Provide a way to set environment variables when using cmake-presets

For example, a preset that uses vcpkg requires a path to vcpkg.cmake, whose location may vary across machines. As the documentation suggests, this can be done by using $env{VCPKG_ROOT}.

Using the command line it is very easy to choose a vcpkg installation on a specific machine, or switch between vcpkg installations (to debug new versions of packages) by prepending the environment variable to the command line.

However, from inside vscode, there’s no easy way to set or modify this variable. This makes it difficult to work with presets with CMake-Tools.

Please add a setting for preset environment variables or enable the existing cmake.environment when using presets.

[globberwops]

This is currently a blocking issue for me and my team, and it is preventing us from switching from caches to presets.

Suppose you have say 3 different configure presets, 1-2 build presets for each configure preset, and maybe 2 different test presets. Now, as a developer, you want to use a compiler launcher, a different compiler or compiler version, or something like @sterin described. You would have to write an awful amount of user presets just to be able to do that and since the build/test presets all refer to a configure preset, you would have to override them as well.

Not being able to modify the environment defeats the whole purpose of the $penv{<variable-name>} macro in presets.

[sterin]

It is definitely possible to this. It is also possible to use a symbolic link to point to the vcpkg installation. I just think this overcomplicates things.

While CMakePresets.json is supposed to be the sole source of truth, the use of environment variables to set machine-specific values is standard practice, it even appears in CMake Tools’ own documentation.

What CMake Tools is missing is a way to set these values, or override these values, from inside vscode without going through hoops.