Make Directionality.of non-null (#69060)

packages/flutter/lib/src/cupertino/date_picker.dart

@@ -1620,7 +1620,7 @@ class _CupertinoTimerPickerState extends State<CupertinoTimerPicker> {
   void didChangeDependencies() {
     super.didChangeDependencies();
 
-    textDirection = Directionality.of(context)!;
+    textDirection = Directionality.of(context);
     localizations = CupertinoLocalizations.of(context);
 
     _measureLabelMetrics();

packages/flutter/lib/src/cupertino/nav_bar.dart

@@ -1374,7 +1374,7 @@ class _BackChevron extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     final TextStyle textStyle = DefaultTextStyle.of(context).style;
 
     // Replicate the Icon logic here to get a tightly sized icon and add
@@ -1588,7 +1588,7 @@ class _NavigationBarTransition extends StatelessWidget {
       animation: animation,
       bottomNavBar: bottomNavBar,
       topNavBar: topNavBar,
-      directionality: Directionality.of(context)!,
+      directionality: Directionality.of(context),
     );
 
     final List<Widget> children = <Widget>[

packages/flutter/lib/src/cupertino/picker.dart

@@ -413,14 +413,14 @@ class _CupertinoPickerSemantics extends SingleChildRenderObjectWidget {
   @override
   RenderObject createRenderObject(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
-    return _RenderCupertinoPickerSemantics(scrollController, Directionality.of(context)!);
+    return _RenderCupertinoPickerSemantics(scrollController, Directionality.of(context));
   }
 
   @override
   void updateRenderObject(BuildContext context, covariant _RenderCupertinoPickerSemantics renderObject) {
     assert(debugCheckHasDirectionality(context));
     renderObject
-      ..textDirection = Directionality.of(context)!
+      ..textDirection = Directionality.of(context)
       ..controller = scrollController;
   }
 }

packages/flutter/lib/src/cupertino/route.dart

@@ -514,7 +514,7 @@ class CupertinoPageTransition extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
-    final TextDirection? textDirection = Directionality.of(context);
+    final TextDirection textDirection = Directionality.of(context);
     return SlideTransition(
       position: _secondaryPositionAnimation,
       textDirection: textDirection,
@@ -578,7 +578,7 @@ class CupertinoFullscreenDialogTransition extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
-    final TextDirection? textDirection = Directionality.of(context);
+    final TextDirection textDirection = Directionality.of(context);
     return SlideTransition(
       position: _secondaryPositionAnimation,
       textDirection: textDirection,
@@ -677,7 +677,7 @@ class _CupertinoBackGestureDetectorState<T> extends State<_CupertinoBackGestureD
   }
 
   double _convertToLogical(double value) {
-    switch (Directionality.of(context)!) {
+    switch (Directionality.of(context)) {
       case TextDirection.rtl:
         return -value;
       case TextDirection.ltr:

packages/flutter/lib/src/cupertino/scrollbar.dart

@@ -283,7 +283,7 @@ class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProv
       _painter = _buildCupertinoScrollbarPainter(context);
     } else {
       _painter!
-        ..textDirection = Directionality.of(context)!
+        ..textDirection = Directionality.of(context)
         ..color = CupertinoDynamicColor.resolve(_kScrollbarColor, context)!
         ..padding = MediaQuery.of(context).padding;
     }
@@ -309,7 +309,7 @@ class _CupertinoScrollbarState extends State<CupertinoScrollbar> with TickerProv
   ScrollbarPainter _buildCupertinoScrollbarPainter(BuildContext context) {
     return ScrollbarPainter(
       color: CupertinoDynamicColor.resolve(_kScrollbarColor, context)!,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       thickness: _thickness,
       fadeoutOpacityAnimation: _fadeoutOpacityAnimation,
       mainAxisMargin: _kScrollbarMainAxisMargin,

packages/flutter/lib/src/cupertino/segmented_control.dart

@@ -448,7 +448,7 @@ class _SegmentedControlRenderWidget<T> extends MultiChildRenderObjectWidget {
   @override
   RenderObject createRenderObject(BuildContext context) {
     return _RenderSegmentedControl<T>(
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       selectedIndex: selectedIndex,
       pressedIndex: pressedIndex,
       backgroundColors: backgroundColors,
@@ -459,7 +459,7 @@ class _SegmentedControlRenderWidget<T> extends MultiChildRenderObjectWidget {
   @override
   void updateRenderObject(BuildContext context, _RenderSegmentedControl<T> renderObject) {
     renderObject
-      ..textDirection = Directionality.of(context)!
+      ..textDirection = Directionality.of(context)
       ..selectedIndex = selectedIndex
       ..pressedIndex = pressedIndex
       ..backgroundColors = backgroundColors

