Support PYTHONSAFEPATH

Author: flying-sheep

coverage/execfile.py

@@ -90,7 +90,10 @@ def prepare(self) -> None:
         This needs to happen before any importing, and without importing anything.
         """
         path0: Optional[str]
-        if self.as_module:
+        if os.environ.get('PYTHONSAFEPATH', ''):
+            # See https://docs.python.org/3/using/cmdline.html#cmdoption-P
+            path0 = None
+        elif self.as_module:
             path0 = os.getcwd()
         elif os.path.isdir(self.arg0):
             # Running a directory means running the __main__.py file in that

tests/test_execfile.py

@@ -13,7 +13,7 @@
 import py_compile
 import re
 import sys
-
+from unittest import mock
 from typing import Any, Iterator
 
 import pytest
@@ -306,6 +306,14 @@ def test_pkg1_init(self) -> None:
         assert out == "pkg1.__init__: pkg1\npkg1.__init__: __main__\n"
         assert err == ""
 
+    def test_pythonpath(self) -> None:
+        with mock.patch.dict(os.environ, {"PYTHONSAFEPATH": "1"}):
+            run_python_module([TRY_EXECFILE])
+        out, err = self.stdouterr()
+        mod_globs = json.loads(out)
+        assert os.cwd() not in mod_globs["path"]
+        assert err == ""
+
     def test_no_such_module(self) -> None:
         with pytest.raises(NoSource, match="No module named '?i_dont_exist'?"):
             run_python_module(["i_dont_exist"])