Revert changes to List<int> body data handling (cfug#1860)

A previous change to improve the performance of binary uploads
accidentally broke the functionality of uploading `List<int>` json
bodies.
Fixes cfug#1858

dio/CHANGELOG.md

@@ -7,6 +7,10 @@ See the [Migration Guide][] for the complete breaking changes list.**
 
 *None.*
 
+## 5.2.0+2
+
+- Revert changes to handling of `List<int>` body data.
+
 ## 5.2.0+1
 
 - Fix `DioErrorType` deprecation hint.
@@ -20,7 +24,6 @@ See the [Migration Guide][] for the complete breaking changes list.**
   Dio 6.0.0 - Please use the replacement `IOHttpClientAdapter.createHttpClient` instead.
 - Using `CancelToken` no longer closes and re-creates `HttpClient` for each request when `IOHttpClientAdapter` is used.
 - Fix timeout handling for browser `receiveTimeout`.
-- Using `CancelToken` no longer closes and re-creates `HttpClient` for each request when `IOHttpClientAdapter` is used. 
 - Improve performance when sending binary data (`List<int>`/`Uint8List`). 
 
 ## 5.1.2

dio/lib/src/dio_mixin.dart

@@ -640,9 +640,6 @@ abstract class DioMixin implements Dio {
         if (data is Uint8List) {
           // Handle binary data which does not need to be transformed
           bytes = data;
-        } else if (data is List<int>) {
-          // Handle binary data which does not need to be transformed
-          bytes = Uint8List.fromList(data);
         } else {
           // Call request transformer for anything else
           final transformed = await transformer.transformRequest(options);

dio/test/upload_test.dart

@@ -1,34 +1,40 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 
 import 'package:dio/dio.dart';
-import 'package:mockito/mockito.dart';
 import 'package:test/test.dart';
 
-import 'mock/http_mock.mocks.dart';
-
 void main() {
   late Dio dio;
 
   setUp(() {
     dio = Dio()..options.baseUrl = 'https://httpbun.com/';
   });
 
-  test('binary data should not be transformed', () async {
-    final bytes = List.generate(1024, (index) => index);
-    final transformer = MockTransformer();
-    when(transformer.transformResponse(any, any)).thenAnswer(
-      (i) => i.positionalArguments[1],
-    );
+  test('Uint8List should not be transformed', () async {
+    final bytes = Uint8List.fromList(List.generate(10, (index) => index));
+    final transformer = dio.transformer = _TestTransformer();
     final r = await dio.put(
       '/put',
       data: bytes,
     );
-    verifyNever(transformer.transformRequest(any));
+    expect(transformer.requestTransformed, isFalse);
     expect(r.statusCode, 200);
   });
 
+  test('List<int> should be transformed', () async {
+    final ints = List.generate(10, (index) => index);
+    final transformer = dio.transformer = _TestTransformer();
+    final r = await dio.put(
+      '/put',
+      data: ints,
+    );
+    expect(transformer.requestTransformed, isTrue);
+    expect(r.data['data'], ints.toString());
+  });
+
   test('stream', () async {
     const str = 'hello 😌';
     final bytes = utf8.encode(str).toList();
@@ -96,3 +102,13 @@ void main() {
     testOn: 'vm',
   );
 }
+
+class _TestTransformer extends BackgroundTransformer {
+  bool requestTransformed = false;
+
+  @override
+  Future<String> transformRequest(RequestOptions options) async {
+    requestTransformed = true;
+    return super.transformRequest(options);
+  }
+}