Cannot return with NULL from Isolate: Exception: Isolate exited without result or error #63590
Description
The following pull request introduced an issue with isolates:
#59666
Steps to Reproduce
- Create a method that should be run by the isolate (my example uses http package to download web requests using isolates), which returns null value
- Call the isolate function using compute()
- An exception is being thrown by the engine (see below)
Expected results:
I can pass null values from functions run via Isolates. Before this pull request it was working as expected.
Actual results:
I receive an engine exception when returning nulls.
Exception details
E/flutter (12100): [ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: 'package:flutter/src/foundation/_isolates_io.dart': Failed assertion: line 55 pos 12: 'resultData is R': is not true.
E/flutter (12100): #0 _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:46:39)
E/flutter (12100): #1 _AssertionError._throwNew (dart:core-patch/errors_patch.dart:36:5)
E/flutter (12100): #2 compute.<anonymous closure> (package:flutter/src/foundation/_isolates_io.dart:55:12)
E/flutter (12100): #3 _rootRunUnary (dart:async/zone.dart:1206:13)
E/flutter (12100): #4 _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter (12100): #5 _CustomZone.runUnaryGuarded (dart:async/zone.dart:1005:7)
E/flutter (12100): #6 _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:357:11)
E/flutter (12100): #7 _BufferingStreamSubscription._add (dart:async/stream_impl.dart:285:7)
E/flutter (12100): #8 _SyncStreamControllerDispatch._sendData (dart:async/stream_controller.dart:808:19)
E/flutter (12100): #9 _StreamController._add (dart:async/stream_controller.dart:682:7)
E/flutter (12100): #10 _StreamController.add (dart:async/stream_controller.dart:624:5)
E/flutter (12100): #11 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)
E/flutter (12100):
I/flutter (12100): 2020-08-12 10:34:59.877287 PD.runMainInit: Completed
I/flutter (12100): 2020-08-12 10:34:59.877803 PD.runMainInit: Completed, setting state
I/flutter (12100): 2020-08-12 10:35:00.756946 Error occured during WebDownloader.getHtml
I/flutter (12100): 2020-08-12 10:35:00.757186 Url:https://test-url.com
I/flutter (12100): Exception: Isolate exited without result or error.
Flutter doctor
[✓] Flutter (Channel stable, 1.20.1, on Mac OS X 10.15.5 19F101, locale en-US)
• Flutter version 1.20.1 at /Users/bkopacz/FlutterDev/flutter
• Framework revision 2ae34518b8 (7 days ago), 2020-08-05 19:53:19 -0700
• Engine revision c8e3b94853
• Dart version 2.9.0
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
• Android SDK at /Users/bkopacz/Library/Android/sdk
• Platform android-29, build-tools 29.0.2
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
• All Android licenses accepted.
[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.6, Build version 11E708
• CocoaPods version 1.9.0
[✓] Android Studio (version 4.0)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 47.1.2
• Dart plugin version 193.7361
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
[✓] Connected device (1 available)
• VOG L29 (mobile) • DUM7N19327008485 • android-arm64 • Android 10 (API 29)
• No issues found!