[go_router] Fix ShellRoute chrome dropped from semantics tree by ModalBarrier - #12353

…lBarrier

Every ModalRoute builds a ModalBarrier wrapped in BlockSemantics, which
drops the semantics of siblings painted before it up to the nearest
semantics boundary. The nested Navigator built for
ShellRoute/StatefulShellRoute branches establishes no such boundary, so
the block escapes it and prunes earlier-painted shell chrome (side rail,
app bar in Row/Column shells). Wraps shell navigators (not the root
navigator) in Semantics(container: true) to contain the block.

Squash of the two commits on the upstream PR branch:
flutter#12353
Fixes flutter/flutter#135656

…er#193289)

Roll Packages from c2b58e1a97fb to 431ea69a42e2 (56 revisions)

flutter/packages@c2b58e1...431ea69

2026-09-24 [email protected] [cross_file]
Updates cross_file to a package separated federated plugin
(flutter/packages#11010)
2026-09-23 [email protected] [material_ui]
Remove static access of `copyWith` from `dart fix` golden tests for
`ThemeData/TextTheme` (flutter/packages#12994)
2026-09-23 [email protected] [camera_avfoundation] Replace
deprecated high-resolution capture APIs (flutter/packages#12372)
2026-09-23 [email protected] [pigeon] update nullish checks to use
new isNullish method (flutter/packages#12985)
2026-09-23 [email protected] [ci] Assign batch release PR approver
as reviewer on sync-back PR (flutter/packages#12976)
2026-09-23 [email protected] [image_picker] Fix scaling 10-bit images
(flutter/packages#12557)
2026-09-23 [email protected] [material_ui] Improve
Autocomplete, DrawerHeader, and Tooltip accessibility
(flutter/packages#12918)
2026-09-23 [email protected] [google_fonts] Decouple GoogleFontsLite
for full tree-shaking and add full feature parity
(flutter/packages#12830)
2026-09-23 [email protected] [file_selector]
Ignore flakey `file_selector_android` tests (flutter/packages#12992)
2026-09-23 [email protected] [CI] Remove
bringup from `Mac_arm64 build_all_packages` targets
(flutter/packages#12978)
2026-09-22 [email protected] [material_ui]
Unskip 5 passing web tests in bottom_app_bar_test and text_field_test
(flutter/packages#12983)
2026-09-22 [email protected]
[cupertino_ui] Unskip 5 passing web tests in
adaptive_text_selection_toolbar_test and text_field_test
(flutter/packages#12984)
2026-09-22 [email protected] [go_router] Fix ShellRoute chrome dropped
from semantics tree by ModalBarrier (flutter/packages#12353)
2026-09-22 [email protected] [material_ui]
Add contrastLevel for M3 ColorScheme (flutter/packages#12743)
2026-09-22 [email protected] [go_router] Preserve nested pushes
during config updates (flutter/packages#12611)
2026-09-22 [email protected] [material_ui]
Migrate M3 Chip template to use new gen_defaults
(flutter/packages#12847)
2026-09-22 [email protected] [material_ui] Fix
LocalHistoryEntry leak when double tapping Drawer scrim
(flutter/packages#12552)
2026-09-22 [email protected] Update suggested reviewers
(flutter/packages#12974)
2026-09-22 [email protected] Sync release-material_ui-1.4.0 to
main (flutter/packages#12966)
2026-09-22 [email protected] Sync release-cupertino_ui-1.1.1 to
main (flutter/packages#12965)
2026-09-21 [email protected] [ci] Update repo
for 3.47 stable release (flutter/packages#12959)
2026-09-21 [email protected] Manual roll Flutter from
27fec0e to 4fcd90b (1 revision) (flutter/packages#12904)
2026-09-21 [email protected] Revert "[go_router_builder] Migrate to
material_ui" (flutter/packages#12962)
2026-09-21 [email protected]
[material_ui] Update `material_ui` tests to prevent them from failing
when framework `TextStyle` changes (flutter/packages#12728)
2026-09-21 [email protected] [go_router_builder] Migrate to
material_ui (flutter/packages#12913)
2026-09-21 [email protected] [material_ui,
cupertino_ui] Bump Flutter version from to 3.47 (flutter/packages#12944)
2026-09-21 [email protected] [cupertino_ui] Work around dart2wasm
optional parameter inference bug in example checkbox tests
(flutter/packages#12961)
2026-09-21 [email protected] [cupertino_ui] Work around dart2wasm
optional parameter inference bug in checkbox_test.dart
(flutter/packages#12956)
2026-09-21 [email protected] [google_sign_in] PR 3/4 Migrate
ViewProvider and GID SDK wrappers from Objective-C to Swift
(flutter/packages#12657)
2026-09-21 [email protected] [google_sign_in] PR 2/4 Migrate
the plugin class from Objective-C to Swift. (flutter/packages#12655)
2026-09-20 [email protected]
[cross_file_darwin] iOS/macOS implementation of `cross_file`
(flutter/packages#12910)
2026-09-20 [email protected]
[cross_file_web] Web implementation of `cross_file`
(flutter/packages#12908)
2026-09-20 [email protected] [material_ui]
Migrate M3 `InputChip` template to use new gen_defaults
(flutter/packages#12850)
2026-09-20 [email protected] [material_ui]
Migrate M3 Checkbox defaults to new gen_defaults
(flutter/packages#12816)
2026-09-20 [email protected] [material_ui]
Migrate M3 `FilterChip` template to use new gen_defaults
(flutter/packages#12849)
2026-09-19 [email protected] [material_ui] Announce PopupMenuButton with a
child as a button (flutter/packages#12585)
2026-09-19 [email protected] Roll Flutter (stable) from
9584c67 to 6a19cca (7 revisions) (flutter/packages#12950)
2026-09-18 [email protected] [material_ui]
Reduce the `material_ui` non-wasm web test suite
(flutter/packages#12763)
2026-09-18 [email protected] Replace
`Mac_x64` builders with `Mac_arm64` ones (flutter/packages#12941)
2026-09-18 [email protected]
[in_app_purchase_storekit] Use `_$SKPaymentDiscountWrapperToJson`
(flutter/packages#12721)
2026-09-18 [email protected] [In_app _purchase] README
excerpt examples and changelog (flutter/packages#12739)
2026-09-18 [email protected] [material_ui] Add alternative
input method for `RangeSlider` in `NavigationMode.directional`
(flutter/packages#12630)
2026-09-18 [email protected]
[cross_file_android] Android implementation of `cross_file`
(flutter/packages#12909)
2026-09-18 [email protected]
[camera_platform_interface] Adds videoOutputPath support to
startVideoRecording (flutter/packages#12667)
2026-09-17 [email protected] [cupertino_ui] Migrate a
snippet in `CupertinoCheckbox`'s API doc to `{@example}` and add unit
tests (flutter/packages#12180)
2026-09-17 [email protected] [material_ui]
Default gen_defaults color helper prefix (flutter/packages#12848)
...

