FileExistsError: File already exists: ./site-packages/cppyy_backend/lib/libcppyy_backend.so

[hofbi]

I try to make cppyy working with bazel and run into an issue looking exactly as bazelbuild/rules_python#1659. In this comment they identified that this issue seems to be an issue of the upstream repo (cppyy or cppyy-backend in this case)

ipython-contrib/jupyter_contrib_nbextensions#1612 and aws/aws-elastic-beanstalk-cli#469 is how other projects fix this. However, I could not find this in your setup.py. Any help guiding me to the right place is appreciated.

[wlav]

I understand neither the problem, nor the proposed solution, but at issue is likely that the backend is split into two PyPI packages, a large one containing Cling and a small one containing just the wrapper. The latter installs libcppyy_backend.so in a directory of the former, which probably violates a bunch of rules. The original idea/hope was that the large package would change infrequently, with most of the work happening in the wrapper, thus simplifying release turnaround.

Anyway, there are 2 setup.py files involved:
https://github.com/wlav/cppyy-backend/blob/master/cling/setup.py
https://github.com/wlav/cppyy-backend/blob/master/clingwrapper/setup.py
and neither has a scripts option.

Again, I have no idea how bazel works, what the error is precisely, or what the intend is here, but if this is a matter of repackaging, then the best thing to do is to combine these two PyPI packages into a single bazel package, thus side-stepping the problem.

[matthew-limbinar]

Assuming combining PyPI packages would fix the problems with Bazel builds, would you accept a PR in that direction? Do you foresee any problems taking that approach?

[wlav]

Yes, upstream has also been asking for a cleanup. There could be a top-level setup.py to combine the two (both packages are sitting in the same repo already; upstream even wants to have a single repo for all packages involved, but there would still be a use for 3 PyPI packages b/c of PyPy, but also b/c the backend is conveniently Python-agnostic). With an extra toplevel setup.py, both choices could live side by side to understand the implications. I don't think there are individual users of cppyy-cling out there, but several exist for the cppyy-backend + cppyy-cling combo.

[Yilliee]

@hofbi This might be unrelated but I ran into the same issue when trying to install cppyy-backend myself and the fix was to revert the changes on clingwrapper/steup.py that happened between v1.5.0 & v1.5.2.
More specifically, reverting these:
wlav/cppyy-backend@25caf98
wlav/cppyy-backend@6f074cf
wlav/cppyy-backend@17ec932

Essentially it's reverting the changes cause by the commit I mentioned last but mentioned others that are related that too.