Allow default block for contentOf (#61)

content_helper.go

@@ -38,7 +38,20 @@ func contentForHelper(name string, help HelperContext) {
 func contentOfHelper(name string, data map[string]interface{}, help HelperContext) (template.HTML, error) {
 	fn, ok := help.Value("contentFor:" + name).(func(data map[string]interface{}) (template.HTML, error))
 	if !ok {
-		return template.HTML(""), errors.WithStack(errors.New("missing contentOf block: " + name))
+		if !help.HasBlock() {
+			return template.HTML(""), errors.WithStack(errors.New("missing contentOf block: " + name))
+		}
+
+		ctx := help.New()
+		for k, v := range data {
+			ctx.Set(k, v)
+		}
+		body, err := help.BlockWith(ctx)
+		if err != nil {
+			return template.HTML(""), errors.WithStack(err)
+		}
+
+		return template.HTML(body), nil
 	}
 	return fn(data)
 }

content_helper_test.go

@@ -47,3 +47,33 @@ func Test_ContentForOf_MissingBlock(t *testing.T) {
 	_, err := Render(input, NewContext())
 	r.EqualError(err, "line 2: missing contentOf block: buttons")
 }
+
+func Test_ContentForOf_MissingBlock_DefaultBlock(t *testing.T) {
+	r := require.New(t)
+	input := `
+	<b0><%= contentOf("my-block") { %>default<% } %></b0>
+	`
+	s, err := Render(input, NewContext())
+	r.NoError(err)
+	r.Contains(s, "<b0>default</b0>")
+}
+
+func Test_ContentForOf_MissingBlock_NoBlockContent(t *testing.T) {
+	r := require.New(t)
+	input := `
+	<b0><%= contentOf("buttons") %></b0>
+	`
+	_, err := Render(input, NewContext())
+	r.EqualError(err, "line 2: missing contentOf block: buttons")
+}
+
+func Test_ContentForOf_DefaultBlock(t *testing.T) {
+	r := require.New(t)
+	input := `
+	<b0><% contentFor("buttons") { %>custom<% } %></b0>
+	<b0><%= contentOf("buttons") { %>default<% } %></b0>
+	`
+	s, err := Render(input, NewContext())
+	r.NoError(err)
+	r.Contains(s, "<b0>custom</b0>")
+}