migrate some material files to nullsafety (#66985)

* migrate some material files to nullsafety

* fix test_private

* address review comments

* fix private test on windows

* use uri in include entry of analysis_options

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 /// Flutter widgets implementing Material Design animated icons.
 library material_animated_icons;
 

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 part of material_animated_icons;
 
 // The code for drawing animated icons is kept in a private API, as we are not
@@ -38,9 +36,9 @@ class AnimatedIcon extends StatelessWidget {
   /// The [progress] and [icon] arguments must not be null.
   /// The [size] and [color] default to the value given by the current [IconTheme].
   const AnimatedIcon({
-    Key key,
-    @required this.icon,
-    @required this.progress,
+    Key? key,
+    required this.icon,
+    required this.progress,
     this.color,
     this.size,
     this.semanticLabel,
@@ -71,14 +69,14 @@ class AnimatedIcon extends StatelessWidget {
   ///
   /// See [Theme] to set the current theme and [ThemeData.brightness]
   /// for setting the current theme's brightness.
-  final Color color;
+  final Color? color;
 
   /// The size of the icon in logical pixels.
   ///
   /// Icons occupy a square with width and height equal to size.
   ///
   /// Defaults to the current [IconTheme] size.
-  final double size;
+  final double? size;
 
   /// The icon to display. Available icons are listed in [AnimatedIcons].
   final AnimatedIconData icon;
@@ -92,7 +90,7 @@ class AnimatedIcon extends StatelessWidget {
   ///
   ///  * [SemanticsProperties.label], which is set to [semanticLabel] in the
   ///    underlying [Semantics] widget.
-  final String semanticLabel;
+  final String? semanticLabel;
 
   /// The text direction to use for rendering the icon.
   ///
@@ -100,18 +98,20 @@ class AnimatedIcon extends StatelessWidget {
   ///
   /// If the text direction is [TextDirection.rtl], the icon will be mirrored
   /// horizontally (e.g back arrow will point right).
-  final TextDirection textDirection;
+  final TextDirection? textDirection;
 
   static final _UiPathFactory _pathFactory = () => ui.Path();
 
   @override
   Widget build(BuildContext context) {
+    assert(debugCheckHasDirectionality(context));
     final _AnimatedIconData iconData = icon as _AnimatedIconData;
     final IconThemeData iconTheme = IconTheme.of(context);
-    final double iconSize = size ?? iconTheme.size;
-    final TextDirection textDirection = this.textDirection ?? Directionality.of(context);
-    final double iconOpacity = iconTheme.opacity;
-    Color iconColor = color ?? iconTheme.color;
+    assert(iconTheme.isConcrete);
+    final double iconSize = size ?? iconTheme.size!;
+    final TextDirection textDirection = this.textDirection ?? Directionality.of(context)!;
+    final double iconOpacity = iconTheme.opacity!;
+    Color iconColor = color ?? iconTheme.color!;
     if (iconOpacity != 1.0)
       iconColor = iconColor.withOpacity(iconColor.opacity * iconOpacity);
     return Semantics(
@@ -135,12 +135,12 @@ typedef _UiPathFactory = ui.Path Function();
 
 class _AnimatedIconPainter extends CustomPainter {
   _AnimatedIconPainter({
-    @required this.paths,
-    @required this.progress,
-    @required this.color,
-    @required this.scale,
-    @required this.shouldMirror,
-    @required this.uiPathFactory,
+    required this.paths,
+    required this.progress,
+    required this.color,
+    required this.scale,
+    required this.shouldMirror,
+    required this.uiPathFactory,
   }) : super(repaint: progress);
 
   // This list is assumed to be immutable, changes to the contents of the list
@@ -163,7 +163,7 @@ class _AnimatedIconPainter extends CustomPainter {
       canvas.translate(-size.width, -size.height);
     }
 
-    final double clampedProgress = progress.value.clamp(0.0, 1.0) as double;
+    final double clampedProgress = progress.value.clamp(0.0, 1.0);
     for (final _PathFrames path in paths)
       path.paint(canvas, color, uiPathFactory, clampedProgress);
   }
@@ -181,26 +181,26 @@ class _AnimatedIconPainter extends CustomPainter {
   }
 
   @override
-  bool hitTest(Offset position) => null;
+  bool? hitTest(Offset position) => null;
 
   @override
   bool shouldRebuildSemantics(CustomPainter oldDelegate) => false;
 
   @override
-  SemanticsBuilderCallback get semanticsBuilder => null;
+  SemanticsBuilderCallback? get semanticsBuilder => null;
 }
 
 class _PathFrames {
   const _PathFrames({
-    @required this.commands,
-    @required this.opacities,
+    required this.commands,
+    required this.opacities,
   });
 
   final List<_PathCommand> commands;
   final List<double> opacities;
 
   void paint(ui.Canvas canvas, Color color, _UiPathFactory uiPathFactory, double progress) {
-    final double opacity = _interpolate<double>(opacities, progress, lerpDouble);
+    final double opacity = _interpolate<double?>(opacities, progress, lerpDouble)!;
     final ui.Paint paint = ui.Paint()
       ..style = PaintingStyle.fill
       ..color = color.withOpacity(color.opacity * opacity);
@@ -232,7 +232,7 @@ class _PathMoveTo extends _PathCommand {
 
