Error handling for malformed session file

pkgs/unified_analytics/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 0.1.3-dev
 
+- Error handling functionality added to prevent malformed session json data from causing a crash
 - Creating a new analytics constructor to point to a test instance of Google Analytics for developers
 
 ## 0.1.2

pkgs/unified_analytics/lib/src/initializer.dart

@@ -77,7 +77,7 @@ $tool=$dateStamp,$toolsMessageVersion
   /// the current session id along with the timestamp for
   /// the last ping which will be used to increment the session
   /// if current timestamp is greater than the session window
-  void createSessionFile({required File sessionFile}) {
+  static void createSessionFile({required File sessionFile}) {
     final DateTime now = clock.now();
     sessionFile.createSync(recursive: true);
     sessionFile.writeAsStringSync(jsonEncode(<String, int>{
@@ -91,7 +91,8 @@ $tool=$dateStamp,$toolsMessageVersion
   /// If it doesn't exist, one will be created there
   ///
   /// Passing [forceReset] as true will only reset the configuration
-  /// file, it won't recreate the client id and session files
+  /// file, it won't recreate the client id, session, and log files
+  /// if they currently exist on disk.
   void run({bool forceReset = false}) {
     // Begin by checking for the config file
     final File configFile = fs.file(

pkgs/unified_analytics/lib/src/session.dart

@@ -9,48 +9,23 @@ import 'package:file/file.dart';
 import 'package:path/path.dart' as p;
 
 import 'constants.dart';
+import 'initializer.dart';
 
 class Session {
   final Directory homeDirectory;
   final FileSystem fs;
   final File _sessionFile;
-  int _sessionId;
-  int _lastPing;
 
-  /// This constructor will go to the session json file in
-  /// the user's home directory and extract the necessary fields from
-  /// the json file
-  factory Session({
-    required Directory homeDirectory,
-    required FileSystem fs,
-  }) {
-    final File sessionFile = fs.file(
-        p.join(homeDirectory.path, kDartToolDirectoryName, kSessionFileName));
+  late int _sessionId;
+  late int _lastPing;
 
-    final String sessionFileContents = sessionFile.readAsStringSync();
-    final Map<String, Object?> sessionObj = jsonDecode(sessionFileContents);
-    final int sessionId = sessionObj['session_id'] as int;
-    final int lastPing = sessionObj['last_ping'] as int;
-
-    return Session._(
-      homeDirectory: homeDirectory,
-      fs: fs,
-      sessionFile: sessionFile,
-      sessionId: sessionId,
-      lastPing: lastPing,
-    );
-  }
-
-  /// Private constructor that will have the variables necessary already parsed
-  Session._({
+  Session({
     required this.homeDirectory,
     required this.fs,
-    required File sessionFile,
-    required int sessionId,
-    required int lastPing,
-  })  : _sessionFile = sessionFile,
-        _sessionId = sessionId,
-        _lastPing = lastPing;
+  }) : _sessionFile = fs.file(p.join(
+            homeDirectory.path, kDartToolDirectoryName, kSessionFileName)) {
+    _refreshSessionData();
+  }
 
   /// This will use the data parsed from the
   /// session json file in the dart-tool directory
@@ -94,15 +69,25 @@ class Session {
 
   /// This will go to the session file within the dart-tool
   /// directory and fetch the latest data from the json to update
-  /// the class's variables
+  /// the class's variables. If the json file is malformed, a new
+  /// session file will be recreated
   ///
   /// This allows the session data in this class to always be up
   /// to date incase another tool is also calling this package and
   /// making updates to the session file
   void _refreshSessionData() {
-    final String sessionFileContents = _sessionFile.readAsStringSync();
-    final Map<String, Object?> sessionObj = jsonDecode(sessionFileContents);
-    _sessionId = sessionObj['session_id'] as int;
-    _lastPing = sessionObj['last_ping'] as int;
+    try {
+      final String sessionFileContents = _sessionFile.readAsStringSync();
+      final Map<String, Object?> sessionObj = jsonDecode(sessionFileContents);
+      _sessionId = sessionObj['session_id'] as int;
+      _lastPing = sessionObj['last_ping'] as int;
+    } on FormatException {
+      Initializer.createSessionFile(sessionFile: _sessionFile);
+
+      final String sessionFileContents = _sessionFile.readAsStringSync();
+      final Map<String, Object?> sessionObj = jsonDecode(sessionFileContents);
+      _sessionId = sessionObj['session_id'] as int;
+      _lastPing = sessionObj['last_ping'] as int;
+    }
   }
 }

pkgs/unified_analytics/test/unified_analytics_test.dart

@@ -130,6 +130,24 @@ void main() {
             'for the initialized tool');
   });
 
+  test('Resetting session file when data is malformed', () {
+    // Purposefully write content to the session file that
+    // can't be decoded as json
+    sessionFile.writeAsStringSync('contents');
+
+    // Define the initial time to start
+    final DateTime start = DateTime(1995, 3, 3, 12, 0);
+
+    // Set the clock to the start value defined above
+    withClock(Clock.fixed(start), () {
+      final String timestamp = clock.now().millisecondsSinceEpoch.toString();
+      expect(sessionFile.readAsStringSync(), 'contents');
+      userProperty.preparePayload();
+      expect(sessionFile.readAsStringSync(),
+          '{"session_id":$timestamp,"last_ping":$timestamp}');
+    });
+  });
+
   test('New tool is successfully added to config file', () {
     // Create a new instance of the analytics class with the new tool
     final Analytics secondAnalytics = Analytics.test(