Fix issue #29 (#34)

* Fix #21

* Fix #29

* updated changelog

* async main needs to return Future<void>

Co-authored-by: István Soós <isoos@users.noreply.github.com>

CHANGELOG.md

@@ -2,7 +2,8 @@
 
 ## 0.5.0
 
-- Improved time parsing.　[#21](https://github.com/agilord/cron/issues/21)
+- Improved time parsing.　[#21](https://github.com/agilord/cron/issues/21) by [myConsciousness](https://github.com/myConsciousness)
+- Improved exception that occurred when parsing cron-like string. Currently throws `ScheduleParseException` if parsing fails. [[#29](https://github.com/agilord/cron/issues/29)] by [myConsciousness](https://github.com/myConsciousness)
 
 ## 0.4.1
 

README.md

@@ -1,22 +1,26 @@
-# A cron-like time-based job scheduler for Dart 
+# A cron-like time-based job scheduler for Dart
 
 Run tasks periodically at fixed times or intervals.
 
 ## Usage
 
 A simple usage example:
 
-    import 'package:cron/cron.dart';
-
-    main() {
-      final cron = Cron();
-      cron.schedule(Schedule.parse('*/3 * * * *'), () async {
-        print('every three minutes');
-      });
-      cron.schedule(Schedule.parse('8-11 * * * *'), () async {
-        print('between every 8 and 11 minutes');
-      });
-    }
+```dart
+import 'package:cron/cron.dart';
+
+main() {
+  final cron = Cron();
+
+  cron.schedule(Schedule.parse('*/3 * * * *'), () async {
+    print('every three minutes');
+  });
+
+  cron.schedule(Schedule.parse('8-11 * * * *'), () async {
+    print('between every 8 and 11 minutes');
+  });
+}
+```
 
 ## Links
 

example/example.dart

@@ -1,10 +1,17 @@
 import 'package:cron/cron.dart';
 
 Future<void> main() async {
-  final cron = Cron()
-    ..schedule(Schedule.parse('*/6 * * * * *'), () {
+  final cron = Cron();
+
+  try {
+    cron.schedule(Schedule.parse('*/6 * * * * *'), () {
       print(DateTime.now());
     });
-  await Future.delayed(Duration(seconds: 20));
-  await cron.close();
+
+    await Future.delayed(Duration(seconds: 20));
+    await cron.close();
+  } on ScheduleParseException {
+    // "ScheduleParseException" is thrown if cron parsing is failed.
+    await cron.close();
+  }
 }

lib/cron.dart

@@ -7,6 +7,8 @@ import 'package:clock/clock.dart';
 
 import 'src/constraint_parser.dart';
 
+export 'package:cron/src/schedule_parse_exception.dart';
+
 final _whitespacesRegExp = RegExp('\\s+');
 
 /// A task may return a Future to indicate when it is completed. If it wouldn't

lib/src/constraint_parser.dart

@@ -1,3 +1,5 @@
+import 'package:cron/src/schedule_parse_exception.dart';
+
 List<int>? parseConstraint(dynamic constraint) {
   if (constraint == null) return null;
   if (constraint is int) return [constraint];
@@ -33,5 +35,6 @@ List<int>? parseConstraint(dynamic constraint) {
       }
     }
   }
-  throw Exception('Unable to parse: $constraint');
+
+  throw ScheduleParseException('Unable to parse: $constraint');
 }

lib/src/schedule_parse_exception.dart

@@ -0,0 +1,9 @@
+// Copyright (c) 2022, Agilord. All rights reserved. Use of this source code
+// is governed by a BSD-style license that can be found in the LICENSE file.
+
+/// Exception thrown when a cron data does not have an expected
+/// format and cannot be parsed or processed.
+class ScheduleParseException extends FormatException {
+  /// Creates a new `FormatException` with an optional error [message].
+  ScheduleParseException([String message = '']) : super(message);
+}

test/src/schedule_parse_test.dart

@@ -0,0 +1,25 @@
+import 'package:cron/src/schedule_parse_exception.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('Test throw without message', () {
+    try {
+      throw ScheduleParseException();
+    } catch (error) {
+      expect(error is ScheduleParseException, isTrue);
+      expect(error is FormatException, isTrue);
+      expect(error is Exception, isTrue);
+    }
+  });
+
+  test('Test throw with message', () {
+    try {
+      throw ScheduleParseException('parse failed');
+    } catch (error) {
+      expect(error.toString(), 'FormatException: parse failed');
+      expect(error is ScheduleParseException, isTrue);
+      expect(error is FormatException, isTrue);
+      expect(error is Exception, isTrue);
+    }
+  });
+}