The situation:
Python <3.11: under Linux the abi string is always -gnu*
Python 3.11-3.12: musl is treated as its own abi in the python build system, but when cross-compiling the build host's libc is used for the target abi string. Cross compiling from glibc to musl gives a -gnu* target abi string and vice versa.
Python >=3.13: musl is treated as its own abi, and when cross-compiling the target libc is used for the target abi string
We backport the fix for python 3.11-3.12, since the intermediate state is almost impossible to model in the nix expression
Python always uses "gnu" prefixed ABI names, and this patch handles this by
doing a musl->gnu string replacement.
With pkgsCross.armv7l-hf-multiplatform.pkgsStatic, the previous name was:
_sysconfigdata__linux_arm-linux-gnu
Now, the corrected name is:
_sysconfigdata__linux_arm-linux-gnueabihf
Since python documentation requires Sphinx to build, documentation is built in
separate derivation to avoid hard recursion/bootstrapping questions and plugged
into main derivation. Care is taken that "python3.doc" derivation feels and
looks as close as possible to as if it were main derivation were multi-output
one.
This change does not cause rebuild of python3 itself.
Add a marker file to the python outputs that tells pip and other tooling
following PEP 668 that they should not be installing things system-wide.
This provides better feedback to the user and also potentially avoids issues in
single-user installs where the /nix/store is owned by the user.
For more details, see <https://peps.python.org/pep-0668/>
Here is how it currently looks like:
$ pip install requests
error: externally-managed-environment
× This environment is externally managed
╰─> This command has been disabled as it tries to modify the immutable
`/nix/store` filesystem.
To use Python with Nix and nixpkgs, have a look at the online documentation:
<https://nixos.org/manual/nixpkgs/stable/#python>.
with structuredAttrs lists will be bash arrays which cannot be exported
which will be a issue with some patches and some wrappers like cc-wrapper
this makes it clearer that NIX_CFLAGS_COMPILE must be a string as lists
in env cause a eval failure
The package set hasn't been working for a long time now, due to infinite
recursions, that nobody was going to fix.
The release is going to go EOL in 2023/06 and we don't want to ship it
in NixOS 23.05 anyway.
Without `--with-system-{ffi,expat}` flags, Python will use its own
embedded libraries that are out-of-date. Thanks to it, they can be a
security issue. So let's use our own libraries instead.
This is already what Python 3.x does, so should be safe.
