How to debug msbuild?

Hey,

So I would like to investigate a problem related to slow RAR in msbuild and while I have been able to initially hack something to debug msbuild, that was very convoluted, copying files around from regular Sdk…etc.

So I would like to do this more cleanly and follow a more deterministic procedure to debug directly MsBuild project from MsBuild.sln solution (so it is issuing a dotnet msbuild.dll or msbuild.exe) for

1. new csproj with .NET Sdk
2. regular old csproj

Which repository should I build, variable that I should set…etc.? (Or I could avoid building by reusing maybe an installed dotnet folder?)

For new csproj

Let’s try just on the new csproj format for now, starting with a plain dotnet new --name Helloworld

Assuming that I built this repository, and I’m setting the MSBuildSDKsPath to point to the artifacts\Debug\bin\Sdks

I’m getting the following error:

Project "C:\Work\tmp\HelloWorld\Helloworld.csproj" on node 1 (default targets).
C:\Code\dotnet\sdk\artifacts\Debug\bin\Sdks\Microsoft.NET.Sdk\Sdk\Sdk.props(33,11): error MSB4226: The imported project
 "C:\Code\msbuild\artifacts\Debug\bin\MSBuild\net472\Current\Microsoft.Common.props" was not found. Also, tried to find
 "Current\Microsoft.Common.props" in the fallback search path(s) for $(MSBuildExtensionsPath) - "C:\Program Files (x86)
\MSBuild" . These search paths are defined in "C:\Code\msbuild\artifacts\Debug\bin\MSBuild\net472\MSBuild.exe.Config".
Confirm that the path in the <Import> declaration is correct, and that the file exists on disk in one of the search pat
hs. [C:\Work\tmp\HelloWorld\Helloworld.csproj]
Done Building Project "C:\Work\tmp\HelloWorld\Helloworld.csproj" (default targets) -- FAILED.

It is trying to resolve artifacts\Debug\bin\MSBuild\net472\Current\Microsoft.Common.props which is not in this folder. Not sure why it is trying Current by default, while the solution seems to build in this file in artifacts\Debug\bin\15.0\Microsoft.Common.props , so assume that the tooling version should be 15.0… but still, can I setup a MsBuild special variable path for pointing to this folder?

So likely after that, it will complain about missing NuGet resolver or similar. How do I pass them through?

cc: @davkean @nguerrera

[xoofx]

Yes. There’s definitely room for improvement, but IIRC we ran into a lot of problems integrating the bootstrap process with the msbuild.exe project, because we produce NuGet packages from the project and must not pollute them with a bunch of extra files.

Ok, it seems to work and better than all the fragile hacks to setup the correct env variables I was previously using… I will try to workaround the iteration maybe by adding a temp task to copy of the relevant assemblies directly to the bootstrap folder. Thanks!

[rainersigwald]

You’re trying to run a just-built MSBuild (in the MSBuild repo) from VS? That doesn’t work. You can build from the command line and run the bootstrapped MSBuild from artifacts\Debug\bootstrap\net472\MSBuild\Current\Bin\MSBuild.exe.

For ease of debugging, you can set MSBUILDDEBUGONSTART=1 (full framework) or =2 (.NET Core) to cause MSBuild to break on start. Be careful combining this with multiproc builds–every MSBuild node will break on start, which is often not what you want.