…lBarrier (flutter#12353)

Shell chrome painted before a `ShellRoute` or `StatefulShellRoute` navigator (a side rail, or an app bar in a `Row`/`Column` based shell) disappears from the semantics tree. Screen readers cannot reach it at all: the nodes are not merely unnamed, they do not exist.

The mechanism: every `ModalRoute` builds a `ModalBarrier` wrapped in `BlockSemantics`, which drops the semantics of everything painted before it up to the nearest semantics boundary. The nested `Navigator` that go_router builds for shell routes does not establish such a boundary, so the block escapes the shell's navigator and prunes the shell's own chrome. Bottom-nav shells are unaffected only because `Scaffold` happens to paint its body before its bars.

This PR wraps the navigator built for `ShellRoute`/`StatefulShellRoute` branches in `Semantics(container: true)`, which contains the block. The root navigator is left unwrapped, since it has no earlier-painted siblings by construction. This is the workaround a framework team member confirmed on the linked issue; applying it inside go_router fixes it for every shell consumer without app-side patches.

Semantics tree of a minimal repro (a `Row` shell: 220px sidebar with three nav buttons, routed content on the right), before and after, captured with `debugDumpSemanticsTree`:

<details>
<summary>Before: 6 nodes, the entire sidebar subtree is missing</summary>

```
SemanticsNode#0
 │ Rect.fromLTRB(0.0, 0.0, 2400.0, 1800.0)
 │
 └─SemanticsNode#1
   │ Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) scaled by 3.0x
   │ textDirection: ltr
   │ sortKey: OrdinalSortKey#39327(order: 0.0)
   │
   └─SemanticsNode#2
     │ Rect.fromLTRB(0.0, 0.0, 800.0, 600.0)
     │ flags: scopesRoute
     │
     └─SemanticsNode#3
       │ Rect.fromLTRB(221.0, 0.0, 800.0, 600.0)
       │ sortKey: OrdinalSortKey#39327(order: 0.0)
       │
       └─SemanticsNode#4
         │ Rect.fromLTRB(0.0, 0.0, 579.0, 600.0)
         │ flags: scopesRoute
         │
         └─SemanticsNode#5
             Rect.fromLTRB(85.5, 284.0, 493.5, 316.0)
             label: "Dashboard content"
             textDirection: ltr
```

Node `flutter#3` starts at `x=221`, right of the 220px sidebar plus a 1px divider. There is no node anywhere for the sidebar: no title, no navigation container, no buttons. The sidebar is painted before the `/dashboard` route (`flutter#4`, `scopesRoute`) inside the same enclosing semantics scope, which is exactly what that route's `BlockSemantics` drops.

