Throw StateError when implicitView is null on wrapWithDefaultView.
#155734
Conversation
This allows us to render a more user-friendly error, instead of failing with an "unexpected null value" a few lines below.
| @@ -1229,6 +1229,12 @@ mixin WidgetsBinding on BindingBase, ServicesBinding, SchedulerBinding, GestureB | |||
| /// The `rootWidget` widget provided to this method must not already be | |||
| /// wrapped in a [View]. | |||
| Widget wrapWithDefaultView(Widget rootWidget) { | |||
| assert( | |||
| platformDispatcher.implicitView != null, | |||
| 'The implicitView is null. Cannot create a default View from `runApp`. ' | |||
There was a problem hiding this comment.
This error uses jargon that most Flutter developers won't know. This might frustrate users.
Perhaps we should add more context? Maybe something like:
runApprequires an implicit view.
runApprenders the widget tree into a view provided by the platform,
called the "implicit view". However, the platform did not provide an
implicit view.Try using
runWidgetinstead ofrunApp.
There was a problem hiding this comment.
Since it's a public API, I think we should not assume it 100% comes from runApp. Maybe
The app requested an implicit view, but the platform doesn't have one.
This is likely because the app called
runAppto start up, which expects the platform to provide a default view to render into ("the implicit view"), while the engine has multi-view mode enabled, which requires the app handle view creation.Try using
runWidgetinstead ofrunApp. See also https://flutter.dev/to/web-runwidget
There was a problem hiding this comment.
@loic-sharma @dkwingsmt I ended up with something like this, I hope it makes more sense!
The app is attempting to render into a default View that isn't available (
platformDispatcher.implicitView == null).
This is likely because the platform has multi-view mode enabled, but the app is callingrunAppto render its root Widget.
Try usingrunWidgetinstead ofrunAppto start your app.runWidgetallows you to provide aViewwidget, without requiring a default on the platform.
See: https://flutter.dev/to/web-multiview-runwidget
(Tried to use lingo closer to that in the wrapWithDefaultView method docs.)
There was a problem hiding this comment.
I slightly prefer Tong's wording.
Some context:
- On desktop, the north star is that the app will call
runAppeven though there's no implicit view.runAppwill know how to create a window to host the widget tree. - On desktop, you can have multiple views while also having an implicit view. Thus, on desktop you can call
runAppeven if you have multi-view mode enabled
Since it's a public API, I think we should not assume it 100% comes from runApp.
Should we move this error to runApp then and then make wrapWithDefaultView assert that platformDispatcher.implicitView != null?
What do y'all think about this? I tried to merge bits from all our messages :)
The app requested an implicit view, but the platform did not provide one.
runAppexpects the platform to provide a default view to render into ("the implicit view").
However, the platform did not provide a default "implicit" view, likely because it has multi-view mode enabled.Try using
runWidgetinstead ofrunAppto start your app.runWidgetallows you to provide aViewwidget, without requiring a default view.
See: https://flutter.dev/to/web-multiview-runwidget
There was a problem hiding this comment.
Looks good!
I think checking it in wrapWithDefaultView is better than runApp since wrapWithDefaultView is also a public API and users can still call it incorrectly (which is a user error and you shouldn't assert on).
There was a problem hiding this comment.
I applied @loic-sharma's suggestion! If @dkwingsmt is happy, I'm happy too, let's autosubmit this :P
(Off-topic)
runAppwill know how to create a window to host the widget tree.
...
you can have multiple views while also having an implicit view
We need to discuss this elsewhere, I'm interested :P
There was a problem hiding this comment.
LGTM with nits.
I'm not familiar with multiview so I'm happy to defer to anyone else that might be, but I know @goderbauer is out for awhile. This looks good from my perspective though. Using throwsA to check the assertion seems fine.
Also it looks like there are failures.
We're adding a more descriptive error when a misconfigured multi-view web app attempts to run (flutter/flutter#155734), and we want a permalink to the relevant bit of the docs. This PR adds a `/to/web-multiview-runwidget` redirect, pointing to the correct part of the docs.
