Fix handling of bogus comments.

docs/changelog.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Fix edge-case crash in `InlineProcessor` with `AtomicString` (#1406).
 * Fix edge-case crash in `codehilite` with an empty `code` tag (#1405).
 * Improve and expand type annotations in the code base (#1401).
+* Fix handling of bogus comments (#1425).
 
 ## [3.5.1] -- 2023-10-31
 

markdown/htmlparser.py

@@ -277,6 +277,15 @@ def parse_html_declaration(self, i: int) -> int:
         self.handle_data('<!')
         return i + 2
 
+    def parse_bogus_comment(self, i: int, report: int = 0) -> int:
+        # Override the default behavior so that bogus comments get passed
+        # through unaltered by setting `report` to `0` (see #1425).
+        pos = super().parse_bogus_comment(i, report)
+        if pos == -1:  # pragma: no cover
+            return -1
+        self.handle_empty_tag(self.rawdata[i:pos], is_block=False)
+        return pos
+
     # The rest has been copied from base class in standard lib to address #1036.
     # As `__startag_text` is private, all references to it must be in this subclass.
     # The last few lines of `parse_starttag` are reversed so that `handle_starttag`

tests/test_syntax/blocks/test_html_blocks.py

@@ -782,16 +782,16 @@ def test_raw_comment_trailing_whitespace(self):
             '<!-- *foo* -->'
         )
 
-    # Note: this is a change in behavior for Python-Markdown, which does *not* match the reference
-    # implementation. However, it does match the HTML5 spec. Declarations must start with either
-    # `<!DOCTYPE` or `<![`. Anything else that starts with `<!` is a comment. According to the
-    # HTML5 spec, a comment without the hyphens is a "bogus comment", but a comment nonetheless.
-    # See https://www.w3.org/TR/html52/syntax.html#markup-declaration-open-state.
-    # If we wanted to change this behavior, we could override `HTMLParser.parse_bogus_comment()`.
     def test_bogus_comment(self):
         self.assertMarkdownRenders(
-            '<!*foo*>',
-            '<!--*foo*-->'
+            '<!invalid>',
+            '<p>&lt;!invalid&gt;</p>'
+        )
+
+    def test_bogus_comment_endtag(self):
+        self.assertMarkdownRenders(
+            '</#invalid>',
+            '<p>&lt;/#invalid&gt;</p>'
         )
 
     def test_raw_multiline_comment(self):