[BUG] Memory leak without disposing 'WhenActivated' returned value

[parisq]

Describe the bug
Hi, I found a memory leak by using WhenActivated in a view.
If we don't dispose the disposable returned by WhenActivated, it seems that the view and their elements are kept in memory.

With memory leak

public BookView()
{
  InitializeComponent();
  this.WhenActivated(d =>  {  ... });
}

Without

public BookView()
{
  InitializeComponent();
  IDisposable l_disp = Disposable.Empty;;
  this.WhenActivated(d =>
  {
    ...
    d(l_disp);
  });
}

Steps To Reproduce

1. Run my simple application WPAFApplication.exe
2. click a lot of time on "add" button to add objects in the list.
   2.1 Left list is the base case with a memory leak
   2.2 Right list is the 'fixed way' by disposing WhenActivated return
3. then click on clear button
4. make a snapshot with dot memory

Expected behaviour
We shouldn't have any view model retained by their views.

Screenshots

Environment

• OS: W10
• ReactiveUI Version: 16.2.6 and 16.2.1

Additional context
Have a good day :)

WpfApplication.zip

[lippling]

I have exactly the same problem.
I thought it was problem with my code, but when I applied this workaround, my leaks were gone, but WhenActivated is never called again).
Is this something that will be fixed?

[lippling]

Ok, I did some further testing:

10.5.30-14.1.1: no memory leaks
>= 14.2.1: memory leaks

Maybe it has something to do with #2793.

[glennawatson]

Thanks for the detective work will have to look into it on the weekend.

[TSSoftware]

I have a quite similar problem. I use finalizer during debug to show an info line when garbage collection takes place for an object. The last version finalizers were called was 13.3.2.

[gerardo-lijs]

I noticed this when upgrading WPF ReactiveUI a couple of months ago. I tested with 14.1.1 it works and it doesn't with 14.2.1, so it's narrowed to changes between those two specific versions. I created this demo sample to check it out after talking about this in Slack channel. Last month I was busy with family issues so I couldn't follow up on this.

https://github.com/gerardo-lijs/ReactiveUI.Demo_DisposableLeak

. There was an specific PR between 14.1.1 and 14.2.1 that I think might be the cause, but I'm not familiar with ReactiveUI internal code so can't be sure. #2793

Maybe @ChrisPulman can help here.

GitHub

GitHub - gerardo-lijs/ReactiveUI.Demo_DisposableLeak

Contribute to gerardo-lijs/ReactiveUI.Demo_DisposableLeak development by creating an account on GitHub.

[hutterm]

Can confirm this as well. The subscription to the Dispatcher shutdown in #2793 seems to keep it in memory

[gerardo-lijs]

@glennawatson thanks for working on this! I updated to ReactiveUI 16.3.10 and now it's not leaking on the main window but still leaks in the DetailViewModels. You can take a look, difference between main branch (13.2.2), reaciveui-14-3-1 branch and the new one reactiveui-16.3.10 branch.

Let me know if you need more details and happy to help in any way. Also, maybe other users who reported this (like @hutterm or @parisq) can confirm part of the leak is still there.