🐛 fix(tk): skip profile scripts during probe

docs/changelog/208.security.rst

@@ -0,0 +1 @@
+Tcl/Tk library detection no longer executes Tk startup profile files from the home or working directory.

src/python_discovery/_py_info_collect.py

@@ -184,8 +184,13 @@ def _get_tcl_tk_libs():  # pragma: no cover # tkinter availability varies; teste
         except ImportError:
             pass
         else:
+            # Tk.__init__ reads profile scripts from HOME or the working directory; probing needs only library metadata.
+            class _TclWithoutProfile(tk.Tk):
+                def readprofile(self, *_args, **_kwargs):  # ruff:ignore[no-self-use] # Tk override must be an instance method.
+                    return None
+
             try:
-                tcl = tk.Tcl()
+                tcl = _TclWithoutProfile(useTk=False)
                 tcl_lib = tcl.eval("info library")
                 tk_lib = PythonInfoCollector._resolve_tk_lib(tcl, tcl_lib)
             except tk.TclError:

tests/test_py_info_collect.py

@@ -19,6 +19,7 @@
 
 if TYPE_CHECKING:
     from collections.abc import Callable
+    from unittest.mock import Mock
 
     from pytest_mock import MockerFixture
 
@@ -304,9 +305,16 @@ class _TclError(Exception):
     """Stands in for tkinter.TclError; an except clause needs a real exception type."""
 
 
-def _fake_tkinter(mocker: MockerFixture, eval_side_effect: object) -> None:
-    module = mocker.MagicMock(TclError=_TclError, **{"Tcl.return_value.eval.side_effect": eval_side_effect})
+def _fake_tkinter(mocker: MockerFixture, eval_side_effect: Callable[[str], str] | Exception) -> Mock:
+    evaluate = mocker.Mock(side_effect=eval_side_effect)
+    profile = mocker.Mock(return_value=None)
+    interpreter = type(
+        "Tk", (), {"__init__": lambda self, **_: self.readprofile("Tk", "Tk"), "readprofile": profile, "eval": evaluate}
+    )
+    module = mocker.MagicMock(TclError=_TclError, Tk=interpreter)
+    module.Tcl.side_effect = lambda: interpreter(useTk=False)
     mocker.patch.dict(sys.modules, {"tkinter": module})
+    return profile
 
 
 def test_tcl_tk_libs_queried_with_env(tmp_path: Path, mocker: MockerFixture) -> None:
@@ -326,6 +334,18 @@ def test_tcl_tk_libs_none_on_tcl_error(tmp_path: Path, mocker: MockerFixture) ->
     assert (info.tcl_lib, info.tk_lib) == (None, None)
 
 
+def test_tcl_tk_libs_skip_tk_profile(tmp_path: Path, mocker: MockerFixture) -> None:
+    profile = _fake_tkinter(mocker, {"info library": "/tcl-lib"}.__getitem__)
+    profile.side_effect = AssertionError("Tk profile loaded")
+    mocker.patch("python_discovery._py_info_collect.PythonInfoCollector._resolve_tk_lib", return_value=None)
+    mocker.patch.dict(os.environ, {"TCL_LIBRARY": str(tmp_path)})
+
+    info = PythonInfo()
+
+    assert info.tcl_lib == "/tcl-lib"
+    profile.assert_not_called()
+
+
 def test_system_stdlib_empty_when_scheme_lacks_path(mocker: MockerFixture) -> None:
     names = tuple(name for name in sysconfig.get_path_names() if name not in {"stdlib", "platstdlib"})
     mocker.patch.object(sysconfig, "get_path_names", return_value=names)