HTMLParser fails to handle charref in attribute value

[jhylton]

BPO	1200313
Nosy	@freddrake, @devdanzin, @ezio-melotti

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/ezio-melotti'
closed_at = <Date 2011-11-08.01:11:30.655>
created_at = <Date 2005-05-12.02:30:55.000>
labels = ['type-feature', 'library']
title = 'HTMLParser fails to handle charref in attribute value'
updated_at = <Date 2011-11-14.17:16:53.339>
user = 'https://bugs.python.org/jhylton'

bugs.python.org fields:

activity = <Date 2011-11-14.17:16:53.339>
actor = 'ezio.melotti'
assignee = 'ezio.melotti'
closed = True
closed_date = <Date 2011-11-08.01:11:30.655>
closer = 'ezio.melotti'
components = ['Library (Lib)']
creation = <Date 2005-05-12.02:30:55.000>
creator = 'jhylton'
dependencies = []
files = []
hgrepos = []
issue_num = 1200313
keywords = []
message_count = 5.0
messages = ['60736', '82199', '147268', '147614', '147621']
nosy_count = 5.0
nosy_names = ['jhylton', 'fdrake', 'ajaksu2', 'ezio.melotti', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue1200313'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']

[jhylton]

The HTML spec describes two ways to encode an attribute
value that contains a URI with an ampersand.

http://www.w3.org/TR/REC-html40/appendix/notes.html#h-B.2.2

>>> from HTMLParser import *
>>> class P(HTMLParser):
...   def handle_starttag(self, tag, attrs):
...     print attrs
...
>>> P().feed("<tag attr=\"&\">")
[('attr', '&')]
>>> P().feed("<tag attr=\"&\">")
[('attr', '&')]

It seems that each string should produce the same
parsed value. I would hazard a guess that the easiest
way to make this happen is to extend the current
unescape() to unescape character references. Is there
any reason not to do that? I'll provide a fix if that
sounds like a reasonable answer.

[devdanzin]

Maybe the charrefs were lost in the SF -> Roundup transition?

[ezio-melotti]

unescape() already converts named, decimal and hexadecimal entities, so this can be closed.