Merge pull request #14 from Workiva/non-null-manage-methods

REF-1399 Fail immediately on null argument

Author: jayudey-wf

lib/disposable.dart

@@ -138,23 +138,32 @@ abstract class Disposable implements _Disposable {
   }
 
   /// Automatically dispose another object when this object is disposed.
+  ///
+  /// The parameter may not be `null`.
   @mustCallSuper
   @protected
   void manageDisposable(Disposable disposable) {
+    _throwIfNull(disposable, 'disposable');
     _internalDisposables.add(disposable);
   }
 
   /// Automatically handle arbitrary disposals using a callback.
+  ///
+  /// The parameter may not be `null`.
   @mustCallSuper
   @protected
   void manageDisposer(Disposer disposer) {
+    _throwIfNull(disposer, 'disposer');
     _internalDisposables.add(new _InternalDisposable(disposer));
   }
 
   /// Automatically cancel a stream controller when this object is disposed.
+  ///
+  /// The parameter may not be `null`.
   @mustCallSuper
   @protected
   void manageStreamController(StreamController controller) {
+    _throwIfNull(controller, 'controller');
     _internalDisposables.add(new _InternalDisposable(() {
       if (!controller.hasListener) {
         controller.stream.listen((_) {});
@@ -164,9 +173,12 @@ abstract class Disposable implements _Disposable {
   }
 
   /// Automatically cancel a stream subscription when this object is disposed.
+  ///
+  /// The parameter may not be `null`.
   @mustCallSuper
   @protected
   void manageStreamSubscription(StreamSubscription subscription) {
+    _throwIfNull(subscription, 'subscription');
     _internalDisposables
         .add(new _InternalDisposable(() => subscription.cancel()));
   }
@@ -181,4 +193,10 @@ abstract class Disposable implements _Disposable {
     _didDispose.complete();
     return null;
   }
+
+  void _throwIfNull(dynamic subscription, String name) {
+    if (subscription == null) {
+      throw new ArgumentError.notNull(name);
+    }
+  }
 }

test/unit/vm/disposable_test.dart

@@ -69,6 +69,10 @@ void main() {
         await thing.dispose();
         expect(childThing.isDisposed, isTrue);
       });
+
+      test('should throw if called with a null argument', () {
+        expect(() => thing.testManageDisposable(null), throwsArgumentError);
+      });
     });
 
     group('manageDisposer', () {
@@ -86,6 +90,10 @@ void main() {
             expectAsync(() => new Future(() {}), count: 1) as Disposer);
         await thing.dispose();
       });
+
+      test('should throw if called with a null argument', () {
+        expect(() => thing.testManageDisposer(null), throwsArgumentError);
+      });
     });
 
     group('manageStreamController', () {
@@ -120,6 +128,11 @@ void main() {
         await thing.dispose();
         expect(controller.isClosed, isTrue);
       });
+
+      test('should throw if called with a null argument', () {
+        expect(
+            () => thing.testManageStreamController(null), throwsArgumentError);
+      });
     });
 
     group('manageStreamSubscription', () {
@@ -134,6 +147,11 @@ void main() {
         await subscription.cancel();
         await controller.close();
       });
+
+      test('should throw if called with a null argument', () {
+        expect(() => thing.testManageStreamSubscription(null),
+            throwsArgumentError);
+      });
     });
   });
 }