Redirect exceptions from the pickers into the TCS (#1547)

Exceptions thrown in the callbacks will not reach the end user, and the task may not even return.

Xamarin.Essentials/Contacts/Contacts.ios.macos.cs

@@ -27,7 +27,16 @@ namespace Xamarin.Essentials
             var picker = new CNContactPickerViewController
             {
                 Delegate = new ContactPickerDelegate(phoneContact =>
-                    source?.TrySetResult(ConvertContact(phoneContact)))
+                {
+                    try
+                    {
+                        source?.TrySetResult(ConvertContact(phoneContact));
+                    }
+                    catch (Exception ex)
+                    {
+                        source?.TrySetException(ex);
+                    }
+                })
             };
 
             uiView.PresentViewController(picker, true, null);
@@ -80,31 +89,20 @@ namespace Xamarin.Essentials
             if (contact == null)
                 return default;
 
-            try
-            {
-                var phones = contact.PhoneNumbers?.Select(
-                   item => new ContactPhone(item?.Value?.StringValue));
-                var emails = contact.EmailAddresses?.Select(
-                   item => new ContactEmail(item?.Value?.ToString()));
+            var phones = contact.PhoneNumbers?.Select(
+                item => new ContactPhone(item?.Value?.StringValue));
+            var emails = contact.EmailAddresses?.Select(
+                item => new ContactEmail(item?.Value?.ToString()));
 
-                return new Contact(
-                    contact.Identifier,
-                    contact.NamePrefix,
-                    contact.GivenName,
-                    contact.MiddleName,
-                    contact.FamilyName,
-                    contact.NameSuffix,
-                    phones,
-                    emails);
-            }
-            catch (Exception ex)
-            {
-                throw ex;
-            }
-            finally
-            {
-                contact.Dispose();
-            }
+            return new Contact(
+                contact.Identifier,
+                contact.NamePrefix,
+                contact.GivenName,
+                contact.MiddleName,
+                contact.FamilyName,
+                contact.NameSuffix,
+                phones,
+                emails);
         }
 
 #if __IOS__

Xamarin.Essentials/FilePicker/FilePicker.ios.cs

@@ -35,10 +35,7 @@ namespace Xamarin.Essentials
                     try
                     {
                         // there was a cancellation
-                        if (urls?.Any() ?? false)
-                            tcs.TrySetResult(urls.Select(url => new UIDocumentFileResult(url)));
-                        else
-                            tcs.TrySetResult(Enumerable.Empty<FileResult>());
+                        tcs.TrySetResult(GetFileResults(urls));
                     }
                     catch (Exception ex)
                     {
@@ -52,7 +49,19 @@ namespace Xamarin.Essentials
             {
                 documentPicker.PresentationController.Delegate = new PickerPresentationControllerDelegate
                 {
-                    PickHandler = urls => tcs.TrySetResult(Enumerable.Empty<FileResult>())
+                    PickHandler = urls =>
+                    {
+                        try
+                        {
+                            // there was a cancellation
+                            tcs.TrySetResult(GetFileResults(urls));
+                        }
+                        catch (Exception ex)
+                        {
+                            // pass exception to task so that it doesn't get lost in the UI main loop
+                            tcs.SetException(ex);
+                        }
+                    }
                 };
             }
 
@@ -63,9 +72,17 @@ namespace Xamarin.Essentials
             return tcs.Task;
         }
 
+        static IEnumerable<FileResult> GetFileResults(NSUrl[] urls)
+        {
+            if (urls?.Length > 0)
+                return urls.Select(url => new UIDocumentFileResult(url));
+            else
+                return Enumerable.Empty<FileResult>();
+        }
+
         class PickerDelegate : UIDocumentPickerDelegate
         {
-            public Action<IEnumerable<NSUrl>> PickHandler { get; set; }
+            public Action<NSUrl[]> PickHandler { get; set; }
 
             public override void WasCancelled(UIDocumentPickerViewController controller)
                 => PickHandler?.Invoke(null);
@@ -74,12 +91,12 @@ namespace Xamarin.Essentials
                 => PickHandler?.Invoke(urls);
 
             public override void DidPickDocument(UIDocumentPickerViewController controller, NSUrl url)
-                => PickHandler?.Invoke(new List<NSUrl> { url });
+                => PickHandler?.Invoke(new NSUrl[] { url });
         }
 
         class PickerPresentationControllerDelegate : UIAdaptivePresentationControllerDelegate
         {
-            public Action<IEnumerable<NSUrl>> PickHandler { get; set; }
+            public Action<NSUrl[]> PickHandler { get; set; }
 
             public override void DidDismiss(UIPresentationController presentationController) =>
                 PickHandler?.Invoke(null);

Xamarin.Essentials/MediaPicker/MediaPicker.ios.cs

@@ -66,7 +66,16 @@ namespace Xamarin.Essentials
             picker.Delegate = new PhotoPickerDelegate
             {
                 CompletedHandler = info =>
-                    tcs.TrySetResult(DictionaryToMediaFile(info))
+                {
+                    try
+                    {
+                        tcs.TrySetResult(DictionaryToMediaFile(info));
+                    }
+                    catch (Exception ex)
+                    {
+                        tcs.TrySetException(ex);
+                    }
+                }
             };
 
             if (picker.PresentationController != null)
@@ -74,7 +83,16 @@ namespace Xamarin.Essentials
                 picker.PresentationController.Delegate = new PhotoPickerPresentationControllerDelegate
                 {
                     CompletedHandler = info =>
-                        tcs.TrySetResult(DictionaryToMediaFile(info))
+                    {
+                        try
+                        {
+                            tcs.TrySetResult(DictionaryToMediaFile(info));
+                        }
+                        catch (Exception ex)
+                        {
+                            tcs.TrySetException(ex);
+                        }
+                    }
                 };
             }