importlib.__import__ does not fail for invalid relative import

[manueljacob]

BPO	26367
Nosy	@brettcannon, @terryjreedy, @ncoghlan, @ericsnowcurrently, @serhiy-storchaka, @manueljacob
Files	relimport-3.5.patch: Patch against 3.5 branch (without changes in Python/importlib.h) relimport-3.6.patch: Patch against default branch (without changes in Python/importlib.h)

^{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/brettcannon'
closed_at = <Date 2016-02-20.21:00:13.507>
created_at = <Date 2016-02-16.00:59:01.193>
labels = ['type-bug']
title = 'importlib.__import__ does not fail for invalid relative import'
updated_at = <Date 2017-07-23.06:44:07.815>
user = 'https://github.com/manueljacob'

bugs.python.org fields:

activity = <Date 2017-07-23.06:44:07.815>
actor = 'serhiy.storchaka'
assignee = 'brett.cannon'
closed = True
closed_date = <Date 2016-02-20.21:00:13.507>
closer = 'brett.cannon'
components = []
creation = <Date 2016-02-16.00:59:01.193>
creator = 'mjacob'
dependencies = []
files = ['41937', '41938']
hgrepos = []
issue_num = 26367
keywords = ['patch']
message_count = 11.0
messages = ['260338', '260461', '260484', '260486', '260491', '260540', '260575', '260576', '260599', '260623', '298891']
nosy_count = 7.0
nosy_names = ['brett.cannon', 'terry.reedy', 'ncoghlan', 'python-dev', 'eric.snow', 'serhiy.storchaka', 'mjacob']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'patch review'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue26367'
versions = ['Python 3.3', 'Python 3.4', 'Python 3.5', 'Python 3.6']

[manueljacob]

Python 3.6.0a0 (default:6c6f7dff597b, Feb 16 2016, 01:24:51) 
[GCC 5.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import importlib
>>> importlib.__import__('array', globals(), locals(), level=1)
<module '.array' from '/home/manu/vcs/cpython/build/lib.linux-x86_64-3.6/array.cpython-36m-x86_64-linux-gnu.so'>
>>> __import__('array', globals(), locals(), level=1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: attempted relative import with no known parent package

Instead of failing, importlib.__import__ returns a module with a wrong name. This happens with both built-in modules and pure python modules. However it fails when replacing 'array' with 'time' (this seems to be related to whether the module is in Modules/Setup.dist).

[manueljacob]

(For some reason, I forgot to submit the previous comment).

The attached patches fix the issue (one for the 3.5 branch, one for the default branch) by bringing importlib.__import__ closer to the builtin __import__.

The extra code in the default / 3.6 branch is because of the changes from bpo-18018.

[brettcannon]

The corresponding code in C that actually does the check: https://hg.python.org/cpython/file/default/Python/import.c#l1498

Manuel, can you sign the CLA at https://www.python.org/psf/contrib/contrib-form/ ? Once you sign it I can officially review your patch, otherwise I technically can't touch your code.

[manueljacob]

Done. I'm a bit surprised this wasn't necessary for my previous two patches, but they were even more trival than this one. ;)

Do we have to wait until my tracker profile is updated?

[brettcannon]

If a contribution is insignificant enough then technically a CLA isn't necessary, but I just make it a habit to ask for one regardless.

And your profile will probably get updated fairly quickly, so I wouldn't worry about it holding anything up (I'm hoping to commit the code tomorrow; I already did a review and it LGTM).

[terryjreedy]

Manuel, welcome to the tracker and thank you for submitting patches. I agree that 5 lines is past the threshhold. Your profile has been CLA-updated, so we are good to go.

[python-dev]

New changeset e523efd47418 by Brett Cannon in branch '3.5':
Issue bpo-26367: Have importlib.__init__() raise RuntimeError when
https://hg.python.org/cpython/rev/e523efd47418

New changeset 8f72bf88f471 by Brett Cannon in branch 'default':
Merge for issue bpo-26367
https://hg.python.org/cpython/rev/8f72bf88f471

[brettcannon]

Thanks for the patch, Manuel!

[manueljacob]

I think the "What's New" entry has two typos. It should be importlib.__import__() instead of importlib.__init__() and SystemError instead of RuntimeError.

[brettcannon]

Thanks for spotting those! And just to clarify on terminology, the typos were in the NEWS file, not "What's New" which is a different thing (https://hg.python.org/cpython/file/default/Doc/whatsnew).

[serhiy-storchaka]

New changeset c824cc8 by Serhiy Storchaka in branch '3.5':
[3.5] Backport bpo-30876 (GH-2639), bpo-18018 and bpo-26367. (bpo-2677)
c824cc8