packages/flutter/lib/src/cupertino/slider.dart

@@ -288,7 +288,7 @@ class _CupertinoSliderRenderObjectWidget extends LeafRenderObjectWidget {
       onChangeStart: onChangeStart,
       onChangeEnd: onChangeEnd,
       vsync: vsync,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
     );
   }
 
@@ -304,7 +304,7 @@ class _CupertinoSliderRenderObjectWidget extends LeafRenderObjectWidget {
       ..onChanged = onChanged
       ..onChangeStart = onChangeStart
       ..onChangeEnd = onChangeEnd
-      ..textDirection = Directionality.of(context)!;
+      ..textDirection = Directionality.of(context);
     // Ticker provider cannot change since there's a 1:1 relationship between
     // the _SliderRenderObjectWidget object and the _SliderState object.
   }

packages/flutter/lib/src/cupertino/sliding_segmented_control.dart

@@ -399,7 +399,7 @@ class _SegmentedControlState<T> extends State<CupertinoSlidingSegmentedControl<T
   Widget build(BuildContext context) {
     debugCheckHasDirectionality(context);
 
-    switch (Directionality.of(context)!) {
+    switch (Directionality.of(context)) {
       case TextDirection.ltr:
         keys = widget.children.keys.toList(growable: false);
         break;

packages/flutter/lib/src/cupertino/switch.dart

@@ -254,7 +254,7 @@ class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderSt
         ..curve = Curves.linear
         ..reverseCurve = Curves.linear;
       final double delta = details.primaryDelta! / _kTrackInnerLength;
-      switch (Directionality.of(context)!) {
+      switch (Directionality.of(context)) {
         case TextDirection.rtl:
           _positionController.value -= delta;
           break;
@@ -302,7 +302,7 @@ class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderSt
         )!,
         trackColor: CupertinoDynamicColor.resolve(widget.trackColor ?? CupertinoColors.secondarySystemFill, context)!,
         onChanged: widget.onChanged,
-        textDirection: Directionality.of(context)!,
+        textDirection: Directionality.of(context),
         state: this,
       ),
     );

packages/flutter/lib/src/material/animated_icons/animated_icons.dart

@@ -109,7 +109,7 @@ class AnimatedIcon extends StatelessWidget {
     final IconThemeData iconTheme = IconTheme.of(context);
     assert(iconTheme.isConcrete);
     final double iconSize = size ?? iconTheme.size!;
-    final TextDirection textDirection = this.textDirection ?? Directionality.of(context)!;
+    final TextDirection textDirection = this.textDirection ?? Directionality.of(context);
     final double iconOpacity = iconTheme.opacity!;
     Color iconColor = color ?? iconTheme.color!;
     if (iconOpacity != 1.0)

packages/flutter/lib/src/material/bottom_navigation_bar.dart

@@ -940,7 +940,7 @@ class _BottomNavigationBarState extends State<BottomNavigationBar> with TickerPr
           child: CustomPaint(
             painter: _RadialPainter(
               circles: _circles.toList(),
-              textDirection: Directionality.of(context)!,
+              textDirection: Directionality.of(context),
             ),
             child: Material( // Splashes.
               type: MaterialType.transparency,

packages/flutter/lib/src/material/chip.dart

@@ -2129,7 +2129,7 @@ class _ChipRenderWidget extends RenderObjectWidget {
   RenderObject createRenderObject(BuildContext context) {
     return _RenderChip(
       theme: theme,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       value: value,
       isEnabled: isEnabled,
       checkmarkAnimation: checkmarkAnimation,

