Support of 'with' statement fo TarFile class

[jaimebuelta]

BPO	7232
Nosy	@gustaebel, @ezio-melotti, @merwok, @bitdancer, @briancurtin, @meadori
Files	tarfileWithSupport.patch: tarfile with statement support patch tarfileWithSupportv2.patch issue7232.diff: minimal patch with test and doc issue7232.2.diff issue7232.3.diff issue7232.4.diff: use assertRaises as a context manager issue7232.5.diff issue7232.6.diff issue7232.7.diff issue7232.8.diff issue7232.9.diff

^{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/gustaebel'
closed_at = <Date 2010-03-03.12:15:01.223>
created_at = <Date 2009-10-29.07:29:33.067>
labels = ['type-feature', 'library']
title = "Support of 'with' statement fo TarFile class"
updated_at = <Date 2010-03-03.12:16:02.794>
user = 'https://bugs.python.org/jaimebuelta'

bugs.python.org fields:

activity = <Date 2010-03-03.12:16:02.794>
actor = 'lars.gustaebel'
assignee = 'lars.gustaebel'
closed = True
closed_date = <Date 2010-03-03.12:15:01.223>
closer = 'lars.gustaebel'
components = ['Library (Lib)']
creation = <Date 2009-10-29.07:29:33.067>
creator = 'jaime.buelta'
dependencies = []
files = ['15220', '16291', '16307', '16367', '16386', '16391', '16394', '16396', '16398', '16400', '16401']
hgrepos = []
issue_num = 7232
keywords = ['patch', 'needs review']
message_count = 18.0
messages = ['94645', '94646', '94647', '99698', '99707', '99761', '100083', '100181', '100193', '100195', '100198', '100199', '100201', '100210', '100216', '100218', '100222', '100339']
nosy_count = 7.0
nosy_names = ['lars.gustaebel', 'ezio.melotti', 'eric.araujo', 'r.david.murray', 'brian.curtin', 'meador.inge', 'jaime.buelta']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue7232'
versions = ['Python 2.7', 'Python 3.2']

[jaimebuelta]

Currently, the TarFile is not supporting the 'with' statement, which I
think it should for coherence with other file classes.

I've already created a patch including it for consideration.

[gustaebel]

Please clean up the patch, and I take another look at it.

[jaimebuelta]

I've cleaned the patch, I don't now why Eclipse added a lot of garbage,
sorry.

[briancurtin]

Here is a patch which expands on Jaime's patch. I was converting tests for bpo-7944 and looked at test_tarfile, and implemented the same feature that he did.

All places where context managers should be used in the test, they are used. Includes a doc update with a small example.

[bitdancer]

Woops, I accidentally deleted one of the patch files. Adding back.

[briancurtin]

The last patch does more than it should for this issue. Here is a minimal patch with the change, test, and doc updates.

[meadori]

Built on Brian's patch by adding the following items:

• Added a unit test case to cover exceptional conditions.
• Added doc strings on __enter__ and __exit__ (more consistent
  with the surrounding code).
• Spelling error in doc update: s/manaager/manager/.
• Link doc update to context manager type documentation (just in
  case the tarfile user is unfamiliar with context manager types).

[gustaebel]

I have taken the most recent patch by Meador, fixed the documentation example and made the test more verbose. I will check in my patch on time before 2.7 alpha 4 is released if no one of you protests.

[briancurtin]

What about changing the exception test to something like what I did in bpo-7232.4.diff?

[meadori]

What about changing the exception test to something like what I did in > bpo-7232.4.diff?

That is definitely more succinct, but Lars' solution provides more information about _why_ the test fails. IMHO, the descriptiveness is
more important than succinctness. Especially when debugging a failed
test.

[briancurtin]

Good point. How about version 5? It uses base Exception in the context manager, which will allow us to differentiate between no exception being raised, and the wrong one being raised. After the context manager, we check the type of the exception to make sure it's correct.

I changed the exception being raised to an IOError. It could be anything, but given that AssertionError is what gets raised by the assert functions, it seemed better to avoid that one specifically. This is fairly minor, though.

If you change the "raise IOError" to be a pass statement, or another type of exception, you can see that the same level of information is given to you as in patch version 3 by Lars.

[merwok]

Hello

Minor note: I think magic methods shouldn’t have docstrings, because their name is enough doc (or at least enough to go read the doc). At most a one-line comment like “context protocol” can be useful. (The exception is __init__, which doesn’t have a defined set of arguments.)

Cheers