[issue32876] HTMLParser raises exception on some inputs
Ezio Melotti
report at bugs.python.org
Fri Sep 14 03:28:22 EDT 2018
Ezio Melotti <ezio.melotti at gmail.com> added the comment:
There are at least a couple of issues here.
The first one is the way the parser handles '<![...'. The linked page contains markup like '<![STAT]-[USER-ACTIVE]!>' and since the parser currently checks for '<![' only, _markupbase.py:parse_marked_section gets called and an error gets incorrectly raised.
However "8.2.4.42. Markup declaration open state"[0], states that after consuming '<!', there are only 4 valid paths forward:
1) if we have '<!--', it's a comment;
2) if we have '<!doctype', it's a doctype declaration;
3) if we have '<![CDATA[', it's a CDATA section;
4) if it's something else, it's a bogus comment;
The above example should therefore fall into 4), and be treated like a bogus comment.
PR-9295 changes parse_html_declaration() to align to the specs and implement path 3), resulting in the webpage being parsed without errors (the invalid markup is considered as a bogus comment).
The second issue is about an EOF in the middle of a bogus markup declaration, like in the minified example provided by OP ("<![\n"). In this case the comment should still be emitted ('[\n'), but currently nothing gets emitted. I'll look more into it either tomorrow or later this month and update the PR accordingly (or perhaps I'll open a separate issue).
[0]: https://www.w3.org/TR/html52/syntax.html#tokenizer-markup-declaration-open-state
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versions: +Python 2.7, Python 3.7, Python 3.8
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