packages/flutter/lib/src/material/drawer.dart

@@ -407,7 +407,7 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
         delta = -delta;
         break;
     }
-    switch (Directionality.of(context)!) {
+    switch (Directionality.of(context)) {
       case TextDirection.rtl:
         _controller.value -= delta;
         break;
@@ -434,7 +434,7 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
           visualVelocity = -visualVelocity;
           break;
       }
-      switch (Directionality.of(context)!) {
+      switch (Directionality.of(context)) {
         case TextDirection.rtl:
           _controller.fling(velocity: -visualVelocity);
           if (widget.drawerCallback != null)
@@ -499,7 +499,7 @@ class DrawerControllerState extends State<DrawerController> with SingleTickerPro
   Widget _buildDrawer(BuildContext context) {
     final bool drawerIsStart = widget.alignment == DrawerAlignment.start;
     final EdgeInsets padding = MediaQuery.of(context).padding;
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
 
     double? dragAreaWidth = widget.edgeDragWidth;
     if (widget.edgeDragWidth == null) {

packages/flutter/lib/src/material/flexible_space_bar.dart

@@ -252,7 +252,7 @@ class _FlexibleSpaceBarState extends State<FlexibleSpaceBar> {
   Alignment _getTitleAlignment(bool effectiveCenterTitle) {
     if (effectiveCenterTitle)
       return Alignment.bottomCenter;
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     assert(textDirection != null);
     switch (textDirection) {
       case TextDirection.rtl:

packages/flutter/lib/src/material/ink_well.dart

@@ -842,7 +842,7 @@ class _InkResponseState extends State<_InkResponseStateWidget>
           customBorder: widget.customBorder,
           rectCallback: widget.getRectCallback!(referenceBox),
           onRemoved: handleInkRemoval,
-          textDirection: Directionality.of(context)!,
+          textDirection: Directionality.of(context),
           fadeDuration: getFadeDurationForType(type),
         );
         updateKeepAlive();
@@ -900,7 +900,7 @@ class _InkResponseState extends State<_InkResponseStateWidget>
       borderRadius: borderRadius,
       customBorder: customBorder,
       onRemoved: onRemoved,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
     );
 
     return splash;

packages/flutter/lib/src/material/input_decorator.dart

@@ -237,7 +237,7 @@ class _BorderContainerState extends State<_BorderContainer> with TickerProviderS
         border: _border,
         gapAnimation: widget.gapAnimation,
         gap: widget.gap,
-        textDirection: Directionality.of(context)!,
+        textDirection: Directionality.of(context),
         fillColor: widget.fillColor,
         hoverColorTween: _hoverColorTween,
         hoverAnimation: _hoverAnimation,
@@ -2311,7 +2311,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
 
     // The _Decoration widget and _RenderDecoration assume that contentPadding
     // has been resolved to EdgeInsets.
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     final EdgeInsets? decorationContentPadding = decoration!.contentPadding?.resolve(textDirection);
 
     final EdgeInsets contentPadding;

packages/flutter/lib/src/material/list_tile.dart

@@ -1067,7 +1067,7 @@ class ListTile extends StatelessWidget {
     }
 
     const EdgeInsets _defaultContentPadding = EdgeInsets.symmetric(horizontal: 16.0);
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     final EdgeInsets resolvedContentPadding = contentPadding?.resolve(textDirection)
       ?? tileTheme.contentPadding?.resolve(textDirection)
       ?? _defaultContentPadding;

packages/flutter/lib/src/material/pickers/calendar_date_picker.dart

@@ -180,7 +180,7 @@ class _CalendarDatePickerState extends State<CalendarDatePicker> {
     assert(debugCheckHasMaterialLocalizations(context));
     assert(debugCheckHasDirectionality(context));
     _localizations = MaterialLocalizations.of(context);
-    _textDirection = Directionality.of(context)!;
+    _textDirection = Directionality.of(context);
     if (!_announcedInitialDate) {
       _announcedInitialDate = true;
       SemanticsService.announce(
@@ -525,7 +525,7 @@ class _MonthPickerState extends State<_MonthPicker> {
   void didChangeDependencies() {
     super.didChangeDependencies();
     _localizations = MaterialLocalizations.of(context);
-    _textDirection = Directionality.of(context)!;
+    _textDirection = Directionality.of(context);
   }
 
   @override
@@ -709,7 +709,7 @@ class _MonthPickerState extends State<_MonthPicker> {
   }
 
   DateTime? _nextDateInDirection(DateTime date, TraversalDirection direction) {
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     DateTime nextDate = utils.addDaysToDate(date, _dayDirectionOffset(direction, textDirection));
     while (!nextDate.isBefore(widget.firstDate) && !nextDate.isAfter(widget.lastDate)) {
       if (_isSelectable(nextDate)) {

packages/flutter/lib/src/material/pickers/calendar_date_range_picker.dart

@@ -340,7 +340,7 @@ class _CalendarKeyboardNavigatorState extends State<_CalendarKeyboardNavigator>
   }
 
