fix(database): handle cross-drive desktop DB migration

close #1022

lib/database/app_database.dart

@@ -570,11 +570,7 @@ LazyDatabase _openConnection() {
 
     // Migrate from old location on desktop (was in Documents subfolder)
     if (!Platform.isAndroid && !Platform.isIOS && !await file.exists()) {
-      final oldFolder = await getApplicationDocumentsDirectory();
-      final oldFile = File(p.join(oldFolder.path, 'plezy_downloads.db'));
-      if (await oldFile.exists()) {
-        await oldFile.rename(file.path);
-      }
+      await migrateLegacyDesktopDatabase(target: file);
     }
 
     return NativeDatabase.createInBackground(
@@ -589,3 +585,56 @@ LazyDatabase _openConnection() {
     );
   });
 }
+
+/// Move the legacy desktop DB from `Documents/` to `ApplicationSupport/`.
+/// `File.rename` only works within a single volume — Windows users with
+/// OneDrive-redirected Documents (or any cross-drive setup) hit
+/// `ERROR_NOT_SAME_DEVICE` (errno 17), and the uncaught throw used to
+/// strand the splash on "Loading servers..." forever (#1022). Falls back
+/// to copy + delete on any [FileSystemException] and swallows all errors
+/// so a failed migration never propagates fatally.
+///
+/// [sourceOverride] and [renameOverride] are test seams — production
+/// callers leave them null.
+Future<void> migrateLegacyDesktopDatabase({
+  required File target,
+  File? sourceOverride,
+  Future<void> Function(File source, String targetPath)? renameOverride,
+}) async {
+  final File oldFile;
+  if (sourceOverride != null) {
+    oldFile = sourceOverride;
+  } else {
+    final oldFolder = await getApplicationDocumentsDirectory();
+    oldFile = File(p.join(oldFolder.path, 'plezy_downloads.db'));
+  }
+  if (!await oldFile.exists()) return;
+
+  try {
+    if (renameOverride != null) {
+      await renameOverride(oldFile, target.path);
+    } else {
+      await oldFile.rename(target.path);
+    }
+    appLogger.i('Moved legacy DB from ${oldFile.path} → ${target.path}');
+    return;
+  } on FileSystemException catch (e) {
+    appLogger.w('Legacy DB rename failed (osError=${e.osError?.errorCode}); falling back to copy', error: e);
+  }
+
+  try {
+    await oldFile.copy(target.path);
+    try {
+      await oldFile.delete();
+    } catch (e) {
+      // Leaving the source behind is non-fatal — the new file is canonical.
+      appLogger.w('Legacy DB copied but old file delete failed: $e');
+    }
+    appLogger.i('Copied legacy DB from ${oldFile.path} → ${target.path}');
+  } catch (e, st) {
+    // Copy itself failed (disk full, source locked by OneDrive sync,
+    // permissions). Leave both files alone — drift will create a fresh
+    // empty DB at the new location, and a future relaunch can retry.
+    appLogger.e('Legacy DB migration failed entirely', error: e, stackTrace: st);
+  }
+}

lib/main.dart

@@ -1083,7 +1083,21 @@ class _SetupScreenState extends State<SetupScreen> with MountedSetStateMixin {
     // through `context` after async gaps trip the use_build_context_synchronously
     // lint, and reading early is safe because the registry is a singleton.
     final connectionRegistry = context.read<ConnectionRegistry>();
-    final allConnections = await connectionRegistry.list();
+    final List<Connection> allConnections;
+    try {
+      allConnections = await connectionRegistry.list();
+    } catch (e, st) {
+      // Defence-in-depth: a DB-open failure here used to propagate
+      // uncaught and strand the splash forever (#1022). Route to auth so
+      // the user is never trapped, and surface to Sentry so an unknown
+      // regression doesn't go silent.
+      appLogger.e('Setup: failed to load connections; returning to auth', error: e, stackTrace: st);
+      unawaited(Sentry.captureException(e, stackTrace: st));
+      if (mounted) {
+        unawaited(Navigator.pushReplacement(context, fadeRoute(const AuthScreen())));
+      }
+      return;
+    }
 
