refactor: pulled out get_virtualenv & better typing

nox/_decorators.py

@@ -66,7 +66,7 @@ def __init__(
         reuse_venv: bool | None = None,
         name: str | None = None,
         venv_backend: Any = None,
-        venv_params: Any = None,
+        venv_params: Sequence[str] = (),
         should_warn: Mapping[str, Any] | None = None,
         tags: Sequence[str] | None = None,
         *,

nox/registry.py

@@ -40,7 +40,7 @@ def session_decorator(
     reuse_venv: bool | None = ...,
     name: str | None = ...,
     venv_backend: Any | None = ...,
-    venv_params: Any | None = ...,
+    venv_params: Sequence[str] = ...,
     tags: Sequence[str] | None = ...,
     *,
     default: bool = ...,
@@ -55,7 +55,7 @@ def session_decorator(
     reuse_venv: bool | None = None,
     name: str | None = None,
     venv_backend: Any | None = None,
-    venv_params: Any | None = None,
+    venv_params: Sequence[str] = (),
     tags: Sequence[str] | None = None,
     *,
     default: bool = True,

nox/sessions.py

@@ -45,7 +45,13 @@
 from nox._decorators import Func
 from nox.logger import logger
 from nox.popen import DEFAULT_INTERRUPT_TIMEOUT, DEFAULT_TERMINATE_TIMEOUT
-from nox.virtualenv import CondaEnv, PassthroughEnv, ProcessEnv, VirtualEnv
+from nox.virtualenv import (
+    CondaEnv,
+    PassthroughEnv,
+    ProcessEnv,
+    VirtualEnv,
+    get_virtualenv,
+)
 
 if TYPE_CHECKING:
     from typing import IO
@@ -991,34 +997,13 @@ def _create_venv(self) -> None:
             or "virtualenv"
         ).split("|")
 
-        # Support fallback backends
-        for bk in backends:
-            if bk not in nox.virtualenv.ALL_VENVS:
-                msg = f"Expected venv_backend one of {list(nox.virtualenv.ALL_VENVS)!r}, but got {bk!r}."
-                raise ValueError(msg)
-
-        for bk in backends[:-1]:
-            if bk not in nox.virtualenv.OPTIONAL_VENVS:
-                msg = f"Only optional backends ({list(nox.virtualenv.OPTIONAL_VENVS)!r}) may have a fallback, {bk!r} is not optional."
-                raise ValueError(msg)
-
-        for bk in backends:
-            if nox.virtualenv.OPTIONAL_VENVS.get(bk, True):
-                backend = bk
-                break
-        else:
-            msg = f"No backends present, looked for {backends!r}."
-            raise ValueError(msg)
-
-        if backend == "none" or self.func.python is False:
-            self.venv = nox.virtualenv.ALL_VENVS["none"]()
-        else:
-            self.venv = nox.virtualenv.ALL_VENVS[backend](
-                self.envdir,
-                interpreter=self.func.python,
-                reuse_existing=reuse_existing,
-                venv_params=self.func.venv_params,
-            )
+        self.venv = get_virtualenv(
+            *backends,
+            reuse_existing=reuse_existing,
+            envdir=self.envdir,
+            interpreter=self.func.python,
+            venv_params=self.func.venv_params,
+        )
 
         self.venv.create()
 

nox/virtualenv.py

@@ -24,7 +24,7 @@
 import shutil
 import subprocess
 import sys
-from collections.abc import Callable, Mapping
+from collections.abc import Callable, Mapping, Sequence
 from pathlib import Path
 from socket import gethostbyname
 from typing import Any, ClassVar
@@ -33,6 +33,7 @@
 
 import nox
 import nox.command
+from nox._typing import Python
 from nox.logger import logger
 
 # Problematic environment variables that are stripped from all commands inside
@@ -286,7 +287,7 @@ def __init__(
         location: str,
         interpreter: str | None = None,
         reuse_existing: bool = False,
-        venv_params: Any = None,
+        venv_params: Sequence[str] = (),
         *,
         conda_cmd: str = "conda",
     ):
@@ -422,7 +423,7 @@ def __init__(
         reuse_existing: bool = False,
         *,
         venv_backend: str = "virtualenv",
-        venv_params: Any = None,
+        venv_params: Sequence[str] = (),
     ):
         self.location_name = location
         self.location = os.path.abspath(location)
@@ -662,3 +663,40 @@ def venv_backend(self) -> str:
     "micromamba": shutil.which("micromamba") is not None,
     "uv": HAS_UV,
 }
+
+
+def get_virtualenv(
+    *backends: str,
+    envdir: str,
+    reuse_existing: bool,
+    interpreter: Python = None,
+    venv_params: Sequence[str] = (),
+) -> ProcessEnv:
+    # Support fallback backends
+    for bk in backends:
+        if bk not in ALL_VENVS:
+            msg = f"Expected venv_backend one of {sorted(ALL_VENVS)!r}, but got {bk!r}."
+            raise ValueError(msg)
+
+    for bk in backends[:-1]:
+        if bk not in OPTIONAL_VENVS:
+            msg = f"Only optional backends ({sorted(OPTIONAL_VENVS)!r}) may have a fallback, {bk!r} is not optional."
+            raise ValueError(msg)
+
+    for bk in backends:
+        if OPTIONAL_VENVS.get(bk, True):
+            backend = bk
+            break
+    else:
+        msg = f"No backends present, looked for {backends!r}."
+        raise ValueError(msg)
+
+    if backend == "none" or interpreter is False:
+        return ALL_VENVS["none"]()
+
+    return ALL_VENVS[backend](
+        envdir,
+        interpreter=interpreter,
+        reuse_existing=reuse_existing,
+        venv_params=venv_params,
+    )

tests/test_sessions.py

@@ -793,7 +793,7 @@ def lint(session):
             if "-x" in session.posargs:
                 raise RuntimeError("invalid option: -x")
 
-        config = _options.options.namespace(posargs=[])
+        config = _options.options.namespace(posargs=[], envdir=".nox")
         manifest = nox.manifest.Manifest(registry, config)
 
         assert manifest["test"].execute()