   DateTime? _nextDateInDirection(DateTime date, TraversalDirection direction) {
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     final DateTime nextDate = utils.addDaysToDate(date, _dayDirectionOffset(direction, textDirection));
     if (!nextDate.isBefore(widget.firstDate) && !nextDate.isAfter(widget.lastDate)) {
       return nextDate;
@@ -707,7 +707,7 @@ class _MonthItemState extends State<_MonthItem> {
     final ColorScheme colorScheme = theme.colorScheme;
     final TextTheme textTheme = theme.textTheme;
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     final Color highlightColor = _highlightColor(context);
     final int day = dayToBuild.day;
 

packages/flutter/lib/src/material/popup_menu.dart

@@ -749,7 +749,7 @@ class _PopupMenuRoute<T> extends PopupRoute<T> {
               position,
               itemSizes,
               selectedItemIndex,
-              Directionality.of(context)!,
+              Directionality.of(context),
             ),
             child: capturedThemes.wrap(menu),
           );

packages/flutter/lib/src/material/progress_indicator.dart

@@ -332,7 +332,7 @@ class _LinearProgressIndicatorState extends State<LinearProgressIndicator> with
 
   @override
   Widget build(BuildContext context) {
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
 
     if (widget.value != null)
       return _buildIndicator(context, _controller.value, textDirection);

packages/flutter/lib/src/material/range_slider.dart

@@ -720,7 +720,7 @@ class _RangeSliderRenderObjectWidget extends LeafRenderObjectWidget {
       onChangeStart: onChangeStart,
       onChangeEnd: onChangeEnd,
       state: state,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       semanticFormatterCallback: semanticFormatterCallback,
       platform: Theme.of(context)!.platform,
     );
@@ -741,7 +741,7 @@ class _RangeSliderRenderObjectWidget extends LeafRenderObjectWidget {
       ..onChanged = onChanged
       ..onChangeStart = onChangeStart
       ..onChangeEnd = onChangeEnd
-      ..textDirection = Directionality.of(context)!
+      ..textDirection = Directionality.of(context)
       ..semanticFormatterCallback = semanticFormatterCallback
       ..platform = Theme.of(context)!.platform;
   }

packages/flutter/lib/src/material/scaffold.dart

@@ -2908,7 +2908,7 @@ class ScaffoldState extends State<Scaffold> with TickerProviderStateMixin {
     assert(debugCheckHasDirectionality(context));
     final MediaQueryData mediaQuery = MediaQuery.of(context);
     final ThemeData themeData = Theme.of(context)!;
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
 
     // TODO(Piinks): Remove old SnackBar API after migrating ScaffoldMessenger
     _accessibleNavigation = mediaQuery.accessibleNavigation;

packages/flutter/lib/src/material/scrollbar.dart

@@ -122,7 +122,7 @@ class _ScrollbarState extends State<Scrollbar> with SingleTickerProviderStateMix
       case TargetPlatform.linux:
       case TargetPlatform.windows:
         _themeColor = theme.highlightColor.withOpacity(1.0);
-        _textDirection = Directionality.of(context)!;
+        _textDirection = Directionality.of(context);
         _materialPainter = _buildMaterialScrollbarPainter();
         _useCupertinoScrollbar = false;
         _triggerScrollbar();

packages/flutter/lib/src/material/slider.dart

@@ -550,7 +550,7 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
 
   void _actionHandler(_AdjustSliderIntent intent) {
     final _RenderSlider renderSlider = _renderObjectKey.currentContext!.findRenderObject()! as _RenderSlider;
-    final TextDirection textDirection = Directionality.of(_renderObjectKey.currentContext!)!;
+    final TextDirection textDirection = Directionality.of(_renderObjectKey.currentContext!);
     switch (intent.type) {
       case _SliderAdjustmentType.right:
         switch (textDirection) {
@@ -825,7 +825,7 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
       onChangeStart: onChangeStart,
       onChangeEnd: onChangeEnd,
       state: state,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       semanticFormatterCallback: semanticFormatterCallback,
       platform: Theme.of(context)!.platform,
       hasFocus: hasFocus,
@@ -847,7 +847,7 @@ class _SliderRenderObjectWidget extends LeafRenderObjectWidget {
       ..onChanged = onChanged
       ..onChangeStart = onChangeStart
       ..onChangeEnd = onChangeEnd
-      ..textDirection = Directionality.of(context)!
+      ..textDirection = Directionality.of(context)
       ..semanticFormatterCallback = semanticFormatterCallback
       ..platform = Theme.of(context)!.platform
       ..hasFocus = hasFocus

