setup.py does not support pip installation inside conda environment using existing libg2c

[lboeman]

When the CONDA_PREFIX envvar is set , setup.py attempts to find libg2c inside the directory at CONDA_PREFIX. If the user has installed their dependencies at one of the typical non-conda locations, e.g. /usr/local then setup.py fails to find the library and throws an exception.

Steps to reproduce:

# Install [NCEPLIBS-g2c](https://github.com/NOAA-EMC/NCEPLIBS-g2c) into a "common" installation path.
conda create -n grib2io-setup-issue python=3.8
conda activate grib2io-setup-issue

# From source directory:
pip install .

This issue can be addressed using the G2C_DIR envvar, but this behavior seems unexpected.

It seems that either a conda-supplied or manually built g2c library could be supported by adjusting this section: https://github.com/NOAA-MDL/grib2io/blob/b9053dc4c76be162bc2311949573a89fa3c06485/setup.py#L26-L29 to prepend the dir at CONDA_PREFIX to the list of common dirs to search.

I'm happy to work up a PR for this issue if it's welcome.

[EricEngle-NOAA]

Hi @lboeman. PRs are welcome. A few things to keep in mind regarding this:

• The point of using G2C_DIR env var is for this exact reason, but I see your point that the manual install is in an expected area (/usr/local).
• NCEPLIBS-g2c is available on conda-forge (conda install -c conda-forge nceplibs-g2c)
• using an manual install of NCEPLIBS-g2c inside conda environment could (but unlikely) introduce compatibulity issues

I am looking to release v2.0.1 in the next week or so. I'd like to get this in for that if possible.

[lboeman]

Hi @EricEngle-NOAA Thanks for the response.

I was unaware that the NCEPLIBS-g2c library was available via conda. I think that between G2C_DIR and conda availability of the libraries, my concerns are addressed since there are workarounds to installing from source/pip within a conda environment.

Considering your final point, this change may generate more problems than allowing users to work through the available options, especially for less experienced users on shared systems. I think that nudging conda users towards a conda installation and leaving G2C_DIR as an alternative is probably less problematic than making that assumption for the user.