   @override
   void apply(Path path, double progress) {
-    final Offset offset = _interpolate<Offset>(points, progress, Offset.lerp);
+    final Offset offset = _interpolate<Offset?>(points, progress, Offset.lerp)!;
     path.moveTo(offset.dx, offset.dy);
   }
 }
@@ -246,9 +246,9 @@ class _PathCubicTo extends _PathCommand {
 
   @override
   void apply(Path path, double progress) {
-    final Offset controlPoint1 = _interpolate<Offset>(controlPoints1, progress, Offset.lerp);
-    final Offset controlPoint2 = _interpolate<Offset>(controlPoints2, progress, Offset.lerp);
-    final Offset targetPoint = _interpolate<Offset>(targetPoints, progress, Offset.lerp);
+    final Offset controlPoint1 = _interpolate<Offset?>(controlPoints1, progress, Offset.lerp)!;
+    final Offset controlPoint2 = _interpolate<Offset?>(controlPoints2, progress, Offset.lerp)!;
+    final Offset targetPoint = _interpolate<Offset?>(targetPoints, progress, Offset.lerp)!;
     path.cubicTo(
       controlPoint1.dx, controlPoint1.dy,
       controlPoint2.dx, controlPoint2.dy,
@@ -265,7 +265,7 @@ class _PathLineTo extends _PathCommand {
 
   @override
   void apply(Path path, double progress) {
-    final Offset point = _interpolate<Offset>(points, progress, Offset.lerp);
+    final Offset point = _interpolate<Offset?>(points, progress, Offset.lerp)!;
     path.lineTo(point.dx, point.dy);
   }
 }
@@ -295,7 +295,7 @@ T _interpolate<T>(List<T> values, double progress, _Interpolator<T> interpolator
   assert(progress >= 0.0);
   if (values.length == 1)
     return values[0];
-  final double targetIdx = lerpDouble(0, values.length -1, progress);
+  final double targetIdx = lerpDouble(0, values.length -1, progress)!;
   final int lowIdx = targetIdx.floor();
   final int highIdx = targetIdx.ceil();
   final double t = targetIdx - lowIdx;

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // This file serves as the interface between the public and private APIs for
 // animated icons.
 // The AnimatedIcons class is public and is used to specify available icons,

packages/flutter/lib/src/material/animated_icons/data/add_event.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/arrow_menu.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/close_menu.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/ellipsis_search.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/event_add.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/home_menu.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/list_view.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/menu_arrow.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/menu_close.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/menu_home.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/pause_play.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/play_pause.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/search_ellipsis.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

packages/flutter/lib/src/material/animated_icons/data/view_list.g.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // AUTOGENERATED FILE DO NOT EDIT!
 // This file was generated by vitool.
 part of material_animated_icons;

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:ui' show hashValues;
 
 import 'package:flutter/foundation.dart';
@@ -61,8 +59,8 @@ class DateTimeRange {
   ///
   /// [start] and [end] must be non-null.
   const DateTimeRange({
-    @required this.start,
-    @required this.end,
+    required this.start,
+    required this.end,
   }) : assert(start != null),
        assert(end != null);
 

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'dart:math' as math;
 
 import 'package:flutter/services.dart';
@@ -102,26 +100,26 @@ const double _inputFormLandscapeHeight = 108.0;
 ///  * [InputDatePickerFormField], which provides a text input field for entering dates.
 ///
 Future<DateTime> showDatePicker({
-  @required BuildContext context,
-  @required DateTime initialDate,
-  @required DateTime firstDate,
-  @required DateTime lastDate,
-  DateTime currentDate,
+  required BuildContext context,
+  required DateTime initialDate,
+  required DateTime firstDate,
+  required DateTime lastDate,
+  DateTime? currentDate,
   DatePickerEntryMode initialEntryMode = DatePickerEntryMode.calendar,
-  SelectableDayPredicate selectableDayPredicate,
-  String helpText,
-  String cancelText,
-  String confirmText,
-  Locale locale,
+  SelectableDayPredicate? selectableDayPredicate,
+  String? helpText,
+  String? cancelText,
+  String? confirmText,
+  Locale? locale,
   bool useRootNavigator = true,
-  RouteSettings routeSettings,
-  TextDirection textDirection,
-  TransitionBuilder builder,
+  RouteSettings? routeSettings,
+  TextDirection? textDirection,
+  TransitionBuilder? builder,
   DatePickerMode initialDatePickerMode = DatePickerMode.day,
-  String errorFormatText,
-  String errorInvalidText,
-  String fieldHintText,
-  String fieldLabelText,
+  String? errorFormatText,
+  String? errorInvalidText,
+  String? fieldHintText,
+  String? fieldLabelText,
 }) async {
   assert(context != null);
   assert(initialDate != null);
@@ -195,11 +193,11 @@ Future<DateTime> showDatePicker({
 
