tpl/transform: Display Chroma highlighting errors

Closes #9642

tpl/transform/integration_test.go

@@ -16,6 +16,7 @@ package transform_test
 import (
 	"testing"
 
+	qt "github.com/frankban/quicktest"
 	"github.com/gohugoio/hugo/hugolib"
 )
 
@@ -85,3 +86,24 @@ a **b**  c
 	<description>&lt;p&gt;a &lt;strong&gt;b&lt;/strong&gt;  c&lt;/p&gt;</description>
 	`)
 }
+
+// Issue #9642
+func TestHighlightError(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+-- layouts/index.html --
+{{ highlight "a" "b" 0 }}
+  `
+	b := hugolib.NewIntegrationTestBuilder(
+		hugolib.IntegrationTestConfig{
+			T:           t,
+			TxtarString: files,
+		},
+	)
+
+	_, err := b.BuildE()
+	b.Assert(err.Error(), qt.Contains, "error calling highlight: invalid Highlight option: 0")
+}

tpl/transform/transform.go

@@ -79,7 +79,10 @@ func (ns *Namespace) Highlight(s any, lang string, opts ...any) (template.HTML,
 	}
 
 	hl := ns.deps.ContentSpec.Converters.GetHighlighter()
-	highlighted, _ := hl.Highlight(ss, lang, optsv)
+	highlighted, err := hl.Highlight(ss, lang, optsv)
+	if err != nil {
+		return "", err
+	}
 	return template.HTML(highlighted), nil
 }