fix: correct suffix boundary lookup for prefixed last names (#100)

The prefix-joining loop located the suffix stop boundary with a
value-based pieces.index() that searched from position 0. When a token
value repeated (a trailing title that is also a suffix acronym, e.g.
the second 'dr' in 'dr Vincent van Gogh dr'), it matched the leading
occurrence, producing an empty slice that duplicated pieces and
corrupted the middle name. Constrain the lookup to start at i + 1,
consistent with the sibling next_prefix lookup.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: derek73

nameparser/parser.py

@@ -980,7 +980,10 @@ def join_on_conjunctions(self, pieces: list[str], additional_parts_count: int =
                     try:
                         # if there are no more prefixes, look for a suffix to stop at
                         stop_at = next(iter(filter(self.is_suffix, pieces[i + 1:])))
-                        j = pieces.index(stop_at)
+                        # search from i + 1 so a repeated token earlier in the
+                        # list (e.g. a leading title that is also a suffix
+                        # acronym) is not matched instead of the trailing one
+                        j = pieces.index(stop_at, i + 1)
                         new_piece = ' '.join(pieces[i:j])
                         pieces = pieces[:i] + [new_piece] + pieces[j:]
                     except StopIteration:

tests/test_prefixes.py

@@ -43,6 +43,18 @@ def test_prefix_before_two_part_last_name_with_acronym_suffix(self) -> None:
         self.m(hn.last, "von bergen wessels", hn)
         self.m(hn.suffix, "M.D.", hn)
 
+    def test_title_before_and_after_prefixed_last_name(self) -> None:
+        # Issue #100: a repeated title/suffix token ("dr") before AND after a
+        # prefixed last name used to corrupt the middle name into
+        # " dr Vincent van" because the suffix-boundary lookup matched the
+        # LEADING "dr" instead of the trailing one.
+        hn = HumanName("dr Vincent van Gogh dr")
+        self.m(hn.title, "dr", hn)
+        self.m(hn.first, "Vincent", hn)
+        self.m(hn.middle, "", hn)
+        self.m(hn.last, "van Gogh", hn)
+        self.m(hn.suffix, "dr", hn)
+
     def test_two_part_last_name_with_suffix_comma(self) -> None:
         hn = HumanName("pennie von bergen wessels, III")
         self.m(hn.first, "pennie", hn)