</details>

<details>
<summary>After: sidebar fully present, routed content unchanged (two nodes for the repro's own toggle switch omitted for brevity)</summary>

```
SemanticsNode#0
 │ Rect.fromLTRB(0.0, 0.0, 2400.0, 1800.0)
 │
 └─SemanticsNode#1
   │ Rect.fromLTRB(0.0, 0.0, 800.0, 600.0) scaled by 3.0x
   │ textDirection: ltr
   │ sortKey: OrdinalSortKey#39327(order: 0.0)
   │
   └─SemanticsNode#2
     │ Rect.fromLTRB(0.0, 0.0, 800.0, 600.0)
     │ flags: scopesRoute
     │
     ├─SemanticsNode#3
     │   Rect.fromLTRB(16.0, 16.0, 204.0, 76.0)
     │   label: "Nested Navigator Semantics"
     │   textDirection: ltr
     │
     ├─SemanticsNode#4
     │ │ Rect.fromLTRB(0.0, 92.0, 220.0, 260.0)
     │ │ label: "Main navigation"
     │ │ textDirection: ltr
     │ │
     │ ├─SemanticsNode#5
     │ │   Rect.fromLTRB(0.0, 0.0, 220.0, 56.0)
     │ │   actions: focus, tap
     │ │   flags: isSelected, isButton, hasEnabledState, isEnabled,
     │ │     isFocusable, hasSelectedState
     │ │   label: "Dashboard"
     │ │   textDirection: ltr
     │ │
     │ ├─SemanticsNode#6
     │ │   Rect.fromLTRB(0.0, 56.0, 220.0, 112.0)
     │ │   actions: focus, tap
     │ │   flags: isButton, hasEnabledState, isEnabled, isFocusable,
     │ │     hasSelectedState
     │ │   label: "Settings"
     │ │   textDirection: ltr
     │ │
     │ └─SemanticsNode#7
     │     Rect.fromLTRB(0.0, 112.0, 220.0, 168.0)
     │     actions: focus, tap
     │     flags: isButton, hasEnabledState, isEnabled, isFocusable,
     │       hasSelectedState
     │     label: "Reports"
     │     textDirection: ltr
     │
     └─SemanticsNode#10
       │ Rect.fromLTRB(221.0, 0.0, 800.0, 600.0)
       │ sortKey: OrdinalSortKey#39327(order: 0.0)
       │
       └─SemanticsNode#11
         │ Rect.fromLTRB(0.0, 0.0, 579.0, 600.0)
         │ flags: scopesRoute
         │
         └─SemanticsNode#12
             Rect.fromLTRB(85.5, 284.0, 493.5, 316.0)
             label: "Dashboard content"
             textDirection: ltr
```

The routed content node ("Dashboard content") is byte-identical in both dumps. The fix does not change the routed content's semantics, only whether the chrome painted before the shell navigator survives alongside it.

</details>

Notes for review:

- Tests: the fix commit adds a `Shell navigator semantics boundary` group to `builder_test.dart` (chrome survives, structural wrap present, root navigator not wrapped), and a second commit adds a `StatefulShellRoute.indexedStack` regression test covering branch switching. Removing the wrap makes the chrome tests fail with `Found 0 widgets with a semantics label`.
- Version/CHANGELOG: go_router uses batch release, so this PR adds a file under `pending_changelogs/` (`version: patch`) instead of touching `pubspec.yaml` or `CHANGELOG.md`.
- Interaction with flutter/flutter#181519 (replacing `BlockSemantics` in modal routes with `AccessibilityFocusBlockType.blockSubtree`): the fix establishes a semantics container boundary at the shell navigator, which is where a nested navigator should scope its routes' blocking regardless of the blocking mechanism. If that migration later makes the containment unnecessary, the wrap stays harmless.

Fixes flutter/flutter#135656
Related: flutter/flutter#55758, flutter/flutter#150978

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