Blazor Wasm: debugging broken by attribute with type parameter

[zbecknell]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When a generic attribute is applied in a hosted Blazor Web Assembly project, debugging is broken.

Reproduction is here: https://github.com/zbecknell/UndebuggableV2

Notice Index.razor is applying @attribute [Bad<App>]. Remove that line and debugging now works.

Clues as to how to fix this would hopefully be found in this old previous issue dotnet/aspnetcore#25380 where the same thing would happen when an attribute had an enum parameter.

Expected Behavior

Debugging the client web assembly application hits breakpoints as expected.

Steps To Reproduce

Run and attempt to debug the client side of this hosted web assembly app: https://github.com/zbecknell/UndebuggableV2

Exceptions (if any)

The console outputs this when failure occurs:

[13:14:55] fail: DevToolsProxy[0]
      Failed to load https://localhost:7129/_framework/DebugTest.Client.dll (Specified cast is not valid.)

.NET Version

7.0.302

Anything else?

System info (though this is reproduced across OSs):

.NET SDK:
 Version:   7.0.302
 Commit:    990cf98a27

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  13.3
 OS Platform: Darwin
 RID:         osx.13-arm64
 Base Path:   /usr/local/share/dotnet/sdk/7.0.302/

Host:
  Version:      7.0.5
  Architecture: arm64
  Commit:       8042d61b17

.NET SDKs installed:
  7.0.100 [/usr/local/share/dotnet/sdk]
  7.0.200 [/usr/local/share/dotnet/sdk]
  7.0.203 [/usr/local/share/dotnet/sdk]
  7.0.302 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 7.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 7.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.5 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

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Issue Details

---

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When a generic attribute is applied in a hosted Blazor Web Assembly project, debugging is broken.

Reproduction is here: https://github.com/zbecknell/UndebuggableV2

Notice Index.razor is applying @attribute [Bad<App>]. Remove that line and debugging now works.

Clues as to how to fix this would hopefully be found in this old previous issue dotnet/aspnetcore#25380 where the same thing would happen when an attribute had an enum parameter.

Expected Behavior

Debugging the client web assembly application hits breakpoints as expected.

Steps To Reproduce

Run and attempt to debug the client side of this hosted web assembly app: https://github.com/zbecknell/UndebuggableV2

Exceptions (if any)

The console outputs this when failure occurs:

[13:14:55] fail: DevToolsProxy[0]
      Failed to load https://localhost:7129/_framework/DebugTest.Client.dll (Specified cast is not valid.)

.NET Version

7.0.302

Anything else?

System info (though this is reproduced across OSs):

.NET SDK:
 Version:   7.0.302
 Commit:    990cf98a27

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  13.3
 OS Platform: Darwin
 RID:         osx.13-arm64
 Base Path:   /usr/local/share/dotnet/sdk/7.0.302/

Host:
  Version:      7.0.5
  Architecture: arm64
  Commit:       8042d61b17

.NET SDKs installed:
  7.0.100 [/usr/local/share/dotnet/sdk]
  7.0.200 [/usr/local/share/dotnet/sdk]
  7.0.203 [/usr/local/share/dotnet/sdk]
  7.0.302 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 7.0.0 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.3 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.5 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 7.0.0 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.3 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.5 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

Author:	zbecknell
Assignees:	-
Labels:	area-Debugger-mono
Milestone:	-

[lewing]

@lambdageek are there any known mono issues lurking here?

[lambdageek]

@lewing yea we had some issue with generic custom attributes. Don't recall if it was resolved. The debugger is an interesting twist - I didn't know it looks at custom attributes.

[lewing]

@lewing yea we had some issue with generic custom attributes. Don't recall if it was resolved. The debugger is an interesting twist - I didn't know it looks at custom attributes.

It walks them for debugger hints. @ilonatommy it looks like there is at least one places in DebugStore where it makes assumptions about the attribute metadata and casts without a guard, can you take a look.

[lambdageek]

@lewing @ilonatommy The runtime issue that I was thinking of was resolved already. This works with both Mono and CoreCLR:

using System;
using System.Reflection;

[AttributeUsage(AttributeTargets.Method, AllowMultiple=true)]
public class BadAttribute<T> : Attribute
{
        public BadAttribute() {}
                
}

public class P
{
        [Bad<int>]
        [Bad<double>]
        public static void Main() {
                var mi = typeof(P).GetMethod("Main", BindingFlags.Static | BindingFlags.Public);
                var cattrs = mi.GetCustomAttributes (typeof(BadAttribute<>));
                foreach (var ca in cattrs)
                        Console.WriteLine ($"generic: {ca}");

                var cattr = mi.GetCustomAttribute(typeof(BadAttribute<int>));
                Console.WriteLine ($"instance<int>: {cattr}");

                cattr = mi.GetCustomAttribute(typeof(BadAttribute<double>));
                Console.WriteLine ($"instance<double>: {cattr}");

                cattr = mi.GetCustomAttribute(typeof(BadAttribute<string>));
                Console.WriteLine ($"instance<string>: {cattr}");
                
        }
}

Output:

generic: BadAttribute`1[System.Int32]
generic: BadAttribute`1[System.Double]
instance<int>: BadAttribute`1[System.Int32]
instance<double>: BadAttribute`1[System.Double]
instance<string>:

[ilonatommy]

@lewing @ilonatommy The runtime issue that I was thinking of was resolved already. This works with both Mono and CoreCLR:

Could you, please give the link to the issue? I cannot find it and I just checked the above code pasted into hosted WASM to the Client and result is as described:

[09:49:50] fail: DevToolsProxy[0]
      Failed to load https://localhost:5001/_framework/HostedBlazorWebassemblyApp.Client.wasm (Specified cast is not valid.)
[09:49:52] fail: DevToolsProxy[0]
      Failed to load assembly: (Stream does not contain a valid Webcil file)

edit: actually not that important, found the problem.

[zbecknell]

Thank you everyone for fixing this so quickly!