adds support for nested map options:

{data: {remote: true, method: "PUT"}}
<data-remote="true" data-method="PUT">

options.go

@@ -12,18 +12,27 @@ type Options map[string]interface{}
 
 func (o Options) String() string {
 	var out = make([]string, 0, len(o))
-	var tmp = make([]string, 2)
 	for k, v := range o {
-		tmp[0] = template.HTMLEscaper(k)
-		if v != nil {
-			tmp[1] = fmt.Sprintf("\"%s\"", template.HTMLEscaper(v))
-			out = append(out, strings.Join(tmp, "="))
-		} else {
-			// nil attribute value is interpreted as empty attribute notation
-			// https://www.w3.org/TR/html5/syntax.html#elements-attributes
-			out = append(out, tmp[0])
+		if m, ok := v.(map[string]interface{}); ok {
+			for mk, mv := range m {
+				out = append(out, kv(fmt.Sprintf("%s-%s", k, mk), mv))
+			}
+			continue
 		}
+		out = append(out, kv(k, v))
 	}
 	sort.Strings(out)
 	return strings.Join(out, " ")
 }
+
+func kv(k string, v interface{}) string {
+	var tmp = make([]string, 2)
+	tmp[0] = template.HTMLEscaper(k)
+	if v != nil {
+		tmp[1] = fmt.Sprintf("\"%s\"", template.HTMLEscaper(v))
+		return strings.Join(tmp, "=")
+	}
+	// nil attribute value is interpreted as empty attribute notation
+	// https://www.w3.org/TR/html5/syntax.html#elements-attributes
+	return tmp[0]
+}

options_test.go

@@ -36,3 +36,18 @@ func Test_Options_String_Empty_Attribute(t *testing.T) {
 	s := o.String()
 	r.Equal(`checked value="Mark"`, s)
 }
+
+func Test_Options_Data_Map(t *testing.T) {
+	r := require.New(t)
+	o := tags.Options{
+		"value": "Mark",
+		"id":    "foo-bar",
+		"class": "foo bar baz",
+		"data": map[string]interface{}{
+			"remote": true,
+			"method": "PUT",
+		},
+	}
+	s := o.String()
+	r.Equal(`class="foo bar baz" data-method="PUT" data-remote="true" id="foo-bar" value="Mark"`, s)
+}