Commits on Apr 18, 2024

1. [controls] fix leak in ImageSource, caused by Task that never completes …

   Context: https://github.com/AdamEssenmacher/MemoryToolkit.Maui/tree/main/samples
   
   Testing the above sample, I saw some odd results in a `.gcdump`
   related to `UriImageSource` inside a `CollectionView`:
   
       AsyncTaskMethodBuilder+AsyncStateMachineBox<VoidTaskResult, Microsoft.Maui.Controls.ImageElement+<CancelOldValue>d__10>, Count: 182
           Dictionary+Entry<Int32, Task>[], Count: 182
               Dictionary<Int32, Task> [Static variable Task.s_currentActiveTasks], Count: 1
   
   It appears that we `await` a `Task` that never completes, which is:
   
   https://github.com/dotnet/maui/blob/8e4450cbc14932a6c74aeb8b7bfee9c94eca18b0/src/Controls/src/Core/ImageElement.cs#L129
   
   The `Task` also holds onto the `ImageSource` and whatever memory it
   happened to use. That would be ok if the `Task` completed.
   
   I could reproduce the problem in a test:
   
       [Fact]
       public async Task CancelCompletes()
       {
           var imageSource = new StreamImageSource
           {
               Stream = _ => Task.FromResult<Stream>(new MemoryStream())
           };
           await ((IStreamImageSource)imageSource).GetStreamAsync();
           await imageSource.Cancel(); // This should complete!
       }
   
   This non-completing `Task` can occur when changing `Image.Source`,
   which would certainly be bad while scrolling a `CollectionView`!
   
   To fix, I refactored the code slightly and had the problematic case
   return:
   
       return Task.FromResult(false);

   

   jonathanpeppers committed Apr 18, 2024
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