 class _DatePickerDialog extends StatefulWidget {
   _DatePickerDialog({
-    Key key,
-    @required DateTime initialDate,
-    @required DateTime firstDate,
-    @required DateTime lastDate,
-    DateTime currentDate,
+    Key? key,
+    required DateTime initialDate,
+    required DateTime firstDate,
+    required DateTime lastDate,
+    DateTime? currentDate,
     this.initialEntryMode = DatePickerEntryMode.calendar,
     this.selectableDayPredicate,
     this.cancelText,
@@ -233,7 +231,7 @@ class _DatePickerDialog extends StatefulWidget {
       'initialDate ${this.initialDate} must be on or before lastDate ${this.lastDate}.'
     );
     assert(
-      selectableDayPredicate == null || selectableDayPredicate(this.initialDate),
+      selectableDayPredicate == null || selectableDayPredicate!(this.initialDate),
       'Provided initialDate ${this.initialDate} must satisfy provided selectableDayPredicate'
     );
   }
@@ -253,29 +251,29 @@ class _DatePickerDialog extends StatefulWidget {
   final DatePickerEntryMode initialEntryMode;
 
   /// Function to provide full control over which [DateTime] can be selected.
-  final SelectableDayPredicate selectableDayPredicate;
+  final SelectableDayPredicate? selectableDayPredicate;
 
   /// The text that is displayed on the cancel button.
-  final String cancelText;
+  final String? cancelText;
 
   /// The text that is displayed on the confirm button.
-  final String confirmText;
+  final String? confirmText;
 
   /// The text that is displayed at the top of the header.
   ///
   /// This is used to indicate to the user what they are selecting a date for.
-  final String helpText;
+  final String? helpText;
 
   /// The initial display of the calendar picker.
   final DatePickerMode initialCalendarMode;
 
-  final String errorFormatText;
+  final String? errorFormatText;
 
-  final String errorInvalidText;
+  final String? errorInvalidText;
 
-  final String fieldHintText;
+  final String? fieldHintText;
 
-  final String fieldLabelText;
+  final String? fieldLabelText;
 
   @override
   _DatePickerDialogState createState() => _DatePickerDialogState();
@@ -283,9 +281,9 @@ class _DatePickerDialog extends StatefulWidget {
 
 class _DatePickerDialogState extends State<_DatePickerDialog> {
 
-  DatePickerEntryMode _entryMode;
-  DateTime _selectedDate;
-  bool _autoValidate;
+  late DatePickerEntryMode _entryMode;
+  late DateTime _selectedDate;
+  late bool _autoValidate;
   final GlobalKey _calendarPickerKey = GlobalKey();
   final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
 
@@ -299,7 +297,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
 
   void _handleOk() {
     if (_entryMode == DatePickerEntryMode.input) {
-      final FormState form = _formKey.currentState;
+      final FormState form = _formKey.currentState!;
       if (!form.validate()) {
         setState(() => _autoValidate = true);
         return;
@@ -321,7 +319,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
           _entryMode = DatePickerEntryMode.input;
           break;
         case DatePickerEntryMode.input:
-          _formKey.currentState.save();
+          _formKey.currentState!.save();
           _entryMode = DatePickerEntryMode.calendar;
           break;
       }
@@ -333,7 +331,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
   }
 
   Size _dialogSize(BuildContext context) {
-    final Orientation orientation = MediaQuery.of(context).orientation;
+    final Orientation orientation = MediaQuery.of(context)!.orientation;
     switch (_entryMode) {
       case DatePickerEntryMode.calendar:
         switch (orientation) {
@@ -342,7 +340,6 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
           case Orientation.landscape:
             return _calendarLandscapeDialogSize;
         }
-        break;
       case DatePickerEntryMode.input:
         switch (orientation) {
           case Orientation.portrait:
@@ -350,9 +347,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
           case Orientation.landscape:
             return _inputLandscapeDialogSize;
         }
-        break;
     }
-    return null;
   }
 
   static final Map<LogicalKeySet, Intent> _formShortcutMap = <LogicalKeySet, Intent>{
@@ -362,22 +357,20 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
 
   @override
   Widget build(BuildContext context) {
-    final ThemeData theme = Theme.of(context);
+    final ThemeData theme = Theme.of(context)!;
     final ColorScheme colorScheme = theme.colorScheme;
-    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
-    final Orientation orientation = MediaQuery.of(context).orientation;
+    final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
+    final Orientation orientation = MediaQuery.of(context)!.orientation;
     final TextTheme textTheme = theme.textTheme;
     // Constrain the textScaleFactor to the largest supported value to prevent
     // layout issues.
-    final double textScaleFactor = math.min(MediaQuery.of(context).textScaleFactor, 1.3);
+    final double textScaleFactor = math.min(MediaQuery.of(context)!.textScaleFactor, 1.3);
 
