fix: more details about PYTHONSAFEPATH. #1696

temp: fix lint errors from rebases

docs: a note to ourselves about interpreting test failures

test: one more safepath test

fix: use sys.flags instead of reading the PYTHONSAFEPATH

test: skip the test that show Windows gets PYTHONSAFEPATH wrong

Author: nedbat

CHANGES.rst

@@ -23,7 +23,14 @@ upgrading your version of coverage.py.
 Unreleased
 ----------
 
-Nothing yet.
+- Fix: the PYTHONSAFEPATH environment variable new in Python 3.11 is properly
+  supported, closing `issue 1696`_.  Thanks, `Philipp A. <pull 1700_>`_.  This
+  works properly except for a detail when using the ``coverage`` command on
+  Windows.  There you can use ``python -m coverage`` instead if you need exact
+  emulation.
+
+.. _issue 1696: https://github.com/nedbat/coveragepy/issues/1696
+.. _pull 1700: https://github.com/nedbat/coveragepy/pull/1700
 
 
 .. start-releases

coverage/execfile.py

@@ -17,6 +17,7 @@
 from types import CodeType, ModuleType
 from typing import Any
 
+from coverage import env
 from coverage.exceptions import CoverageException, _ExceptionDuringRun, NoCode, NoSource
 from coverage.files import canonical_filename, python_reported_file
 from coverage.misc import isolate_module
@@ -89,7 +90,7 @@ def prepare(self) -> None:
         This needs to happen before any importing, and without importing anything.
         """
         path0: str | None
-        if env.PYVERSION >= (3, 11) and os.environ.get('PYTHONSAFEPATH', ''):
+        if env.PYVERSION >= (3, 11) and getattr(sys.flags, "safe_path"):
             # See https://docs.python.org/3/using/cmdline.html#cmdoption-P
             path0 = None
         elif self.as_module:

tests/test_execfile.py

@@ -14,7 +14,6 @@
 import re
 import sys
 
-from pathlib import Path
 from typing import Any
 from collections.abc import Iterator
 
@@ -25,7 +24,6 @@
 from coverage.files import python_reported_file
 
 from tests.coveragetest import CoverageTest, TESTS_DIR, UsingModulesMixin
-from tests.helpers import change_dir
 
 TRY_EXECFILE = os.path.join(TESTS_DIR, "modules/process_test/try_execfile.py")
 
@@ -309,15 +307,6 @@ def test_pkg1_init(self) -> None:
         assert out == "pkg1.__init__: pkg1\npkg1.__init__: __main__\n"
         assert err == ""
 
-    def test_pythonpath(self, tmp_path: Path) -> None:
-        self.set_environ("PYTHONSAFEPATH", "1")
-        with change_dir(tmp_path):
-            run_python_module(["process_test.try_execfile"])
-        out, err = self.stdouterr()
-        mod_globs = json.loads(out)
-        assert tmp_path 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"])

tests/test_process.py

@@ -666,6 +666,7 @@ def assert_tryexecfile_output(self, expected: str, actual: str) -> None:
         """
         # First, is this even credible try_execfile.py output?
         assert '"DATA": "xyzzy"' in actual
+        # If this fails, "+" is actual, and "-" is expected
         assert actual == expected
 
     def test_coverage_run_is_like_python(self) -> None:
@@ -807,6 +808,11 @@ def test_coverage_zip_is_like_python(self) -> None:
         actual = self.run_command(f"python {cov_main} run run_me.py")
         self.assert_tryexecfile_output(expected, actual)
 
+    @pytest.mark.skipif(env.PYVERSION < (3, 11), reason="PYTHONSAFEPATH is new in 3.11")
+    @pytest.mark.skipif(
+        env.WINDOWS,
+        reason="Windows gets this wrong: https://github.com/python/cpython/issues/131484",
+    )
     def test_pythonsafepath(self) -> None:
         with open(TRY_EXECFILE) as f:
             self.make_file("run_me.py", f.read())
@@ -815,6 +821,15 @@ def test_pythonsafepath(self) -> None:
         actual = self.run_command("coverage run run_me.py")
         self.assert_tryexecfile_output(expected, actual)
 
+    @pytest.mark.skipif(env.PYVERSION < (3, 11), reason="PYTHONSAFEPATH is new in 3.11")
+    def test_pythonsafepath_dashm_runme(self) -> None:
+        with open(TRY_EXECFILE) as f:
+            self.make_file("run_me.py", f.read())
+        self.set_environ("PYTHONSAFEPATH", "1")
+        expected = self.run_command("python run_me.py")
+        actual = self.run_command("python -m coverage run run_me.py")
+        self.assert_tryexecfile_output(expected, actual)
+
     @pytest.mark.skipif(env.PYVERSION < (3, 11), reason="PYTHONSAFEPATH is new in 3.11")
     def test_pythonsafepath_dashm(self) -> None:
         with open(TRY_EXECFILE) as f: