Check for NaN in sliver constraints, improve error messaging (#46995)

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

@@ -416,32 +416,54 @@ class SliverConstraints extends Constraints {
     InformationCollector informationCollector,
   }) {
     assert(() {
+      bool hasErrors = false;
+      final StringBuffer errorMessage = StringBuffer('\n');
       void verify(bool check, String message) {
         if (check)
           return;
-        throw FlutterError.fromParts(<DiagnosticsNode>[
-          ErrorSummary('$runtimeType is not valid: $message'),
-          if (informationCollector != null)
-            ...informationCollector(),
-          DiagnosticsProperty<SliverConstraints>('The offending constraints were', this, style: DiagnosticsTreeStyle.errorProperty),
-        ]);
+        hasErrors = true;
+        errorMessage.writeln('  $message');
+      }
+      void verifyDouble(double property, String name, {bool mustBePositive = false, bool mustBeNegative = false}) {
+        verify(property != null, 'The "$name" is null.');
+        if (property.isNaN) {
+          String additional = '.';
+          if (mustBePositive) {
+            additional = ', expected greater than or equal to zero.';
+          } else if (mustBeNegative) {
+            additional = ', expected less than or equal to zero.';
+          }
+          verify(false, 'The "$name" is NaN$additional');
+        } else if (mustBePositive) {
+          verify(property >= 0.0, 'The "$name" is negative.');
+        } else if (mustBeNegative) {
+          verify(property <= 0.0, 'The "$name" is positive.');
+        }
       }
       verify(axis != null, 'The "axis" is null.');
       verify(growthDirection != null, 'The "growthDirection" is null.');
-      verify(scrollOffset != null, 'The "scrollOffset" is null.');
-      verify(overlap != null, 'The "overlap" is null.');
-      verify(remainingPaintExtent != null, 'The "remainingPaintExtent" is null.');
-      verify(crossAxisExtent != null, 'The "crossAxisExtent" is null.');
-      verify(viewportMainAxisExtent != null, 'The "viewportMainAxisExtent" is null.');
-      verify(scrollOffset >= 0.0, 'The "scrollOffset" is negative.');
-      verify(crossAxisExtent >= 0.0, 'The "crossAxisExtent" is negative.');
+      verifyDouble(scrollOffset, 'scrollOffset');
+      verifyDouble(overlap, 'overlap');
+      verifyDouble(remainingPaintExtent, 'remainingPaintExtent');
+      verifyDouble(crossAxisExtent, 'crossAxisExtent');
+      verifyDouble(viewportMainAxisExtent, 'viewportMainAxisExtent');
+      verifyDouble(scrollOffset, 'scrollOffset', mustBePositive: true);
       verify(crossAxisDirection != null, 'The "crossAxisDirection" is null.');
       verify(axisDirectionToAxis(axisDirection) != axisDirectionToAxis(crossAxisDirection), 'The "axisDirection" and the "crossAxisDirection" are along the same axis.');
-      verify(viewportMainAxisExtent >= 0.0, 'The "viewportMainAxisExtent" is negative.');
-      verify(remainingPaintExtent >= 0.0, 'The "remainingPaintExtent" is negative.');
-      verify(remainingCacheExtent >= 0.0, 'The "remainingCacheExtent" is negative.');
-      verify(cacheOrigin <= 0.0, 'The "cacheOrigin" is positive.');
+      verifyDouble(viewportMainAxisExtent, 'viewportMainAxisExtent', mustBePositive: true);
+      verifyDouble(remainingPaintExtent, 'remainingPaintExtent', mustBePositive: true);
+      verifyDouble(remainingCacheExtent, 'remainingCacheExtent', mustBePositive: true);
+      verifyDouble(cacheOrigin, 'cacheOrigin', mustBeNegative: true);
+      verifyDouble(precedingScrollExtent, 'precedingScrollExtent', mustBePositive: true);
       verify(isNormalized, 'The constraints are not normalized.'); // should be redundant with earlier checks
+      if (hasErrors) {
+        throw FlutterError.fromParts(<DiagnosticsNode>[
+          ErrorSummary('$runtimeType is not valid: $errorMessage'),
+          if (informationCollector != null)
+            ...informationCollector(),
+          DiagnosticsProperty<SliverConstraints>('The offending constraints were', this, style: DiagnosticsTreeStyle.errorProperty),
+        ]);
+      }
       return true;
     }());
     return true;