-    final String dateText = _selectedDate != null
-      ? localizations.formatMediumDate(_selectedDate)
-      : localizations.unspecifiedDate;
+    final String dateText = localizations.formatMediumDate(_selectedDate);
     final Color dateColor = colorScheme.brightness == Brightness.light
       ? colorScheme.onPrimary
       : colorScheme.onSurface;
-    final TextStyle dateStyle = orientation == Orientation.landscape
+    final TextStyle? dateStyle = orientation == Orientation.landscape
       ? textTheme.headline5?.copyWith(color: dateColor)
       : textTheme.headline4?.copyWith(color: dateColor);
 
@@ -474,7 +467,7 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
         duration: _dialogSizeAnimationDuration,
         curve: Curves.easeIn,
         child: MediaQuery(
-          data: MediaQuery.of(context).copyWith(
+          data: MediaQuery.of(context)!.copyWith(
             textScaleFactor: textScaleFactor,
           ),
           child: Builder(builder: (BuildContext context) {
@@ -508,7 +501,6 @@ class _DatePickerDialogState extends State<_DatePickerDialog> {
                   ],
                 );
             }
-            return null;
           }),
         ),
       ),

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/widgets.dart';
 
 import '../color_scheme.dart';
@@ -35,16 +33,16 @@ const double _headerPaddingLandscape = 16.0;
 class DatePickerHeader extends StatelessWidget {
   /// Creates a header for use in a date picker dialog.
   const DatePickerHeader({
-    Key key,
-    @required this.helpText,
-    @required this.titleText,
+    Key? key,
+    required this.helpText,
+    required this.titleText,
     this.titleSemanticsLabel,
-    @required this.titleStyle,
-    @required this.orientation,
+    required this.titleStyle,
+    required this.orientation,
     this.isShort = false,
-    @required this.icon,
-    @required this.iconTooltip,
-    @required this.onIconPressed,
+    required this.icon,
+    required this.iconTooltip,
+    required this.onIconPressed,
   }) : assert(helpText != null),
        assert(orientation != null),
        assert(isShort != null),
@@ -59,10 +57,10 @@ class DatePickerHeader extends StatelessWidget {
   final String titleText;
 
   /// The semantic label associated with the [titleText].
-  final String titleSemanticsLabel;
+  final String? titleSemanticsLabel;
 
   /// The [TextStyle] that the title text is displayed with.
-  final TextStyle titleStyle;
+  final TextStyle? titleStyle;
 
   /// The orientation is used to decide how to layout its children.
   final Orientation orientation;
@@ -93,7 +91,7 @@ class DatePickerHeader extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final ThemeData theme = Theme.of(context);
+    final ThemeData theme = Theme.of(context)!;
     final ColorScheme colorScheme = theme.colorScheme;
     final TextTheme textTheme = theme.textTheme;
 
@@ -102,7 +100,7 @@ class DatePickerHeader extends StatelessWidget {
     final Color primarySurfaceColor = isDark ? colorScheme.surface : colorScheme.primary;
     final Color onPrimarySurfaceColor = isDark ? colorScheme.onSurface : colorScheme.onPrimary;
 
-    final TextStyle helpStyle = textTheme.overline?.copyWith(
+    final TextStyle? helpStyle = textTheme.overline?.copyWith(
       color: onPrimarySurfaceColor,
     );
 
@@ -189,6 +187,5 @@ class DatePickerHeader extends StatelessWidget {
           ),
         );
     }
-    return null;
   }
 }

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // Common date utility functions used by the date picker implementation
 
 // This is an internal implementation file. Even though there are public
@@ -27,7 +25,7 @@ DateTimeRange datesOnly(DateTimeRange range) {
 
 /// Returns true if the two [DateTime] objects have the same day, month, and
 /// year, or are both null.
-bool isSameDay(DateTime dateA, DateTime dateB) {
+bool isSameDay(DateTime? dateA, DateTime? dateB) {
   return
     dateA?.year == dateB?.year &&
     dateA?.month == dateB?.month &&
@@ -36,7 +34,7 @@ bool isSameDay(DateTime dateA, DateTime dateB) {
 
