[Debugger] Async Break broken due to incorrect Thread Event behavior.

[chuckries]

We thought this was a VS Code issue but they are marking it by design.

Steps to reproduce

1. Launch or Attach to a .NET Core app.
2. Press the "Pause" (Async Break) button in the editor.

Expected behavior

Debugger stops

Actual behavior

Nothing Happens

Here is a comment explaining VS Code's behavior. We respond to the initial 'threads' request after configurationDone with no threads, which I believe is correct in our case. Later, we fire a Thread Event when our main thread is created. The issue appears to be that after the Thread Event, the 'threads' request is sent again and we respond with null.

Sample Log:

E initialized: {"type":"initialized"}
E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/Launch","data":{"VS.Diagnostics.Debugger.ImplementationName":"Microsoft.MIDebugEngine","VS.Diagnostics.Debugger.EngineVersion":"14.0.31028.1","VS.Diagnostics.Debugger.HostVersion":"1.0.21028.2","VS.Diagnostics.Debugger.AdapterId":"coreclr","VS.Diagnostics.Debugger.Launch.Duration":362,"VS.Diagnostics.Debugger.Launch.IsCoreDump":false},"type":"output"}
 R: {"success":true,"message":null,"request_seq":2,"command":"launch","body":null,"running":false,"refs":null,"seq":0,"type":"response"}
C setExceptionBreakpoints: {"filters":["user-unhandled"]}
 R: {"success":true,"message":null,"request_seq":3,"command":"setExceptionBreakpoints","body":{},"running":false,"refs":null,"seq":0,"type":"response"}
C configurationDone: null
 R: {"success":true,"message":null,"request_seq":4,"command":"configurationDone","body":null,"running":false,"refs":null,"seq":0,"type":"response"}
C threads: null
 R: {"success":true,"message":null,"request_seq":5,"command":"threads","body":{"threads":[]},"running":false,"refs":null,"seq":0,"type":"response"}
E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/clrdbg/ProcessCreate","data":{"VS.Diagnostics.Debugger.clrdbg.Version":"15.0.26013.0 built by: PREVIEW.DBG2","VS.Diagnostics.Debugger.clrdbg.OSFamily":"Windows","VS.Diagnostics.Debugger.clrdbg.WindowsVersion":"10.0.14393"},"type":"output"}
E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/clrdbg/TargetRuntimeLoaded","data":{"VS.Diagnostics.Debugger.clrdbg.TargetRuntimeVersion.MS":262150,"VS.Diagnostics.Debugger.clrdbg.TargetRuntimeVersion.LS":1599733761,"VS.Diagnostics.Debugger.clrdbg.Version":"15.0.26013.0 built by: PREVIEW.DBG2","VS.Diagnostics.Debugger.clrdbg.OSFamily":"Windows","VS.Diagnostics.Debugger.clrdbg.WindowsVersion":"10.0.14393"},"type":"output"}
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Private.CoreLib.ni.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Private.CoreLib.ni.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'c:\\Users\\chuckr\\Source\\scratch\\bin\\Debug\\netcoreapp1.0\\scratch.dll'. Symbols loaded.\r\n","data":null,"type":"output"}
Loaded 'c:\Users\chuckr\Source\scratch\bin\Debug\netcoreapp1.0\scratch.dll'. Symbols loaded.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Runtime.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Runtime.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\mscorlib.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\mscorlib.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Threading.Thread.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Threading.Thread.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Console.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Console.dll'. Cannot find or open the symbol file.
E thread: {"reason":"started","threadId":30804,"type":"thread"}
C threads: null
 R: {"success":true,"message":null,"request_seq":6,"command":"threads","body":{"threads":[]},"running":false,"refs":null,"seq":0,"type":"response"}

[chuckries]

It looks like if we are not stopped, OpenDebugAD7 always returns empty threads.

