fix: handle uvx like uv (#920)

Signed-off-by: Henry Schreiner <[email protected]>

nox/sessions.py

@@ -608,14 +608,17 @@ def _run(
         if callable(args[0]):
             return self._run_func(args[0], args[1:])  # type: ignore[unreachable]
 
-        # Using `"uv"` when `uv` is the backend is guaranteed to work, even if it was co-installed with nox.
-        if (
-            self.virtualenv.venv_backend == "uv"
-            and args[0] == "uv"
-            and nox.virtualenv.UV != "uv"
-            and shutil.which("uv", path=self.bin) is None  # Session uv takes priority
-        ):
-            args = (nox.virtualenv.UV, *args[1:])
+        # Using `"uv"` or `"uvx" when `uv` is the backend is guaranteed to
+        # work, even if it was co-installed with nox.
+        if self.virtualenv.venv_backend == "uv" and nox.virtualenv.UV != "uv":
+            if (
+                args[0] == "uv"
+                and shutil.which("uv", path=self.bin)
+                is None  # Session uv takes priority
+            ):
+                args = (nox.virtualenv.UV, *args[1:])
+            elif args[0] == "uvx" and shutil.which("uvx", path=self.bin) is None:
+                args = (f"{nox.virtualenv.UV}x", *args[1:])
 
         # Combine the env argument with our virtualenv's env vars.
         env = self.virtualenv._get_env(env or {}, include_outer_env=include_outer_env)

nox/virtualenv.py

@@ -461,7 +461,7 @@ class VirtualEnv(ProcessEnv):
     """
 
     is_sandboxed = True
-    allowed_globals = (UV,)
+    allowed_globals = (UV, f"{UV}x")
 
     def __init__(
         self,

tests/test_sessions.py

@@ -995,6 +995,17 @@ class SessionNoSlots(nox.sessions.Session):
                 "urllib3",
             )
 
+        # User runs uvx
+        with mock.patch.object(nox.command, "run", autospec=True) as run:
+            session.run("uvx", "cowsay")
+            run.assert_called_once()
+
+            ((call_args,), _) = run.call_args
+            assert call_args == (
+                "/some/uvx",
+                "cowsay",
+            )
+
         # user installs uv in the session venv
         monkeypatch.setattr(
             shutil, "which", lambda x, path="": path + "/uv" if x == "uv" else None