Apply changes, ensure min 1 char on line

Author: tiptenbrink

Lib/test/test_textwrap.py

@@ -1118,18 +1118,31 @@ def test_shorten_placeholder(self):
                            text_len=self.text_len)
 
 
-class ZeroWidthTestCase(BaseTestCase):
+class CustomWidthTestCase(BaseTestCase):
     def text_len(self, text):
+        lengths = {
+            'A': 4,
+            'B': 2,
+            'Q': 0,
+        }
+
         return sum(
-            0 if c == 'Q' else 1
+            lengths[c] if c in lengths else 1
             for c in text
         )
 
     def test_zero_width_text_len(self):
-
         text = "0QQ1234QQ56789"
         self.check_wrap(text, 6, ["0QQ1234QQ5", "6789"], text_len=self.text_len)
 
+    def test_char_longer_than_width(self):
+        text = "AA0123"
+        self.check_wrap(text, 3, ["A", "A", "012", "3"], text_len=self.text_len)
+
+    def test_next_char_overflow(self):
+        text = "BB0123"
+        self.check_wrap(text, 3, ["B", "B0", "123"], text_len=self.text_len)
+
 
 if __name__ == '__main__':
     unittest.main()

Lib/textwrap.py

@@ -200,21 +200,23 @@ def _fix_sentence_endings(self, chunks):
                 i += 1
 
     def _find_width_index(self, text, width):
-        """_find_width_index(text : string, width: int)
+        """_find_length_index(text : string, width : int)
 
-        Find at which index the text has the required width.
+        Find at which index the text has the required width, since when using a
+        different text_len, this index will not be equal to the required width.
         """
-        # In most cases text_len will just use the number of characters, so this heuristic prevents calculating width
-        # for each character
+        # When using default len as self.text_len, the required index and width
+        # will be equal, this prevents calculation time.
         if self.text_len(text[:width]) == width:
-            # For character widths greater than one, width can be more than the number of characters
+            # For character widths greater than one, width can be more than the
+            # number of characters
             return min(width, len(text))
         cur_text = ''
         for i, c in enumerate(text):
             cur_text += c
             cur_width = self.text_len(cur_text)
-            if cur_width >= width:
-                return i+1
+            if cur_width > width:
+                return max(i, 1)
 
     def _handle_long_word(self, reversed_chunks, cur_line, cur_len, width):
         """_handle_long_word(chunks : [string],