missing __enter__ + __getattr__ forwarding

[ocean-city]

BPO	1581357
Nosy	@birkenfeld
Files	a.py: the script to reproduce problem a.patch: simply solve only codecs.open

^{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/birkenfeld'
closed_at = <Date 2006-10-29.14:47:51.000>
created_at = <Date 2006-10-20.15:17:13.000>
labels = ['library']
title = 'missing __enter__ + __getattr__ forwarding'
updated_at = <Date 2006-10-29.14:47:51.000>
user = 'https://bugs.python.org/ocean-city'

bugs.python.org fields:

activity = <Date 2006-10-29.14:47:51.000>
actor = 'georg.brandl'
assignee = 'georg.brandl'
closed = True
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2006-10-20.15:17:13.000>
creator = 'ocean-city'
dependencies = []
files = ['2190', '2191']
hgrepos = []
issue_num = 1581357
keywords = []
message_count = 2.0
messages = ['30327', '30328']
nosy_count = 2.0
nosy_names = ['georg.brandl', 'ocean-city']
pr_nums = []
priority = 'high'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1581357'
versions = ['Python 2.5']

[ocean-city]

Hello. I encountered some unexpected behavior on "with"
statement.

First, please run attached "a.py" file.

# traditional way
<open file 'a.txt', mode 'wb' at 0x009373C8> shift_jis
<type 'instance'> True
# with statement
<open file 'a.txt', mode 'wb' at 0x009373C8> None <type
'file'> False
Traceback (most recent call last):
  File "R:\a.py", line 15, in <module>
    test(io)
  File "R:\a.py", line 8, in test
    io.write(u"�����")
UnicodeEncodeError: 'ascii' codec can't encode
characters in position 0-4: ordin
al not in range(128)

"traditional way" runs as expected, but "with
statement" crashes. This happens because....

1. codecs.open returns codecs.StreamReaderWriter
2. codecs.StreamReaderWriter defines __getattr__
   like this.

    def __getattr__(self, name,
                    getattr=getattr):

    """ Inherit all other methods from the
        underlying stream.
    """
    return getattr(self.stream, name)

3. But codecs.StreamReaderWriter doesn't have its
   __enter__ definition, so

    srw = StreamReaderWriter(stream, ...
    srw.__enter__() # actually calls stream.__enter__
                      which returns stream not srw
                      via __getattr__

 And more worse, with statement doesn't complain
 StreamReaderWriter (currently) doesn't support
 context manager.

Is this intended behavior? If not, only this problem
can be solved by attached "a.patch". I greped library
files, I found many __getattr__ without __enter__...

[birkenfeld]

Logged In: YES
user_id=849994

This is a duplicate of bpo-1586513 which has been fixed today.