feat: support templating map struct fields whose map values are also map

structtemplater.go

@@ -1,6 +1,7 @@
 package gomplate
 
 import (
+	"encoding/json"
 	"reflect"
 	"strings"
 
@@ -60,13 +61,34 @@ func (w StructTemplater) StructField(f reflect.StructField, v reflect.Value) err
 					return err
 				}
 
-				if val.Kind() == reflect.String {
-					newVal, err := w.Template(val.String())
+				concreteVal := reflect.ValueOf(val.Interface())
+				switch concreteVal.Kind() {
+				case reflect.String:
+					newVal, err := w.Template(concreteVal.String())
 					if err != nil {
 						return err
 					}
 					newMap.SetMapIndex(newKey, reflect.ValueOf(newVal))
-				} else {
+
+				case reflect.Map:
+					marshalled, err := json.Marshal(val.Interface())
+					if err != nil {
+						newMap.SetMapIndex(newKey, val)
+					} else {
+						templated, err := w.Template(string(marshalled))
+						if err != nil {
+							return err
+						}
+
+						var unmarshalled map[string]any
+						if err := json.Unmarshal([]byte(templated), &unmarshalled); err != nil {
+							newMap.SetMapIndex(newKey, val)
+						} else {
+							newMap.SetMapIndex(newKey, reflect.ValueOf(unmarshalled))
+						}
+					}
+
+				default:
 					newMap.SetMapIndex(newKey, val)
 				}
 			}

structtemplater_test.go

@@ -10,6 +10,7 @@ type Test struct {
 	Template   string `template:"true"`
 	NoTemplate string
 	Inner      Inner
+	JSONMap    map[string]any    `template:"true"`
 	Labels     map[string]string `template:"true"`
 	LabelsRaw  map[string]string
 }
@@ -108,6 +109,48 @@ var tests = []test{
 			},
 		},
 	},
+	{
+		name: "deeply nested map",
+		StructTemplater: StructTemplater{
+			RequiredTag:    "template",
+			ValueFunctions: true,
+			Values: map[string]interface{}{
+				"msg": "world",
+			},
+		},
+		Input: &Test{
+			Template: "{{msg}}",
+			JSONMap: map[string]any{
+				"a": map[string]any{
+					"b": map[string]any{
+						"c": "{{msg}}",
+					},
+					"j": []map[string]any{
+						{
+							"l": "{{msg}}",
+						},
+					},
+				},
+				"e": "hello {{msg}}",
+			},
+		},
+		Output: &Test{
+			Template: "world",
+			JSONMap: map[string]any{
+				"a": map[string]any{
+					"b": map[string]any{
+						"c": "world",
+					},
+					"j": []any{
+						map[string]any{
+							"l": "world",
+						},
+					},
+				},
+				"e": "hello world",
+			},
+		},
+	},
 }
 
 func TestMain(t *testing.T) {