It is a common pattern to have an active conda base env (that sets
`CONDA_PREFIX`) and then create a venv on top of that (setting
`VIRTUAL_ENV`).
Previously, we would error when both `VIRTUAL_ENV` and `CONDA_PREFIX`
were set, now `VIRTUAL_ENV` takes precedence over `CONDA_PREFIX`.
Fixes#2028
## Summary
In reality, there's no such thing as the `site-packages` directory for a
given virtualenv. Rather, Python defines both `purelib` and `platlib`,
where the former is for pure-Python packages and the latter is for
packages that contain native code. These are almost always set to the
same thing... but they don't _have_ to be, and in fact of Fedora they
are not.
This PR changes the `site_packages` method to return an iterator of
directories.
Closes https://github.com/astral-sh/uv/issues/2527.
The architecture of uv does not necessarily match that of the python
interpreter (#2326). In cross compiling/testing scenarios the operating
system can also mismatch. To solve this, we move arch and os detection
to python, vendoring the relevant pypa/packaging code, preventing
mismatches between what the python interpreter was compiled for and what
uv was compiled for.
To make the scripts more manageable, they are now a directory in a
tempdir and we run them with `python -m` . I've simplified the
pypa/packaging code since we're still building the tags in rust. A
`Platform` is now instantiated by querying the python interpreter for
its platform. The pypa/packaging files are copied verbatim for easier
updates except a `lru_cache()` python 3.7 backport.
Error handling is done by a `"result": "success|error"` field that allow
passing error details to rust:
```console
$ uv venv --no-cache
× Can't use Python at `/home/konsti/projects/uv/.venv/bin/python3`
╰─▶ Unknown operation system `linux`
```
I've used the [maturin sysconfig
collection](855f6d2cb1/sysconfig)
as reference. I'm unsure how to test these changes across the wide
variety of platforms.
Fixes#2326
Preparing for #2058, i found it hard to follow where which discovery
function gets called. I moved all the discovery functions to a
`find_python` module (some exposed through `PythonEnvironment`) and
documented which subcommand uses which python discovery strategy.
No functional changes.

## Summary
In #2102, I did some refactor, and changed a method to return the Python
executable path rather than the parent directory path. But I missed this
one codepath for Conda on Windows.
Closes https://github.com/astral-sh/uv/issues/2269.
## Test Plan
- Installed micromamba on my Windows machine.
- Reproduced the failure in the linked issue.
- Verified that `python.exe` exists at `${CONDA_PREFIX}\python.exe`.
- Ran with this change; installed successfully.
## Summary
This PR adds support for pip's `--no-build-isolation`. When enabled,
build requirements won't be installed during PEP 517-style builds, but
the source environment _will_ be used when executing the build steps
themselves.
Closes https://github.com/astral-sh/uv/issues/1715.
## Summary
Right now, we have virtualenv construction encoded in a few different
places. Namely, it happens in both `gourgeist` and
`virtualenv_layout.rs` -- _and_ `interpreter.rs` also encodes some
knowledge about how they work, by way of reconstructing the
`SysconfigPaths`.
Instead, `gourgeist` now returns the complete layout, enumerating all
the directories it created. So, rather than returning a root directory,
and re-creating all those paths in `uv-interpreter`, we pass the data
directly back to it.
## Summary
`PythonPlatform` only exists to format paths to directories within
virtual environments based on a root and an OS, so it's now
`VirtualenvLayout`.
`Virtualenv` is now used for non-virtual environment Pythons, so it's
now `PythonEnvironment`.