feat(graphql_flutter): support flutter 3.0 and 2.x

Suggested-by: @fabis94

Signed-off-by: Vincenzo Palazzo <[email protected]>

Author: vincenzopalazzo

.github/workflows/graphql_flutter_build.yml

@@ -10,6 +10,5 @@ jobs:
       - uses: subosito/flutter-action@v1
         with:
           channel: 'stable'
-          flutter-version: '2.10.5'
       - run: make dep
       - run: make ci_fmt_flutter

packages/graphql_flutter/lib/src/widgets/cache_provider.dart

@@ -20,11 +20,19 @@ class _CacheProviderState extends State<CacheProvider>
     with WidgetsBindingObserver {
   GraphQLClient? client;
 
+  /// This allows a value of type T or T?
+  /// to be treated as a value of type T?.
+  ///
+  /// We use this so that APIs that have become
+  /// non-nullable can still be used with `!` and `?`
+  /// to support older versions of the API as well.
+  T? _ambiguate<T>(T? value) => value;
+
   @override
   void initState() {
     super.initState();
 
-    WidgetsBinding.instance!.addObserver(this);
+    _ambiguate(WidgetsBinding.instance)!.addObserver(this);
   }
 
   @override
@@ -42,7 +50,7 @@ class _CacheProviderState extends State<CacheProvider>
   void dispose() {
     super.dispose();
 
-    WidgetsBinding.instance!.removeObserver(this);
+    _ambiguate(WidgetsBinding.instance)!.removeObserver(this);
   }
 
 /*