 /// Returns true if the two [DateTime] objects have the same month, and
 /// year, or are both null.
-bool isSameMonth(DateTime dateA, DateTime dateB) {
+bool isSameMonth(DateTime? dateA, DateTime? dateB) {
   return
     dateA?.year == dateB?.year &&
     dateA?.month == dateB?.month;
@@ -148,7 +146,7 @@ int getDaysInMonth(int year, int month) {
 /// is in the same year as the `endDate` then it will use the short month
 /// day format (i.e. 'Jan 21'). Otherwise it will return the short date format
 /// (i.e. 'Jan 21, 2020').
-String formatRangeStartDate(MaterialLocalizations localizations, DateTime startDate, DateTime endDate) {
+String formatRangeStartDate(MaterialLocalizations localizations, DateTime? startDate, DateTime? endDate) {
   return startDate == null
     ? localizations.dateRangeStartLabel
     : (endDate == null || startDate.year == endDate.year)
@@ -162,7 +160,7 @@ String formatRangeStartDate(MaterialLocalizations localizations, DateTime startD
 /// is in the same year as the `startDate` and the `currentDate` then it will
 /// just use the short month day format (i.e. 'Jan 21'), otherwise it will
 /// include the year (i.e. 'Jan 21, 2020').
-String formatRangeEndDate(MaterialLocalizations localizations, DateTime startDate, DateTime endDate, DateTime currentDate) {
+String formatRangeEndDate(MaterialLocalizations localizations, DateTime? startDate, DateTime? endDate, DateTime currentDate) {
   return endDate == null
     ? localizations.dateRangeEndLabel
     : (startDate != null && startDate.year == endDate.year && startDate.year == currentDate.year)

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
@@ -50,10 +48,10 @@ class InputDatePickerFormField extends StatefulWidget {
   /// [firstDate], [lastDate], and [autofocus] must be non-null.
   ///
   InputDatePickerFormField({
-    Key key,
-    DateTime initialDate,
-    @required DateTime firstDate,
-    @required DateTime lastDate,
+    Key? key,
+    DateTime? initialDate,
+    required DateTime firstDate,
+    required DateTime lastDate,
     this.onDateSubmitted,
     this.onDateSaved,
     this.selectableDayPredicate,
@@ -74,21 +72,21 @@ class InputDatePickerFormField extends StatefulWidget {
       'lastDate ${this.lastDate} must be on or after firstDate ${this.firstDate}.'
     );
     assert(
-      initialDate == null || !this.initialDate.isBefore(this.firstDate),
+      initialDate == null || !this.initialDate!.isBefore(this.firstDate),
       'initialDate ${this.initialDate} must be on or after firstDate ${this.firstDate}.'
     );
     assert(
-      initialDate == null || !this.initialDate.isAfter(this.lastDate),
+      initialDate == null || !this.initialDate!.isAfter(this.lastDate),
       'initialDate ${this.initialDate} must be on or before lastDate ${this.lastDate}.'
     );
     assert(
-      selectableDayPredicate == null || initialDate == null || selectableDayPredicate(this.initialDate),
+      selectableDayPredicate == null || initialDate == null || selectableDayPredicate!(this.initialDate!),
       'Provided initialDate ${this.initialDate} must satisfy provided selectableDayPredicate.'
     );
   }
 
   /// If provided, it will be used as the default value of the field.
-  final DateTime initialDate;
+  final DateTime? initialDate;
 
   /// The earliest allowable [DateTime] that the user can input.
   final DateTime firstDate;
@@ -99,36 +97,36 @@ class InputDatePickerFormField extends StatefulWidget {
   /// An optional method to call when the user indicates they are done editing
   /// the text in the field. Will only be called if the input represents a valid
   /// [DateTime].
-  final ValueChanged<DateTime> onDateSubmitted;
+  final ValueChanged<DateTime>? onDateSubmitted;
 
   /// An optional method to call with the final date when the form is
   /// saved via [FormState.save]. Will only be called if the input represents
   /// a valid [DateTime].
-  final ValueChanged<DateTime> onDateSaved;
+  final ValueChanged<DateTime>? onDateSaved;
 
   /// Function to provide full control over which [DateTime] can be selected.
-  final SelectableDayPredicate selectableDayPredicate;
+  final SelectableDayPredicate? selectableDayPredicate;
 
   /// The error text displayed if the entered date is not in the correct format.
-  final String errorFormatText;
+  final String? errorFormatText;
 
   /// The error text displayed if the date is not valid.
   ///
   /// A date is not valid if it is earlier than [firstDate], later than
   /// [lastDate], or doesn't pass the [selectableDayPredicate].
-  final String errorInvalidText;
+  final String? errorInvalidText;
 
   /// The hint text displayed in the [TextField].
   ///
   /// If this is null, it will default to the date format string. For example,
   /// 'mm/dd/yyyy' for en_US.
-  final String fieldHintText;
+  final String? fieldHintText;
 
   /// The label text displayed in the [TextField].
   ///
   /// If this is null, it will default to the words representing the date format
   /// string. For example, 'Month, Day, Year' for en_US.
-  final String fieldLabelText;
+  final String? fieldLabelText;
 
   /// {@macro flutter.widgets.editableText.autofocus}
   final bool autofocus;
@@ -139,8 +137,8 @@ class InputDatePickerFormField extends StatefulWidget {
 
 class _InputDatePickerFormFieldState extends State<InputDatePickerFormField> {
   final TextEditingController _controller = TextEditingController();
-  DateTime _selectedDate;
-  String _inputText;
+  DateTime? _selectedDate;
+  String? _inputText;
   bool _autoSelected = false;
 
