fixed issues where import wouldn't get included

Author: matthewnitschke-wk

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/DartDioClientCodegen.java

@@ -658,16 +658,6 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
                 }
             }
 
-            if (SERIALIZATION_LIBRARY_JSON_SERIALIZABLE.equals(library)) {
-                // built_value serialization uses Uint8List for all MultipartFile types
-                // in json_serialization, MultipartFile is used as the file parameter type, but
-                // MultipartFile isn't readable, instead we convert this to a Uin8List
-                if (op.isResponseFile) {
-                    op.returnType = "Uint8List";
-                    op.returnBaseType = "Uint8List";
-                }
-            }
-
             // The MultipartFile handling above changes the type of some parameters from
             // `UInt8List`, the default for files, to `MultipartFile`.
             //
@@ -680,6 +670,17 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
                 op.imports.remove("Uint8List");
             }
 
+            if (SERIALIZATION_LIBRARY_JSON_SERIALIZABLE.equals(library)) {
+                // built_value serialization uses Uint8List for all MultipartFile types
+                // in json_serialization, MultipartFile is used as the file parameter type, but
+                // MultipartFile isn't readable, instead we convert this to a Uin8List
+                if (op.isResponseFile) {
+                    op.imports.add("Uint8List");
+                    op.returnType = "Uint8List";
+                    op.returnBaseType = "Uint8List";
+                }
+            }
+
             resultImports.addAll(rewriteImports(op.imports, false));
 
             if (SERIALIZATION_LIBRARY_BUILT_VALUE.equals(library)) {

samples/openapi3/client/petstore/dart-dio/petstore_client_lib_fake-json_serializable/lib/src/api/pet_api.dart

@@ -9,6 +9,7 @@ import 'dart:convert';
 import 'package:openapi/src/deserialize.dart';
 import 'package:dio/dio.dart';
 
+import 'dart:typed_data';
 import 'package:openapi/src/model/api_response.dart';
 import 'package:openapi/src/model/pet.dart';