Blazor: #32901 breaks a JS invocation from the IAsyncDisposable.DisposeAsync method

[pos777]

Hello,

It looks like the #32901 fix breaks an existing blazor component.
The issue is related to #32901 (comment).
In .NET 5 I have to handle the TaskCanceledException exception when invoke any JS inside the IAsyncDisposable.DisposeAsync to process component's disposing when a browser page is closed (https://github.com/pos777/Blazor_DisposeAsync_Sample/blob/632378bc60e8e1930b73a273c417f61458018b62/NET5/NET5/Shared/TestComponent.razor#L13):

async ValueTask IAsyncDisposable.DisposeAsync()
{
    try
    {
        await JS.InvokeVoidAsync("console.log", "TestComponent.DisposeAsync");
    }
    catch (TaskCanceledException) { }
}

This code does not work under .NET 6. The JSDisconnectedException exception occurs in .NET 6.
Since the JSDisconnectedException is a new class and it is not available in .NET 5, I cannot handle it in .NET 5.
I need to keep using the net5.0 target in my component library project. But it should also work in .NET 6. Please advise, how it is supposed to process the scenario?

To Reproduce

.NET 5:

• Run the Blazor_DisposeAsync_Sample\NET5.sln project;
• Refresh a browser page;
• Wait for a while;
• There is no error in log.

.NET 6:

• Run the Blazor_DisposeAsync_Sample\NET6.sln project;
• Refresh a browser page;
• The unhandled JSDisconnectedException exception is logged.
  

Exceptions

fail: Microsoft.AspNetCore.Components.Server.Circuits.CircuitHost[111]
      Unhandled exception in circuit 'DTYIfmJRu2-bAa8jKA_vxbF6NESzfXcAYlgt5ZPDRgY'.
      Microsoft.JSInterop.JSDisconnectedException: JavaScript interop calls cannot be issued at this time. This is because the circuit has disconnected and is being disposed.
         at Microsoft.AspNetCore.Components.Server.Circuits.RemoteJSRuntime.BeginInvokeJS(Int64 asyncHandle, String identifier, String argsJson, JSCallResultType resultType, Int64 targetInstanceId) in Microsoft.AspNetCore.Components.Server.dll:token 0x6000245+0x1a
         at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, CancellationToken cancellationToken, Object[] args) inMicrosoft.JSInterop.dll:token 0x600003a+0xda
         at Microsoft.JSInterop.JSRuntime.InvokeAsync[TValue](Int64 targetInstanceId, String identifier, Object[] args) in Microsoft.JSInterop.dll:token 0x6000039+0x48
         at Microsoft.JSInterop.JSRuntimeExtensions.InvokeVoidAsync(IJSRuntime jsRuntime, String identifier, Object[] args) in Microsoft.JSInterop.dll:token 0x6000046+0x82
         at NET6.Shared.TestComponent.System.IAsyncDisposable.DisposeAsync() ind:\NET6\NET6\Shared\TestComponent.razor:line 11
         at Microsoft.AspNetCore.Components.RenderTree.Renderer.<Dispose>g__HandleAsyncExceptions|62_0(List`1 tasks) in Microsoft.AspNetCore.Components.dll:token 0x6000248+0x91

Further technical details

C:\>dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100-preview.6.21306.2
 Commit:    c83bef2f34

Runtime Environment:
 OS Name:     Windows
 OS Version:  6.3.9600
 OS Platform: Windows
 RID:         win81-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-preview.6.21306.2\

Host (useful for support):
  Version: 6.0.0-preview.6.21306.1
  Commit:  5b8e1780ad

.NET SDKs installed:
  2.1.524 [C:\Program Files\dotnet\sdk]
  2.1.815 [C:\Program Files\dotnet\sdk]
  2.2.108 [C:\Program Files\dotnet\sdk]
  3.0.100 [C:\Program Files\dotnet\sdk]
  3.1.408 [C:\Program Files\dotnet\sdk]
  5.0.300 [C:\Program Files\dotnet\sdk]
  6.0.100-preview.6.21306.2 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0-preview.6.21306.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0-preview.6.21306.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.0-preview.6.21305.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Thanks,
Ilya

Thanks for contacting us.

We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
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[SteveSandersonMS]

One option is that you can make your class library multitarget both net5.0 and net6.0. Then, you can use #if like this to have a conditional block of code that references JSDisconnectedException and applies only in .NET 6.

Alternatively if you don't want to multitarget, you could do something like this:

            try
            {
                // ...
            }
            catch (Exception ex) when (ex.GetType().Name == "JSDisconnectedException")
            {
                // ...
            }

[pos777]

Hello @SteveSandersonMS,

Thank you for your answer.
As I see in the #32901 (comment), people with existing code were taken into account. I want to point that this change affects these people too. And it may be difficult to find places in existing code that should be updated. Moreover, such "broken" code may be in third-party libraries, where you cannot update the code.
I understand that the JSDisconnectedException exception exactly determines the scenario with disconnected browser. But may be there is another solution for the original issue (#32808) that will not require existing code update?

[SteveSandersonMS]

@pos777 Unfortunately I don't have a suggestion for a different solution. Delaying disposal by 1 minute is not a good situation to be in, so something will have to change to make the call end sooner, and that can only be an exception since there is no successful result we can supply.

If we do hear a lot of customer feedback that this is problematic, we could consider having some kind of back-compat switch that just disables the change (and brings back the original problem from before). However if this only affects a small number of people it would be much better to fix those particular applications.

Moreover, such "broken" code may be in third-party libraries, where you cannot update the code.

Are there specific libraries that are concerning? I'd be happy to get in touch with the library owners to help them produce an updated version that behaves correctly.

[pos777]

@SteveSandersonMS

Delaying disposal by 1 minute is not a good situation to be in

Totally agree. But you can throw the TaskCanceledException instead of the JSDisconnectedException =) Although it looks like a hack.

Are there specific libraries that are concerning?

I have notified all I know =) May be some entry in the Breaking changes in .NET 6 article will cover more interested people. May be there is appropriate place in documentation that should be updated.

Ok, I'll use the #33336 (comment) solution. Thank you for your help.

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