pydoc -k IndexError on empty docstring

[dimaqq]

BPO	21548
Nosy	@terryjreedy, @benjaminp, @berkerpeksag, @dimaqq, @serhiy-storchaka
Files	issue21548.patch issue21548.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 = None
closed_at = <Date 2015-02-20.10:10:26.778>
created_at = <Date 2014-05-21.08:43:03.290>
labels = ['easy', 'type-bug', 'library']
title = 'pydoc -k IndexError on empty docstring'
updated_at = <Date 2015-02-20.10:10:26.777>
user = 'https://github.com/dimaqq'

bugs.python.org fields:

activity = <Date 2015-02-20.10:10:26.777>
actor = 'berker.peksag'
assignee = 'none'
closed = True
closed_date = <Date 2015-02-20.10:10:26.778>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2014-05-21.08:43:03.290>
creator = 'Dima.Tisnek'
dependencies = []
files = ['35516', '37841']
hgrepos = []
issue_num = 21548
keywords = ['patch', 'easy']
message_count = 8.0
messages = ['218865', '218998', '219956', '219971', '234641', '236117', '236119', '236261']
nosy_count = 7.0
nosy_names = ['terry.reedy', 'benjamin.peterson', 'python-dev', 'berker.peksag', 'Dima.Tisnek', 'serhiy.storchaka', 'Yuyang.Guo']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue21548'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[dimaqq]

While trying to track down another bug, I disabled some packages:

[dima@bmg tmp]$ chmod a-x /usr/lib/python3.4/site-packages/speechd*

Then ran pydoc -k:

[dima@bmg tmp]$ pydoc3.4 -k n688954789
Traceback (most recent call last):
  File "/usr/bin/pydoc3.4", line 5, in <module>
    pydoc.cli()
  File "/usr/lib/python3.4/pydoc.py", line 2548, in cli
    apropos(val)
  File "/usr/lib/python3.4/pydoc.py", line 2080, in apropos
    ModuleScanner().run(callback, key, onerror=onerror)
  File "/usr/lib/python3.4/pydoc.py", line 2061, in run
    desc = (module.__doc__ or '').splitlines()[0]
IndexError: list index out of range

Clearly "".splitlines() is always empty; missing doc is not handled correctly.

[terryjreedy]

Replacing 2061 with the following should work for all versions.
desc = module.__doc__.splitlines()[0] if module.__doc__ else ''

[YuyangGuo]

Made change based on Terry J. Reedy's suggestion

[benjaminp]

Thanks for the patch! It looks like the "synopsis" function also has this bug. Could you fix that, too?

[berkerpeksag]

Here's a patch with tests.

[serhiy-storchaka]

LGTM.

[python-dev]

New changeset 9436f43b6df2 by Benjamin Peterson in branch '3.4':
fix pydoc.apropos and pydoc.synopsis on modules with empty docstrings (bpo-21548)
https://hg.python.org/cpython/rev/9436f43b6df2

New changeset 534b26837a13 by Benjamin Peterson in branch 'default':
merge 3.4 (bpo-21548)
https://hg.python.org/cpython/rev/534b26837a13

[python-dev]

New changeset 43641e03692a by Berker Peksag in branch '2.7':
Issue bpo-21548: Fix pydoc.synopsis() and pydoc.apropos() on modules with empty
https://hg.python.org/cpython/rev/43641e03692a