feat: support for uv-installed pythons (#842)

* dummy support for uv python installs

* attempt install before confirming the interpreter is available

* adding some tests

* change version output to json so it's consistent in linux vs windows

* skip test with uv-python-support in windows

* fix using the wrong variable

caused problems with pypy

* change min supported uv version

* remove if statement

* change global variable and handle uv missing in uv_version

* typo

nox/virtualenv.py

@@ -17,6 +17,7 @@
 import abc
 import contextlib
 import functools
+import json
 import os
 import platform
 import re
@@ -28,6 +29,8 @@
 from socket import gethostbyname
 from typing import Any, ClassVar
 
+from packaging import version
+
 import nox
 import nox.command
 from nox.logger import logger
@@ -65,7 +68,39 @@ def find_uv() -> tuple[bool, str]:
  return uv_on_path is not None, "uv"
 
 
+def uv_version() -> version.Version:
+ """Returns uv's version defaulting to 0.0 if uv is not available"""
+ try:
+ ret = subprocess.run(
+ [UV, "version", "--output-format", "json"],
+ check=False,
+ text=True,
+ capture_output=True,
+ )
+ except FileNotFoundError:
+ logger.info("uv binary not found.")
+ return version.Version("0.0")
+
+ if ret.returncode == 0 and ret.stdout:
+ return version.Version(json.loads(ret.stdout).get("version"))
+ else:
+ logger.info("Failed to establish uv's version.")
+ return version.Version("0.0")
+
+
+def uv_install_python(python_version: str) -> bool:
+ """Attempts to install a given python version with uv"""
+ ret = subprocess.run(
+ [UV, "python", "install", python_version],
+ check=False,
+ )
+ return ret.returncode == 0
+
+
 HAS_UV, UV = find_uv()
+# supported since uv 0.3 but 0.4.16 is the first version that doesn't cause
+# issues for nox with pypy/cpython confusion
+UV_PYTHON_SUPPORT = uv_version() >= version.Version("0.4.16")
 
 
 class InterpreterNotFound(OSError):
@@ -526,6 +561,12 @@ def _resolved_interpreter(self) -> str:
  self._resolved = cleaned_interpreter
  return self._resolved
 
+ if HAS_UV and UV_PYTHON_SUPPORT:
+ uv_python_success = uv_install_python(cleaned_interpreter)
+ if uv_python_success:
+ self._resolved = cleaned_interpreter
+ return self._resolved
+
  # The rest of this is only applicable to Windows, so if we don't have
  # an interpreter by now, raise.
  if _SYSTEM != "Windows":

tests/test_virtualenv.py

@@ -269,6 +269,11 @@ def test_uv_creation(make_one):
  assert venv._check_reused_environment_type()
 
 
+@has_uv
+def test_uv_managed_python(make_one):
+ make_one(interpreter="cpython3.12", venv_backend="uv")
+
+
 def test_constructor_defaults(make_one):
  venv, _ = make_one()
  assert venv.location
@@ -620,6 +625,50 @@ def find_uv_bin():
  assert nox.virtualenv.find_uv() == (found, path)
 
 
+@pytest.mark.parametrize(
+ ["return_code", "stdout", "expected_result"],
+ [
+ (0, '{"version": "0.2.3", "commit_info": null}', "0.2.3"),
+ (1, None, "0.0"),
+ (1, '{"version": "9.9.9", "commit_info": null}', "0.0"),
+ ],
+)
+def test_uv_version(monkeypatch, return_code, stdout, expected_result):
+ def mock_run(*args, **kwargs):
+ return subprocess.CompletedProcess(
+ args=["uv", "version", "--output-format", "json"],
+ stdout=stdout,
+ returncode=return_code,
+ )
+
+ monkeypatch.setattr(subprocess, "run", mock_run)
+ assert nox.virtualenv.uv_version() == version.Version(expected_result)
+
+
+def test_uv_version_no_uv(monkeypatch):
+ def mock_exception(*args, **kwargs):
+ raise FileNotFoundError
+
+ monkeypatch.setattr(subprocess, "run", mock_exception)
+ assert nox.virtualenv.uv_version() == version.Version("0.0")
+
+
+@pytest.mark.parametrize(
+ ["requested_python", "expected_result"],
+ [
+ ("3.11", True),
+ ("pypy3.8", True),
+ ("cpython3.9", True),
+ ("python3.12", True),
+ ("nonpython9.22", False),
+ ("java11", False),
+ ],
+)
+@has_uv
+def test_uv_install(requested_python, expected_result):
+ assert nox.virtualenv.uv_install_python(requested_python) == expected_result
+
+
 def test_create_reuse_venv_environment(make_one, monkeypatch):
  # Making the reuse requirement more strict
  monkeypatch.setenv("NOX_ENABLE_STALENESS_CHECK", "1")
@@ -840,6 +889,7 @@ def special_run(cmd, *args, **kwargs):
 
 
 @mock.patch("nox.virtualenv._SYSTEM", new="Windows")
+@mock.patch("nox.virtualenv.UV_PYTHON_SUPPORT", new=False)
 def test__resolved_interpreter_windows_path_and_version(make_one, patch_sysfind):
  # Establish that if we get a standard pythonX.Y path, we look it
  # up via the path on Windows.
@@ -865,6 +915,7 @@ def test__resolved_interpreter_windows_path_and_version(make_one, patch_sysfind)
 @pytest.mark.parametrize("sysfind_result", [r"c:\python37-x64\python.exe", None])
 @pytest.mark.parametrize("sysexec_result", ["3.7.3\\n", RAISE_ERROR])
 @mock.patch("nox.virtualenv._SYSTEM", new="Windows")
+@mock.patch("nox.virtualenv.UV_PYTHON_SUPPORT", new=False)
 def test__resolved_interpreter_windows_path_and_version_fails(
  input_, sysfind_result, sysexec_result, make_one, patch_sysfind
 ):