fix(windows): tolerate unavailable log files at startup

lib/services/logger/file_log_writer.dart

@@ -0,0 +1,29 @@
+import 'dart:io';
+
+/// Best-effort file output for errors that have already been logged to console.
+///
+/// File errors must not escape into the same zone that reports app errors.
+class FileLogWriter {
+  final Future<File?> _file;
+
+  FileLogWriter(Future<File> Function() getFile) : _file = _resolve(getFile);
+
+  static Future<File?> _resolve(Future<File> Function() getFile) async {
+    try {
+      return await getFile();
+    } catch (_) {
+      return null;
+    }
+  }
+
+  Future<void> write(String message) async {
+    final file = await _file;
+    if (file == null) return;
+
+    try {
+      await file.writeAsString(message, mode: FileMode.writeOnlyAppend);
+    } catch (_) {
+      // The console remains available if permissions change after startup.
+    }
+  }
+}

lib/services/logger/logger.dart

@@ -11,6 +11,8 @@ import 'package:path_provider/path_provider.dart';
 import 'package:spotube/utils/platform.dart';
 import 'package:logging/logging.dart' as logging;
 
+import 'file_log_writer.dart';
+
 final _loggingToLoggerLevel = {
   logging.Level.ALL: Level.all,
   logging.Level.FINEST: Level.trace,
@@ -26,7 +28,7 @@ final _loggingToLoggerLevel = {
 
 class AppLogger {
   static late final Logger log;
-  static late final File logFile;
+  static FileLogWriter? _fileLogWriter;
 
   static initialize(bool verbose) {
     log = Logger(
@@ -39,17 +41,15 @@ class AppLogger {
     logging.hierarchicalLoggingEnabled = true;
     logging.Logger('YoutubeExplode.StreamsClient')
       ..level = logging.Level.SEVERE
-      ..onRecord.listen(
-        (record) {
-          log.log(
-            _loggingToLoggerLevel[record.level] ?? Level.info,
-            record.message,
-            error: record.error,
-            stackTrace: record.stackTrace,
-            time: record.time,
-          );
-        },
-      );
+      ..onRecord.listen((record) {
+        log.log(
+          _loggingToLoggerLevel[record.level] ?? Level.info,
+          record.message,
+          error: record.error,
+          stackTrace: record.stackTrace,
+          time: record.time,
+        );
+      });
   }
 
   static R? runZoned<R>(R Function() body) {
@@ -70,17 +70,14 @@ class AppLogger {
           Isolate.current.addErrorListener(
             RawReceivePort((pair) async {
               final isolateError = pair as List<dynamic>;
-              reportError(
-                isolateError.first.toString(),
-                isolateError.last,
-              );
+              reportError(isolateError.first.toString(), isolateError.last);
             }).sendPort,
           );
         }
 
         _initInternalPackageLoggers();
 
-        getLogsPath().then((value) => logFile = value);
+        _fileLogWriter = FileLogWriter(getLogsPath);
 
         return body();
       },
@@ -91,7 +88,11 @@ class AppLogger {
   }
 
   static Future<File> getLogsPath() async {
-    String dir = (await getApplicationDocumentsDirectory()).path;
+    // Documents can be protected by Windows Controlled Folder Access.
+    String dir = (kIsWindows
+            ? await getApplicationSupportDirectory()
+            : await getApplicationDocumentsDirectory())
+        .path;
     if (kIsAndroid) {
       dir = (await getExternalStorageDirectory())?.path ?? "";
     }
@@ -119,11 +120,10 @@ class AppLogger {
     log.e(message, error: error, stackTrace: stackTrace);
 
     if (kReleaseMode) {
-      await logFile.writeAsString(
+      await _fileLogWriter?.write(
         "[${DateTime.now()}]---------------------\n"
         "$error\n$stackTrace\n"
         "----------------------------------------\n",
-        mode: FileMode.writeOnlyAppend,
       );
     }
   }

pubspec.lock

@@ -1767,7 +1767,7 @@ packages:
     source: hosted
     version: "2.2.1"
   path_provider_platform_interface:
-    dependency: transitive
+    dependency: "direct dev"
     description:
       name: path_provider_platform_interface
       sha256: "88f5779f72ba699763fa3a3b06aa4bf6de76c8e5de842cf6f29e2e06476c2334"

