More better toStrings and more vigorous smoke testing of gallery (#8237)

* More better toStrings and more vigorous smoke testing of gallery

* Update scroll_controller.dart

* Update sliver.dart

examples/flutter_gallery/test/smoke_test.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:collection' show LinkedHashSet;
+import 'dart:math' as math;
 
 import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
@@ -25,6 +26,36 @@ Finder findGalleryItemByRouteName(WidgetTester tester, String routeName) {
   });
 }
 
+int errors = 0;
+
+void reportToStringError(String name, String route, int lineNumber, List<String> lines, String message) {
+  // If you're on line 12, then it has index 11.
+  // If you want 1 line before and 1 line after, then you want lines with index 10, 11, and 12.
+  // That's (lineNumber-1)-margin .. (lineNumber-1)+margin, or lineNumber-(margin+1) .. lineNumber+(margin-1)
+  int margin = 5;
+  int firstLine = math.max(0, lineNumber - margin);
+  int lastLine = math.min(lines.length, lineNumber + margin);
+  print('$name : $route : line $lineNumber of ${lines.length} : $message; nearby lines were:\n  ${lines.sublist(firstLine, lastLine).join("\n  ")}');
+  errors += 1;
+}
+
+void verifyToStringOutput(String name, String route, String testString) {
+  int lineNumber = 0;
+  List<String> lines = testString.split('\n');
+  if (!testString.endsWith('\n'))
+    reportToStringError(name, route, lines.length, lines, 'does not end with a line feed');
+  for (String line in lines) {
+    lineNumber += 1;
+    if (line == '' && lineNumber != lines.length) {
+      reportToStringError(name, route, lineNumber, lines, 'found empty line');
+    } else if (line.contains('Instance of ')) {
+      reportToStringError(name, route, lineNumber, lines, 'found a class that does not have its own toString');
+    } else if (line.endsWith(' ')) {
+      reportToStringError(name, route, lineNumber, lines, 'found a line with trailing whitespace');
+    }
+  }
+}
+
 // Start a gallery demo and then go back. This function assumes that the
 // we're starting on the home route and that the submenu that contains
 // the item for a demo that pushes route 'routeName' is already open.
@@ -33,12 +64,43 @@ Future<Null> smokeDemo(WidgetTester tester, String routeName) async {
   final Finder menuItem = findGalleryItemByRouteName(tester, routeName);
   expect(menuItem, findsOneWidget);
 
+  // Don't use pumpUntilNoTransientCallbacks in this function, because some of
+  // the smoketests have infinitely-running animations (e.g. the progress
+  // indicators demo).
+
   await tester.tap(menuItem);
   await tester.pump(); // Launch the demo.
-  await tester.pump(const Duration(seconds: 1)); // Wait until the demo has opened.
-
+  await tester.pump(const Duration(milliseconds: 400)); // Wait until the demo has opened.
   expect(find.text(kCaption), findsNothing);
-  await tester.pump(const Duration(seconds: 1)); // Leave the demo on the screen briefly for manual testing.
+
+  // Leave the demo on the screen briefly for manual testing.
+  await tester.pump(const Duration(milliseconds: 400));
+
+  // Scroll the demo around a bit.
+  await tester.flingFrom(const Point(400.0, 300.0), const Offset(-100.0, 0.0), 500.0);
+  await tester.flingFrom(const Point(400.0, 300.0), const Offset(0.0, -100.0), 500.0);
+  await tester.pump();
+  await tester.pump(const Duration(milliseconds: 50));
+  await tester.pump(const Duration(milliseconds: 200));
+  await tester.pump(const Duration(milliseconds: 400));
+
+  // Verify that the dumps are pretty.
+  verifyToStringOutput('debugDumpApp', routeName, WidgetsBinding.instance.renderViewElement.toStringDeep());
+  verifyToStringOutput('debugDumpRenderTree', routeName, RendererBinding.instance?.renderView?.toStringDeep());
+  verifyToStringOutput('debugDumpLayerTree', routeName, RendererBinding.instance?.renderView?.debugLayer?.toStringDeep());
+
+  // Scroll the demo around a bit more.
+  await tester.flingFrom(const Point(400.0, 300.0), const Offset(-200.0, 0.0), 500.0);
+  await tester.pump();
+  await tester.pump(const Duration(milliseconds: 50));
+  await tester.pump(const Duration(milliseconds: 200));
+  await tester.pump(const Duration(milliseconds: 400));
+  await tester.flingFrom(const Point(400.0, 300.0), const Offset(100.0, 0.0), 500.0);
+  await tester.pump();
+  await tester.pump(const Duration(milliseconds: 400));
+  await tester.flingFrom(const Point(400.0, 300.0), const Offset(0.0, 400.0), 1000.0);
+  await tester.pump();
+  await tester.pump(const Duration(milliseconds: 400));
 
