Apps with null safety throw

[mit-mit]

The fix for #59879 just landed via a837557. We now seem to have a issue with simple material apps (example/hello_world doesn't throw):

Repro steps:

1. flutter create foobar
2. Edit pubspec.yaml to change sdk: ">=2.7.0 <3.0.0" to sdk: ">=2.11.0-0.0 <3.0.0"
3. Replace the contents of lib/main.dart with:

   import 'package:flutter/material.dart';
   
   void main() {
   runApp(MyApp());
   }
   
   class MyApp extends StatelessWidget {
     @override
     Widget build(BuildContext context) {
       return MaterialApp(
       home: Scaffold(
           body: Center(
           child: Text('Material Hello'),
           ),
       ),
       );
     }
   }

4. Run flutter run --enable-experiment=non-nullable

Expected result: no errors

Actual result: Three errors

An Observatory debugger and profiler on Android SDK built for x86 is available at: http://127.0.0.1:61913/ktKfMJw2gr4=/
D/EGL_emulation(17133): eglMakeCurrent: 0xe81a7ba0: ver 3 0 (tinfo 0xe010f620)
D/eglCodecCommon(17133): setVertexArrayObject: set vao to 0 (0) 1 0
I/flutter (17133): ══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (17133): The following _TypeError was thrown during a scheduler callback:
I/flutter (17133): type 'Null' is not a subtype of type 'EngineLayer' of 'function result'
I/flutter (17133):
I/flutter (17133): When the exception was thrown, this was the stack:
I/flutter (17133): #0      SceneBuilder._pushPhysicalShape (dart:ui/compositing.dart)
I/flutter (17133): #1      SceneBuilder.pushPhysicalShape (dart:ui/compositing.dart:577:5)
I/flutter (17133): #2      PhysicalModelLayer.addToScene (package:flutter/src/rendering/layer.dart:1988:29)
I/flutter (17133): #3      Layer._addToSceneWithRetainedRendering (package:flutter/src/rendering/layer.dart:440:5)
I/flutter (17133): #4      ContainerLayer.addChildrenToScene (package:flutter/src/rendering/layer.dart:1027:15)
I/flutter (17133): #5      OffsetLayer.addToScene (package:flutter/src/rendering/layer.dart:1164:5)
I/flutter (17133): #6      Layer._addToSceneWithRetainedRendering (package:flutter/src/rendering/layer.dart:440:5)
I/flutter (17133): #7      ContainerLayer.addChildrenToScene (package:flutter/src/rendering/layer.dart:1027:15)
I/flutter (17133): #8      OffsetLayer.addToScene (package:flutter/src/rendering/layer.dart:1164:5)
I/flutter (17133): #9      Layer._addToSceneWithRetainedRendering (package:flutter/src/rendering/layer.dart:440:5)
I/flutter (17133): #10     ContainerLayer.addChildrenToScene (package:flutter/src/rendering/layer.dart:1027:15)
I/flutter (17133): #11     TransformLayer.addToScene (package:flutter/src/rendering/layer.dart:1609:5)
I/flutter (17133): #12     ContainerLayer.buildScene (package:flutter/src/rendering/layer.dart:765:5)
I/flutter (17133): #13     RenderView.compositeFrame (package:flutter/src/rendering/view.dart:231:37)
I/flutter (17133): #14     RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:447:18)
I/flutter (17133): #15     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:907:13)
I/flutter (17133): #16     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:309:5)
I/flutter (17133): #17     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
I/flutter (17133): #18     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1055:9)
I/flutter (17133): #19     SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:864:7)
I/flutter (17133): (elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
I/flutter (17133): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter (17133): Another exception was thrown: type 'Null' is not a subtype of type 'EngineLayer' of 'function result'

SDK version

mit-macbookpro4:nulltest mit$ flutter --version
Flutter 1.23.0-19.0.pre.95 • channel master • https://github.com/flutter/flutter.git
Framework • revision a837557634 (30 minutes ago) • 2020-10-18 06:12:02 -0400
Engine • revision 499a70f5e2
Tools • Dart 2.11.0 (build 2.11.0-234.0.dev)

[mit-mit]

cc @chinmaygarde @a14n not clear to me from that log if this is in the engine or the framework

I run into the same issue. It works if you remove Scaffold or replace it with CupertinoPageScaffold.

