fix(_balanced_quotes_shadow): handle trailing comments correctly

Author: 5j9

tests/wikitext/test_get_bolds_and_italics.py

@@ -185,3 +185,9 @@ def test_four_apostrophe_to_three_to_two():
     assert [repr(i) for i in parse("''''a''b").get_bolds_and_italics()] == [
         "Italic(\"''a''\")"
     ]
+
+
+def test_comment_at_end_of_four():
+    assert [
+        repr(i) for i in parse("''''<!---->a''b").get_bolds_and_italics()
+    ] == ["Italic(\"''<!---->a''\")"]

wikitextparser/_wikitext.py

@@ -1071,12 +1071,12 @@ def repl(m) -> bytes:
             if n == 4:  # four apostrophes -> hide the first one
                 s = starts[1]
                 append_bold_start(s)
-                return b'_' * (s - starts[0]) + m.string[s : starts[-1] + 1]
+                return b'_' * (s - starts[0]) + m.string[s : m.end()]
             if n > 5:  # more than 5 apostrophes -> hide the prior ones
                 odd_bold_italics ^= True
                 odd_italics ^= True
                 s = starts[-5]
-                return b'_' * (s - starts[0]) + m.string[s : starts[-1] + 1]
+                return b'_' * (s - starts[0]) + m.string[s : m.end()]
 
         return bytearray(b'\n').join(
             [