pydoc.Helper.help() ignores input/output init parameters

[tws5]

BPO	940286
Nosy	@birkenfeld, @abalkin, @devdanzin, @merwok, @berkerpeksag, @miss-islington
PRs	bpo-940286: Fix pydoc to show cross refs correctly #8390 [3.7] bpo-940286: Fix pydoc to show cross refs correctly (GH-8390) #8402 [3.6] bpo-940286: Fix pydoc to show cross refs correctly (GH-8390) #8403
Files	helpredirect.diff: patch for issue 940286

^{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/berkerpeksag'
closed_at = <Date 2018-07-23.06:53:53.396>
created_at = <Date 2004-04-22.20:11:10.000>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'pydoc.Helper.help() ignores input/output init parameters'
updated_at = <Date 2018-07-23.06:53:53.395>
user = 'https://bugs.python.org/tws5'

bugs.python.org fields:

activity = <Date 2018-07-23.06:53:53.395>
actor = 'berker.peksag'
assignee = 'berker.peksag'
closed = True
closed_date = <Date 2018-07-23.06:53:53.396>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2004-04-22.20:11:10.000>
creator = 'tws5'
dependencies = []
files = ['19756']
hgrepos = []
issue_num = 940286
keywords = ['patch']
message_count = 15.0
messages = ['60481', '82047', '122002', '122004', '122009', '122599', '123198', '127840', '128199', '190051', '322131', '322173', '322175', '322183', '322184']
nosy_count = 8.0
nosy_names = ['georg.brandl', 'belopolsky', 'ajaksu2', 'tws5', 'eric.araujo', 'bkad', 'berker.peksag', 'miss-islington']
pr_nums = ['8390', '8402', '8403']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue940286'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[tws5]

The ourput of pydoc.Helper help() method is always sent
to sys.stdout, even if Helper was supplied with
different input/output streams at initialization. Other
methods: listtopics etc. work as expected.

Example:
########################

import sys, pydoc
from StringIO import StringIO

buf=StringIO()
H=pydoc.Helper(sys.stdin,buf)

H.listtopics()
H.help("pydoc")
#at this point help on pydoc is printed to stdout
H.listtopics()

ss=buf.getvalue()
print ss
#at this point the list of topics is printed twice

########################

sys.version:
'2.3 (#46, Aug 11 2003, 09:34:05) [MSC v.1200 32 bit
(Intel)]'

The problem persists in pydoc.py version 1.90 from CVS.

The reason for such behaviour is a call to global (in
module scope) function doc() at line 1628 in pydoc.py 1.90.
which doesn't care about Helper.input Helper.output
settings.

[devdanzin]

Confirmed. Is it relevant?

[bkad]

This patch redirects output from Helper.help to whatever output stream is passed to the Helper constructor. If no output stream is specified, the fault behavior is to pass the output to the OS pager.

[bkad]

Created a rietveld review
http://codereview.appspot.com/3202042

[merwok]

Thanks for the patch. I commented there.

[merwok]

Patchset 3 on codereview looks good. I’d like another review, so I’m adding the latest developers who touched pydoc.

[birkenfeld]

Looks good; committed in r86957.