数据和测试案例按照架构来处理

apps/im_app/lib/app/notifiers/user_notifier.dart

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+import 'package:im_app/app/di/user_provider.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+import 'package:im_app/data/local/drift/app_database.dart';
+import 'package:im_app/domain/entities/user.dart';
+import 'package:im_app/domain/repositories/user_repository.dart';
+
+part 'user_notifier.g.dart';
+
+/// 单个用户状态管理 (family — 每个 uid 独立 notifier)
+///
+/// ## 用法
+/// ```dart
+/// // 监听 — 自动重建
+/// final userAsync = ref.watch(userNotifierProvider(123));
+///
+/// // 即时读取，无需 await
+/// final user = ref.read(userNotifierProvider(123).notifier).current;
+///
+/// // 部分更新
+/// ref.read(userNotifierProvider(123).notifier).updateFields(
+///   UsersCompanion(nickname: Value('New Name')),
+/// );
+/// ```
+@riverpod
+class UserNotifier extends _$UserNotifier {
+  User? _cached;
+
+  UserRepository get _repo => ref.watch(userRepositoryProvider);
+
+  @override
+  Future<User?> build(int uid) async {
+    ref.onDispose(() => _cached = null);
+
+    // Stream starts automatically — uid is the family arg
+    _repo.watchUser(uid).listen((user) {
+      _cached = user;
+      state = AsyncData(user);
+    });
+
+    // Return initial DB value
+    return _repo.getUser(uid);
+  }
+
+  // ── 即时访问，无需 await ──────────────────────────────────────────────────
+
+  User? get current => _cached;
+
+  // ── 写入 ─────────────────────────────────────────────────────────────────
+
+  Future<void> saveUser(User user) async {
+    await _repo.saveUser(user);
+  }
+
+  Future<void> updateFields(UsersCompanion companion) async {
+    await _repo.updateFields(uid, companion); // uid from build arg
+  }
+
+  Future<void> updateUser(User user) async {
+    await _repo.saveUser(user);
+  }
+
+  // ── 删除 ─────────────────────────────────────────────────────────────────
+
+  Future<void> deleteUser() async {
+    await _repo.deleteUser(uid);
+    _cached = null;
+    state = const AsyncData(null);
+  }
+}