Expat sax parser silently ignores the InputSource protocol

[ygale]

BPO	2175
Nosy	@loewis, @freddrake, @birkenfeld, @tiran, @ezio-melotti, @serhiy-storchaka
Dependencies	bpo-17089: Expat parser parses strings only when XML encoding is UTF-8
Files	sax_character_stream.patch: Patch for 3.x sax_character_stream-2.7.patch: Patch for 2.7 sax_character_stream_3.patch

^{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/serhiy-storchaka'
closed_at = <Date 2015-04-02.20:31:57.464>
created_at = <Date 2008-02-24.14:03:02.470>
labels = ['expert-XML', 'type-bug', 'library', 'expert-unicode']
title = 'Expat sax parser silently ignores the InputSource protocol'
updated_at = <Date 2015-04-02.20:31:57.463>
user = 'https://bugs.python.org/ygale'

bugs.python.org fields:

activity = <Date 2015-04-02.20:31:57.463>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2015-04-02.20:31:57.464>
closer = 'serhiy.storchaka'
components = ['Library (Lib)', 'Unicode', 'XML']
creation = <Date 2008-02-24.14:03:02.470>
creator = 'ygale'
dependencies = ['17089']
files = ['29061', '29062', '38696']
hgrepos = []
issue_num = 2175
keywords = ['patch', 'needs review']
message_count = 10.0
messages = ['62901', '62903', '116975', '116984', '117170', '181383', '182055', '231555', '239311', '239936']
nosy_count = 9.0
nosy_names = ['loewis', 'fdrake', 'georg.brandl', 'ygale', 'christian.heimes', 'ezio.melotti', 'tshepang', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'critical'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue2175'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[ygale]

The expat sax parser in xml.sax.expatreader
does not fully support the InputSource protocol
in xml.sax.xmlreader. It only accepts
byte streams. It ignores the encoding
indicated in the InputStream object and
only uses the encoding read from
the XML or defaults to UTF-8.

Rather than silently doing the wrong thing,
it should raise an error when fed a character stream,
or when given an encoding, via the InputSource
interface.

And most importantly, these limitations should be mentioned
in the documentation.

[ygale]

See also: bpo-1483 and bpo-2174.

[BreamoreBoy]

As nobody appears to be interested I'll close this in a couple of weeks unless someone objects.

[ygale]

Perhaps more people would be interested if
you raise the priority. This bug can cause
serious data corruption, or even crashes.
It should also be tagged as "easy".

An alternative would be to remove the expat
sax parser from the libraries, since we don't
support it. But that seems a little extreme.

[birkenfeld]

I'll have a look.