[go: nahoru, domu]
Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Make tester.startGesture less async, for better stack traces #123946

Merged
merged 2 commits into from
Apr 6, 2023
Merged

Make tester.startGesture less async, for better stack traces #123946

merged 2 commits into from
Apr 6, 2023

Conversation

gnprice
Copy link
Member
@gnprice gnprice commented Apr 1, 2023

Toward #85160.

When tests interfere with each other over gestures, debugging the problem can get confusing. One reason is that the stack traces are obscured by asynchrony, in a way that turns out to have an easy fix. This PR makes that fix.

For example, here's a stack trace I encountered when debugging one of the state leaks in widgets/draggable_test.dart:

══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞════════════════════════════════════════════════════
The following assertion was thrown running a test:
Pointer of PointerDownEvent#21bfd(position: Offset(400.0, 72.0), pointer: 7, kind: touch, buttons:
1, down: true) unexpectedly has a HitTestResult associated with it.
'package:flutter/src/gestures/binding.dart':
Failed assertion: line 369 pos 14: '!_hitTests.containsKey(event.pointer)'

Either the assertion indicates an error in the framework itself, or we should provide substantially
more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new?template=2_bug.md

When the exception was thrown, this was the stack:
#2      GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:369:14)
#3      GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:363:5)
#4      TestWidgetsFlutterBinding.handlePointerEventForSource.<anonymous closure> (package:flutter_test/src/binding.dart:614:42)
#5      TestWidgetsFlutterBinding.withPointerEventSource (package:flutter_test/src/binding.dart:624:11)
#6      TestWidgetsFlutterBinding.handlePointerEventForSource (package:flutter_test/src/binding.dart:614:5)
#7      WidgetTester.sendEventToBinding.<anonymous closure> (package:flutter_test/src/widget_tester.dart:849:15)
#10     TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:68:41)
#11     WidgetTester.sendEventToBinding (package:flutter_test/src/widget_tester.dart:848:27)
#12     TestGesture.down.<anonymous closure> (package:flutter_test/src/test_pointer.dart:456:25)
#15     TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:68:41)
#16     TestGesture.down (package:flutter_test/src/test_pointer.dart:455:27)
#17     WidgetController.startGesture (package:flutter_test/src/controller.dart:1183:20)
<asynchronous suspension>
<asynchronous suspension>
(elided 7 frames from class _AssertionError, dart:async, and package:stack_trace)

The test description was:
  Drag and drop - dragging over button
════════════════════════════════════════════════════════════════════════════════════════════════════

That test, "Drag and drop - dragging over button", is 90 lines long. So the first thing one wants to know to debug it is where in the test the error occurred — what steps have already happened to get us to the state where the assertion detected a problem, and what step we were on that triggered the assert.

And unfortunately this stack trace doesn't tell us that; it doesn't contain any frames from the test. The outermost frame is in WidgetController.startGesture, inside the flutter_test library.

The test does call that method, though — on line 451 and line 467. So one might guess that one of those calls triggered the failure.

That turns out to be the wrong track.

After applying this PR, here's the stack trace from the same debugging attempt:

