bpo-31845: Fix reading flags from environment (GH-4105)

The startup refactoring means command line settings
are now applied after settings are read from the
environment.

This updates the way command line settings are applied
to account for that, ensures more settings are first read
from the environment in _PyInitializeCore, and adds a
simple test case covering the flags that are easy to check.

1 files changed, 34 insertions, 1 deletions

diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index 28ddb2ba1b..1b584ebb7c 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -12,7 +12,6 @@ from test.support.script_helper import (
     spawn_python, kill_python, assert_python_ok, assert_python_failure
 )
 
-
 # XXX (ncoghlan): Move to script_helper and make consistent with run_python
 def _kill_python_and_exit_code(p):
     data = kill_python(p)
@@ -486,6 +485,26 @@ class CmdLineTest(unittest.TestCase):
                                           cwd=tmpdir)
             self.assertEqual(out.strip(), b"ok")
 
+    def test_sys_flags_set(self):
+        # Issue 31845: a startup refactoring broke reading flags from env vars
+        for value, expected in (("", 0), ("1", 1), ("text", 1), ("2", 2)):
+            env_vars = dict(
+                PYTHONDEBUG=value,
+                PYTHONOPTIMIZE=value,
+                PYTHONDONTWRITEBYTECODE=value,
+                PYTHONVERBOSE=value,
+            )
+            code = (
+                "import sys; "
+                "sys.stderr.write(str(sys.flags)); "
+                f"""sys.exit(not (
+                    sys.flags.debug == sys.flags.optimize ==
+                    sys.flags.dont_write_bytecode == sys.flags.verbose ==
+                    {expected}
+                ))"""
+            )
+            with self.subTest(envar_value=value):
+                assert_python_ok('-c', code, **env_vars)
 
 class IgnoreEnvironmentTest(unittest.TestCase):
 
@@ -506,6 +525,20 @@ class IgnoreEnvironmentTest(unittest.TestCase):
         self.run_ignoring_vars("sys.flags.hash_randomization == 1",
                                PYTHONHASHSEED="0")
 
+    def test_sys_flags_not_set(self):
+        # Issue 31845: a startup refactoring broke reading flags from env vars
+        expected_outcome = """
+            (sys.flags.debug == sys.flags.optimize ==
+             sys.flags.dont_write_bytecode == sys.flags.verbose == 0)
+        """
+        self.run_ignoring_vars(
+            expected_outcome,
+            PYTHONDEBUG="1",
+            PYTHONOPTIMIZE="1",
+            PYTHONDONTWRITEBYTECODE="1",
+            PYTHONVERBOSE="1",
+        )
+
 
 def test_main():
     test.support.run_unittest(CmdLineTest, IgnoreEnvironmentTest)