Fix debugPaintSize throws 'Null Check error' (#106108)

packages/flutter/lib/src/rendering/box.dart

@@ -2738,6 +2738,7 @@ abstract class RenderBox extends RenderObject {
   ///
   /// Called for every [RenderBox] when [debugPaintSizeEnabled] is true.
   @protected
+  @visibleForTesting
   void debugPaintSize(PaintingContext context, Offset offset) {
     assert(() {
       final Paint paint = Paint()

packages/flutter/lib/src/rendering/proxy_box.dart

@@ -1580,9 +1580,11 @@ class RenderClipRect extends _RenderCustomClip<Rect> {
     assert(() {
       if (child != null) {
         super.debugPaintSize(context, offset);
+        if (clipBehavior != Clip.none) {
           context.canvas.drawRect(_clip!.shift(offset), _debugPaint!);
           _debugText!.paint(context.canvas, offset + Offset(_clip!.width / 8.0, -_debugText!.text!.style!.fontSize! * 1.1));
         }
+      }
       return true;
     }());
   }
@@ -1687,9 +1689,11 @@ class RenderClipRRect extends _RenderCustomClip<RRect> {
     assert(() {
       if (child != null) {
         super.debugPaintSize(context, offset);
+        if (clipBehavior != Clip.none) {
           context.canvas.drawRRect(_clip!.shift(offset), _debugPaint!);
           _debugText!.paint(context.canvas, offset + Offset(_clip!.tlRadiusX, -_debugText!.text!.style!.fontSize! * 1.1));
         }
+      }
       return true;
     }());
   }
@@ -1773,9 +1777,11 @@ class RenderClipOval extends _RenderCustomClip<Rect> {
     assert(() {
       if (child != null) {
         super.debugPaintSize(context, offset);
+        if (clipBehavior != Clip.none) {
           context.canvas.drawPath(_getClipPath(_clip!).shift(offset), _debugPaint!);
           _debugText!.paint(context.canvas, offset + Offset((_clip!.width - _debugText!.width) / 2.0, -_debugText!.text!.style!.fontSize! * 1.1));
         }
+      }
       return true;
     }());
   }
@@ -1851,9 +1857,11 @@ class RenderClipPath extends _RenderCustomClip<Path> {
     assert(() {
       if (child != null) {
         super.debugPaintSize(context, offset);
+        if (clipBehavior != Clip.none) {
           context.canvas.drawPath(_clip!.shift(offset), _debugPaint!);
           _debugText!.paint(context.canvas, offset);
         }
+      }
       return true;
     }());
   }

packages/flutter/test/rendering/proxy_box_test.dart

@@ -9,6 +9,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import 'mock_canvas.dart';
 import 'rendering_tester.dart';
 
