Add MANPAGER envvar to specify pager for pydoc

[jsbronder]

BPO	8637
Nosy	@doko42, @abalkin, @pitrou, @merwok, @jsbronder, @vadmium
Files	python-2.7-pydoc-manpager.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 = None
closed_at = <Date 2016-06-14.06:40:45.065>
created_at = <Date 2010-05-06.15:33:44.967>
labels = ['type-feature', 'library']
title = 'Add MANPAGER envvar to specify pager for pydoc'
updated_at = <Date 2016-06-14.07:05:47.009>
user = 'https://github.com/jsbronder'

bugs.python.org fields:

activity = <Date 2016-06-14.07:05:47.009>
actor = 'martin.panter'
assignee = 'none'
closed = True
closed_date = <Date 2016-06-14.06:40:45.065>
closer = 'doko'
components = ['Library (Lib)']
creation = <Date 2010-05-06.15:33:44.967>
creator = 'jsbronder'
dependencies = []
files = ['17238']
hgrepos = []
issue_num = 8637
keywords = ['patch']
message_count = 18.0
messages = ['105151', '105153', '105154', '127833', '127836', '127841', '127843', '128122', '128123', '128124', '128126', '268525', '268526', '268527', '268529', '268532', '268533', '268534']
nosy_count = 7.0
nosy_names = ['doko', 'belopolsky', 'pitrou', 'eric.araujo', 'jsbronder', 'python-dev', 'martin.panter']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue8637'
versions = ['Python 3.6']

[jsbronder]

Similar to man(1), pydoc should respect the environment variable MANPAGER over PAGER. The current behavior causes issues when using a PAGER that does not support man pages.

Patch based off of trunk, r80871

[abalkin]

Similar logic can be written simpler as

use_pager = os.environ.get('MANPAGER') or os.environ.get('PAGER')
if use_pager:
  ...
(yes, I think ignoring empty *PAGER is preferable to an error)

I am not sure, pydoc should respect MANPAGER. Why not PYDOCPAGER?

In any case this is a feature request rather than a bug.

[jsbronder]

I chose MANPAGER as the command line pydoc utility already clones some of the man functionality, but I'm fine with PYDOCPAGER or anything else that allows me to use pydoc without having to change PAGER first.

[merwok]

Is there a standard documenting MANPAGER somewhere?

[abalkin]

On Thu, Feb 3, 2011 at 7:09 PM, Éric Araujo <report@bugs.python.org> wrote:

Éric Araujo <merwok@netwok.org> added the comment:

Is there a standard documenting MANPAGER somewhere?

Not really a standard, but man page for man on my OSX laptop says:

"""
-P pager
Specify which pager to use. This option overrides the
MANPAGER environment variable, which in turn overrides the PAGER
variable.
"""

POSIX only mandates PAGER. See
<http://pubs.opengroup.org/onlinepubs/007908799/xcu/man.html\>.

As I said before, since pydoc is not man, if we want a pydoc-specific
variable to override PAGER, it should be callled PYDOCPAGER.

[merwok]

My man(1) also respects MANPAGER (it’s the one from http://man-db.nongnu.org/), but given the lack of a standard, I agree with you.

However, I’m reluctant to add another env variable. There are workarounds, for example using a shell alias like “docpy="PAGER=most pydoc"”. I think this warrants a python-ideas discussion.

Justin: what exactly is a pager that does not support man pages?

[abalkin]

On Thu, Feb 3, 2011 at 7:39 PM, Éric Araujo <report@bugs.python.org> wrote:
..

Justin: what exactly is a pager that does not support man pages?

I may know the answer to this one. A common PAGER setting is "less
-rs" which makes less skip whitespace lines and passes through
terminal control chars. Nether of these options are needed for pydoc,
but I don't know if they cause any harm.

[jsbronder]

On Thu, Feb 3, 2011 at 7:39 PM, Éric Araujo <report@bugs.python.org> wrote:
..

Justin: what exactly is a pager that does not support man pages?

vimpager is the one I'm using. For man pages there's vimmanpager.

[merwok]

Excuse me if I was unclear: I wasn’t asking for program names but for a definition of “don’t support” or description of problematic behavior.

[pitrou]

Reusing MANPAGER is practical. Yet another PY* environment variable doesn't seem warranted in this case.
Agreed with Alexander's simpler logic proposal in msg105153.

[jsbronder]

Éric Araujo <merwok@netwok.org> added the comment:

Excuse me if I was unclear: I wasn’t asking for program names but for a definition of “don’t support” or description of problematic behavior.

In headers with vimpager ^H is not rendered(?) correctly.

For instance, 'pydoc os' shows:

---
Help on module os:

N^HNA^HAM^HME^HE

F^HFI^HIL^HLE^HE
/usr/lib/python2.6/os.py

---

And so on.

[doko42]

adding MANPAGER, with the simpler logic.

[python-dev]

New changeset 820d21c97d66 by doko in branch 'default':

• Issue bpo-8637: Honor a pager set by the env var MANPAGER (in preference to
  https://hg.python.org/cpython/rev/820d21c97d66

[doko42]

fixed for 3.6.0a3

[vadmium]

Matthias: your change causes pydoc to raise KeyError if I set MANPAGER but not PAGER. I’m guessing you intended something else?

[python-dev]

New changeset dea9f9b5582b by doko in branch 'default':

• Issue bpo-8637: Honor a pager set by the env var MANPAGER (in preference to
  https://hg.python.org/cpython/rev/dea9f9b5582b

[doko42]

sorry, updated.

[vadmium]

Thanks, that version looks more sensible