bpo-39337: encodings.normalize_encoding() now ignores non-ASCII characters

Doc/whatsnew/3.10.rst

@@ -186,6 +186,11 @@ by :func:`curses.color_content`, :func:`curses.init_color`,
 support is provided by the underlying ncurses library.
 (Contributed by Jeffrey Kintscher and Hans Petter Jansson in :issue:`36982`.)
 
+encodings
+---------
+:func:`encodings.normalize_encoding` now ignores non-ASCII letters.
+(Contributed by Hai Shi in :issue:`39337`.)
+
 glob
 ----
 

Lib/encodings/__init__.py

@@ -61,7 +61,8 @@ def normalize_encoding(encoding):
         if c.isalnum() or c == '.':
             if punct and chars:
                 chars.append('_')
-            chars.append(c)
+            if c.isascii():
+                chars.append(c)
             punct = False
         else:
             punct = True

Lib/test/test_codecs.py

@@ -3417,7 +3417,7 @@ def test_rot13_func(self):
 
 class CodecNameNormalizationTest(unittest.TestCase):
     """Test codec name normalization"""
-    def test_normalized_encoding(self):
+    def test_codecs_lookup(self):
         FOUND = (1, 2, 3, 4)
         NOT_FOUND = (None, None, None, None)
         def search_function(encoding):
@@ -3439,6 +3439,18 @@ def search_function(encoding):
         self.assertEqual(NOT_FOUND, codecs.lookup('BBB.8'))
         self.assertEqual(NOT_FOUND, codecs.lookup('a\xe9\u20ac-8'))
 
+    def test_encodings_normalize_encoding(self):
+        # encodings.normalize_encoding() ignores non-ASCII letters.
+        normalize = encodings.normalize_encoding
+        self.assertEqual(normalize('utf_8'), 'utf_8')
+        self.assertEqual(normalize('utf\xE9\u20AC\U0010ffff-8'), 'utf_8')
+        self.assertEqual(normalize('utf   8'), 'utf_8')
+        # encodings.normalize_encoding() doesn't convert
+        # characters to lower case.
+        self.assertEqual(normalize('UTF 8'), 'UTF_8')
+        self.assertEqual(normalize('utf.8'), 'utf.8')
+        self.assertEqual(normalize('utf...8'), 'utf...8')
+
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Library/2020-09-13-02-02-18.bpo-39337.L3NXTt.rst

@@ -0,0 +1 @@
+:func:`encodings.normalize_encoding` now ignores non-ASCII letters.