packages/flutter/lib/src/material/switch.dart

@@ -476,7 +476,7 @@ class _SwitchRenderObjectWidget extends LeafRenderObjectWidget {
       inactiveTrackColor: inactiveTrackColor,
       configuration: configuration,
       onChanged: onChanged != null ? _handleValueChanged : null,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       additionalConstraints: additionalConstraints,
       hasFocus: hasFocus,
       hovering: hovering,
@@ -501,7 +501,7 @@ class _SwitchRenderObjectWidget extends LeafRenderObjectWidget {
       ..inactiveTrackColor = inactiveTrackColor
       ..configuration = configuration
       ..onChanged = onChanged != null ? _handleValueChanged : null
-      ..textDirection = Directionality.of(context)!
+      ..textDirection = Directionality.of(context)
       ..additionalConstraints = additionalConstraints
       ..dragStartBehavior = dragStartBehavior
       ..hasFocus = hasFocus

packages/flutter/lib/src/material/tabs.dart

@@ -918,7 +918,7 @@ class _TabBarState extends State<TabBar> {
     if (!widget.isScrollable)
       return 0.0;
     double tabCenter = _indicatorPainter!.centerOf(index);
-    switch (Directionality.of(context)!) {
+    switch (Directionality.of(context)) {
       case TextDirection.rtl:
         tabCenter = _tabStripWidth - tabCenter;
         break;

packages/flutter/lib/src/material/time_picker.dart

@@ -1266,7 +1266,7 @@ class _DialState extends State<_Dial> with SingleTickerProviderStateMixin {
           accentColor: accentColor,
           dotColor: theme.colorScheme.surface,
           theta: _theta.value,
-          textDirection: Directionality.of(context)!,
+          textDirection: Directionality.of(context),
         ),
       ),
     );
@@ -2210,5 +2210,5 @@ Future<TimeOfDay?> showTimePicker({
 }
 
 void _announceToAccessibility(BuildContext context, String message) {
-  SemanticsService.announce(message, Directionality.of(context)!);
+  SemanticsService.announce(message, Directionality.of(context));
 }

packages/flutter/lib/src/material/toggle_buttons.dart

@@ -577,7 +577,7 @@ class ToggleButtons extends StatelessWidget {
     );
     final ThemeData theme = Theme.of(context)!;
     final ToggleButtonsThemeData toggleButtonsTheme = ToggleButtonsTheme.of(context);
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
 
     return IntrinsicHeight(
       child: Row(
@@ -901,7 +901,7 @@ class _SelectToggleButton extends SingleChildRenderObjectWidget {
     borderRadius,
     isFirstButton,
     isLastButton,
-    Directionality.of(context)!,
+    Directionality.of(context),
   );
 
   @override
@@ -913,7 +913,7 @@ class _SelectToggleButton extends SingleChildRenderObjectWidget {
       ..borderRadius = borderRadius
       ..isFirstButton = isFirstButton
       ..isLastButton = isLastButton
-      ..textDirection = Directionality.of(context)!;
+      ..textDirection = Directionality.of(context);
   }
 }
 

packages/flutter/lib/src/material/tooltip.dart

@@ -332,7 +332,7 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
     // updated values from happening to leak into the overlay when the overlay
     // rebuilds.
     final Widget overlay = Directionality(
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       child: _TooltipOverlay(
         message: widget.message,
         height: height,

packages/flutter/lib/src/material/user_accounts_drawer_header.dart

@@ -138,7 +138,7 @@ class _AccountDetailsState extends State<_AccountDetails> with SingleTickerProvi
 