   @override
@@ -159,14 +157,14 @@ class _InputDatePickerFormFieldState extends State<InputDatePickerFormField> {
   void didChangeDependencies() {
     super.didChangeDependencies();
     if (_selectedDate != null) {
-      final MaterialLocalizations localizations = MaterialLocalizations.of(context);
-      _inputText = localizations.formatCompactDate(_selectedDate);
+      final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
+      _inputText = localizations.formatCompactDate(_selectedDate!);
       TextEditingValue textEditingValue = _controller.value.copyWith(text: _inputText);
       // Select the new text if we are auto focused and haven't selected the text before.
       if (widget.autofocus && !_autoSelected) {
         textEditingValue = textEditingValue.copyWith(selection: TextSelection(
           baseOffset: 0,
-          extentOffset: _inputText.length,
+          extentOffset: _inputText!.length,
         ));
         _autoSelected = true;
       }
@@ -174,55 +172,55 @@ class _InputDatePickerFormFieldState extends State<InputDatePickerFormField> {
     }
   }
 
-  DateTime _parseDate(String text) {
-    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
+  DateTime? _parseDate(String? text) {
+    final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
     return localizations.parseCompactDate(text);
   }
 
-  bool _isValidAcceptableDate(DateTime date) {
+  bool _isValidAcceptableDate(DateTime? date) {
     return
       date != null &&
       !date.isBefore(widget.firstDate) &&
       !date.isAfter(widget.lastDate) &&
-      (widget.selectableDayPredicate == null || widget.selectableDayPredicate(date));
+      (widget.selectableDayPredicate == null || widget.selectableDayPredicate!(date));
   }
 
-  String _validateDate(String text) {
-    final DateTime date = _parseDate(text);
+  String? _validateDate(String? text) {
+    final DateTime? date = _parseDate(text);
     if (date == null) {
-      return widget.errorFormatText ?? MaterialLocalizations.of(context).invalidDateFormatLabel;
+      return widget.errorFormatText ?? MaterialLocalizations.of(context)!.invalidDateFormatLabel;
     } else if (!_isValidAcceptableDate(date)) {
-      return widget.errorInvalidText ?? MaterialLocalizations.of(context).dateOutOfRangeLabel;
+      return widget.errorInvalidText ?? MaterialLocalizations.of(context)!.dateOutOfRangeLabel;
     }
     return null;
   }
 
-  void _handleSaved(String text) {
+  void _handleSaved(String? text) {
     if (widget.onDateSaved != null) {
-      final DateTime date = _parseDate(text);
+      final DateTime? date = _parseDate(text);
       if (_isValidAcceptableDate(date)) {
         _selectedDate = date;
         _inputText = text;
-        widget.onDateSaved(date);
+        widget.onDateSaved!(date!);
       }
     }
   }
 
   void _handleSubmitted(String text) {
     if (widget.onDateSubmitted != null) {
-      final DateTime date = _parseDate(text);
+      final DateTime? date = _parseDate(text);
       if (_isValidAcceptableDate(date)) {
         _selectedDate = date;
         _inputText = text;
-        widget.onDateSubmitted(date);
+        widget.onDateSubmitted!(date!);
       }
     }
   }
 
   @override
   Widget build(BuildContext context) {
-    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
-    final InputDecorationTheme inputTheme = Theme.of(context).inputDecorationTheme;
+    final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
+    final InputDecorationTheme inputTheme = Theme.of(context)!.inputDecorationTheme;
     return TextFormField(
       decoration: InputDecoration(
         border: inputTheme.border ?? const UnderlineInputBorder(),

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
@@ -24,13 +22,13 @@ class InputDateRangePicker extends StatefulWidget {
   /// Creates a row with two text fields configured to accept the start and end dates
   /// of a date range.
   InputDateRangePicker({
-    Key key,
-    DateTime initialStartDate,
-    DateTime initialEndDate,
-    @required DateTime firstDate,
-    @required DateTime lastDate,
-    @required this.onStartDateChanged,
-    @required this.onEndDateChanged,
+    Key? key,
+    DateTime? initialStartDate,
+    DateTime? initialEndDate,
+    required DateTime firstDate,
+    required DateTime lastDate,
+    required this.onStartDateChanged,
+    required this.onEndDateChanged,
     this.helpText,
     this.errorFormatText,
     this.errorInvalidText,
@@ -54,10 +52,10 @@ class InputDateRangePicker extends StatefulWidget {
         super(key: key);
 
   /// The [DateTime] that represents the start of the initial date range selection.
-  final DateTime initialStartDate;
+  final DateTime? initialStartDate;
 
   /// The [DateTime] that represents the end of the initial date range selection.
-  final DateTime initialEndDate;
+  final DateTime? initialEndDate;
 
   /// The earliest allowable [DateTime] that the user can select.
   final DateTime firstDate;
@@ -66,38 +64,38 @@ class InputDateRangePicker extends StatefulWidget {
   final DateTime lastDate;
 
   /// Called when the user changes the start date of the selected range.
-  final ValueChanged<DateTime> onStartDateChanged;
+  final ValueChanged<DateTime>? onStartDateChanged;
 
