gh-129061: Fix FORCE_COLOR and NO_COLOR when empty strings

Lib/_colorize.py

@@ -42,11 +42,11 @@ def can_colorize(*, file=None) -> bool:
             return False
         if os.environ.get("PYTHON_COLORS") == "1":
             return True
-    if "NO_COLOR" in os.environ:
+    if os.environ.get("NO_COLOR"):
         return False
     if not COLORIZE:
         return False
-    if "FORCE_COLOR" in os.environ:
+    if os.environ.get("FORCE_COLOR"):
         return True
     if os.environ.get("TERM") == "dumb":
         return False

Lib/test/test__colorize.py

@@ -42,28 +42,40 @@ def test_colorized_detection_checks_for_environment_variables(self):
             stdout_mock.isatty.return_value = True
             stderr_mock.fileno.return_value = 2
             stderr_mock.isatty.return_value = True
-            with unittest.mock.patch("os.environ", {'TERM': 'dumb'}):
-                self.assertEqual(_colorize.can_colorize(), False)
-            with unittest.mock.patch("os.environ", {'PYTHON_COLORS': '1'}):
-                self.assertEqual(_colorize.can_colorize(), True)
-            with unittest.mock.patch("os.environ", {'PYTHON_COLORS': '0'}):
-                self.assertEqual(_colorize.can_colorize(), False)
-            with unittest.mock.patch("os.environ", {'NO_COLOR': '1'}):
-                self.assertEqual(_colorize.can_colorize(), False)
-            with unittest.mock.patch("os.environ",
-                                     {'NO_COLOR': '1', "PYTHON_COLORS": '1'}):
-                self.assertEqual(_colorize.can_colorize(), True)
-            with unittest.mock.patch("os.environ", {'FORCE_COLOR': '1'}):
-                self.assertEqual(_colorize.can_colorize(), True)
-            with unittest.mock.patch("os.environ",
-                                     {'FORCE_COLOR': '1', 'NO_COLOR': '1'}):
-                self.assertEqual(_colorize.can_colorize(), False)
-            with unittest.mock.patch("os.environ",
-                                     {'FORCE_COLOR': '1', "PYTHON_COLORS": '0'}):
-                self.assertEqual(_colorize.can_colorize(), False)
+
+            for env_vars, expected in [
+                ({"TERM": "dumb"}, False),
+                ({"PYTHON_COLORS": "1"}, True),
+                ({"PYTHON_COLORS": "0"}, False),
+                ({"NO_COLOR": "1"}, False),
+                ({"NO_COLOR": "0"}, False),
+                ({"NO_COLOR": "1", "PYTHON_COLORS": "1"}, True),
+                ({"FORCE_COLOR": "1"}, True),
+                ({"FORCE_COLOR": "1", "NO_COLOR": "1"}, False),
+                ({"FORCE_COLOR": "1", "NO_COLOR": "0"}, False),
+                ({"FORCE_COLOR": "1", "NO_COLOR": ""}, True),
+                ({"FORCE_COLOR": "0", "NO_COLOR": "1"}, False),
+                ({"FORCE_COLOR": "", "NO_COLOR": "1"}, False),
+                ({"FORCE_COLOR": "1", "PYTHON_COLORS": "0"}, False),
+                ({"FORCE_COLOR": "0", "PYTHON_COLORS": "0"}, False),
+            ]:
+                with self.subTest(env_vars=env_vars, expected=expected):
+                    with unittest.mock.patch("os.environ", env_vars):
+                        self.assertEqual(_colorize.can_colorize(), expected)
+
+            with unittest.mock.patch("os.environ", {"NO_COLOR": ""}):
+                if sys.platform == "win32":
+                    vt_mock.return_value = False
+                    self.assertEqual(_colorize.can_colorize(), False)
+
+                    vt_mock.return_value = True
+                    self.assertEqual(_colorize.can_colorize(), True)
+                else:
+                    self.assertEqual(_colorize.can_colorize(), True)
 
             with unittest.mock.patch("os.environ", {}):
                 if sys.platform == "win32":
+                    vt_mock.return_value = False
                     self.assertEqual(_colorize.can_colorize(), False)
 
                     vt_mock.return_value = True

Misc/NEWS.d/next/Library/2025-01-21-18-52-32.gh-issue-129061.4idD_B.rst

@@ -0,0 +1 @@
+Fix FORCE_COLOR and NO_COLOR when empty strings. Patch by Hugo van Kemenade.