     Widget accountDetails = CustomMultiChildLayout(
       delegate: _AccountDetailsLayout(
-        textDirection: Directionality.of(context)!,
+        textDirection: Directionality.of(context),
       ),
       children: <Widget>[
         if (widget.accountName != null)

packages/flutter/lib/src/widgets/banner.dart

@@ -304,9 +304,9 @@ class Banner extends StatelessWidget {
     return CustomPaint(
       foregroundPainter: BannerPainter(
         message: message,
-        textDirection: textDirection ?? Directionality.of(context)!,
+        textDirection: textDirection ?? Directionality.of(context),
         location: location,
-        layoutDirection: layoutDirection ?? Directionality.of(context)!,
+        layoutDirection: layoutDirection ?? Directionality.of(context),
         color: color,
         textStyle: textStyle,
       ),

packages/flutter/lib/src/widgets/basic.dart

@@ -100,17 +100,23 @@ class Directionality extends InheritedWidget {
   /// the given context.
   ///
   /// If there is no [Directionality] ancestor widget in the tree at the given
-  /// context, then this will return null.
+  /// context, then this will throw a descriptive [FlutterError] in debug mode
+  /// and an exception in release mode.
   ///
   /// Typical usage is as follows:
   ///
   /// ```dart
   /// TextDirection textDirection = Directionality.of(context);
   /// ```
-  // TODO(goderbauer): Make this non-null when customers have upgraded to Directionality.maybeOf.
-  static TextDirection? of(BuildContext context) {
-    final Directionality? widget = context.dependOnInheritedWidgetOfExactType<Directionality>();
-    return widget?.textDirection;
+  ///
+  /// See also:
+  ///
+  ///  * [maybeOf], which will return null if no [Directionality] ancestor
+  ///    widget is in the tree.
+  static TextDirection of(BuildContext context) {
+    assert(debugCheckHasDirectionality(context));
+    final Directionality widget = context.dependOnInheritedWidgetOfExactType<Directionality>()!;
+    return widget.textDirection;
   }
 
   /// The text direction from the closest instance of this class that encloses
@@ -124,6 +130,11 @@ class Directionality extends InheritedWidget {
   /// ```dart
   /// TextDirection? textDirection = Directionality.maybeOf(context);
   /// ```
+  ///
+  /// See also:
+  ///
+  ///  * [of], which will throw if no [Directionality] ancestor widget is in the
+  ///    tree.
   static TextDirection? maybeOf(BuildContext context) {
     final Directionality? widget = context.dependOnInheritedWidgetOfExactType<Directionality>();
     return widget?.textDirection;
@@ -3135,7 +3146,7 @@ AxisDirection getAxisDirectionFromAxisReverseAndDirectionality(
   switch (axis) {
     case Axis.horizontal:
       assert(debugCheckHasDirectionality(context));
-      final TextDirection textDirection = Directionality.of(context)!;
+      final TextDirection textDirection = Directionality.of(context);
       final AxisDirection axisDirection = textDirectionToAxisDirection(textDirection);
       return reverse ? flipAxisDirection(axisDirection) : axisDirection;
     case Axis.vertical:
@@ -3866,7 +3877,7 @@ class PositionedDirectional extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Positioned.directional(
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       start: start,
       top: top,
       end: end,
@@ -5376,7 +5387,7 @@ class RichText extends MultiChildRenderObjectWidget {
     assert(textDirection != null || debugCheckHasDirectionality(context));
     return RenderParagraph(text,
       textAlign: textAlign,
-      textDirection: textDirection ?? Directionality.of(context)!,
+      textDirection: textDirection ?? Directionality.of(context),
       softWrap: softWrap,
       overflow: overflow,
       textScaleFactor: textScaleFactor,
@@ -5394,7 +5405,7 @@ class RichText extends MultiChildRenderObjectWidget {
     renderObject
       ..text = text
       ..textAlign = textAlign
-      ..textDirection = textDirection ?? Directionality.of(context)!
+      ..textDirection = textDirection ?? Directionality.of(context)
       ..softWrap = softWrap
       ..overflow = overflow
       ..textScaleFactor = textScaleFactor

packages/flutter/lib/src/widgets/dismissible.dart

@@ -274,7 +274,7 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
     if (extent == 0.0)
       return null;
     if (_directionIsXAxis) {
-      switch (Directionality.of(context)!) {
+      switch (Directionality.of(context)) {
         case TextDirection.rtl:
           return extent < 0 ? DismissDirection.startToEnd : DismissDirection.endToStart;
         case TextDirection.ltr:
@@ -332,7 +332,7 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
         break;
 
