tpl/transform: Optional options for highlight func

Closes #9249
Fixes gohugoio/hugoDocs#63

tpl/transform/transform.go

@@ -59,13 +59,21 @@ func (ns *Namespace) Emojify(s interface{}) (template.HTML, error) {
 
 // Highlight returns a copy of s as an HTML string with syntax
 // highlighting applied.
-func (ns *Namespace) Highlight(s interface{}, lang, opts string) (template.HTML, error) {
+func (ns *Namespace) Highlight(s interface{}, lang string, opts ...interface{}) (template.HTML, error) {
 	ss, err := cast.ToStringE(s)
 	if err != nil {
 		return "", err
 	}
 
-	highlighted, _ := ns.deps.ContentSpec.Converters.Highlight(ss, lang, opts)
+	sopts := ""
+	if len(opts) > 0 {
+		sopts, err = cast.ToStringE(opts[0])
+		if err != nil {
+			return "", err
+		}
+	}
+
+	highlighted, _ := ns.deps.ContentSpec.Converters.Highlight(ss, lang, sopts)
 	return template.HTML(highlighted), nil
 }
 

tpl/transform/transform_test.go

@@ -26,7 +26,6 @@ import (
 	"github.com/gohugoio/hugo/helpers"
 	"github.com/gohugoio/hugo/hugofs"
 	"github.com/gohugoio/hugo/langs"
-	
 )
 
 type tstNoStringer struct{}
@@ -71,10 +70,11 @@ func TestHighlight(t *testing.T) {
 	for _, test := range []struct {
 		s      interface{}
 		lang   string
-		opts   string
+		opts   interface{}
 		expect interface{}
 	}{
 		{"func boo() {}", "go", "", "boo"},
+		{"func boo() {}", "go", nil, "boo"},
 		// Issue #4179
 		{`<Foo attr=" &lt; "></Foo>`, "xml", "", `&amp;lt;`},
 		{tstNoStringer{}, "go", "", false},