   /// Called when the user changes the end date of the selected range.
-  final ValueChanged<DateTime> onEndDateChanged;
+  final ValueChanged<DateTime>? onEndDateChanged;
 
   /// The text that is displayed at the top of the header.
   ///
   /// This is used to indicate to the user what they are selecting a date for.
-  final String helpText;
+  final String? helpText;
 
   /// Error text used to indicate the text in a field is not a valid date.
-  final String errorFormatText;
+  final String? errorFormatText;
 
   /// Error text used to indicate the date in a field is not in the valid range
   /// of [firstDate] - [lastDate].
-  final String errorInvalidText;
+  final String? errorInvalidText;
 
   /// Error text used to indicate the dates given don't form a valid date
   /// range (i.e. the start date is after the end date).
-  final String errorInvalidRangeText;
+  final String? errorInvalidRangeText;
 
   /// Hint text shown when the start date field is empty.
-  final String fieldStartHintText;
+  final String? fieldStartHintText;
 
   /// Hint text shown when the end date field is empty.
-  final String fieldEndHintText;
+  final String? fieldEndHintText;
 
   /// Label used for the start date field.
-  final String fieldStartLabelText;
+  final String? fieldStartLabelText;
 
   /// Label used for the end date field.
-  final String fieldEndLabelText;
+  final String? fieldEndLabelText;
 
   /// {@macro flutter.widgets.editableText.autofocus}
   final bool autofocus;
@@ -114,14 +112,14 @@ class InputDateRangePicker extends StatefulWidget {
 /// The current state of an [InputDateRangePicker]. Can be used to
 /// [validate] the date field entries.
 class InputDateRangePickerState extends State<InputDateRangePicker> {
-  String _startInputText;
-  String _endInputText;
-  DateTime _startDate;
-  DateTime _endDate;
-  TextEditingController _startController;
-  TextEditingController _endController;
-  String _startErrorText;
-  String _endErrorText;
+  late String _startInputText;
+  late String _endInputText;
+  DateTime? _startDate;
+  DateTime? _endDate;
+  late TextEditingController _startController;
+  late TextEditingController _endController;
+  String? _startErrorText;
+  String? _endErrorText;
   bool _autoSelected = false;
 
   @override
@@ -143,16 +141,16 @@ class InputDateRangePickerState extends State<InputDateRangePicker> {
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
+    final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
     if (_startDate != null) {
-      _startInputText = localizations.formatCompactDate(_startDate);
+      _startInputText = localizations.formatCompactDate(_startDate!);
       final bool selectText = widget.autofocus && !_autoSelected;
       _updateController(_startController, _startInputText, selectText);
       _autoSelected = selectText;
     }
 
     if (_endDate != null) {
-      _endInputText = localizations.formatCompactDate(_endDate);
+      _endInputText = localizations.formatCompactDate(_endDate!);
       _updateController(_endController, _endInputText, false);
     }
   }
@@ -164,11 +162,11 @@ class InputDateRangePickerState extends State<InputDateRangePicker> {
   /// return false and display an appropriate error message under one of the
   /// text fields.
   bool validate() {
-    String startError = _validateDate(_startDate);
-    final String endError = _validateDate(_endDate);
+    String? startError = _validateDate(_startDate);
+    final String? endError = _validateDate(_endDate);
     if (startError == null && endError == null) {
-      if (_startDate.isAfter(_endDate)) {
-        startError = widget.errorInvalidRangeText ?? MaterialLocalizations.of(context).invalidDateRangeLabel;
+      if (_startDate!.isAfter(_endDate!)) {
+        startError = widget.errorInvalidRangeText ?? MaterialLocalizations.of(context)!.invalidDateRangeLabel;
       }
     }
     setState(() {
@@ -178,16 +176,16 @@ class InputDateRangePickerState extends State<InputDateRangePicker> {
     return startError == null && endError == null;
   }
 
-  DateTime _parseDate(String text) {
-    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
+  DateTime? _parseDate(String? text) {
+    final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
     return localizations.parseCompactDate(text);
   }
 
-  String _validateDate(DateTime date) {
+  String? _validateDate(DateTime? date) {
     if (date == null) {
-      return widget.errorFormatText ?? MaterialLocalizations.of(context).invalidDateFormatLabel;
+      return widget.errorFormatText ?? MaterialLocalizations.of(context)!.invalidDateFormatLabel;
     } else if (date.isBefore(widget.firstDate) || date.isAfter(widget.lastDate)) {
-      return widget.errorInvalidText ?? MaterialLocalizations.of(context).dateOutOfRangeLabel;
+      return widget.errorInvalidText ?? MaterialLocalizations.of(context)!.dateOutOfRangeLabel;
     }
     return null;
   }
@@ -207,7 +205,7 @@ class InputDateRangePickerState extends State<InputDateRangePicker> {
     setState(() {
       _startInputText = text;
       _startDate = _parseDate(text);
-      widget.onStartDateChanged?.call(_startDate);
+      widget.onStartDateChanged?.call(_startDate!);
     });
     if (widget.autovalidate) {
       validate();
@@ -218,7 +216,7 @@ class InputDateRangePickerState extends State<InputDateRangePicker> {
     setState(() {
       _endInputText = text;
       _endDate = _parseDate(text);
-      widget.onEndDateChanged?.call(_endDate);
+      widget.onEndDateChanged?.call(_endDate!);
     });
     if (widget.autovalidate) {
       validate();
@@ -227,8 +225,8 @@ class InputDateRangePickerState extends State<InputDateRangePicker> {
 
