PowerShell/docs/debugging

Debugging

VS Code

Experimental .NET Core Debugging in VS Code enables cross-platform debugging with the Visual Studio Code editor. This is made possible by the OmniSharp extension for VS Code.

Please review their detailed instructions. In addition to being able to build PowerShell, you need:

• C# Extension for VS Code installed
• powershell executable in your path (self-host if not on Windows)

The committed .vscode folder in the root of this repository contains the launch.json and tasks.json files which provide Core PowerShell debugging configurations and a build task.

The "build" task will run Start-PSBuild.

The ".NET Core Launch" configuration will build and start a powershell process, with justMyCode disabled, and stopAtEntry enabled. The debugger is highly experimental, so if it does not break at Main, try again.

Note that the debugger does not yet provide stdin handles, so once ReadKey is called in the ReadLine loop, System.Console will throw exceptions. The options around this are 1) provide [ "-c", "... ; exit" ] to the "Launch" configuration's args so that the ReadLine listener is never called, 2) ignore the exceptions and only debug code before the listener, or 3) use the "Attach" configuration.

The ".NET Core Attach" configuration will start listening for a process named powershell, and will attach to it. If you need more fine grained control, replace processName with processId and provide a PID. (Please be careful not to commit such a change).

Important Note

Debugging is very sensitive to the versions of our .NET Core packages, VS Code, and the C# extension.

• Use the VS Code Insiders build
• Use the latest pre-release of the C# extension
• Refer to the pre-release documentation

PowerShell

The Trace-Command cmdlet can be used to enable tracing of certain PowerShell subsystems. Use Get-TraceSource for a list of tracers:

• CmdletProviderClasses
• CommandDiscovery
• CommandSearch
• ConsoleHost
• ConsoleHostRunspaceInit
• ConsoleHostUserInterface
• ConsoleLineOutput
• DisplayDataQuery
• ETS
• FileSystemProvider
• FormatFileLoading
• FormatViewBinding
• LocationGlobber
• MemberResolution
• Modules
• MshSnapinLoadUnload
• ParameterBinderBase
• ParameterBinderController
• ParameterBinding
• PathResolution
• PSDriveInfo
• PSSnapInLoadUnload
• RunspaceInit
• SessionState
• TypeConversion
• TypeMatch

Then trace it like this:

Trace-Command -Expression { Get-ChildItem . } -Name PathResolution -PSHost

The -PSHost specifies the sink, in this case the console host, so we can see the tracing messages.

LLDB with SOS plugin

The ./tools/debug.sh script can be used to launch PowerShell inside of LLDB with the SOS plugin provided by .NET Core. This provides an additional way to debug PowerShell on Linux, but VS Code is recommended for a better user experience (and its single-stepping capabilities).

The script is self-documented and contains a link to the CoreCLR debugging help .

corehost

The native executable prouduced by .NET CLI will produce trace output if launched with COREHOST_TRACE=1 ./powershell.

CoreCLR PAL

The native code in the CLR has debug channels to selectively output information to the console. These are controlled by the PAL_DBG_CHANNELS, e.g., export PAL_DBG_CHANNELS="+all.all", as detailed in the dbgmsg.h header.