When the exception was thrown, this was the stack:
#2      GestureBinding._handlePointerEventImmediately (package:flutter/src/gestures/binding.dart:369:14)
#3      GestureBinding.handlePointerEvent (package:flutter/src/gestures/binding.dart:363:5)
#4      TestWidgetsFlutterBinding.handlePointerEventForSource.<anonymous closure> (package:flutter_test/src/binding.dart:614:42)
#5      TestWidgetsFlutterBinding.withPointerEventSource (package:flutter_test/src/binding.dart:624:11)
#6      TestWidgetsFlutterBinding.handlePointerEventForSource (package:flutter_test/src/binding.dart:614:5)
#7      WidgetTester.sendEventToBinding.<anonymous closure> (package:flutter_test/src/widget_tester.dart:849:15)
#10     TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:68:41)
#11     WidgetTester.sendEventToBinding (package:flutter_test/src/widget_tester.dart:848:27)
#12     TestGesture.down.<anonymous closure> (package:flutter_test/src/test_pointer.dart:456:25)
#15     TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:68:41)
#16     TestGesture.down (package:flutter_test/src/test_pointer.dart:455:27)
#17     WidgetController.startGesture (package:flutter_test/src/controller.dart:1187:20)
#18     WidgetController.tapAt.<anonymous closure> (package:flutter_test/src/controller.dart:560:41)
#21     TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:68:41)
#22     WidgetController.tapAt (package:flutter_test/src/controller.dart:559:27)
#23     WidgetController.tap (package:flutter_test/src/controller.dart:554:12)
#24     main.<anonymous closure> (file:///home/greg/n/flutter/flutter/packages/flutter/test/widgets/draggable_test.dart:476:18)
<asynchronous suspension>
<asynchronous suspension>
(elided 9 frames from class _AssertionError, dart:async, and package:stack_trace)

This immediately tells us the error is happening on line 476 of the test file. That's several steps later than the tester.startGesture calls; it's instead a call to tester.tap. The startGesture call on the stack was an internal one.

With that information in hand, we avoid some fruitless paths of debugging, and can instead go straight to investigating why that particular tap call found itself in this situation.

Pre-launch Checklist

  • I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • I read the Tree Hygiene wiki page, which explains my responsibilities.
  • I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
  • I signed the CLA.
  • I listed at least one issue that this PR fixes in the description above.
  • I updated/added relevant documentation (doc comments with ///).
  • I added new tests to check the change I am making, or this PR is test-exempt.
  • All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

@flutter-dashboard flutter-dashboard bot added a: tests "flutter test", flutter_test, or one of our tests framework flutter/packages/flutter repository. See also f: labels. labels Apr 1, 2023
@flutter-dashboard
Copy link

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat (don't just cc him here, he won't see it! He's on Discord!).

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

@gnprice
Copy link
Member Author
gnprice commented Apr 3, 2023

Test added.

@goderbauer goderbauer requested a review from chunhtai April 4, 2023 22:13
chunhtai
chunhtai approved these changes Apr 6, 2023
View reviewed changes
Copy link
Contributor
@chunhtai chunhtai left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

LGTM

@chunhtai chunhtai added the autosubmit Merge PR when tree becomes green via auto submit App label Apr 6, 2023
@auto-submit auto-submit bot merged commit 09940e4 into flutter:master Apr 6, 2023
@gnprice gnprice deleted the pr-startgesture-stack branch April 7, 2023 04:41
@engine-flutter-autoroll engine-flutter-autoroll mentioned this pull request Apr 7, 2023
Merged
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Apr 7, 2023
@engine-flutter-autoroll
09940e4a3 Make tester.startGesture less async, for better stack traces (
e56864b 
flutter/flutter#123946)
@HansMuller HansMuller mentioned this pull request Apr 7, 2023
Open
exaby73 pushed a commit to NevercodeHQ/flutter that referenced this pull request Apr 17, 2023
@gnprice @exaby73
Make tester.startGesture less async, for better stack traces (flutter…
5facf96 
…#123946)

Make tester.startGesture less async, for better stack traces
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 10, 2023
@engine-flutter-autoroll
09940e4a3 Make tester.startGesture less async, for better stack traces (
82c8dcf 
flutter/flutter#123946)
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 10, 2023
@engine-flutter-autoroll
09940e4a3 Make tester.startGesture less async, for better stack traces (
b67d9e1 
flutter/flutter#123946)
@gnprice gnprice mentioned this pull request Aug 18, 2023
Open
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Reviewers

@chunhtai chunhtai chunhtai approved these changes

Assignees
No one assigned
Labels
a: tests "flutter test", flutter_test, or one of our tests autosubmit Merge PR when tree becomes green via auto submit App framework flutter/packages/flutter repository. See also f: labels.
Projects
None yet
Milestone
No milestone
Development

Successfully merging this pull request may close these issues.

None yet
2 participants
@gnprice @chunhtai