bpo-46421: Fix unittest filename evaluation when called as a module (GH-30654)

(cherry picked from commit a0db11b)

Co-authored-by: Bader Zaidan <bader@zaidan.pw>

Author: miss-islington

Lib/test/test_cmd_line.py

@@ -137,6 +137,17 @@ def test_run_module_bug1764407(self):
         self.assertTrue(data.find(b'1 loop') != -1)
         self.assertTrue(data.find(b'__main__.Timer') != -1)
 
+    def test_relativedir_bug46421(self):
+        # Test `python -m unittest` with a relative directory beginning with ./
+        # Note: We have to switch to the project's top module's directory, as per
+        # the python unittest wiki. We will switch back when we are done.
+        defaultwd = os.getcwd()
+        projectlibpath = os.path.dirname(__file__).removesuffix("test")
+        with os_helper.change_cwd(projectlibpath):
+            # Testing with and without ./
+            assert_python_ok('-m', 'unittest', "test/test_longexp.py")
+            assert_python_ok('-m', 'unittest', "./test/test_longexp.py")
+
     def test_run_code(self):
         # Test expected operation of the '-c' switch
         # Switch needs an argument

Lib/unittest/main.py

@@ -39,7 +39,7 @@ def _convert_name(name):
             name = rel_path
         # on Windows both '\' and '/' are used as path
         # separators. Better to replace both than rely on os.path.sep
-        return name[:-3].replace('\\', '.').replace('/', '.')
+        return os.path.normpath(name)[:-3].replace('\\', '.').replace('/', '.')
     return name
 
 def _convert_names(names):

Misc/ACKS

@@ -1983,6 +1983,7 @@ Masazumi Yoshikawa
 Arnaud Ysmal
 Bernard Yue
 Moshe Zadka
+Bader Zaidan
 Elias Zamaria
 Milan Zamazal
 Artur Zaprzala

Misc/NEWS.d/next/Library/2022-01-18-01-29-38.bpo-46421.9LdmNr.rst

@@ -0,0 +1,3 @@
+Fix a unittest issue where if the command was invoked as ``python -m
+unittest`` and the filename(s) began with a dot (.), a ``ValueError`` is
+returned.