Update OutlinedButton default outline geometry to be backwards compatible (#70393)

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

@@ -242,7 +242,7 @@ class OutlinedButton extends ButtonStyleButton {
         color: Theme.of(context).colorScheme.onSurface.withOpacity(0.12),
         width: 1,
       ),
-      shape: const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(4))),
+      shape: const _Outline(borderRadius: BorderRadius.all(Radius.circular(4))),
       enabledMouseCursor: SystemMouseCursors.click,
       disabledMouseCursor: SystemMouseCursors.forbidden,
       visualDensity: theme.visualDensity,
@@ -349,3 +349,69 @@ class _OutlinedButtonWithIconChild extends StatelessWidget {
     );
   }
 }
+
+
+// This subclass only exists for the sake of backwards compatibility with the
+// outline drawn by the original OutlineButton widget. The paint override
+// draws a Path that's stroked with BorderSide, rather than filling a rounded
+// rect whose inner path is the outer path inset by the BorderSide's width.
+class _Outline extends RoundedRectangleBorder {
+  const _Outline({
+    BorderSide side = BorderSide.none,
+    required BorderRadiusGeometry borderRadius,
+  }) : super(side: side, borderRadius: borderRadius);
+
+  @override
+  ShapeBorder scale(double t) {
+    return _Outline(
+      side: side.scale(t),
+      borderRadius: borderRadius * t,
+    );
+  }
+
+  @override
+  ShapeBorder? lerpFrom(ShapeBorder? a, double t) {
+    assert(t != null);
+    if (a is _Outline) {
+      return _Outline(
+        side: BorderSide.lerp(a.side, side, t),
+        borderRadius: BorderRadiusGeometry.lerp(a.borderRadius, borderRadius, t)!,
+      );
+    }
+    return super.lerpFrom(a, t);
+  }
+
+  @override
+  ShapeBorder? lerpTo(ShapeBorder? b, double t) {
+    assert(t != null);
+    if (b is _Outline) {
+      return _Outline(
+        side: BorderSide.lerp(side, b.side, t),
+        borderRadius: BorderRadiusGeometry.lerp(borderRadius, b.borderRadius, t)!,
+      );
+    }
+    return super.lerpTo(b, t);
+  }
+
+  @override
+  _Outline copyWith({ BorderSide? side, BorderRadius? borderRadius }) {
+    return _Outline(
+      side: side ?? this.side,
+      borderRadius: borderRadius ?? this.borderRadius,
+    );
+  }
+
+  @override
+  void paint(Canvas canvas, Rect rect, { TextDirection? textDirection }) {
+    switch (side.style) {
+      case BorderStyle.none:
+        break;
+      case BorderStyle.solid:
+        if (side.width == 0.0) {
+          super.paint(canvas, rect, textDirection: textDirection);
+        } else {
+          canvas.drawPath(getOuterPath(rect, textDirection: textDirection), side.toPaint());
+        }
+    }
+  }
+}

