Do not use environment variables when empty

[corrodedHash]

Hello,
thank you for making this!
Worked almost flawlessly, but CMake had one error:

CMake Error (dev) at cmake/FindPytest.cmake:74 (cmake_path):
  uninitialized variable 'LD_LIBRARY_PATH'
Call Stack (most recent call first):
  test/CMakeLists.txt:3 (pytest_discover_tests)
This error is for project developers. Use -Wno-error=dev to suppress it.

CMake Error (dev) at cmake/FindPytest.cmake:75 (cmake_path):
  uninitialized variable 'PYTHONPATH'
Call Stack (most recent call first):
  test/CMakeLists.txt:3 (pytest_discover_tests)
This error is for project developers. Use -Wno-error=dev to suppress it.

It seemed unhappy when the environment variables were not defined.
I am uncertain if I am using it wrong, or maybe this check is only done in newer versions of CMake, I made a little change to only convert the paths if the environment variables are not empty.

[buddly27]

@corrodedHash Hi, thanks for contributing!

I am a bit surprised by this issue, as neither cmake_path nor the environment getter syntax ($ENV{...}) should trigger an error for uninitialized variables. But maybe I'm missing something.

I couldn't reproduce this issue with the following example:

cmake_path(CONVERT "UNINITIALIZED_VAR" TO_CMAKE_PATH_LIST RESULT)
cmake_path(CONVERT "$ENV{UNINITIALIZED_VAR}" TO_CMAKE_PATH_LIST RESULT)

Could you give me more details about your use case? (Cmake version, platform, etc)

[corrodedHash]

I now know this error came from my CMakePreset.txt configuration, which I copied from a template and invested too little time in to understand.
This is the relevant part:

"warnings": {
  "uninitialized": true,
},
"errors": {
  "dev": true,
}

Or the CMake flags -Werror=dev --warn-uninitialized.

I copied the two Pytest CMake files into my tree, which is probably why the linting is also triggering there.

As such, this is not a defect of this project.

[buddly27]

I'm still struggling to reproduce this error with your presets, or their corresponding command line options:
https://godbolt.org/z/bT71K65vs

Is there anything I'm missing?

Safeguarding against uninitialized variables can be indeed important in the context of restricted settings, but I just want to ensure I can reliably reproduce this issue for confirmation.

[corrodedHash]

The godbolt explorer was a great idea, thank you!

It seems to be doing some work in the background, if I execute the two lines on my system, I get warnings that I should use project and cmake_minimum_required.

With cmake_minimum_required(VERSION 3.29) I get at least a warning; -Werror=dev has no effect:
https://godbolt.org/z/vrcdYonec

[buddly27]

Ah, I see! CMake behaves differently when used as a script vs. as a project builder, that's a strange one. Good catch!