Fixed a case found by Mengyuhan where html.parser giving up on

  markup would result in an AssertionError instead of a
  ParserRejectedMarkup exception.

4 files changed, 6 insertions, 1 deletions

diff --git a/CHANGELOG b/CHANGELOG
index 94f1209..644b318 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -5,6 +5,10 @@
   of .hidden is not a documented or supported feature, so don't do this,
   but it's not too difficult to keep the old behavior working.
 
+* Fixed a case found by Mengyuhan where html.parser giving up on
+  markup would result in an AssertionError instead of a
+  ParserRejectedMarkup exception.
+
 = 4.12.2 (20230407)
 
 * Fixed an unhandled exception in BeautifulSoup.decode_contents
diff --git a/bs4/builder/_htmlparser.py b/bs4/builder/_htmlparser.py
index e065096..3cc187f 100644
--- a/bs4/builder/_htmlparser.py
+++ b/bs4/builder/_htmlparser.py
@@ -378,10 +378,10 @@ class HTMLParserTreeBuilder(HTMLTreeBuilder):
         parser.soup = self.soup
         try:
             parser.feed(markup)
+            parser.close()
         except AssertionError as e:
             # html.parser raises AssertionError in rare cases to
             # indicate a fatal problem with the markup, especially
             # when there's an error in the doctype declaration.
             raise ParserRejectedMarkup(e)
-        parser.close()
         parser.already_closed_empty_element = []
diff --git a/bs4/tests/fuzz/crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a.testcase b/bs4/tests/fuzz/crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a.testcase
new file mode 100644
index 0000000..8857115
--- /dev/null
+++ b/bs4/tests/fuzz/crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a.testcase
diff --git a/bs4/tests/test_fuzz.py b/bs4/tests/test_fuzz.py
index 2857830..f29802d 100644
--- a/bs4/tests/test_fuzz.py
+++ b/bs4/tests/test_fuzz.py
@@ -68,6 +68,7 @@ class TestFuzz(object):
     @pytest.mark.parametrize(
         "filename", [
             "clusterfuzz-testcase-minimized-bs4_fuzzer-5703933063462912",
+            "crash-ffbdfa8a2b26f13537b68d3794b0478a4090ee4a",
         ]
     )
     def test_rejected_markup(self, filename):