       case DismissDirection.endToStart:
-        switch (Directionality.of(context)!) {
+        switch (Directionality.of(context)) {
           case TextDirection.rtl:
             if (_dragExtent + delta > 0)
               _dragExtent += delta;
@@ -345,7 +345,7 @@ class _DismissibleState extends State<Dismissible> with TickerProviderStateMixin
         break;
 
       case DismissDirection.startToEnd:
-        switch (Directionality.of(context)!) {
+        switch (Directionality.of(context)) {
           case TextDirection.rtl:
             if (_dragExtent + delta < 0)
               _dragExtent += delta;

packages/flutter/lib/src/widgets/editable_text.dart

@@ -2429,9 +2429,9 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
   }
 
   TextDirection get _textDirection {
-    final TextDirection? result = widget.textDirection ?? Directionality.of(context);
+    final TextDirection result = widget.textDirection ?? Directionality.of(context);
     assert(result != null, '$runtimeType created without a textDirection and with no ambient Directionality.');
-    return result!;
+    return result;
   }
 
   /// The renderer for this widget's descendant.

packages/flutter/lib/src/widgets/icon.dart

@@ -152,7 +152,7 @@ class Icon extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(this.textDirection != null || debugCheckHasDirectionality(context));
-    final TextDirection textDirection = this.textDirection ?? Directionality.of(context)!;
+    final TextDirection textDirection = this.textDirection ?? Directionality.of(context);
 
     final IconThemeData iconTheme = IconTheme.of(context);
 

packages/flutter/lib/src/widgets/implicit_animations.dart

@@ -1307,7 +1307,7 @@ class _AnimatedPositionedDirectionalState extends AnimatedWidgetBaseState<Animat
   Widget build(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
     return Positioned.directional(
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       child: widget.child,
       start: _start?.evaluate(animation!),
       top: _top?.evaluate(animation!),

packages/flutter/lib/src/widgets/navigation_toolbar.dart

@@ -61,7 +61,7 @@ class NavigationToolbar extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasDirectionality(context));
-    final TextDirection textDirection = Directionality.of(context)!;
+    final TextDirection textDirection = Directionality.of(context);
     return CustomMultiChildLayout(
       delegate: _ToolbarLayout(
         centerMiddle: centerMiddle,

packages/flutter/lib/src/widgets/overflow_bar.dart

@@ -225,7 +225,7 @@ class OverflowBar extends MultiChildRenderObjectWidget {
       overflowSpacing: overflowSpacing,
       overflowAlignment: overflowAlignment,
       overflowDirection: overflowDirection,
-      textDirection: textDirection ?? Directionality.of(context)!,
+      textDirection: textDirection ?? Directionality.of(context),
       clipBehavior: clipBehavior,
     );
   }
@@ -237,7 +237,7 @@ class OverflowBar extends MultiChildRenderObjectWidget {
       ..overflowSpacing = overflowSpacing
       ..overflowAlignment = overflowAlignment
       ..overflowDirection = overflowDirection
-      ..textDirection = textDirection ?? Directionality.of(context)!
+      ..textDirection = textDirection ?? Directionality.of(context)
       ..clipBehavior = clipBehavior;
   }
 

packages/flutter/lib/src/widgets/overlay.dart

@@ -547,7 +547,7 @@ class _Theatre extends MultiChildRenderObjectWidget {
   _RenderTheatre createRenderObject(BuildContext context) {
     return _RenderTheatre(
       skipCount: skipCount,
-      textDirection: Directionality.of(context)!,
+      textDirection: Directionality.of(context),
       clipBehavior: clipBehavior,
     );
   }
@@ -556,7 +556,7 @@ class _Theatre extends MultiChildRenderObjectWidget {
   void updateRenderObject(BuildContext context, _RenderTheatre renderObject) {
     renderObject
       ..skipCount = skipCount
-      ..textDirection = Directionality.of(context)!
+      ..textDirection = Directionality.of(context)
       ..clipBehavior = clipBehavior;
   }
 

packages/flutter/lib/src/widgets/page_view.dart

@@ -846,7 +846,7 @@ class _PageViewState extends State<PageView> {
     switch (widget.scrollDirection) {
       case Axis.horizontal:
         assert(debugCheckHasDirectionality(context));
-        final TextDirection textDirection = Directionality.of(context)!;
+        final TextDirection textDirection = Directionality.of(context);
         final AxisDirection axisDirection = textDirectionToAxisDirection(textDirection);
         return widget.reverse ? flipAxisDirection(axisDirection) : axisDirection;
       case Axis.vertical:

packages/flutter/lib/src/widgets/platform_view.dart

@@ -491,7 +491,7 @@ class _AndroidViewState extends State<AndroidView> {
 
   TextDirection _findLayoutDirection() {
     assert(widget.layoutDirection != null || debugCheckHasDirectionality(context));
-    return widget.layoutDirection ?? Directionality.of(context)!;
+    return widget.layoutDirection ?? Directionality.of(context);
   }
 