 void main() {
@@ -770,6 +771,81 @@ void main() {
       Offset.zero & renderClipRect.size,
     );
   });
+
+  // Simulate painting a RenderBox as if 'debugPaintSizeEnabled == true'
+  Function(PaintingContext, Offset) debugPaint(RenderBox renderBox) {
+    layout(renderBox);
+    pumpFrame(phase: EnginePhase.compositingBits);
+    return (PaintingContext context, Offset offset) {
+      renderBox.paint(context, offset);
+      renderBox.debugPaintSize(context, offset);
+    };
+  }
+
+  test('RenderClipPath.debugPaintSize draws a path and a debug text when clipBehavior is not Clip.none', () {
+    Function(PaintingContext, Offset) debugPaintClipRect(Clip clip) {
+      final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
+      final RenderClipPath renderClipPath = RenderClipPath(clipBehavior: clip, child: child);
+      return debugPaint(renderClipPath);
+    }
+
+    // RenderClipPath.debugPaintSize draws when clipBehavior is not Clip.none
+    expect(debugPaintClipRect(Clip.hardEdge), paintsExactlyCountTimes(#drawPath, 1));
+    expect(debugPaintClipRect(Clip.hardEdge), paintsExactlyCountTimes(#drawParagraph, 1));
+
+    // RenderClipPath.debugPaintSize does not draw when clipBehavior is Clip.none
+    // Regression test for https://github.com/flutter/flutter/issues/105969
+    expect(debugPaintClipRect(Clip.none), paintsExactlyCountTimes(#drawPath, 0));
+    expect(debugPaintClipRect(Clip.none), paintsExactlyCountTimes(#drawParagraph, 0));
+  });
+
+  test('RenderClipRect.debugPaintSize draws a rect and a debug text when clipBehavior is not Clip.none', () {
+    Function(PaintingContext, Offset) debugPaintClipRect(Clip clip) {
+      final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
+      final RenderClipRect renderClipRect = RenderClipRect(clipBehavior: clip, child: child);
+      return debugPaint(renderClipRect);
+    }
+
+    // RenderClipRect.debugPaintSize draws when clipBehavior is not Clip.none
+    expect(debugPaintClipRect(Clip.hardEdge), paintsExactlyCountTimes(#drawRect, 1));
+    expect(debugPaintClipRect(Clip.hardEdge), paintsExactlyCountTimes(#drawParagraph, 1));
+
+    // RenderClipRect.debugPaintSize does not draw when clipBehavior is Clip.none
+    expect(debugPaintClipRect(Clip.none), paintsExactlyCountTimes(#drawRect, 0));
+    expect(debugPaintClipRect(Clip.none), paintsExactlyCountTimes(#drawParagraph, 0));
+  });
+
+  test('RenderClipRRect.debugPaintSize draws a rounded rect and a debug text when clipBehavior is not Clip.none', () {
+    Function(PaintingContext, Offset) debugPaintClipRRect(Clip clip) {
+      final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
+      final RenderClipRRect renderClipRRect = RenderClipRRect(clipBehavior: clip, child: child);
+      return debugPaint(renderClipRRect);
+    }
+
+    // RenderClipRRect.debugPaintSize draws when clipBehavior is not Clip.none
+    expect(debugPaintClipRRect(Clip.hardEdge), paintsExactlyCountTimes(#drawRRect, 1));
+    expect(debugPaintClipRRect(Clip.hardEdge), paintsExactlyCountTimes(#drawParagraph, 1));
+
+    // RenderClipRRect.debugPaintSize does not draw when clipBehavior is Clip.none
+    expect(debugPaintClipRRect(Clip.none), paintsExactlyCountTimes(#drawRRect, 0));
+    expect(debugPaintClipRRect(Clip.none), paintsExactlyCountTimes(#drawParagraph, 0));
+  });
+
+  test('RenderClipOval.debugPaintSize draws a path and a debug text when clipBehavior is not Clip.none', () {
+    Function(PaintingContext, Offset) debugPaintClipOval(Clip clip) {
+      final RenderBox child = RenderConstrainedBox(additionalConstraints: const BoxConstraints.tightFor(width: 200, height: 200));
+      final RenderClipOval renderClipOval = RenderClipOval(clipBehavior: clip, child: child);
+      return debugPaint(renderClipOval);
+    }
+
+    // RenderClipOval.debugPaintSize draws when clipBehavior is not Clip.none
+    expect(debugPaintClipOval(Clip.hardEdge), paintsExactlyCountTimes(#drawPath, 1));
+    expect(debugPaintClipOval(Clip.hardEdge), paintsExactlyCountTimes(#drawParagraph, 1));
+
+    // RenderClipOval.debugPaintSize does not draw when clipBehavior is Clip.none
+    expect(debugPaintClipOval(Clip.none), paintsExactlyCountTimes(#drawPath, 0));
+    expect(debugPaintClipOval(Clip.none), paintsExactlyCountTimes(#drawParagraph, 0));
+  });
 }
 
 class _TestRectClipper extends CustomClipper<Rect> {