sliverGridDelegate mainAxisExtent add assert (#148470)

* sliverGridDelegate mainAxisExtent add assert,Avoid incorrect use *

Fixes flutter/flutter#138871

Author: hello-coder-xu

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

@@ -348,7 +348,8 @@ class SliverGridDelegateWithFixedCrossAxisCount extends SliverGridDelegate {
   }) : assert(crossAxisCount > 0),
        assert(mainAxisSpacing >= 0),
        assert(crossAxisSpacing >= 0),
-       assert(childAspectRatio > 0);
+       assert(childAspectRatio > 0),
+       assert(mainAxisExtent == null || mainAxisExtent >= 0);
 
   /// The number of children in the cross axis.
   final int crossAxisCount;
@@ -446,7 +447,8 @@ class SliverGridDelegateWithMaxCrossAxisExtent extends SliverGridDelegate {
   }) : assert(maxCrossAxisExtent > 0),
        assert(mainAxisSpacing >= 0),
        assert(crossAxisSpacing >= 0),
-       assert(childAspectRatio > 0);
+       assert(childAspectRatio > 0),
+       assert(mainAxisExtent == null || mainAxisExtent >= 0);
 
   /// The maximum extent of tiles in the cross axis.
   ///

packages/flutter/test/widgets/grid_view_test.dart

@@ -898,4 +898,53 @@ void main() {
     expect(controller.position.maxScrollExtent, 472.0);
     expect(controller.position.pixels, 472.0);
   });
+
+  testWidgets('SliverGridDelegate mainAxisExtent add assert', (WidgetTester tester) async {
+    Widget buildGridView(SliverGridDelegate delegate) {
+      return Directionality(
+        textDirection: TextDirection.ltr,
+        child: GridView.builder(
+          gridDelegate: delegate,
+          itemBuilder: (BuildContext context, int index) {
+            return Container(
+              height: 50,
+              alignment: Alignment.center,
+              child: Text('$index'),
+            );
+          },
+          itemCount: 50,
+        ),
+      );
+    }
+
+    expect(
+      () => tester.pumpWidget(buildGridView(SliverGridDelegateWithFixedCrossAxisCount(
+        crossAxisCount: 3,
+        mainAxisSpacing: 8,
+        crossAxisSpacing: 8,
+        mainAxisExtent: -100,
+      ))),
+      throwsA(isAssertionError.having(
+        (AssertionError e) => e.toString(),
+        '.toString()',
+        contains("'mainAxisExtent == null || mainAxisExtent >= 0': is not true."),
+      )),
+    );
+
+    expect(
+      () => tester.pumpWidget(buildGridView(SliverGridDelegateWithMaxCrossAxisExtent(
+        maxCrossAxisExtent: 100,
+        mainAxisSpacing: 8,
+        crossAxisSpacing: 8,
+        mainAxisExtent: -100,
+      ))),
+      throwsA(isAssertionError.having(
+        (AssertionError e) => e.toString(),
+        '.toString()',
+        contains("'mainAxisExtent == null || mainAxisExtent >= 0': is not true."),
+      )),
+    );
+  });
+
+
 }