Exception in flutter microbenchmarks #17963
Description
When running Flutter's microbenchmarks the error below (at the end of the bug-report) is printed on the console.
Due to timing issues, this error is handled differently with sync-async and makes the benchmark go red.
I'm adding a work-around to the benchmark, but that just treats the symptom.
I have debugged this. Here are my findings:
lib/stocks/layout_bench.dartruns the following statements in a loop:
Timer.run(() { ui.window.onBeginFrame(new Duration(milliseconds: iterations * 16)); });
Timer.run(() { ui.window.onDrawFrame(); });
- The
onDrawFramedepends ononBeginFrameto set_doDrawThisFrametotrueorfalse. - Normally these functions are only called from the loop, but from time to time they are also called from the framework. This can be seen by observing the stacktraces.
This stacktrace is printed when called from the loop (line numbers might be off because of debug lines).
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #0 LiveTestWidgetsFlutterBinding.handleBeginFrame (package:flutter_test/src/binding.dart:1011)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #1 _TestWidgetsFlutterBinding&BindingBase&SchedulerBinding._handleBeginFrame (package:flutter/src/scheduler/binding.dart:834)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #2 main.<anonymous closure>.<anonymous closure> (file:///usr/local/google/home/floitsch/code/flutter/flutter/dev/benchmarks/microbenchmarks/lib/stocks/layout_bench.dart:65)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #3 _rootRun (dart:async/zone.dart:1122)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #4 _CustomZone.run (dart:async/zone.dart:1023)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #5 _CustomZone.runGuarded (dart:async/zone.dart:925)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #6 _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:965)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #7 _rootRun (dart:async/zone.dart:1126)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #8 _CustomZone.run (dart:async/zone.dart:1023)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #9 _CustomZone.bindCallback.<anonymous closure> (dart:async/zone.dart:949)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #10 Timer._createTimer.<anonymous closure> (dart:async/runtime/libtimer_patch.dart:21)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #11 _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #12 _Timer._handleMessage (d
This stacktrace is the one from the framework (line numbers might be off because of debug lines):
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #0 LiveTestWidgetsFlutterBinding.handleBeginFrame (package:flutter_test/src/binding.dart:1004)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #1 _TestWidgetsFlutterBinding&BindingBase&SchedulerBinding._handleBeginFrame (package:flutter/src/scheduler/binding.dart:834)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #2 _invoke1 (dart:ui/hooks.dart:134)
[microbenchmarks] [STDOUT] [ ] I/flutter (21815): #3 _beginFrame (dart:ui/hooks.dart:105)
For some reason the framework sometimes invokes handleBeginFrame and doDrawFrame. However, if these calls happen in the middle of the two Timer.run, then the second Timer.run call will have an exception.
Here is the exception that is thrown and printed on the console.
The following command was used: dart bin/run.dart -t microbenchmarks
[microbenchmarks] [STDOUT] [+1554 ms] I/flutter ( 3592): ══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): The following assertion was thrown running a test (but after the test had completed):
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): Failed assertion: boolean expression must not be null
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592):
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): Either the assertion indicates an error in the framework itself, or we should provide substantially
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): more information in this error message to help you determine and fix the underlying cause.
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): In either case, please report this assertion by filing a bug on GitHub:
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): https://github.com/flutter/flutter/issues/new
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592):
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): When the exception was thrown, this was the stack:
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): #0 LiveTestWidgetsFlutterBinding.handleDrawFrame (package:flutter_test/src/binding.dart:0)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): #1 _TestWidgetsFlutterBinding&BindingBase&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): #2 main.<anonymous closure>.<anonymous closure> (file:///usr/local/google/home/floitsch/code/flutter/flutter/dev/benchmarks/microbenchmarks/lib/stocks/layout_bench.dart:51)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): #11 _Timer._runTimers (dart:isolate/runtime/libtimer_impl.dart:382)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): #12 _Timer._handleMessage (dart:isolate/runtime/libtimer_impl.dart:416)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): #13 _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): (elided 8 frames from package dart:async)
[microbenchmarks] [STDOUT] [ ] I/flutter ( 3592): ══════════════════════════════════════════════════════════════════════════════════════════════════