Issues with the new .NET 9+ Mono Debugger

[dlemstra]

Description

We have a big application that executes .NET code in the browser with WASM. We are now testing with net9.0-rc2 to check if upgrading would resolve an out of memory issue. But with this upgrade we are running into other issues. One of these issues is that the new .NET 9+ Mono Debugger doesn't work with our application. The breakpoints that we set in our code are never hit when we use the new debugger. When the debugger is disabled the breakpoints work again. I have not successfully been able to reproduce our situation but I was able to to find an issue that might be the cause that the new debugger doesn't work for us.

Reproduction Steps

Our application uses Angular and when debugging locally we proxy /path to the .NET application that is running with a debugger attached. I have recreated that situation with a Yarp proxy in the following project: DebugIssue.zip

This project contains .slnLaunch.user to make sure both application start when debugging is started. Once the website (http://localhost:8000/test-debug) is show do the following:

• Set a breakpoint in Program.cs of TestDebug on line 15.
• Press the button in the website to verify that the breakpoint is hit (This works here but not in our application)
• Continue the application
• View the source of the running page (ctrl-u)
• Switch back to the first tab and press F5
• Press the button and notice that the breakpoint is not hit.

Expected behavior

Breakpoints work.

Actual behavior

Breakpoints are not always working.

Regression?

No response

Known Workarounds

No response

Configuration

9.0.100-rc.2.24474.11
Visual Studio 2022 Preview (17.20.0 Preview 3.0)

Other information

No response

[ScottNorton]

Have you ensured the inspectUri is set in launchSettings.json? I've noticed issues loading breakpoints using Kestrel for the debugging host instead of IIS. IIS, with inspectUri set correctly has the browser link working properly for me in my project:
https://www.voxelml.com/

launchSettings.json
Edited this for you to attempt an IIS launch, try it out

[thaystg]

Can you please provide a sample for us to reproduce it?

[dlemstra]

There is a sample in my original message? Can you no longer reproduce it with that?

[ScottNorton]

Are you still unable to hit breakpoints? I will try to make some steps to get it working from your sample later today.

[dlemstra]

I haven't tested this recently so it might have been fixed. I can take another look at my sample this weekend if you cannot reproduce my issue anymore.

[ScottNorton]

I tested some, and in my project I can certainly set a breakpoint, debugger pauses there, I can continue and reload the page, the breakpoint is the same. In your test sample this does not work the same. But it does pause at breakpoints prior to a page refresh.

Since you're using the reverse proxy, I believe it's similar to making a second connection to the debugger, which is not supported without some fancy approach... is the reverse proxy necessary for something? I'm not sure we could call an issue introduced by a 3rd party appliance a breakfix situation.