Override toxworkdir with --workdir.

docs/changelog/2654.bugfix.rst

@@ -0,0 +1 @@
+Override toxworkdir with --workdir.

src/tox/config/sets.py

@@ -191,10 +191,14 @@ def register_config(self) -> None:
         def work_dir_builder(conf: Config, env_name: str | None) -> Path:  # noqa: U100
             return (conf.work_dir if conf.work_dir is not None else cast(Path, self["tox_root"])) / ".tox"
 
+        def work_dir_post_process(value: Path) -> Path:
+            return self._conf.work_dir if self._conf.options.work_dir else value
+
         self.add_config(
             keys=["work_dir", "toxworkdir"],
             of_type=Path,
             default=work_dir_builder,
+            post_process=work_dir_post_process,
             desc="working directory",
         )
         self.add_config(

tests/config/test_sets.py

@@ -171,3 +171,11 @@ def test_set_env_raises_on_non_str(mocker: MockerFixture) -> None:
     env_set.loaders.insert(0, MemoryLoader(set_env=1))
     with pytest.raises(TypeError, match="1"):
         assert env_set["set_env"]
+
+
+@pytest.mark.parametrize("work_dir", ["a", ""])
+def test_config_work_dir(tox_project: ToxProjectCreator, work_dir: str) -> None:
+    project = tox_project({"tox.ini": "[tox]\ntoxworkdir=b"})
+    result = project.run("c", *(["--workdir", str(project.path / work_dir)] if work_dir else []))
+    expected = project.path / work_dir if work_dir else Path("b")
+    assert expected == result.state.conf.core["work_dir"]