attrib='val'] Selects all elements with the given attribute set to val
     [tag]           Selects all elements with a child element named tag
     [tag='val']     Selects all elements with a child element named tag
-                      and text equal to val
+                      and text matching val
+    [text()='val']  Selects all elements whose text matches val
 
 Examples:
 
@@ -41,9 +42,14 @@ Starting from the current element, select all children of book elements
 with an attribute 'language' set to 'english':
     ./book/*[@language='english']
 
+Starting from the current element, select all children of book elements
+containing the text 'special':
+    ./book/*[text()='special']
+
 Select all descendant book elements whose title element has an attribute
 'language' set to 'french':
     //book/title[@language='french']/..
+
 */
 type Path struct {
 	segments []segment
@@ -254,7 +260,7 @@ func (c *compiler) parseFilter(path string) filter {
 		return nil
 	}
 
-	// Filter contains [@attr='val'] or [tag='val']?
+	// Filter contains [@attr='val'], [text()='val'], or [tag='val']?
 	eqindex := strings.Index(path, "='")
 	if eqindex >= 0 {
 		rindex := nextIndex(path, "'", eqindex+2)
@@ -265,6 +271,8 @@ func (c *compiler) parseFilter(path string) filter {
 		switch {
 		case path[0] == '@':
 			return newFilterAttrVal(path[1:eqindex], path[eqindex+2:rindex])
+		case strings.HasPrefix(path, "text()"):
+			return newFilterTextVal(path[eqindex+2 : rindex])
 		default:
 			return newFilterChildText(path[:eqindex], path[eqindex+2:rindex])
 		}
@@ -420,6 +428,25 @@ func (f *filterAttrVal) apply(p *pather) {
 	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
 }
 
+// filterTextVal filters the candidate list for elements having
+// text equal to the specified value.
+type filterTextVal struct {
+	val string
+}
+
+func newFilterTextVal(value string) *filterTextVal {
+	return &filterTextVal{value}
+}
+
+func (f *filterTextVal) apply(p *pather) {
+	for _, c := range p.candidates {
+		if c.Text() == f.val {
+			p.scratch = append(p.scratch, c)
+		}
+	}
+	p.candidates, p.scratch = p.scratch, p.candidates[0:0]
+}
+
 // filterChild filters the candidate list for elements having
 // a child element with the specified tag.
 type filterChild struct {
diff --git a/path_test.go b/path_test.go
index 60abf57..12a4e21 100644
--- a/path_test.go
+++ b/path_test.go
@@ -93,6 +93,8 @@ var tests = []test{
 	{"./bookstore/book[author='Vaidyanathan Nagarajan']/title", "XQuery Kick Start"},
 	{"//book[p:price='29.99']/title", "Harry Potter"},
 	{"//book[price='29.99']/title", "Harry Potter"},
+	{"//book/price[text()='29.99']", "29.99"},
+	{"//book/author[text()='Kurt Cagle']", "Kurt Cagle"},
 
 	// attribute queries
 	{"./bookstore/book[@category='WEB']/title", []string{"XQuery Kick Start", "Learning XML"}},