## Description

This removes all of the comments that are of the form "so-and-so (must not be null|can ?not be null|must be non-null)" from the cases where those values are defines as non-nullable values.

This PR removes them from the widgets library.

This was done by hand, since it really didn't lend itself to scripting, so it needs to be more than just spot-checked, I think. I was careful to leave any comment that referred to parameters that were nullable, but I may have missed some.

In addition to being no longer relevant after null safety has been made the default, these comments were largely fragile, in that it was easy for them to get out of date, and not be accurate anymore anyhow.

This did create a number of constructor comments which basically say "Creates a [Foo].", but I don't really know how to avoid that in a large scale change, since there's not much you can really say in a lot of cases.  I think we might consider some leniency for constructors to the "Comment must be meaningful" style guidance (which we de facto have already, since there are a bunch of these).

## Related PRs
- https://github.com/flutter/flutter/pull/134984
- https://github.com/flutter/flutter/pull/134991
- https://github.com/flutter/flutter/pull/134993
- https://github.com/flutter/flutter/pull/134994

## Tests
 - Documentation only change.

Reverts flutter/flutter#134953

Several failures on CI

fixes https://github.com/flutter/flutter/issues/134854

## 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].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

…te to no… (#130841)"

This reverts commit 0f3bd90d.

Internal test needs migration

## 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].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

…t trap the focus

fixes https://github.com/flutter/flutter/issues/112567

Several things I done:

1. add new enum `parentScope`
2. refactor _sortAllDescendants so that it doesn't recursively looking
into its descendant when it encounter a FocusScopeNode.
3. When the nextFocus try to focus into a FocusScopeNode, it will try to
find the first focusable FocusNode in traversal order and focus it
instead if it doesn't have a first focus.
4. Change the default in Navigator to always be `parentScope`
5. Only the root navigator will use `leaveFlutterView` if platform is
web.


Previously 2 and 3 are not needed because once a focusscope trapped the
focus, there isn't a chance where the parent focusscope have to deal
with next focus.

If we don't do 2 and 3 after the change, it will cause it to stuck in
the current scope again. Because once the focus leave the current scope,
it needs to also remove the first focus in that scope (so that it can
start fresh when focus traversal back to the scope in the future). At
this point the current scope will have the primary focus without the
first focus. The parent scope will then try to find the next focus, and
it will place the focus to the first traversal child in the current
scope again.

## 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].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[test-exempt]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat

Currently if the focus is on a focusnode that `skipTraversal = true`, the tab won't be able to traverse focus out of the node.

this pr fixes it

This PR exposes a requestFocusCallback on `FocusTraversalPolicy` and it's inheritors.

Fixes #83175.

Revert "Workaround for exhaustivness bug in dart2js (#123242)"

Workaround for exhaustiveness bug in dart2js

Remove 1745 decorative breaks

Refine the directional traversal algorithm for out of band widgets

* Modify focus traversal policy search to use focus tree instead of widget tree

* Eliminate unnecessary inherited widget

* Remove unintentional change

* Look for focus nodes without creating a dependency.

* Add test

* Review Changes

* Fix debug_test.dart

* Rebase onto master

* Fix typos

* lowercase animated & opacity

* Undo typo fix

---------
Co-authored-by: Michael Goderbauer <goderbauer@google.com>

* Add getInheritedWidgetOfExactType to BuildContext

* Use the new API in all the places

* Fix doc error

* Review Changes

* dart fix --apply

* manual fixes

* Fix focus area documentation typos

* Restore intentional spaces that illustrate bigger buttons

* Rename _*Marker classes to be _*Scope, for consistency

* [EMPTY] Commit to refresh the tree that is currently red (#118062)

* Fix remaining tests
Co-authored-by: Drew Roen <102626803+drewroengoogle@users.noreply.github.com>

* allow focus to leave FlutterView

* fix tests and docs

* small doc update

* fix analysis lint

* use closed loop for dialogs

* add tests for new API

* address comments

* test FocusScopeNode.traversalEdgeBehavior setter; reverse wrap-around

* rename actionResult to invokeResult

* address comments

* Use distance instead of coord

* Sort by distance prefer axis

* Switch initial sort back to sort by coordinate.

* revert test change

* Fix tests

* Simplify test case

* Add a test for irregular grids

* Review Changes

This does a cleanup of the examples, removing all of the "section" markers and extra comments that we don't need anymore now that the samples are no longer in the source code. It also removes the --template arguments from the {@tool dartpad} and {@tool sample} directives, since those are no longer used. It converts two examples that I discovered were still embedded into linked examples in the examples folder.

I didn't delete the templates from the snippets config folder yet, because there are still embedded samples in the dart:ui package from the engine that use them. Once dart:ui no longer uses the templates, they can be removed.

I bumped the version of the snippets package to pick up a change that allows removal of the --template argument.

This extracts the sample code out from the API doc comments, and places them in separate files on disk, allowing running of the examples locally, testing them, and building of slightly larger examples.

When a focus traversal group has no entries, but traversal is requested, we were throwing an exception because we couldn't find the group marker's scope in the list of candidates. This fixes that, and adds a test.

Update samples to use repo analysis options, Fix sample templates and a ton of analyzer issues (#77868)