[chuckries]

Additionally, in the case of attach it looks like we don't ever send a Thread Event:

E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/clrdbg/ProcessCreate","data":{"VS.Diagnostics.Debugger.clrdbg.Version":"15.0.26013.0 built by: PREVIEW.DBG2","VS.Diagnostics.Debugger.clrdbg.OSFamily":"Windows","VS.Diagnostics.Debugger.clrdbg.WindowsVersion":"10.0.14393"},"type":"output"}
E initialized: {"type":"initialized"}
E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/Attach","data":{"VS.Diagnostics.Debugger.ImplementationName":"Microsoft.MIDebugEngine","VS.Diagnostics.Debugger.EngineVersion":"14.0.31028.1","VS.Diagnostics.Debugger.HostVersion":"1.0.21028.2","VS.Diagnostics.Debugger.AdapterId":"coreclr","VS.Diagnostics.Debugger.Attach.Duration":294},"type":"output"}
 R: {"success":true,"message":null,"request_seq":2,"command":"attach","body":null,"running":false,"refs":null,"seq":0,"type":"response"}
C setExceptionBreakpoints: {"filters":["user-unhandled"]}
 R: {"success":true,"message":null,"request_seq":3,"command":"setExceptionBreakpoints","body":{},"running":false,"refs":null,"seq":0,"type":"response"}
C configurationDone: null
 R: {"success":true,"message":null,"request_seq":4,"command":"configurationDone","body":null,"running":false,"refs":null,"seq":0,"type":"response"}
C threads: null
 R: {"success":true,"message":null,"request_seq":5,"command":"threads","body":{"threads":[]},"running":false,"refs":null,"seq":0,"type":"response"}
E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/clrdbg/TargetRuntimeLoaded","data":{"VS.Diagnostics.Debugger.clrdbg.TargetRuntimeVersion.MS":262150,"VS.Diagnostics.Debugger.clrdbg.TargetRuntimeVersion.LS":1599733761,"VS.Diagnostics.Debugger.clrdbg.Version":"15.0.26013.0 built by: PREVIEW.DBG2","VS.Diagnostics.Debugger.clrdbg.OSFamily":"Windows","VS.Diagnostics.Debugger.clrdbg.WindowsVersion":"10.0.14393"},"type":"output"}
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Private.CoreLib.ni.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Private.CoreLib.ni.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Users\\chuckr\\Source\\scratch\\bin\\Debug\\netcoreapp1.0\\scratch.dll'. Symbols loaded.\r\n","data":null,"type":"output"}
Loaded 'C:\Users\chuckr\Source\scratch\bin\Debug\netcoreapp1.0\scratch.dll'. Symbols loaded.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Runtime.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Runtime.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\mscorlib.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\mscorlib.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Threading.Thread.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Threading.Thread.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Console.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Console.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Threading.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Threading.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.IO.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.IO.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.IO.FileSystem.Primitives.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.IO.FileSystem.Primitives.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Text.Encoding.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Text.Encoding.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Text.Encoding.Extensions.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Text.Encoding.Extensions.dll'. Cannot find or open the symbol file.
E output: {"category":"console","output":"Loaded 'C:\\Program Files\\dotnet\\shared\\Microsoft.NETCore.App\\1.0.1\\System.Threading.Tasks.dll'. Cannot find or open the symbol file.\r\n","data":null,"type":"output"}
Loaded 'C:\Program Files\dotnet\shared\Microsoft.NETCore.App\1.0.1\System.Threading.Tasks.dll'. Cannot find or open the symbol file.
C disconnect: {"restart":false}
E output: {"category":"console","output":"Debugger has disconnected from the program ''.\r\n","data":null,"type":"output"}
Debugger has disconnected from the program ''.
E exited: {"exitCode":0,"type":"exited"}
E terminated: {"type":"terminated"}
E output: {"category":"telemetry","output":"VS/Diagnostics/Debugger/DebugCompleted","data":{"VS.Diagnostics.Debugger.ImplementationName":"Microsoft.MIDebugEngine","VS.Diagnostics.Debugger.EngineVersion":"14.0.31028.1","VS.Diagnostics.Debugger.HostVersion":"1.0.21028.2","VS.Diagnostics.Debugger.AdapterId":"coreclr","VS.Diagnostics.Debugger.DebugCompleted.BreakCounter":0},"type":"output"}
 R: {"success":true,"message":null,"request_seq":6,"command":"disconnect","body":null,"running":false,"refs":null,"seq":0,"type":"response"}