conda venv not recognized by ngen

[RY4GIT]

We (@RY4GIT and @taddyb) attempted to integrate our own Python model into NGen using the BMI Python. However, we encountered the following issues.

Current behavior

• Python virtual environment not recognized or found in ngen. It seems that the variable VIRTUAL_ENV needs to be defined, but we couldn't find where in ngen codebase defines it (see the screenshot)
  

Expected behavior

• Python virtual environment recognized and set in ngen

Steps to replicate behavior

1. Git clone the Python model of interest
   git clone https://github.com/NWC-CUAHSI-Summer-Institute/cfe_py/tree/add-bmi2
2. Build python environment using cfe_py/environment.yml
   conda env create -f environment.yml
3. Activate the venv conda activate cfe
4. Build the ngen following this instruction. Before running the building code (cmake -B /ngen -S . && cmake --build . --target ngen), turn on the debugging option using target_compile_options (ngen PUBLIC -g) in the root CMakeList.txt, as described here
5. Run the ngen ./ngen, and it prints the following. You can see the issue described in the current behavior, where VIRTUAL_ENV is not set. I also tried building ngen outside of venv (i.e., conda base), but it was the same.

Build Info:
  NGen version: 0.1.0
  Python active
    Embedded interpreter version: 3.10.12

Python Environment Info:
  VIRTUAL_ENV environment variable: (not set)
  Discovered venv: None
  System paths:

    /home/flipl/miniconda3/lib/python310.zip
    /home/flipl/miniconda3/lib/python3.10
    /home/flipl/miniconda3/lib/python3.10/lib-dynload
    /home/flipl/.local/lib/python3.10/site-packages
    /home/flipl/miniconda3/lib/python3.10/site-packages
    /home/flipl/cfe_py

Some other info

• OS: WSL on Windows 11
• NGen version: 0.1.0

[mattw-nws]

It looks like your issue was resolved in the above-referenced PR, but as was said there, yes I think ngen is behaving as expected here. VIRTUAL_ENV is not set by ngen, rather it is set by the activate script of a venv virtual environment. You're not using any venv and are using conda, which should also work as long as your custom Python BMI module is installed/available at one of the Python system paths listed in the output above. In a nutshell, a Python BMI module needs (usually) to be installed into the Python environment (whether venv, conda, or native/local/system), and the ngen output above is just giving you information about what that Python environment looks like.