   // Go back
   Finder backButton = find.byTooltip('Back');
@@ -46,7 +108,7 @@ Future<Null> smokeDemo(WidgetTester tester, String routeName) async {
   await tester.tap(backButton);
   await tester.pump(); // Start the pop "back" operation.
   await tester.pump(); // Complete the willPop() Future.
-  await tester.pump(const Duration(seconds: 1)); // Wait until it has finished.
+  await tester.pump(const Duration(milliseconds: 400)); // Wait until it has finished.
   return null;
 }
 
@@ -71,6 +133,8 @@ Future<Null> runSmokeTest(WidgetTester tester) async {
     tester.binding.debugAssertNoTransientCallbacks('A transient callback was still active after leaving route $routeName');
   }
 
+  expect(errors, 0);
+
   Finder navigationMenuButton = find.byTooltip('Open navigation menu');
   expect(navigationMenuButton, findsOneWidget);
   await tester.tap(navigationMenuButton);

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

@@ -555,6 +555,11 @@ class _SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
         || expandedHeight != oldDelegate.expandedHeight
         || topPadding != oldDelegate.topPadding;
   }
+
+  @override
+  String toString() {
+    return '$runtimeType#$hashCode(topPadding: ${topPadding.toStringAsFixed(1)}, bottomHeight: ${_bottomHeight.toStringAsFixed(1)}, ...)';
+  }
 }
 
 class SliverAppBar extends StatelessWidget {

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

@@ -266,7 +266,7 @@ void debugDumpRenderTree() {
 
 /// Prints a textual representation of the entire layer tree.
 void debugDumpLayerTree() {
-  debugPrint(RendererBinding.instance?.renderView?.layer?.toStringDeep());
+  debugPrint(RendererBinding.instance?.renderView?.debugLayer?.toStringDeep());
 }
 
 /// Prints a textual representation of the entire semantics tree.

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

@@ -403,6 +403,6 @@ class RenderEditable extends RenderBox {
     return '$prefix \u2558\u2550\u2566\u2550\u2550 text \u2550\u2550\u2550\n'
            '${text.toString("$prefix   \u2551 ")}' // TextSpan includes a newline
            '$prefix   \u255A\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n'
-           '$prefix\n';
+           '${prefix.trimRight()}\n';
   }
 }

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

@@ -87,9 +87,13 @@ abstract class Layer {
     List<String> description = <String>[];
     debugFillDescription(description);
     result += description.map((String description) => "$descriptionPrefix$description\n").join();
-    if (childrenDescription == '')
-      result += '$prefixOtherLines\n';
-    result += childrenDescription;
+    if (childrenDescription == '') {
+      String prefix = prefixOtherLines.trimRight();
+      if (prefix != '')
+        result += '$prefix\n';
+    } else {
+      result += childrenDescription;
+    }
     return result;
   }
 

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

@@ -1903,12 +1903,31 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
   OffsetLayer _layer;
   /// The compositing layer that this render object uses to repaint.
   ///
-  /// Call only when [isRepaintBoundary] is true.
+  /// Call only when [isRepaintBoundary] is true and the render object has
+  /// already painted.
+  ///
+  /// To access the layer in debug code, even when it might be inappropriate to
+  /// access it (e.g. because it is dirty), consider [debugLayer].
   OffsetLayer get layer {
     assert(isRepaintBoundary);
     assert(!_needsPaint);
     return _layer;
   }
+  /// In debug mode, the compositing layer that this render object uses to repaint.
+  ///
+  /// This getter is intended for debugging purposes only. In release builds, it
+  /// always returns null. In debug builds, it returns the layer even if the layer
+  /// is dirty.
+  ///
+  /// For production code, consider [layer].
+  OffsetLayer get debugLayer {
+    OffsetLayer result;
+    assert(() {
+      result = _layer;
+      return true;
+    });
+    return result;
+  }
 
