xmlrpc.server assumes sys.stdout will have a buffer attribute

[ncoghlan]

BPO	7165
Nosy	@loewis, @ncoghlan, @pitrou, @vstinner, @bitdancer
Files	test_xmlrpc.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/ncoghlan'
closed_at = <Date 2010-01-31.06:24:20.289>
created_at = <Date 2009-10-18.12:40:47.468>
labels = ['type-bug', 'library']
title = 'xmlrpc.server assumes sys.stdout will have a buffer attribute'
updated_at = <Date 2010-01-31.06:24:20.288>
user = 'https://github.com/ncoghlan'

bugs.python.org fields:

activity = <Date 2010-01-31.06:24:20.288>
actor = 'loewis'
assignee = 'ncoghlan'
closed = True
closed_date = <Date 2010-01-31.06:24:20.289>
closer = 'loewis'
components = ['Library (Lib)']
creation = <Date 2009-10-18.12:40:47.468>
creator = 'ncoghlan'
dependencies = []
files = ['15176']
hgrepos = []
issue_num = 7165
keywords = ['patch']
message_count = 8.0
messages = ['94212', '94317', '94469', '94476', '94479', '94514', '94516', '98591']
nosy_count = 5.0
nosy_names = ['loewis', 'ncoghlan', 'pitrou', 'vstinner', 'r.david.murray']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue7165'
versions = ['Python 3.1', 'Python 3.2']

[ncoghlan]

The xmlrpc tests were changed to use a StringIO object instead of a
temporary file (this change reflects the corresponding change made on
the 2.x trunk).

The tests then started failing, since xmlrpc.server assumes sys.stdout
will provide the buffer attribute, which is not a valid assumption. From
the io.TestIOBase documentation:

buffer
The underlying binary buffer (a BufferedIOBase instance) that
TextIOBase deals with. This is not part of the TextIOBase API and may
not exist on some implementations.

Assuming this attribute exists is a bug in xmlrpc.server that should be
fixed.

[pitrou]

Well this is in the CGI implementation, and it's reasonable to assume
that CGI will only be used with a real stream. Besides, the encoding
used with stdout must be the xmlrpc encoding (probably utf-8), not the
default encoding of standard streams on the system, which means direct
access to the underlying binary stream must be possible.

(however, _marshaled_dispatch() is quite strange in that it accepts str
but returns bytes)

I propose to fix test_xmlrpc instead so that it uses a BytesIO wrapped
in a TextIOWrapper. Patch included.

[bitdancer]

I think Antoine's suggestion is reasonable, and that we should apply the
patch to stop the buildbots from failing, but leave this issue open
until someone with more xmlrpc knowledge can respond to Nick and
Antoine's questions.

[loewis]

I agree with Antoine that CGIXML... is right in accessing
sys.stdout.buffer; this really needs binary IO.

Consequentially, his patch also looks right to me; please apply.

[bitdancer]

Patch applied in r75710.

[ncoghlan]

Fine by me (I was very close to changing the test when I first triggered
the problem, but wasn't sure silencing the error was the right thing to do).

Assigning back to myself to add a comment to the relevant line (i.e.
that relying on the buffer attribute being present is a deliberate
design choice).

[pitrou]

Assigning back to myself to add a comment to the relevant line (i.e.
that relying on the buffer attribute being present is a deliberate
design choice).

The remaining question, however, is why it doesn't also rely on
stdin.buffer.

[vstinner]

antoine's patch (fixing this issue) is commited. Can we close this issue?