The loose consensus is that "fetch" doesn't have much meaning and that a
boolean flag makes more sense from the command line.
1. Adds `--allow-python-downloads` (hidden, default) and
`--no-python-downloads` to the CLI to quickly enable or disable
downloads
2. Deprecates `--python-fetch` in favor of the options from (1)
3. Removes `python-fetch` in favor of a `python-downloads` setting
5. Adds a `never` variant to the enum, allowing even explicit installs
to be disabled via the configuration file
## Test plan
I tested this with various `pyproject.toml`-level settings and `uv venv
--preview --python 3.12.2` and `uv python install 3.12.2` with and
without the new CLI flags.
## Summary
It's fine for this to be in the cache, I think, since we don't
necessarily need to colocate it with the Python directory.
Closes https://github.com/astral-sh/uv/issues/5747.
Collapses the previous default into "managed" and makes the "managed"
behavior match "installed". People should use "only-managed" if they
want that behavior, it seems overly complicated otherwise.
> DEBUG Found `cpython-3.12.1-macos-aarch64-none` at
`/Users/zb/Library/Application
Support/uv/python/cpython-3.12.1-macos-aarch64-none/bin/python3`
(managed installations)
Instead of `<implementation> <version>`
> DEBUG Found cpython 3.12.1 at `/Users/zb/Library/Application
Support/uv/python/cpython-3.12.1-macos-aarch64-none/bin/python3`
(managed installations)
## 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
Closes https://github.com/astral-sh/uv/issues/4848.
## Test Plan
```
> cargo run -- run -vv --preview --isolated --python 3.12.4 python -V
error: No interpreter found for Python 3.12.4 in virtual environments or managed installations or system path
```
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)
Charlie Marsh
Zanie Blue
Jo