packages/flutter/test/rendering/slivers_test.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:flutter/foundation.dart';
 import 'package:flutter/gestures.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
@@ -921,6 +922,84 @@ void main() {
       crossAxisPositions.clear();
     });
   });
+
+  test('SliverConstraints check for NaN on all double properties', () {
+    const SliverConstraints constraints = SliverConstraints(
+      axisDirection: AxisDirection.down,
+      cacheOrigin: double.nan,
+      crossAxisDirection: AxisDirection.left,
+      crossAxisExtent: double.nan,
+      growthDirection: GrowthDirection.forward,
+      overlap: double.nan,
+      precedingScrollExtent: double.nan,
+      remainingCacheExtent: double.nan,
+      remainingPaintExtent: double.nan,
+      scrollOffset: double.nan,
+      userScrollDirection: ScrollDirection.idle,
+      viewportMainAxisExtent: double.nan,
+    );
+    bool threw = false;
+    try {
+      constraints.debugAssertIsValid();
+    } on FlutterError catch (error) {
+      expect(
+        error.message,
+        'SliverConstraints is not valid:\n'
+        '  The "scrollOffset" is NaN.\n'
+        '  The "overlap" is NaN.\n'
+        '  The "remainingPaintExtent" is NaN.\n'
+        '  The "crossAxisExtent" is NaN.\n'
+        '  The "viewportMainAxisExtent" is NaN.\n'
+        '  The "scrollOffset" is NaN, expected greater than or equal to zero.\n'
+        '  The "viewportMainAxisExtent" is NaN, expected greater than or equal to zero.\n'
+        '  The "remainingPaintExtent" is NaN, expected greater than or equal to zero.\n'
+        '  The "remainingCacheExtent" is NaN, expected greater than or equal to zero.\n'
+        '  The "cacheOrigin" is NaN, expected less than or equal to zero.\n'
+        '  The "precedingScrollExtent" is NaN, expected greater than or equal to zero.\n'
+        '  The constraints are not normalized.\n'
+        'The offending constraints were:\n'
+        '  SliverConstraints(AxisDirection.down, GrowthDirection.forward, ScrollDirection.idle, scrollOffset: NaN, remainingPaintExtent: NaN, overlap: NaN, crossAxisExtent: NaN, crossAxisDirection: AxisDirection.left, viewportMainAxisExtent: NaN, remainingCacheExtent: NaN cacheOrigin: NaN )',
+      );
+      threw = true;
+    }
+    expect(threw, true);
+  });
+
+  test('SliverConstraints check for sign on relevant double properties', () {
+    const SliverConstraints constraints = SliverConstraints(
+      axisDirection: AxisDirection.down,
+      cacheOrigin: 1.0,
+      crossAxisDirection: AxisDirection.left,
+      crossAxisExtent: 0.0,
+      growthDirection: GrowthDirection.forward,
+      overlap: 0.0,
+      precedingScrollExtent: -1.0,
+      remainingCacheExtent: -1.0,
+      remainingPaintExtent: -1.0,
+      scrollOffset: -1.0,
+      userScrollDirection: ScrollDirection.idle,
+      viewportMainAxisExtent: 0.0,
+    );
+    bool threw = false;
+    try {
+      constraints.debugAssertIsValid();
+    } on FlutterError catch (error) {
+      expect(
+        error.message,
+        'SliverConstraints is not valid:\n'
+        '  The "scrollOffset" is negative.\n'
+        '  The "remainingPaintExtent" is negative.\n'
+        '  The "remainingCacheExtent" is negative.\n'
+        '  The "cacheOrigin" is positive.\n'
+        '  The "precedingScrollExtent" is negative.\n'
+        '  The constraints are not normalized.\n'
+        'The offending constraints were:\n'
+        '  SliverConstraints(AxisDirection.down, GrowthDirection.forward, ScrollDirection.idle, scrollOffset: -1.0, remainingPaintExtent: -1.0, crossAxisExtent: 0.0, crossAxisDirection: AxisDirection.left, viewportMainAxisExtent: 0.0, remainingCacheExtent: -1.0 cacheOrigin: 1.0 )',
+      );
+      threw = true;
+    }
+    expect(threw, true);
+  });
 }
 
 class _DummyHitTestTarget implements HitTestTarget {