[flutter_tools] Clean up outdated widget preview TODOs and refactor static state - #189437

Roll Flutter from 4249ccbc18a3 to 426be968b5eb (44 revisions)

flutter/flutter@4249ccb...426be96

2026-10-14 [email protected] Allow color delta tolerance in in-memory fuzzy image comparator (flutter/flutter#193937)
2026-10-14 [email protected] [web] Drop stale composing range after text is replaced mid-composition (flutter/flutter#194096)
2026-10-14 [email protected] Roll Skia from 2a2bbea66844 to acde3755d2e2 (1 revision) (flutter/flutter#194376)
2026-10-14 [email protected] Roll Skia from 128c983b12de to 2a2bbea66844 (1 revision) (flutter/flutter#194371)
2026-10-14 [email protected] Roll Skia from 48a294ed4955 to 128c983b12de (3 revisions) (flutter/flutter#194353)
2026-10-14 [email protected] feat(flutter_tools): extract WebDebugConfig from DebuggingOptions (flutter/flutter#194312)
2026-10-14 [email protected] Roll Skia from ea6781c5b6d1 to 48a294ed4955 (2 revisions) (flutter/flutter#194349)
2026-10-14 [email protected] Include <vector> in Android proc_table.h. (flutter/flutter#194325)
2026-10-14 [email protected] Roll Dart SDK from 5933cb486b4a to 6b50116630d0 (28 revisions) (flutter/flutter#194341)
2026-10-14 [email protected] Move GLES3 instancing API entry points to FOR_EACH_IMPELLER_GLES3_PROC (flutter/flutter#194319)
2026-10-14 [email protected] feat(flutter_tools): extract AndroidGradleConfig and move toGradleConfig to AndroidBuildInfo (flutter/flutter#194016)
2026-10-14 [email protected] Roll Skia from ae297bec6012 to ea6781c5b6d1 (8 revisions) (flutter/flutter#194331)
2026-10-14 [email protected] [flutter_tools] Migrate gradle_errors and deferred_components_prebuild_validator away from globals (flutter/flutter#193649)
2026-10-14 [email protected] [Impeller] Cache GLES sampler configuration in RenderPassStateCache (flutter/flutter#193922)
2026-10-14 [email protected] Roll pub packages (flutter/flutter#194332)
2026-10-13 [email protected] [tool] Migrate RunCommand to modular dependency injection (flutter/flutter#190791)
2026-10-13 [email protected] Include `engine/src/flutter/.ci.yaml` in quarterly `goldctl` checklist (flutter/flutter#194316)
2026-10-13 [email protected] [flutter_tools] Remove the last AMD module system support (flutter/flutter#193607)
2026-10-13 [email protected] Roll Skia from 8b3394a60654 to ae297bec6012 (5 revisions) (flutter/flutter#194310)
2026-10-13 [email protected] [web] Remove the a11y placeholder only after the gesture ends (flutter/flutter#194109)
2026-10-13 [email protected] Upgrade goldctl to the latest version (flutter/flutter#193932)
2026-10-13 [email protected] [flutter_tools] Lazily initialize AndroidStudio validation and optimize candidate selection (flutter/flutter#191968)
2026-10-13 [email protected] [flutter_tools] Clean up outdated widget preview TODOs and refactor static state (flutter/flutter#189437)
2026-10-13 [email protected] Roll Skia from e5b5db6d0d6f to 8b3394a60654 (2 revisions) (flutter/flutter#194306)
2026-10-13 [email protected] Redistribute TESTOWNERS for Android team (flutter/flutter#193861)
2026-10-13 [email protected] feat(flutter_tools): introduce Test and Drive specification objects (flutter/flutter#194017)
2026-10-13 [email protected] [Impeller] Keep the aspect ratio when shrinking images to the max texture size (flutter/flutter#194010)
2026-10-13 [email protected] [flutter tool] preserve inherited `DASH__SUPPRESS_ANALYTICS=true` for sub-tools (flutter/flutter#194261)
2026-10-13 [email protected] Roll Packages from d8d9e97 to a1ed23c (9 revisions) (flutter/flutter#194302)
2026-10-13 [email protected] Use PE/COFF AOT snapshots for Windows x64 (flutter/flutter#187594)
2026-10-13 [email protected] Fix Expansible crash when PageStorage holds a non-bool value (flutter/flutter#192195)
2026-10-13 [email protected] Roll Skia from ffeccb3ca58a to e5b5db6d0d6f (1 revision) (flutter/flutter#194297)
2026-10-13 [email protected] Explain why initState() is too early to depend on an inherited widget (flutter/flutter#192727)
2026-10-13 [email protected] Refactor TestPlatformDispatcher (flutter/flutter#192747)
2026-10-13 [email protected] Roll Skia from 3de0984208ec to ffeccb3ca58a (2 revisions) (flutter/flutter#194291)
2026-10-13 [email protected] Roll Skia from 0580c2b780f6 to 3de0984208ec (2 revisions) (flutter/flutter#194281)
2026-10-13 [email protected] Roll Skia from f641d55e07a8 to 0580c2b780f6 (3 revisions) (flutter/flutter#194275)
2026-10-13 [email protected] Roll Skia from 0e5d8d1be81b to f641d55e07a8 (1 revision) (flutter/flutter#194266)
2026-10-13 [email protected] Scaffold view metrics overrides (flutter/flutter#192764)
2026-10-13 [email protected] [web] Add SemanticsRole.listBox and SemanticsRole.option (flutter/flutter#192971)
2026-10-13 [email protected] Pin mac_unopt to macOS 15 (flutter/flutter#194254)
2026-10-13 [email protected] Roll pub packages (flutter/flutter#194257)
2026-10-12 [email protected] Roll Skia from 17f6986c226c to 0e5d8d1be81b (4 revisions) (flutter/flutter#194249)
2026-10-12 [email protected] Make DisplayLists' use of DlPaint, SkPaint, and impeller::Paint agree on the default isAntiAlias (flutter/flutter#193939)

If this roll has caused a breakage, revert this CL and set the roller
...

…tatic state (flutter#189437)

[flutter_tools] Clean up outdated widget preview TODOs and refactor
static state in tests

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This PR cleans up outdated TODO comments and refactors static state in
`WidgetPreviewStartCommand` related to the generation of the widget
preview scaffold.

Specifically, GitHub issue **flutter#179036** ("Stop generating scaffold under
`$TMP`") has been resolved, and the scaffold is now correctly placed in
`.widget_preview/` under the target project directory. This PR:
- Removes the static `widgetPreviewScaffold` field and replaces it with
a local `final Directory widgetPreviewScaffold` inside the `runCommand`
method.
- Removes the `fs.currentDirectory = widgetPreviewScaffold;` change,
which was mutating global process CWD and causing directory safety lock
issues.
- Cleans up obsolete comments referencing the temporary directories
(`$TMP`) and the now-resolved issue flutter#179036.
- Refactors the test helpers in `widget_preview_test.dart` to resolve
the scaffold directory relative to the project directory
(`.widget_preview`) instead of accessing
`WidgetPreviewStartCommand.widgetPreviewScaffold`, and renames the test
cases to refer to `.widget_preview`.

Fixes part of flutter#179036.

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---------

Co-authored-by: Ben Konyi <[email protected]>
Co-authored-by: Sam Rawlins <[email protected]>