hugolib: Extend the sections API

This commit adds some section related methods that have been asked for:

* .CurrentSection
* .IsDescendant
* .IsAncestor

Fixes #3591

helpers/general.go

@@ -194,6 +194,38 @@ func ReaderContains(r io.Reader, subslice []byte) bool {
 	return false
 }
 
+// HasStringsPrefix tests whether the string slice s begins with prefix slice s.
+func HasStringsPrefix(s, prefix []string) bool {
+	return len(s) >= len(prefix) && compareStringSlices(s[0:len(prefix)], prefix)
+}
+
+// HasStringsSuffix tests whether the string slice s ends with suffix slice s.
+func HasStringsSuffix(s, suffix []string) bool {
+	return len(s) >= len(suffix) && compareStringSlices(s[len(s)-len(suffix):], suffix)
+}
+
+func compareStringSlices(a, b []string) bool {
+	if a == nil && b == nil {
+		return true
+	}
+
+	if a == nil || b == nil {
+		return false
+	}
+
+	if len(a) != len(b) {
+		return false
+	}
+
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+
+	return true
+}
+
 // ThemeSet checks whether a theme is in use or not.
 func (p *PathSpec) ThemeSet() bool {
 	return p.theme != ""

helpers/general_test.go

@@ -64,6 +64,45 @@ func TestFirstUpper(t *testing.T) {
 	}
 }
 
+func TestHasStringsPrefix(t *testing.T) {
+	for i, this := range []struct {
+		s      []string
+		prefix []string
+		expect bool
+	}{
+		{[]string{"a"}, []string{"a"}, true},
+		{[]string{}, []string{}, true},
+		{[]string{"a", "b", "c"}, []string{"a", "b"}, true},
+		{[]string{"d", "a", "b", "c"}, []string{"a", "b"}, false},
+		{[]string{"abra", "ca", "dabra"}, []string{"abra", "ca"}, true},
+		{[]string{"abra", "ca"}, []string{"abra", "ca", "dabra"}, false},
+	} {
+		result := HasStringsPrefix(this.s, this.prefix)
+		if result != this.expect {
+			t.Fatalf("[%d] got %t but expected %t", i, result, this.expect)
+		}
+	}
+}
+
+func TestHasStringsSuffix(t *testing.T) {
+	for i, this := range []struct {
+		s      []string
+		suffix []string
+		expect bool
+	}{
+		{[]string{"a"}, []string{"a"}, true},
+		{[]string{}, []string{}, true},
+		{[]string{"a", "b", "c"}, []string{"b", "c"}, true},
+		{[]string{"abra", "ca", "dabra"}, []string{"abra", "ca"}, false},
+		{[]string{"abra", "ca", "dabra"}, []string{"ca", "dabra"}, true},
+	} {
+		result := HasStringsSuffix(this.s, this.suffix)
+		if result != this.expect {
+			t.Fatalf("[%d] got %t but expected %t", i, result, this.expect)
+		}
+	}
+}
+
 var containsTestText = (`На берегу пустынных волн
 Стоял он, дум великих полн,
 И вдаль глядел. Пред ним широко