inspect.getcallargs() raises the wrong error if 3+ arguments are missing

[jlowin]

BPO	20817
Nosy	@ncoghlan, @larryhastings, @1st1
Files	issue20817.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/1st1'
closed_at = <Date 2014-03-27.22:45:42.214>
created_at = <Date 2014-03-01.16:35:04.836>
labels = ['type-bug', 'library']
title = 'inspect.getcallargs() raises the wrong error if 3+ arguments are missing'
updated_at = <Date 2014-03-27.22:46:06.513>
user = 'https://bugs.python.org/jlowin'

bugs.python.org fields:

activity = <Date 2014-03-27.22:46:06.513>
actor = 'yselivanov'
assignee = 'yselivanov'
closed = True
closed_date = <Date 2014-03-27.22:45:42.214>
closer = 'python-dev'
components = ['Library (Lib)']
creation = <Date 2014-03-01.16:35:04.836>
creator = 'jlowin'
dependencies = []
files = ['34261']
hgrepos = []
issue_num = 20817
keywords = ['patch']
message_count = 4.0
messages = ['212514', '212515', '214988', '214989']
nosy_count = 5.0
nosy_names = ['ncoghlan', 'larry', 'python-dev', 'yselivanov', 'jlowin']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue20817'
versions = ['Python 3.3', 'Python 3.4']

[jlowin]

If inspect.getcallargs() is called on a function and three or more arguments are missing, an IndexError is raised instead of the expected TypeError.

This bug is present in Python 3.3 and 3.4.0 rc1 (5e05d7d3db9c). However, it worked as expected in Python 2.7.6.

Example:

>> import inspect
>> def fn(a, b, c):
>> pass
>> inspect.getcallargs(fn)

Result:
IndexError: tuple index out of range
Expected:
TypeError: fn() missing 3 required positional arguments: 'a', 'b' and 'c'

[jlowin]

The bug is caused by a list of names not getting properly expanded when generating the error message. This patch fixes it (simply by adding a * in the appropriate place) and tests that a TypeError, not an IndexError, is raised.

[python-dev]

New changeset 35302cc4fc93 by Yury Selivanov in branch 'default':
inspect: Fix getcallargs() to fail correctly if more than 3 args are missing.
http://hg.python.org/cpython/rev/35302cc4fc93

New changeset 9f06cbb7962b by Yury Selivanov in branch '3.4':
inspect: Fix getcallargs() to fail correctly if more than 3 args are missing.
http://hg.python.org/cpython/rev/9f06cbb7962b

[1st1]

Fixed for 3.4.1 and 3.5.
Thanks for the contribution!