pubspec.yaml

@@ -164,6 +164,7 @@ dev_dependencies:
     sdk: flutter
   integration_test:
     sdk: flutter
+  path_provider_platform_interface: ^2.1.2
   json_serializable: ^6.6.2
   freezed: ^2.5.2
   process_run: ^0.14.2

test/services/logger/file_log_writer_test.dart

@@ -0,0 +1,87 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotube/services/logger/file_log_writer.dart';
+
+void main() {
+  late Directory directory;
+
+  setUp(() async {
+    directory = await Directory.systemTemp.createTemp('spotube-log-test-');
+  });
+
+  tearDown(() async {
+    await directory.delete(recursive: true);
+  });
+
+  test('appends errors without replacing earlier entries', () async {
+    final file = File('${directory.path}/errors.log');
+    final writer = FileLogWriter(() async => file);
+
+    await writer.write('first\n');
+    await writer.write('second\n');
+
+    expect(await file.readAsString(), 'first\nsecond\n');
+  });
+
+  test('waits for file initialization before writing', () async {
+    final file = File('${directory.path}/errors.log');
+    final ready = Completer<File>();
+    final writer = FileLogWriter(() => ready.future);
+    final write = writer.write('startup error\n');
+
+    expect(await file.exists(), isFalse);
+    ready.complete(file);
+    await write;
+
+    expect(await file.readAsString(), 'startup error\n');
+  });
+
+  test('contains synchronous initialization errors', () async {
+    final writer = FileLogWriter(() {
+      throw const FileSystemException('Permission denied');
+    });
+
+    await expectLater(writer.write('error\n'), completes);
+  });
+
+  test(
+    'contains asynchronous initialization errors before any report',
+    () async {
+      final writer = FileLogWriter(() async {
+        throw const FileSystemException('Permission denied');
+      });
+
+      // Initialization must be safe even when no error report is being written.
+      await Future<void>.delayed(Duration.zero);
+      await expectLater(writer.write('error\n'), completes);
+    },
+  );
+
+  test(
+    'contains initialization failures with a pending error report',
+    () async {
+      final ready = Completer<File>();
+      final writer = FileLogWriter(() => ready.future);
+      final write = writer.write('startup error\n');
+
+      ready.completeError(const FileSystemException('Permission denied'));
+
+      await expectLater(write, completes);
+    },
+  );
+
+  test('contains write errors after successful initialization', () async {
+    final file = File('${directory.path}/errors.log');
+    final writer = FileLogWriter(() async => file);
+    await writer.write('first\n');
+
+    // A directory at the log path fails writes on every supported desktop OS.
+    await file.delete();
+    await Directory(file.path).create();
+
+    await expectLater(writer.write('second\n'), completes);
+    await expectLater(writer.write('third\n'), completes);
+  });
+}

test/services/logger/logger_test.dart

@@ -0,0 +1,49 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:path/path.dart';
+import 'package:path_provider_platform_interface/path_provider_platform_interface.dart';
+import 'package:spotube/services/logger/logger.dart';
+
+class _ProtectedDocumentsPathProvider extends PathProviderPlatform {
+  final String supportPath;
+  int documentsRequests = 0;
+
+  _ProtectedDocumentsPathProvider(this.supportPath);
+
+  @override
+  Future<String?> getApplicationSupportPath() async => supportPath;
+
+  @override
+  Future<String?> getApplicationDocumentsPath() async {
+    documentsRequests++;
+    throw const FileSystemException('Documents access denied');
+  }
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  test(
+    'Windows logging does not require access to Documents',
+    () async {
+      final directory = await Directory.systemTemp.createTemp(
+        'spotube-path-test-',
+      );
+      final original = PathProviderPlatform.instance;
+      final provider = _ProtectedDocumentsPathProvider(directory.path);
+      PathProviderPlatform.instance = provider;
+      addTearDown(() async {
+        PathProviderPlatform.instance = original;
+        await directory.delete(recursive: true);
+      });
+
+      final file = await AppLogger.getLogsPath();
+
+      expect(file.path, join(directory.path, '.spotube_logs'));
+      expect(await file.exists(), isTrue);
+      expect(provider.documentsRequests, 0);
+    },
+    skip: !Platform.isWindows,
+  );
+}