fix: keep the pin cite on an Id. citation that refers to a section

CHANGES.md

@@ -19,6 +19,10 @@ Fixes:
 - Fix 2 `TypeError`s raised in `get_citations(markup_text=...)` when
   `clean_steps` was omitted or lacked `"html"`. The documented fallback that
   prepends the `html` step was both unreachable and broken.
+- Keep the pin cite on an `Id.` citation that refers to a section, like
+  `Id. § 1985`. The section mark is its own token and used to stop the pin
+  cite scan, so the pin cite was lost and the mark was reported as a separate
+  `UnknownCitation`. #299
 
 ## Current
 

eyecite/helpers.py

@@ -19,12 +19,14 @@
     PlaceholderCitationToken,
     ReferenceCitation,
     ResourceCitation,
+    SectionToken,
     ShortCaseCitation,
     StopWordToken,
     SupraCitation,
     SupraToken,
     Token,
     Tokens,
+    UnknownCitation,
 )
 from eyecite.regexes import (
     POST_FULL_CITATION_REGEX,
@@ -1015,7 +1017,9 @@ def match_on_tokens(
         token = words[index]
 
         # check for stop token
-        if strings_only and not isinstance(token, str):
+        # A section mark is a marker, not a citation: its text is ordinary
+        # pin cite vocabulary, so scanning has to see it rather than stop.
+        if strings_only and not isinstance(token, str | SectionToken):
             break
         if isinstance(token, ParagraphToken):
             break
@@ -1109,6 +1113,11 @@ def filter_citations(citations: list[CitationBase]) -> list[CitationBase]:
                 filtered_citations.append(citation)
                 continue
 
+            # A section mark the previous citation took as its pin cite
+            # is that pin cite, not a citation of its own.
+            if isinstance(citation, UnknownCitation):
+                continue
+
             # Known overlap case are parallel full citations
             if not (
                 isinstance(citation, FullCaseCitation)

tests/test_FindTest.py

@@ -947,6 +947,44 @@ def test_no_duplicate_editions(self):
         self.assertEqual(len(ambiguous.all_editions), 2)
         self.assertEqual(len(set(ambiguous.all_editions)), 2)
 
+    def test_id_citation_with_section_pin_cite(self):
+        """Does an Id. cite keep a section pin cite? (#299)
+
+        The section mark is its own token, and the pin cite scan used to stop
+        at any non-string token, so "Id. § 5" lost the pin cite and left the
+        mark behind as a citation of its own.
+        """
+        # fmt: off
+        test_pairs = (
+            ('42 U.S.C. § 1983. Id. § 1985.',
+             [law_citation('42 U.S.C. § 1983', reporter='U.S.C.',
+                           groups={'title': '42', 'section': '1983'}),
+              id_citation('Id.', metadata={'pin_cite': '§ 1985'})]),
+            ('Foo v. Bar 1 U.S. 12. Id. §§ 5-7.',
+             [case_citation(page='12',
+                            metadata={'plaintiff': 'Foo', 'defendant': 'Bar'}),
+              id_citation('Id.', metadata={'pin_cite': '§§ 5-7'})]),
+            # The mark is glued to the number, so it is one token.
+            ('Foo v. Bar 1 U.S. 12. Id. §5.',
+             [case_citation(page='12',
+                            metadata={'plaintiff': 'Foo', 'defendant': 'Bar'}),
+              id_citation('Id.', metadata={'pin_cite': '§5'})]),
+            ('Foo v. Bar 1 U.S. 12. Id. § 5, 7.',
+             [case_citation(page='12',
+                            metadata={'plaintiff': 'Foo', 'defendant': 'Bar'}),
+              id_citation('Id.', metadata={'pin_cite': '§ 5, 7'})]),
+            # A page pin cite still works.
+            ('Foo v. Bar 1 U.S. 12. Id. at 5.',
+             [case_citation(page='12',
+                            metadata={'plaintiff': 'Foo', 'defendant': 'Bar'}),
+              id_citation('Id.', metadata={'pin_cite': 'at 5'})]),
+            # A mark that no citation absorbs is still reported on its own.
+            ('lorem ipsum see § 99 of the U.S. code.',
+             [unknown_citation('§')]),
+        )
+        # fmt: on
+        self.run_test_pairs(test_pairs, "Id. citation with a section pin cite")
+
     def test_find_law_citations(self):
         """Can we find citations from laws.json?"""
         # fmt: off