Use the same code to determine isolated environment paths at
dependency install time and at environment setup time. We do not care
about the exact paths but the paths needs to be consistent at package
installation time and environment setup.
This should fix issues observed on platforms that customize the
installation schemes, such as Debian and Homebrew, where dependency
installation and isolated build environment setup resolved to
different paths.
The PEP 668 expects an override mechanism to ease the transition.
This provides an override.
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Co-authored-by: Pradyun Gedam <pradyunsg@gmail.com>
The fix merged in 3b60e36289 also fixed
the wheel cache; this cherry-picks the test and news from the other pull
request to validate and document the fact.
This implements the PEP 668 logic to 'pip install' and 'pip uninstall'.
Are there any other commands that may need it?
This implementation disables the check is any of --prefix, --home, or
--target is provided, since those can indicate the command does not
actually install into the environment. Note that it is still possible
the command is still modifying the environment, but we don't have a
way to stop the user *that* determined to break the environment anyway
(they can always just use those flags in a virtual environment).
Also not sure how best this can be tested.
The scripts path was looked up passing explicitly the scheme to be
used using "nt" on Windows and "posix_prefix" everywhere else.
However, when the isolated build environment is created, packages are
installed using the default scheme for the platform. On most platforms
this works because normally "nt" and "posix_prefix" are the default
schemes.
However, Debian customizes sysconfig to use a "posix_local" scheme by
default and under this scheme the scripts path does not match the one
of the "posix_prefix" scheme. This results in scripts installed as
part of the build dependencies not to be found during the build, as
reported here https://github.com/mesonbuild/meson-python/issues/109
and here https://bugs.debian.org/1019293.
The problem can be solved omitting to specify a scheme when looking up
the scripts path. To future proof the path lookup, use the "venv"
scheme if available as done in #11598. For uniformity use similar
functions as used to lookup the library paths.
get_prefixed_libs() computes the Python path for libraries in a pip
isolation environment. Python 3.11 introduced the "venv" path scheme
to be used in these cases. Use it if available.
This solves a bug on Homebrew's Python 3.10 and later where the
default paths scheme when Python is invoked outside a virtual
environment is "osx_framework_library" and does not relative to the
"{base}" or "{platbase}" variables.
Fixes#11539.
