Close tags more correctly, even if the end tag has trailing text

changelog.d/20260731_095409_kurtmckee_fix_closing_tags_with_trailing_content.rst

@@ -0,0 +1,7 @@
+Fixed
+-----
+
+*   Close tags more correctly, even if the end tag has trailing text.
+
+    For example, ``</tag bonus>`` now closes ``<tag>`` correctly.
+    The trailing content is not available to parsers.

src/feedparser_sgmllib/__init__.py

@@ -361,6 +361,8 @@ def finish_starttag(
 
     # Internal -- finish processing of end tag
     def finish_endtag(self, tag: str) -> None:
+        if (match := tagfind.match(tag)) is not None:
+            tag = match.group(0)
         if not tag:
             found = len(self.stack) - 1
             if found < 0:

tests/test_sgmllib.py

@@ -484,6 +484,45 @@ def test_endtag_closes_innermost_matching_tag(nested_tag_collector):
     assert nested_tag_collector.stack == ["a"]
 
 
+@pytest.mark.parametrize(
+    "trailing_text",
+    (
+        " bonus",
+        "/",
+        "=x",
+        ";",
+        ",",
+    ),
+)
+def test_endtag_with_trailing_content_still_closes_tag(
+    cdata_event_collector, trailing_text
+):
+    """Verify that a closing tag with trailing content still closes the tag."""
+
+    cdata_event_collector.check_events(
+        f"<cdata>content</cdata{trailing_text}>after",
+        [
+            ("starttag", "cdata", []),
+            ("data", "content"),
+            ("endtag", "cdata"),
+            ("data", "after"),
+        ],
+    )
+    assert cdata_event_collector.stack == []
+
+
+def test_endtag_with_no_valid_tag_name_does_not_close_open_tag(nested_tag_collector):
+    """Verify invalid tag names do not close any open tags."""
+
+    nested_tag_collector.feed("<a>content</123>after")
+
+    assert nested_tag_collector.events == [
+        ("start_a", []),
+        ("unknown_endtag", "123"),
+    ]
+    assert nested_tag_collector.stack == ["a"]
+
+
 # XXX These tests have been disabled by prefixing their names with
 # an underscore.  The first two exercise outstanding bugs in the
 # sgmllib module, and the third exhibits questionable behavior