This works for me:

void main() {
  final String? mode = null;
  print('mode: $mode');

  runApp(
    MaterialApp(
      home: CupertinoPageScaffold(
        child: Center(
          child: Text(mode ?? 'mode is null :-('),
        ),
      ),
    ),
  );
}

[jonahwilliams]

I encountered a similar issue in #68377, fix is to just adjust the type signature . It seems like null assertions do not run on the native binding code

[TahaTesser]

logs

Launching lib/main.dart on RMX2001 in debug mode...
Running Gradle task 'assembleDebug'...                                  
Running Gradle task 'assembleDebug'... Done                        35.1s
✓ Built build/app/outputs/flutter-apk/app-debug.apk.
Installing build/app/outputs/flutter-apk/app.apk...                 4.7s
Waiting for RMX2001 to report its views...                          11ms
I/.example.fooba(17284): ProcessProfilingInfo new_methods=396 is saved saved_to_disk=1 resolve_classes_delay=5000
Syncing files to device RMX2001...                                 403ms

Flutter run key commands.
r Hot reload. 🔥🔥🔥
R Hot restart.
h Repeat this help message.
d Detach (terminate "flutter run" but leave application running).
c Clear the screen
q Quit (terminate the application on the device).
An Observatory debugger and profiler on RMX2001 is available at: http://127.0.0.1:54286/ByBqfXLB-yY=/
I/flutter (17284): ══╡ EXCEPTION CAUGHT BY SCHEDULER LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (17284): The following _TypeError was thrown during a scheduler callback:
I/flutter (17284): type 'Null' is not a subtype of type 'EngineLayer' of 'function result'
I/flutter (17284): 
I/flutter (17284): When the exception was thrown, this was the stack:
I/flutter (17284): #0      SceneBuilder._pushPhysicalShape (dart:ui/compositing.dart)
I/flutter (17284): #1      SceneBuilder.pushPhysicalShape (dart:ui/compositing.dart:577:5)
I/flutter (17284): #2      PhysicalModelLayer.addToScene (package:flutter/src/rendering/layer.dart:1988:29)
I/flutter (17284): #3      Layer._addToSceneWithRetainedRendering (package:flutter/src/rendering/layer.dart:440:5)
I/flutter (17284): #4      ContainerLayer.addChildrenToScene (package:flutter/src/rendering/layer.dart:1027:15)
I/flutter (17284): #5      OffsetLayer.addToScene (package:flutter/src/rendering/layer.dart:1164:5)
I/flutter (17284): #6      Layer._addToSceneWithRetainedRendering (package:flutter/src/rendering/layer.dart:440:5)
I/flutter (17284): #7      ContainerLayer.addChildrenToScene (package:flutter/src/rendering/layer.dart:1027:15)
I/flutter (17284): #8      OffsetLayer.addToScene (package:flutter/src/rendering/layer.dart:1164:5)
I/flutter (17284): #9      Layer._addToSceneWithRetainedRendering (package:flutter/src/rendering/layer.dart:440:5)
I/flutter (17284): #10     ContainerLayer.addChildrenToScene (package:flutter/src/rendering/layer.dart:1027:15)
I/flutter (17284): #11     TransformLayer.addToScene (package:flutter/src/rendering/layer.dart:1609:5)
I/flutter (17284): #12     ContainerLayer.buildScene (package:flutter/src/rendering/layer.dart:765:5)
I/flutter (17284): #13     RenderView.compositeFrame (package:flutter/src/rendering/view.dart:231:37)
I/flutter (17284): #14     RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:447:18)
I/flutter (17284): #15     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:907:13)
I/flutter (17284): #16     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:309:5)
I/flutter (17284): #17     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
I/flutter (17284): #18     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1055:9)
I/flutter (17284): #19     SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:864:7)
I/flutter (17284): (elided 11 frames from class _RawReceivePortImpl, class _Timer, dart:async, and dart:async-patch)
I/flutter (17284): ════════════════════════════════════════════════════════════════════════════════════════════════════
V/PhoneWindow(17284): DecorView setVisiblity: visibility = 0, Parent = android.view.ViewRootImpl@5188d14, this = DecorView@bb5d681[MainActivity]
D/Surface (17284): Surface::connect(this=0x79c32fc000,api=1)
I/SurfaceView(17284): 242482098 visibleChanged:true -> SurfaceHolder.Callback.surfaceCreated
D/Surface (17284): Surface::connect(this=0x797291d000,api=1)
D/mali_winsys(17284): EGLint new_window_surface(egl_winsys_display *, void *, EGLSurface, EGLConfig, egl_winsys_surface **, EGLBoolean) returns 0x3000
D/Surface (17284): Surface::setBufferCount(this=0x79c32fc000,bufferCount=4)
D/mali_winsys(17284): EGLint new_window_surface(egl_winsys_display *, void *, EGLSurface, EGLConfig, egl_winsys_surface **, EGLBoolean) returns 0x3000
D/ViewRootImpl(17284): setSurfaceViewCreated, created:true
I/SurfaceView(17284): 242482098 surfaceChanged -- format=4 w=1080 h=2400 visibleChanged:true -> SurfaceHolder.Callback.surfaceChanged
D/SurfaceView(17284): updateScreenMode w:1080 h:2400 ViewRoot w:1080 h:2400
D/SurfaceView(17284): try to resquest 60Hz
D/ViewRootImpl(17284): set screen refresh mode 1 due to SurfaceView-242482098
D/SurfaceView(17284): updateScreenMode w:1080 h:2400 ViewRoot w:1080 h:2400
D/SurfaceView(17284): try to resquest 60Hz
W/Gralloc3(17284): mapper 3.x is not supported
E/gralloc (17284): Arm Module v1.0
E/ion     (17284): ioctl c0044901 failed with code -1: Invalid argument
W/gralloc (17284): WARNING: internal format modifier bits not mutually exclusive. AFBC basic bit is always set, so extended AFBC support bits must always be checked.
I/Choreographer(17284): Skipped 1 frames!  The application may be doing too much work on its main thread.
I/flutter (17284): Another exception was thrown: type 'Null' is not a subtype of type 'EngineLayer' of 'function result'

