As described in #4242, we're currently incorrectly downloading glibc
python-build-standalone on musl target, but we also can't fix this by
using musl python-build-standalone on musl targets since the musl builds
are effectively broken.
We reintroduce the libc detection previously removed in #2381, using it
to detect which libc is the current one before we have a python
interpreter. I changed the strategy a big to support an empty `PATH`
which we use in the tests.
For simplicity, i've decided to just filter out the musl
python-build-standalone archives from the list of available archive,
given this is temporary. This means we show the same error message as if
we don't have a build for the platform. We could also add a dedicated
error message for musl.
Fixes#4242
## Test Plan
Tested manually.
On my ubuntu host, python downloads continue to pass:
```
target/x86_64-unknown-linux-musl/debug/uv python install
```
On alpine, we fail:
```
$ docker run -it --rm -v .:/io alpine /io/target/x86_64-unknown-linux-musl/debug/uv python install
Searching for Python installations
error: No download found for request: cpython-any-linux-x86_64-musl
```
## Summary
Resolves#5139
`PythonInstallationKey` was sorted as a string, which caused `3.8` to
appear before `3.11`. This update changes the sorting of
`PythonInstallationKey` to be a descending order by version.
## Test Plan
```sh
$ cargo run -- python install 3.8 3.12
$ cargo run -- tool run -v python -V
DEBUG uv 0.2.25
warning: `uv tool run` is experimental and may change without warning.
DEBUG Searching for Python interpreter in managed installations, system path, or `py` launcher
DEBUG Searching for managed installations at `C:\Users\xx\AppData\Roaming\uv\data\python`
DEBUG Found managed Python `cpython-3.12.3-windows-x86_64-none`
DEBUG Found cpython 3.12.3 at `C:\Users\xx\AppData\Roaming\uv\data\python\cpython-3.12.3-windows-x86_64-none\install\python.exe` (managed installations)
DEBUG Using request timeout of 30s
DEBUG Using request timeout of 30s
DEBUG Acquired lock for `C:\Users\nigel\AppData\Roaming\uv\data\tools`
DEBUG Using existing environment for tool `httpx`: C:\Users\xx\AppData\Roaming\uv\data\tools\httpx
DEBUG Using existing tool `httpx`
DEBUG Running `httpx -v`
```
## Summary
Resolves#4834
## Test Plan
```sh
# 3.12.3 is a `install_only` archive
$ cargo run -- python install --preview --force 3.12.3
# 3.9.4 has only `full` archive
$ cargo run -- python install --preview --force 3.9.4
```
Whew this is a lot.
The user-facing changes are:
- `uv toolchain` to `uv python` e.g. `uv python find`, `uv python
install`, ...
- `UV_TOOLCHAIN_DIR` to` UV_PYTHON_INSTALL_DIR`
- `<UV_STATE_DIR>/toolchains` to `<UV_STATE_DIR>/python` (with
[automatic
migration](https://github.com/astral-sh/uv/pull/4735/files#r1663029330))
- User-facing messages no longer refer to toolchains, instead using
"Python", "Python versions" or "Python installations"
The internal changes are:
- `uv-toolchain` crate to `uv-python`
- `Toolchain` no longer referenced in type names
- Dropped unused `SystemPython` type (previously replaced)
- Clarified the type names for "managed Python installations"
- (more little things)
Zanie Blue