[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Irit Katriel]

Change by Irit Katriel :


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stage:  -> resolved
status: open -> closed

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Roy Smith]

Roy Smith  added the comment:

It's nice to see this is still being worked on after all these years :-)

I'm not actually convinced the proposed fix makes sense.  It swaps out one 
incorrect behavior for a different incorrect behavior.  If it really is more 
effort than it's worth to fix this (and given msg223371, I agree it probably 
is), then at least the original behavior makes more sense, as it's got years of 
history behind it and dropping an extra blank line is less arbitrary than 
adding an extra space.  

I've long since forgotten what real-world issue led me to open this, but it 
seems like it be easier to just document that extra trailing whitespace may not 
be honored.

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status: pending -> open

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Irit Katriel]

Irit Katriel  added the comment:

Adding a space as Paul suggests works. I'll close this soon if nobody objects.

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nosy: +iritkatriel
resolution:  -> wont fix
status: open -> pending

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Mark Lawrence]

Change by Mark Lawrence :


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nosy:  -BreamoreBoy

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[paul j3]

paul j3 added the comment:

A user could preserve blank lines by including a space (or more) in each.  That 
is, instead of ending with '\n', end with '\n \n'.

epilog = 'Epilog: No wrap text %(prog)s\n\tNext line\n \n'

---

I just checked a simple help.  The description and epilog get an extra blank 
line during assembly.  If 'epilog=None', there are 2 blank lines, which 
normally get reduced to one \n. 

So the philosophy of the formatter is to freely add \n between sections, 
regardless of whether they are empty (None) or not, and then deal with excess 
\n at the end.  Preserving blank lines during Raw requires rethinking that 
underlying philosophy.

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[paul j3]

paul j3 added the comment:

I suspect fixing this isn't going to be easy.

Extra lines are removed by the top most `formatter` function: 

def format_help(self):
help = self._root_section.format_help()
if help:
help = self._long_break_matcher.sub('\n\n', help)
help = help.strip('\n') + '\n'
return help

RawDescriptionHelpFormatter on the other hand just changes one deeply embedded 
function:

def _fill_text(self, text, width, indent):
return ''.join(indent + line for line in text.splitlines(keepends=True))

That `format_help` function has no way of distinguishing between '\n' that were 
part of the raw text, and which were added while assembling the various parts.

It could be instructive to try this version of format_help and see just how 
many \n are being removed:

def format_help(self):
help = self._root_section.format_help()
return help

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Mark Lawrence]

Mark Lawrence added the comment:

Can we have this followed up please.

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nosy: +BreamoreBoy, paul.j3
versions: +Python 3.4, Python 3.5

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Chris Jerdonek]

Changes by Chris Jerdonek :


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nosy: +bethard, chris.jerdonek

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[issue17113] argparse.RawDescriptionHelpFormatter should not delete blank lines

[Roy Smith]

New submission from Roy Smith:

The following code, when run with "--help", omits the trailing newlines from 
the epilog.  It should just emit the string verbatim.  If the developer didn't 
want the extra newlines, he/she wouldn't have put them there.


import argparse
parser = 
argparse.ArgumentParser(formatter_class=argparse.RawDescriptionHelpFormatter,
 epilog="foo\n\n")
parser.parse_args()

--
components: Library (Lib)
messages: 181267
nosy: roysmith
priority: normal
severity: normal
status: open
title: argparse.RawDescriptionHelpFormatter should not delete blank lines
type: behavior
versions: Python 2.7

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