Override toxworkdir with --workdir.

docs/changelog/2654.bugfix.rst

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

src/tox/config/sets.py

@@ -188,13 +188,14 @@ def register_config(self) -> None:
             desc="the root directory (where the configuration file is found)",
         )
 
-        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 / ".tox" if self._conf.work_dir is not None else value
 
         self.add_config(
             keys=["work_dir", "toxworkdir"],
             of_type=Path,
-            default=work_dir_builder,
+            default=self["tox_root"] / ".tox",
+            post_process=work_dir_post_process,
             desc="working directory",
         )
         self.add_config(

tests/config/test_sets.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 from collections import OrderedDict
 from pathlib import Path
 from typing import Callable, Dict, Optional, Set, TypeVar
@@ -171,3 +172,10 @@ 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"]
+
+
+def test_config_work_dir(tox_project: ToxProjectCreator) -> None:
+    project = tox_project({"tox.ini": "[tox]\ntoxworkdir=/tmp/foo"})
+    work_dir_flag = "/tmp/bar"
+    result = project.run("c", "-k", "toxworkdir", "--core", "--workdir", work_dir_flag)
+    assert f"work_dir = {os.path.join(work_dir_flag,'.tox')}{os.linesep}" in result.out