flutter doctor -v

[✓] Flutter (Channel master, 1.23.0-19.0.pre.95, on Mac OS X 10.15.7 19H2
    darwin-x64, locale en-GB)
    • Flutter version 1.23.0-19.0.pre.95 at
      /Users/tahatesser/Code/flutter_master
    • Framework revision a837557634 (29 hours ago), 2020-10-18 06:12:02 -0400
    • Engine revision 499a70f5e2
    • Dart version 2.11.0 (build 2.11.0-234.0.dev)

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
    • Android SDK at /Users/tahatesser/Code/sdk
    • Platform android-30, build-tools 30.0.2
    • ANDROID_HOME = /Users/tahatesser/Code/sdk
    • 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 12.0.1)
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    • Xcode 12.0.1, Build version 12A7300
    • CocoaPods version 1.10.0.rc.1

[✓] Chrome - develop for the web
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[✓] Android Studio (version 4.1)
    • Android Studio at /Applications/Android Studio.app/Contents
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    • Java version OpenJDK Runtime Environment (build
      1.8.0_242-release-1644-b3-6222593)

[✓] VS Code (version 1.50.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.15.1

[✓] Connected device (5 available)
    • RMX2001 (mobile)   • EUYTFEUSQSRGDA6D                     • android-arm64
      • Android 10 (API 29)
    • iPhone 11 (mobile) • 193EBBC9-CC2A-4477-B8A0-A5F12BB51400 • ios
      • com.apple.CoreSimulator.SimRuntime.iOS-14-0 (simulator)
    • macOS (desktop)    • macos                                • darwin-x64
      • Mac OS X 10.15.7 19H2 darwin-x64
    • Web Server (web)   • web-server                           • web-javascript
      • Flutter Tools
    • Chrome (web)       • chrome                               • web-javascript
      • Google Chrome 86.0.4240.80

• No issues found!