   bool _needsCompositingBitsUpdate = false; // set to true when a child is added
   /// Mark the compositing state for this render object as dirty.
@@ -2422,9 +2441,13 @@ abstract class RenderObject extends AbstractNode implements HitTestTarget {
       .expand((String description) => debugWordWrap(description, 65, wrapIndent: '  '))
       .map<String>((String line) => "$descriptionPrefix$line\n")
       .join();
-    if (childrenDescription == '')
-      result += '$prefixOtherLines\n';
-    result += childrenDescription;
+    if (childrenDescription == '') {
+      String prefix = prefixOtherLines.trimRight();
+      if (prefix != '')
+        result += '$prefix\n';
+    } else {
+      result += childrenDescription;
+    }
     _debugActiveLayout = debugPreviousActiveLayout;
     return result;
   }

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

@@ -342,6 +342,6 @@ class RenderParagraph extends RenderBox {
     return '$prefix \u2558\u2550\u2566\u2550\u2550 text \u2550\u2550\u2550\n'
            '${text.toString("$prefix   \u2551 ")}' // TextSpan includes a newline
            '$prefix   \u255A\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\u2550\n'
-           '$prefix\n';
+           '${prefix.trimRight()}\n';
   }
 }

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

@@ -178,12 +178,12 @@ abstract class RenderSliverPersistentHeader extends RenderSliver with RenderObje
     try {
       description.add('maxExtent: ${maxExtent.toStringAsFixed(1)}');
     } catch (e) {
-      description.add('maxExtent: EXCEPTION (${e.runtimeType}) WHILE COMPUTING MAX EXTENT');
+      description.add('maxExtent: EXCEPTION (${e.runtimeType})');
     }
     try {
       description.add('child position: ${childMainAxisPosition(child).toStringAsFixed(1)}');
     } catch (e) {
-      description.add('child position: EXCEPTION (${e.runtimeType}) WHILE COMPUTING CHILD POSITION');
+      description.add('child position: EXCEPTION (${e.runtimeType})');
     }
   }
 }

packages/flutter/lib/src/widgets/scroll_controller.dart

@@ -118,4 +118,21 @@ class ScrollController {
       oldPosition: oldPosition,
     );
   }
+
+  @override
+  String toString() {
+    final StringBuffer result = new StringBuffer();
+    result.write('$runtimeType#$hashCode(');
+    if (initialScrollOffset != 0.0)
+      result.write('initialScrollOffset: ${initialScrollOffset.toStringAsFixed(1)}, ');
+    if (_positions.isEmpty) {
+      result.write('no clients');
+    } else if (_positions.length == 1) {
+      result.write('one client, offset $offset');
+    } else {
+      result.write('${_positions.length} clients');
+    }
+    result.write(')');
+    return result.toString();
+  }
 }

packages/flutter/lib/src/widgets/sliver.dart

@@ -39,6 +39,24 @@ abstract class SliverChildDelegate {
   ) => null;
 
   bool shouldRebuild(@checked SliverChildDelegate oldDelegate);
+
+  @override
+  String toString() {
+    List<String> description = <String>[];
+    debugFillDescription(description);
+    return '$runtimeType#$hashCode(${description.join(", ")})';
+  }
+
+  @protected
+  void debugFillDescription(List<String> description) {
+    try {
+      final int children = estimatedChildCount;
+      if (children != null)
+        description.add('estimated child count: $children');
+    } catch (e) {
+      description.add('estimated child count: EXCEPTION (${e.runtimeType})');
+    }
+  }
 }
 
 class SliverChildBuilderDelegate extends SliverChildDelegate {

packages/flutter/test/foundation/service_extensions_test.dart

@@ -130,7 +130,6 @@ void main() {
         r'   window size: Size\(800\.0, 600\.0\) \(in physical pixels\)\n'
         r'   device pixel ratio: 1\.0 \(physical pixels per logical pixel\)\n'
         r'   configuration: Size\(800\.0, 600\.0\) at 1\.0x \(in logical pixels\)\n'
-        r'\n'
       ),
     ]);
     console.clear();