   @override
@@ -616,7 +616,7 @@ class _UiKitViewState extends State<UiKitView> {
 
   TextDirection _findLayoutDirection() {
     assert(widget.layoutDirection != null || debugCheckHasDirectionality(context));
-    return widget.layoutDirection ?? Directionality.of(context)!;
+    return widget.layoutDirection ?? Directionality.of(context);
   }
 
   @override

packages/flutter/lib/src/widgets/table.dart

@@ -249,7 +249,7 @@ class Table extends RenderObjectWidget {
       rows: children.length,
       columnWidths: columnWidths,
       defaultColumnWidth: defaultColumnWidth,
-      textDirection: textDirection ?? Directionality.of(context)!,
+      textDirection: textDirection ?? Directionality.of(context),
       border: border,
       rowDecorations: _rowDecorations,
       configuration: createLocalImageConfiguration(context),
@@ -266,7 +266,7 @@ class Table extends RenderObjectWidget {
     renderObject
       ..columnWidths = columnWidths
       ..defaultColumnWidth = defaultColumnWidth
-      ..textDirection = textDirection ?? Directionality.of(context)!
+      ..textDirection = textDirection ?? Directionality.of(context)
       ..border = border
       ..rowDecorations = _rowDecorations
       ..configuration = createLocalImageConfiguration(context)

packages/flutter/lib/src/widgets/viewport.dart

@@ -147,7 +147,7 @@ class Viewport extends MultiChildRenderObjectWidget {
           why: 'to determine the cross-axis direction when the viewport has an \'up\' axisDirection',
           alternative: 'Alternatively, consider specifying the \'crossAxisDirection\' argument on the Viewport.',
         ));
-        return textDirectionToAxisDirection(Directionality.of(context)!);
+        return textDirectionToAxisDirection(Directionality.of(context));
       case AxisDirection.right:
         return AxisDirection.down;
       case AxisDirection.down:
@@ -156,7 +156,7 @@ class Viewport extends MultiChildRenderObjectWidget {
           why: 'to determine the cross-axis direction when the viewport has a \'down\' axisDirection',
           alternative: 'Alternatively, consider specifying the \'crossAxisDirection\' argument on the Viewport.',
         ));
-        return textDirectionToAxisDirection(Directionality.of(context)!);
+        return textDirectionToAxisDirection(Directionality.of(context));
       case AxisDirection.left:
         return AxisDirection.down;
     }

packages/flutter/test/widgets/directionality_test.dart

@@ -10,7 +10,7 @@ void main() {
     final List<TextDirection> log = <TextDirection>[];
     final Widget inner = Builder(
       builder: (BuildContext context) {
-        log.add(Directionality.of(context)!);
+        log.add(Directionality.of(context));
         return const Placeholder();
       }
     );
@@ -80,4 +80,26 @@ void main() {
     expect(Directionality.maybeOf(noDirectionality.currentContext!), isNull);
     expect(Directionality.maybeOf(hasDirectionality.currentContext!), TextDirection.rtl);
   });
+
+  testWidgets('Directionality.of', (WidgetTester tester) async {
+    final GlobalKey hasDirectionality = GlobalKey();
+    final GlobalKey noDirectionality = GlobalKey();
+    await tester.pumpWidget(
+      Container(
+        key: noDirectionality,
+        child: Directionality(
+          textDirection: TextDirection.rtl,
+          child: Container(
+            key: hasDirectionality,
+          ),
+        ),
+      ),
+    );
+    expect(() => Directionality.of(noDirectionality.currentContext!), throwsA(isAssertionError.having(
+      (AssertionError e) => e.message,
+      'message',
+      contains('No Directionality widget found.'),
+    )));
+    expect(Directionality.of(hasDirectionality.currentContext!), TextDirection.rtl);
+  });
 }