Minor changes

- Allow calling `.init()` multiple times, instead of throwing error Hive will print warning to console
- Hive will warn developers when registering adapters for `dynamic` type

hive/lib/src/hive_impl.dart

@@ -55,8 +55,11 @@ class HiveImpl extends TypeRegistryImpl implements HiveInterface {
 
   @override
   void init(String path) {
-    if (homePath != null) {
-      throw HiveError('Instance has already been initialized.');
+    if (homePath == path) {
+      print(
+        'Hive instance has already been initialized. Please call Hive.init '
+        'only once if possible.',
+      );
     }
     homePath = path;
   }

hive/lib/src/registry/type_registry_impl.dart

@@ -73,6 +73,16 @@ class TypeRegistryImpl implements TypeRegistry {
     bool internal = false,
     bool override = false,
   }) {
+    if (T == dynamic || T == Object) {
+      print(
+        'Registering type adapters for dynamic type is must be avoided, '
+        'otherwise all the write requests to Hive will be handled by given '
+        'adapter. Please explicitly provide adapter type on registerAdapter '
+        'method to avoid this kind of issues. For example if you want to '
+        'register MyTypeAdapter for MyType class you can call like this: '
+        'registerAdapter<MyType>(MyTypeAdapter())',
+      );
+    }
     var typeId = adapter.typeId;
     if (!internal) {
       if (typeId < 0 || typeId > 223) {

hive/test/tests/registry/type_registry_impl_test.dart

@@ -60,6 +60,11 @@ void main() {
         expect(() => registry.registerAdapter(TestAdapter()),
             throwsHiveError('already a TypeAdapter for typeId'));
       });
+
+      test('dynamic type', () {
+        var registry = TypeRegistryImpl();
+        registry.registerAdapter<dynamic>(TestAdapter());
+      });
     });
 
     test('.findAdapterForTypeId()', () {

hive_flutter/lib/src/hive_extensions.dart

@@ -9,11 +9,7 @@ extension HiveX on HiveInterface {
     WidgetsFlutterBinding.ensureInitialized();
     if (!kIsWeb) {
       var appDir = await getApplicationDocumentsDirectory();
-      if (appDir != null) {
-        init(path_helper.join(appDir.path, subDir));
-      } else {
-        NullThrownError();
-      }
+      init(path_helper.join(appDir.path, subDir));
     }
   }
 }