   @override
   Widget build(BuildContext context) {
-    final MaterialLocalizations localizations = MaterialLocalizations.of(context);
-    final InputDecorationTheme inputTheme = Theme.of(context).inputDecorationTheme;
+    final MaterialLocalizations localizations = MaterialLocalizations.of(context)!;
+    final InputDecorationTheme inputTheme = Theme.of(context)!.inputDecorationTheme;
     return Row(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: <Widget>[

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

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // Date Picker public API
 export 'calendar_date_picker.dart' show CalendarDatePicker;
 export 'date_picker_common.dart' show

packages/flutter/test_private/bin/test_private.dart

@@ -193,9 +193,9 @@ class TestCase {
     makeAbsolute(pubspec, workingDirectory: privateTestsDir)
         .copySync(path.join(tmpdir.absolute.path, 'pubspec.yaml'));
 
-    // Copy Flutter's analysis_options.yaml file to the root of the tmpdir.
-    makeAbsolute(File('analysis_options.yaml'), workingDirectory: flutterRoot)
-        .copySync(path.join(tmpdir.absolute.path, 'analysis_options.yaml'));
+    // Use Flutter's analysis_options.yaml file from packages/flutter.
+    File(path.join(tmpdir.absolute.path, 'analysis_options.yaml'))
+        .writeAsStringSync('include: ${path.toUri(path.join(flutterRoot.path, 'packages', 'flutter', 'analysis_options.yaml'))}');
 
     return true;
   }
@@ -225,7 +225,7 @@ class TestCase {
     for (final File test in tests) {
       final String testPath = path.join(path.dirname(test.path), 'lib', path.basenameWithoutExtension(test.path));
       final ProcessRunnerResult result = await runner.runProcess(
-        <String>[flutter, 'test', testPath],
+        <String>[flutter, 'test', '--enable-experiment=non-nullable', '--null-assertions', testPath],
         failOk: true,
       );
       if (result.exitCode != 0) {

packages/flutter/test_private/test/animated_icons_private_test.dart.tmpl

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// @dart = 2.8
-
 // This is the test for the private implementation of animated icons.
 // To make the private API accessible from the test we do not import the
 // material material_animated_icons library, but instead, this test file is an
@@ -17,7 +15,6 @@ import 'dart:ui' as ui show Paint, Path, Canvas;
 
 import 'package:flutter/animation.dart';
 import 'package:flutter/widgets.dart';
-import 'package:meta/meta.dart';
 
 import 'test/flutter_test_alternative.dart';
 
@@ -82,10 +79,10 @@ void main() {
 
   group('_AnimatedIconPainter', () {
     const Size size = Size(48.0, 48.0);
-    MockPath mockPath;
-    MockCanvas mockCanvas;
-    List<MockPath> generatedPaths;
-    _UiPathFactory pathFactory;
+    late MockPath mockPath;
+    late MockCanvas mockCanvas;
+    late List<MockPath> generatedPaths;
+    late _UiPathFactory pathFactory;
 
     setUp(() {
       generatedPaths = <MockPath>[];
@@ -365,12 +362,12 @@ class MockCall {
   final Symbol memberSymbol;
   String get memberName {
     final RegExp symbolMatch = RegExp(r'Symbol\("(?<name>.*)"\)');
-    final RegExpMatch match = symbolMatch.firstMatch(memberSymbol.toString());
+    final RegExpMatch? match = symbolMatch.firstMatch(memberSymbol.toString());
     assert(match != null);
-    return match.namedGroup('name');
+    return match!.namedGroup('name')!;
   }
 
-  final List<dynamic> positionalArguments;
+  final List<dynamic>? positionalArguments;
   final bool acceptAny;
 
   @override
@@ -399,10 +396,10 @@ class Mock {
               '${expected[count].memberName} instead.');
       if (call.positionalArguments != null && !expected[count].acceptAny) {
         int countArg = 0;
-        for (final dynamic arg in call.positionalArguments) {
-          expect(arg, equals(expected[count].positionalArguments[countArg]),
+        for (final dynamic arg in call.positionalArguments!) {
+          expect(arg, equals(expected[count].positionalArguments![countArg]),
               reason: 'Failed at call $count. Positional argument $countArg to ${call.memberName} '
-                  'not as expected. Expected ${expected[count].positionalArguments[countArg]} '
+                  'not as expected. Expected ${expected[count].positionalArguments![countArg]} '
                   'and received $arg');
           countArg++;
         }