[Dart2] Added better double handling to 'mapValueOfType<T>', which previously would fail when deserding doubles (#17808)

Author: 0xNF

modules/openapi-generator/src/main/resources/dart2/api_helper.mustache

@@ -69,6 +69,9 @@ Future<String> _decodeBodyBytes(Response response) async {
 /// Returns a valid [T] value found at the specified Map [key], null otherwise.
 T? mapValueOfType<T>(dynamic map, String key) {
   final dynamic value = map is Map ? map[key] : null;
+  if (T == double && value is int) {
+    return value.toDouble() as T;
+  }
   return value is T ? value : null;
 }
 

samples/openapi3/client/petstore/dart2/petstore_client_lib/lib/api_helper.dart

@@ -70,6 +70,9 @@ Future<String> _decodeBodyBytes(Response response) async {
 /// Returns a valid [T] value found at the specified Map [key], null otherwise.
 T? mapValueOfType<T>(dynamic map, String key) {
   final dynamic value = map is Map ? map[key] : null;
+  if (T == double && value is int) {
+    return value.toDouble() as T;
+  }
   return value is T ? value : null;
 }
 

samples/openapi3/client/petstore/dart2/petstore_client_lib_fake/lib/api_helper.dart

@@ -88,6 +88,9 @@ Future<String> _decodeBodyBytes(Response response) async {
 /// Returns a valid [T] value found at the specified Map [key], null otherwise.
 T? mapValueOfType<T>(dynamic map, String key) {
   final dynamic value = map is Map ? map[key] : null;
+  if (T == double && value is int) {
+    return value.toDouble() as T;
+  }
   return value is T ? value : null;
 }