fix: sprig dict funcs are failing on dicts nested under arrays (#646)

Fixes #643

pkg/maputil/maputil.go

@@ -15,32 +15,18 @@ func CastKeysToStrings(s interface{}) (map[string]interface{}, error) {
 				return nil, fmt.Errorf("unexpected type of key in map: expected string, got %T: value=%v, map=%v", typed_k, typed_k, src)
 			}
 
-			var casted_v interface{}
-			switch typed_v := v.(type) {
-			case map[interface{}]interface{}:
-				tmp, err := CastKeysToStrings(typed_v)
-				if err != nil {
-					return nil, err
-				}
-				casted_v = tmp
-			default:
-				casted_v = typed_v
+			casted_v, err := recursivelyStringifyMapKey(v)
+			if err != nil {
+				return nil, err
 			}
 
 			new[str_k] = casted_v
 		}
 	case map[string]interface{}:
 		for k, v := range src {
-			var casted_v interface{}
-			switch typed_v := v.(type) {
-			case map[interface{}]interface{}:
-				tmp, err := CastKeysToStrings(typed_v)
-				if err != nil {
-					return nil, err
-				}
-				casted_v = tmp
-			default:
-				casted_v = typed_v
+			casted_v, err := recursivelyStringifyMapKey(v)
+			if err != nil {
+				return nil, err
 			}
 
 			new[k] = casted_v
@@ -49,6 +35,31 @@ func CastKeysToStrings(s interface{}) (map[string]interface{}, error) {
 	return new, nil
 }
 
+func recursivelyStringifyMapKey(v interface{}) (interface{}, error) {
+	var casted_v interface{}
+	switch typed_v := v.(type) {
+	case map[interface{}]interface{}, map[string]interface{}:
+		tmp, err := CastKeysToStrings(typed_v)
+		if err != nil {
+			return nil, err
+		}
+		casted_v = tmp
+	case []interface{}:
+		a := []interface{}{}
+		for i := range typed_v {
+			res, err := recursivelyStringifyMapKey(typed_v[i])
+			if err != nil {
+				return nil, err
+			}
+			a = append(a, res)
+		}
+		casted_v = a
+	default:
+		casted_v = typed_v
+	}
+	return casted_v, nil
+}
+
 func Set(m map[string]interface{}, key []string, value string) map[string]interface{} {
 	if len(key) == 0 {
 		panic(fmt.Errorf("bug: unexpected length of key: %d", len(key)))