external variants pulled in first

[beckermr]

Similar to openmpi, the mamba solver is pulling in the external variants first. We should deploy the same fix here, namely making sure the external packages have the same deps as the real ones to help the solver.

I have also made a virtual package https://github.com/regro/conda-forge-conda-plugins with the mpich version so that we can try that out.

[beckermr]

cc @jaimergp @minrk

[beckermr]

xref: conda-forge/openmpi-feedstock#153 (comment)

[minrk]

I've come back to this, and I think it may come down to feature minimization, because if there's even one feature in any dependency of the 'real' builds, 'external' will be preferred, no matter how old the build or version is.

weighing down 'external' with enough features may do the trick. For it to work, though, we would need to ensure that external builds have at least as many features as all dependencies combined (plus one?). We would also have to make sure we apply the features to all past external builds.

How would we go about requiring the plugin virtual package? I think it's a really cool idea.

[beckermr]

The plugin exists and works. However, it only works with conda, and not mamba or rattler. So we'd have to solve that issue first. The problem is that the plugin is written in python and mamba + rattler do not have support for it. I made a proposal to fix this as a cep by moving towards executables as plugins but it needs to be voted on and then implemented.

[beckermr]

The cep is here: conda/ceps#78