packages/flutter/test/material/outlined_button_test.dart

@@ -40,13 +40,12 @@ void main() {
     expect(material.color, Colors.transparent);
     expect(material.elevation, 0.0);
     expect(material.shadowColor, const Color(0xff000000));
-    expect(material.shape, RoundedRectangleBorder(
+
-      side: BorderSide(
+    expect(material.shape, isInstanceOf<RoundedRectangleBorder>());
-        width: 1,
+    RoundedRectangleBorder materialShape = material.shape! as RoundedRectangleBorder;
-        color: colorScheme.onSurface.withOpacity(0.12),
+    expect(materialShape.side, BorderSide(width: 1, color: colorScheme.onSurface.withOpacity(0.12)));
-      ),
+    expect(materialShape.borderRadius, BorderRadius.circular(4.0));
-      borderRadius: BorderRadius.circular(4.0),
+
-    ));
     expect(material.textStyle!.color, colorScheme.primary);
     expect(material.textStyle!.fontFamily, 'Roboto');
     expect(material.textStyle!.fontSize, 14);
@@ -71,13 +70,12 @@ void main() {
     expect(material.color, Colors.transparent);
     expect(material.elevation, 0.0);
     expect(material.shadowColor, const Color(0xff000000));
-    expect(material.shape, RoundedRectangleBorder(
+
-      side: BorderSide(
+    expect(material.shape, isInstanceOf<RoundedRectangleBorder>());
-        width: 1,
+    materialShape = material.shape! as RoundedRectangleBorder;
-        color: colorScheme.onSurface.withOpacity(0.12),
+    expect(materialShape.side, BorderSide(width: 1, color: colorScheme.onSurface.withOpacity(0.12)));
-      ),
+    expect(materialShape.borderRadius, BorderRadius.circular(4.0));
-      borderRadius: BorderRadius.circular(4.0),
+
-    ));
     expect(material.textStyle!.color, colorScheme.primary);
     expect(material.textStyle!.fontFamily, 'Roboto');
     expect(material.textStyle!.fontSize, 14);
@@ -113,13 +111,12 @@ void main() {
     expect(material.color, Colors.transparent);
     expect(material.elevation, 0.0);
     expect(material.shadowColor, const Color(0xff000000));
-    expect(material.shape, RoundedRectangleBorder(
+
-      side: BorderSide(
+    expect(material.shape, isInstanceOf<RoundedRectangleBorder>());
-        width: 1,
+    materialShape = material.shape! as RoundedRectangleBorder;
-        color: colorScheme.onSurface.withOpacity(0.12),
+    expect(materialShape.side, BorderSide(width: 1, color: colorScheme.onSurface.withOpacity(0.12)));
-      ),
+    expect(materialShape.borderRadius, BorderRadius.circular(4.0));
-      borderRadius: BorderRadius.circular(4.0),
+
-    ));
     expect(material.textStyle!.color, colorScheme.primary);
     expect(material.textStyle!.fontFamily, 'Roboto');
     expect(material.textStyle!.fontSize, 14);
@@ -147,13 +144,12 @@ void main() {
     expect(material.color, Colors.transparent);
     expect(material.elevation, 0.0);
     expect(material.shadowColor, const Color(0xff000000));
-    expect(material.shape, RoundedRectangleBorder(
+
-      side: BorderSide(
+    expect(material.shape, isInstanceOf<RoundedRectangleBorder>());
-        width: 1,
+    materialShape = material.shape! as RoundedRectangleBorder;
-        color: colorScheme.onSurface.withOpacity(0.12),
+    expect(materialShape.side, BorderSide(width: 1, color: colorScheme.onSurface.withOpacity(0.12)));
-      ),
+    expect(materialShape.borderRadius, BorderRadius.circular(4.0));
-      borderRadius: BorderRadius.circular(4.0),
+
-    ));
     expect(material.textStyle!.color, colorScheme.onSurface.withOpacity(0.38));
     expect(material.textStyle!.fontFamily, 'Roboto');
     expect(material.textStyle!.fontSize, 14);
@@ -546,12 +542,12 @@ void main() {
     final Finder outlinedButton = find.byType(OutlinedButton);
 
     // Default, not disabled.
-    expect(outlinedButton, paints..drrect(color: defaultColor));
+    expect(outlinedButton, paints..path(color: defaultColor));
 
     // Focused.
     focusNode.requestFocus();
     await tester.pumpAndSettle();
-    expect(outlinedButton, paints..drrect(color: focusedColor));
+    expect(outlinedButton, paints..path(color: focusedColor));
 
     // Hovered.
     final Offset center = tester.getCenter(find.byType(OutlinedButton));
@@ -562,12 +558,12 @@ void main() {
     addTearDown(gesture.removePointer);
     await gesture.moveTo(center);
     await tester.pumpAndSettle();
-    expect(outlinedButton, paints..drrect(color: hoverColor));
+    expect(outlinedButton, paints..path(color: hoverColor));
 
     // Highlighted (pressed).
     await gesture.down(center);
     await tester.pumpAndSettle();
-    expect(outlinedButton, paints..drrect(color: pressedColor));
+    expect(outlinedButton, paints..path(color: pressedColor));
   });
 
   testWidgets('OutlinedButton onPressed and onLongPress callbacks are correctly called when non-null', (WidgetTester tester) async {

packages/flutter/test/material/outlined_button_theme_test.dart

@@ -34,10 +34,12 @@ void main() {
     expect(material.color, Colors.transparent);
     expect(material.elevation, 0.0);
     expect(material.shadowColor, Colors.black);
-    expect(material.shape, RoundedRectangleBorder(
+
-      side: BorderSide(width: 1, color: colorScheme.onSurface.withOpacity(0.12)),
+    expect(material.shape, isInstanceOf<RoundedRectangleBorder>());
-      borderRadius: BorderRadius.circular(4.0),
+    final RoundedRectangleBorder materialShape = material.shape! as RoundedRectangleBorder;
-    ));
+    expect(materialShape.side, BorderSide(width: 1, color: colorScheme.onSurface.withOpacity(0.12)));
+    expect(materialShape.borderRadius, BorderRadius.circular(4.0));
+
     expect(material.textStyle!.color, colorScheme.primary);
     expect(material.textStyle!.fontFamily, 'Roboto');
     expect(material.textStyle!.fontSize, 14);