## Description We're adding a more descriptive error when a misconfigured multi-view web app attempts to run (flutter/flutter#155734), and we want a permalink to the relevant bit of the docs. This PR adds a `/to/web-multiview-runwidget` redirect, pointing to the correct part of the docs. ## Issues Needed for flutter/flutter#155734 ## Presubmit checklist - [ ] This PR is marked as draft with an explanation if not meant to land until a future stable release. - [x] This PR doesn’t contain automatically generated corrections (Grammarly or similar). - [x] This PR follows the [Google Developer Documentation Style Guidelines](https://developers.google.com/style) — for example, it doesn’t use _i.e._ or _e.g._, and it avoids _I_ and _we_ (first person). - [ ] This PR uses [semantic line breaks](https://github.com/dart-lang/site-shared/blob/main/doc/writing-for-dart-and-flutter-websites.md#semantic-line-breaks) of 80 characters or fewer.
implicitView != null on wrapWithDefaultView.wrapWithDefaultView.
Manual roll requested by stuartmorgan@google.com flutter/flutter@fa402c8...ead6b0d 2024-09-27 kustermann@google.com Remove left-over traces of "link-dry-run" - which isn't used anywhere in flutter (flutter/flutter#155820) 2024-09-27 engine-flutter-autoroll@skia.org Roll Flutter Engine from e57b440ec4ee to 7c603de2dca7 (5 revisions) (flutter/flutter#155811) 2024-09-27 bruno.leroux@gmail.com Fix DropdownMenu rendered behind AppBar (flutter/flutter#155539) 2024-09-27 engine-flutter-autoroll@skia.org Roll Flutter Engine from 53517772a5b0 to e57b440ec4ee (8 revisions) (flutter/flutter#155799) 2024-09-27 ditman@gmail.com Throw StateError when implicitView is null on `wrapWithDefaultView`. (flutter/flutter#155734) 2024-09-27 34871572+gmackall@users.noreply.github.com Roll packages manually (flutter/flutter#155786) 2024-09-27 rmolivares@renzo-olivares.dev fix: SelectableText should handle focus changes (flutter/flutter#155771) 2024-09-27 34871572+gmackall@users.noreply.github.com Use flutter from in same repo (not path) in `generate_gradle_lockfiles.dart` (again) (flutter/flutter#155794) 2024-09-26 34871572+gmackall@users.noreply.github.com Use flutter from in same repo (not path) in `generate_gradle_lockfiles.dart` (flutter/flutter#155790) 2024-09-26 rmolivares@renzo-olivares.dev `RenderParagraph` should invalidate its `_SelectableFragment`s cached rects on window size updates (flutter/flutter#155719) 2024-09-26 zeqinjie@qq.com Fix broken text field with set hint and min and max lines(#153183) (flutter/flutter#153235) 2024-09-26 engine-flutter-autoroll@skia.org Roll Flutter Engine from 9e6133e8d906 to 53517772a5b0 (1 revision) (flutter/flutter#155772) 2024-09-26 ian@hixie.ch Fix line-wrapping in `flutter create` error message. (flutter/flutter#150325) 2024-09-26 christopherfujino@gmail.com remove fujino from CODEOWNERS (flutter/flutter#155369) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC camillesimon@google.com,stuartmorgan@google.com on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
This PR tweaks
wrapWithDefaultView(used byrunApp) to raise a StateError with a legible error message when theplatformDispatcher.implicitViewis missing (for example, when enabling multi-view embedding on the web), instead of crashing with an unexpectednullChecka few lines below.Before:
After:
Issues
Unexpected null valueerror appears when running multiView on Flutter Web #153198Tests
Added a test to ensure the assertion is thrown when the
implicitViewis missing. Had to hack a little because I couldn't find any clean way of overriding theimplicitView. The problem is that the flutter_test bindings userunAppinternally a couple of times, so I can only disable the implicitView inside the test body (and must re-enable it before returning). Not sure if it's the best way, but it seems to do the trick for this simple test case!Pre-launch Checklist
///).If you need help, consider asking for advice on the #hackers-new channel on Discord.