     if (allConnections.isEmpty) {
       if (mounted) {

test/database/app_database_test.dart

@@ -137,6 +137,103 @@ class _AppDatabaseTestSuite {
         }
       });
     });
+
+    _registerLegacyDesktopMigrationTests();
+  }
+
+  void _registerLegacyDesktopMigrationTests() {
+    // ============================================================
+    // Legacy desktop DB-file relocation (Documents → AppSupport).
+    // Regression coverage for #1022: cross-drive rename (e.g. OneDrive
+    // Documents on X:, AppData on C:) used to throw an uncaught
+    // FileSystemException out of _openConnection and strand the splash.
+    // ============================================================
+
+    group('legacy desktop DB migration', () {
+      late Directory tempDir;
+
+      setUp(() async {
+        tempDir = await Directory.systemTemp.createTemp('plezy_legacy_migration_test_');
+      });
+
+      tearDown(() async {
+        if (await tempDir.exists()) {
+          await tempDir.delete(recursive: true);
+        }
+      });
+
+      test('no-op when source does not exist', () async {
+        final source = File('${tempDir.path}/Documents/plezy_downloads.db');
+        final target = File('${tempDir.path}/AppData/plezy_downloads.db');
+        await target.parent.create(recursive: true);
+
+        await migrateLegacyDesktopDatabase(sourceOverride: source, target: target);
+
+        expect(await source.exists(), isFalse);
+        expect(await target.exists(), isFalse);
+      });
+
+      test('rename happy path moves the file and preserves content', () async {
+        final source = File('${tempDir.path}/Documents/plezy_downloads.db');
+        final target = File('${tempDir.path}/AppData/plezy_downloads.db');
+        await source.parent.create(recursive: true);
+        await target.parent.create(recursive: true);
+        await source.writeAsBytes([1, 2, 3, 4, 5]);
+
+        await migrateLegacyDesktopDatabase(sourceOverride: source, target: target);
+
+        expect(await source.exists(), isFalse);
+        expect(await target.exists(), isTrue);
+        expect(await target.readAsBytes(), [1, 2, 3, 4, 5]);
+      });
+
+      test('cross-drive rename failure falls back to copy + delete', () async {
+        // Simulate Windows ERROR_NOT_SAME_DEVICE by throwing the same
+        // exception shape `File.rename` would emit when source and target
+        // live on different volumes.
+        final source = File('${tempDir.path}/Documents/plezy_downloads.db');
+        final target = File('${tempDir.path}/AppData/plezy_downloads.db');
+        await source.parent.create(recursive: true);
+        await target.parent.create(recursive: true);
+        await source.writeAsBytes([9, 8, 7]);
+
+        await migrateLegacyDesktopDatabase(
+          sourceOverride: source,
+          target: target,
+          renameOverride: (_, _) => throw const FileSystemException(
+            'Cannot rename file across drives',
+            '',
+            OSError('The system cannot move the file to a different disk drive', 17),
+          ),
+        );
+
+        expect(await source.exists(), isFalse, reason: 'source should be deleted after successful copy');
+        expect(await target.exists(), isTrue);
+        expect(await target.readAsBytes(), [9, 8, 7]);
+      });
+
+      test('copy failure leaves source intact and never throws', () async {
+        final source = File('${tempDir.path}/Documents/plezy_downloads.db');
+        // Point target at a non-existent directory so copy fails. The
+        // helper must swallow the error — splash boot must never see it.
+        final target = File('${tempDir.path}/does-not-exist/AppData/plezy_downloads.db');
+        await source.parent.create(recursive: true);
+        await source.writeAsBytes([0xAA, 0xBB]);
+
+        await expectLater(
+          migrateLegacyDesktopDatabase(
+            sourceOverride: source,
+            target: target,
+            renameOverride: (_, _) => throw const FileSystemException('cross-drive', ''),
+          ),
+          completes,
+        );
+
+        expect(await source.exists(), isTrue, reason: 'source should be preserved when copy fails');
+        expect(await source.readAsBytes(), [0xAA, 0xBB]);
+        expect(await target.exists(), isFalse);
+      });
+    });
   }
 
   void _registerApiCacheTests() {