The buildKitTargetOs is unknown if a kit is defined with toolchainFile only

[RichardLuo0]

Brief Issue Summary

I have a kit like this;

{
  "name": "WASM",
  "toolchainFile": "C:\\emsdk\\upstream\\emscripten\\cmake\\Modules\\Platform\\Emscripten.cmake"
}

The ${buildKitTargetOs} becomes unknown. The compiler is defined in Emscripten.cmake

CMake Tools Diagnostics

Debug Log

Additional Information

No response

[Amy-Li03]

Hi @RichardLuo0, thanks for reporting issue here!
I tried to reproduce your problem as best I could, and then I couldn't. I have recorded a video to show the process, please see the following video.

Additionally, if you can provide a video, repro steps, a demo repro project in a zip file would be great, this will help us investigate this further.

[RichardLuo0]

I mean the ${buildKitTargetOs} in https://github.com/microsoft/vscode-cmake-tools/blob/main/docs/cmake-settings.md#variable-substitution

If you set "cmake.buildDirectory": "${workspaceFolder}/build-${buildKitTargetOs}" in settings, it is substituted by unknown.

[Amy-Li03]

@RichardLuo0, thanks for your reply! If you can provide a demo repro project in a zip file would be great, this will help us investigate this further.

[RichardLuo0]

@Amy-Li03
I did some more tests, and I found that only auto-generated kits (ie. generated by cmake: scan for kit) can use ${buildKitTargetOs}, ${buildKitTriple} and so on, otherwise it becomes none (I remember it was unknown but anyways). Is it by design??? So I guess it just extracts those variables from the kit name?
If that's the case, can you address it in the docs (eg. how do I name my custom kit so that it can be parsed)? However, I think a better way is to allow me to specify them in the kit, maybe adding variables like ${kitCmakeSettings: xxx} that reads from cmakeSettings in the kit.
cmake-test.zip

[Amy-Li03]

@RichardLuo0 thanks for your info!
I can repro your issue on our end, when we select custom kits, ${buildKitTargetOs} is build-none, however, it displays the correct buildKitTargetOs(ie. build-win32) when selecting auto-generated kits.

@gcampbell-msft , could you please confirm whether this is by design?

[gcampbell-msft]

@Amy-Li03 @RichardLuo0 Based on your investigation, it seems that this is by design. However, it's a feature that hasn't had any attention in a long time, so it's understandable that there are questions around it.

Due to our focus on presets, this is a feature request that may not get highly prioritized by us, but we'd be happy to take OSS contributions!