Revert "tmpdir: clean up indirection via config for factories (#6767)"

This reverts commit 8a1633c3b4.

+ add changelog

changelog/6992.bugfix.rst

@@ -0,0 +1 @@
+Revert "tmpdir: clean up indirection via config for factories" #6767 as it breaks pytest-xdist.

src/_pytest/tmpdir.py

@@ -14,6 +14,7 @@ from .pathlib import make_numbered_dir
 from .pathlib import make_numbered_dir_with_cleanup
 from .pathlib import Path
 from _pytest.fixtures import FixtureRequest
+from _pytest.monkeypatch import MonkeyPatch
 
 
 @attr.s
@@ -134,18 +135,35 @@ def get_user() -> Optional[str]:
         return None
 
 
+def pytest_configure(config) -> None:
+    """Create a TempdirFactory and attach it to the config object.
+
+    This is to comply with existing plugins which expect the handler to be
+    available at pytest_configure time, but ideally should be moved entirely
+    to the tmpdir_factory session fixture.
+    """
+    mp = MonkeyPatch()
+    tmppath_handler = TempPathFactory.from_config(config)
+    t = TempdirFactory(tmppath_handler)
+    config._cleanup.append(mp.undo)
+    mp.setattr(config, "_tmp_path_factory", tmppath_handler, raising=False)
+    mp.setattr(config, "_tmpdirhandler", t, raising=False)
+
+
 @pytest.fixture(scope="session")
-def tmpdir_factory(tmp_path_factory) -> TempdirFactory:
+def tmpdir_factory(request: FixtureRequest) -> TempdirFactory:
     """Return a :class:`_pytest.tmpdir.TempdirFactory` instance for the test session.
     """
-    return TempdirFactory(tmp_path_factory)
+    # Set dynamically by pytest_configure() above.
+    return request.config._tmpdirhandler  # type: ignore
 
 
 @pytest.fixture(scope="session")
 def tmp_path_factory(request: FixtureRequest) -> TempPathFactory:
     """Return a :class:`_pytest.tmpdir.TempPathFactory` instance for the test session.
     """
-    return TempPathFactory.from_config(request.config)
+    # Set dynamically by pytest_configure() above.
+    return request.config._tmp_path_factory  # type: ignore
 
 
 def _mk_tmp(request: FixtureRequest, factory: TempPathFactory) -> Path: