Paint the shape border in the Material widget (#14383)

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

@@ -130,6 +130,10 @@ abstract class MaterialInkController {
 ///      rounded edges. The edge radii is specified by [kMaterialEdges].
 ///    - [MaterialType.transparency]: the default material shape is a rectangle.
 ///
+/// ## Border
+///
+/// If [shape] is not null, then its border will also be painted (if any).
+///
 /// ## Layout change notifications
 ///
 /// If the layout changes (e.g. because there's a list on the material, and it's
@@ -327,7 +331,7 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
     final ShapeBorder shape = _getShape();
 
     if (widget.type == MaterialType.transparency)
-      return _clipToShape(shape: shape, contents: contents);
+      return _transparentInterior(shape: shape, contents: contents);
     
     return new _MaterialInterior(
       curve: Curves.fastOutSlowIn,
@@ -338,12 +342,14 @@ class _MaterialState extends State<Material> with TickerProviderStateMixin {
       shadowColor: widget.shadowColor,
       child: contents,
     );
-
   }
 
-  static Widget _clipToShape({ShapeBorder shape, Widget contents}) {
+  static Widget _transparentInterior({ShapeBorder shape, Widget contents}) {
     return new ClipPath(
-      child: contents,
+      child: new _ShapeBorderPaint(
+        child: contents,
+        shape: shape,
+      ),
       clipper: new ShapeBorderClipper(
         shape: shape,
       ),
@@ -625,10 +631,14 @@ class _MaterialInteriorState extends AnimatedWidgetBaseState<_MaterialInterior>
 
   @override
   Widget build(BuildContext context) {
+    final ShapeBorder shape = _border.evaluate(animation);
     return new PhysicalShape(
-      child: widget.child,
+      child: new _ShapeBorderPaint(
+        child: widget.child,
+        shape: shape,
+      ),
       clipper: new ShapeBorderClipper(
-        shape: _border.evaluate(animation),
+        shape: shape,
         textDirection: Directionality.of(context)
       ),
       elevation: _elevation.evaluate(animation),
@@ -637,3 +647,37 @@ class _MaterialInteriorState extends AnimatedWidgetBaseState<_MaterialInterior>
     );
   }
 }
+
+class _ShapeBorderPaint extends StatelessWidget {
+  const _ShapeBorderPaint({
+    @required this.child,
+    @required this.shape,
+  });
+
+  final Widget child;
+  final ShapeBorder shape;
+
+  @override
+  Widget build(BuildContext context) {
+    return new CustomPaint(
+      child: child,
+      foregroundPainter: new _ShapeBorderPainter(shape, Directionality.of(context)),
+    );
+  }
+}
+
+class _ShapeBorderPainter extends CustomPainter {
+  _ShapeBorderPainter(this.border, this.textDirection);
+  final ShapeBorder border;
+  final TextDirection textDirection;
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    border.paint(canvas, Offset.zero & size, textDirection: textDirection);
+  }
+
+  @override
+  bool shouldRepaint(_ShapeBorderPainter oldDelegate) {
+    return oldDelegate.border != border;
+  }
+}

packages/flutter/test/material/material_test.dart

@@ -7,6 +7,8 @@ import 'package:flutter/painting.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import '../rendering/mock_canvas.dart';
+
 class NotifyMaterial extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
@@ -404,4 +406,62 @@ void main() {
       ));
     });
   });
+
+  group('Border painting', () {
+    testWidgets('border is painted on physical layers', (WidgetTester tester) async {
+      final GlobalKey materialKey = new GlobalKey();
+      await tester.pumpWidget(
+        new Material(
+          key: materialKey,
+          type: MaterialType.button,
+          child: const SizedBox(width: 100.0, height: 100.0),
+          color: const Color(0xFF0000FF),
+          shape: const CircleBorder(
+            side: const BorderSide(
+              width: 2.0,
+              color: const Color(0xFF0000FF),
+            )
+          ),
+        )
+      );
+
+      final RenderBox box = tester.renderObject(find.byKey(materialKey));
+      expect(box, paints..circle());
+    });
+
+    testWidgets('border is painted for transparent material', (WidgetTester tester) async {
+      final GlobalKey materialKey = new GlobalKey();
+      await tester.pumpWidget(
+        new Material(
+          key: materialKey,
+          type: MaterialType.transparency,
+          child: const SizedBox(width: 100.0, height: 100.0),
+          shape: const CircleBorder(
+            side: const BorderSide(
+              width: 2.0,
+              color: const Color(0xFF0000FF),
+            )
+          ),
+        )
+      );
+
+      final RenderBox box = tester.renderObject(find.byKey(materialKey));
+      expect(box, paints..circle());
+    });
+
+    testWidgets('border is not painted for when border side is none', (WidgetTester tester) async {
+      final GlobalKey materialKey = new GlobalKey();
+      await tester.pumpWidget(
+        new Material(
+          key: materialKey,
+          type: MaterialType.transparency,
+          child: const SizedBox(width: 100.0, height: 100.0),
+          shape: const CircleBorder(),
+        )
+      );
+
+      final RenderBox box = tester.renderObject(find.byKey(materialKey));
+      expect(box, isNot(paints..circle()));
+    });
+  });
 }

packages/flutter/test/rendering/mock_canvas.dart

@@ -42,7 +42,7 @@ import 'recording_canvas.dart';
 /// To match something which asserts instead of painting, see [paintsAssertion].
 PaintPattern get paints => new _TestRecordingCanvasPatternMatcher();
 
-/// Matches objects or functions that paint an empty display list.
+/// Matches objects or functions that does not paint anything on the canvas.
 Matcher get paintsNothing => new _TestRecordingCanvasPaintsNothingMatcher();
 
 /// Matches objects or functions that assert when they try to paint.
@@ -539,14 +539,27 @@ class _TestRecordingCanvasPaintsNothingMatcher extends _TestRecordingCanvasMatch
 
   @override
   bool _evaluatePredicates(Iterable<RecordedInvocation> calls, StringBuffer description) {
-    if (calls.isEmpty)
+    final Iterable<RecordedInvocation> paintingCalls = _filterCanvasCalls(calls);
+    if (paintingCalls.isEmpty)
       return true;
     description.write(
       'painted something, the first call having the following stack:\n'
-      '${calls.first.stackToString(indent: "  ")}\n'
+      '${paintingCalls.first.stackToString(indent: "  ")}\n'
     );
     return false;
   }
+
+  static const List<Symbol> _nonPaintingOperations = const <Symbol> [
+    #save,
+    #restore,
+  ];
+
+  // Filters out canvas calls that are not painting anything.
+  static Iterable<RecordedInvocation> _filterCanvasCalls(Iterable<RecordedInvocation> canvasCalls) {
+    return canvasCalls.where((RecordedInvocation canvasCall) =>
+      !_nonPaintingOperations.contains(canvasCall.invocation.memberName)
+    );
+  }
 }
 
 class _TestRecordingCanvasPaintsAssertionMatcher extends Matcher {