[flutter_adaptive_scaffold] allow users to override navigation rail padding from AdaptiveScaffold constructor (#8433)

1. Moved the default padding value into the body of `AdaptiveScaffold.standardNavigationRail`, and made the `padding` property an optional nullable value. 
2. Added an optional nullable `EdgeInsetsGeometry` parameter `AdaptiveScaffold.navigationRailPadding` to the constructor, which is passed into the navigation rail in `build`.

Fixes flutter/flutter#161670

Author: jmiller-pwi

packages/flutter_adaptive_scaffold/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.3.3
+
+* Adds `navigationRailPadding` padding to `AdaptiveScaffold` for specifying custom padding around the navigation rail.
+
 ## 0.3.2
 
 * Fixes some memory leaks by disposing curved animations and value notifiers.

packages/flutter_adaptive_scaffold/lib/src/adaptive_scaffold.dart

@@ -28,6 +28,9 @@ const double kMaterialMediumAndUpMargin = 24;
 /// design 3 spec.
 const double kMaterialPadding = 4;
 
+/// Padding value of the default padding for the navigation rail
+const double kNavigationRailDefaultPadding = 8;
+
 /// Signature for a builder used by [AdaptiveScaffold.navigationRailDestinationBuilder] that converts a
 /// [NavigationDestination] to a [NavigationRailDestination].
 typedef NavigationRailDestinationBuilder = NavigationRailDestination Function(
@@ -94,6 +97,8 @@ class AdaptiveScaffold extends StatefulWidget {
     this.leadingUnextendedNavRail,
     this.leadingExtendedNavRail,
     this.trailingNavRail,
+    this.navigationRailPadding =
+        const EdgeInsets.all(kNavigationRailDefaultPadding),
     this.smallBody,
     this.body,
     this.mediumLargeBody,
@@ -148,6 +153,9 @@ class AdaptiveScaffold extends StatefulWidget {
   /// navigation rail at the largest breakpoint.
   final Widget? trailingNavRail;
 
+  /// Option to apply custom padding to the navigation rail.
+  final EdgeInsetsGeometry navigationRailPadding;
+
   /// The alignment of the destinations in the navigation rail.
   final double? groupAlignment;
 
@@ -343,7 +351,8 @@ class AdaptiveScaffold extends StatefulWidget {
     int? selectedIndex,
     bool extended = false,
     Color? backgroundColor,
-    EdgeInsetsGeometry padding = const EdgeInsets.all(8.0),
+    EdgeInsetsGeometry padding =
+        const EdgeInsets.all(kNavigationRailDefaultPadding),
     Widget? leading,
     Widget? trailing,
     void Function(int)? onDestinationSelected,
@@ -608,6 +617,7 @@ class _AdaptiveScaffoldState extends State<AdaptiveScaffold> {
                 width: widget.navigationRailWidth,
                 leading: widget.leadingUnextendedNavRail,
                 trailing: widget.trailingNavRail,
+                padding: widget.navigationRailPadding,
                 selectedIndex: widget.selectedIndex,
                 destinations: destinations,
                 onDestinationSelected: widget.onSelectedIndexChange,
@@ -627,6 +637,7 @@ class _AdaptiveScaffoldState extends State<AdaptiveScaffold> {
                 extended: true,
                 leading: widget.leadingExtendedNavRail,
                 trailing: widget.trailingNavRail,
+                padding: widget.navigationRailPadding,
                 selectedIndex: widget.selectedIndex,
                 destinations: destinations,
                 onDestinationSelected: widget.onSelectedIndexChange,
@@ -646,6 +657,7 @@ class _AdaptiveScaffoldState extends State<AdaptiveScaffold> {
                 extended: true,
                 leading: widget.leadingExtendedNavRail,
                 trailing: widget.trailingNavRail,
+                padding: widget.navigationRailPadding,
                 selectedIndex: widget.selectedIndex,
                 destinations: widget.destinations
                     .map((NavigationDestination destination) =>
@@ -666,6 +678,7 @@ class _AdaptiveScaffoldState extends State<AdaptiveScaffold> {
                 extended: true,
                 leading: widget.leadingExtendedNavRail,
                 trailing: widget.trailingNavRail,
+                padding: widget.navigationRailPadding,
                 selectedIndex: widget.selectedIndex,
                 destinations: widget.destinations
                     .map((NavigationDestination destination) =>

packages/flutter_adaptive_scaffold/pubspec.yaml

@@ -1,6 +1,6 @@
 name: flutter_adaptive_scaffold
 description: Widgets to easily build adaptive layouts, including navigation elements.
-version: 0.3.2
+version: 0.3.3
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+flutter_adaptive_scaffold%22
 repository: https://github.com/flutter/packages/tree/main/packages/flutter_adaptive_scaffold
 

packages/flutter_adaptive_scaffold/test/adaptive_scaffold_test.dart

@@ -863,6 +863,33 @@ void main() {
       expect(rail.labelType, NavigationRailLabelType.all);
     },
   );
+
+  testWidgets(
+      'adaptive scaffold builds correctly with and without navigation rail padding specified',
+      (WidgetTester tester) async {
+    // without navigation rail padding specified
+    await tester.pumpWidget(MaterialApp(
+      home: AdaptiveScaffold(
+        destinations: const <NavigationDestination>[
+          NavigationDestination(icon: Icon(Icons.inbox), label: 'Inbox'),
+          NavigationDestination(icon: Icon(Icons.article), label: 'Articles'),
+        ],
+      ),
+    ));
+    expect(tester.takeException(), isNull);
+
+    // with navigation rail padding specified
+    await tester.pumpWidget(MaterialApp(
+      home: AdaptiveScaffold(
+        destinations: const <NavigationDestination>[
+          NavigationDestination(icon: Icon(Icons.inbox), label: 'Inbox'),
+          NavigationDestination(icon: Icon(Icons.article), label: 'Articles'),
+        ],
+        navigationRailPadding: const EdgeInsets.only(left: 10),
+      ),
+    ));
+    expect(tester.takeException(), isNull);
+  });
 }
 
 /// An empty widget that implements [PreferredSizeWidget] to ensure that