readline does not offer partial saves

[bru]

BPO	22940
Files	0001-Add-readline.append_history_file-function.patch: Patch adding readline.append_history_file(nelements, [filepath])

^{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 2014-11-26.19:58:42.436>
created_at = <Date 2014-11-25.14:30:57.143>
labels = ['type-feature', 'library']
title = 'readline does not offer partial saves'
updated_at = <Date 2014-11-26.21:03:20.317>
user = 'https://bugs.python.org/bru'

bugs.python.org fields:

activity = <Date 2014-11-26.21:03:20.317>
actor = 'python-dev'
assignee = 'none'
closed = True
closed_date = <Date 2014-11-26.19:58:42.436>
closer = 'python-dev'
components = ['Library (Lib)']
creation = <Date 2014-11-25.14:30:57.143>
creator = 'bru'
dependencies = []
files = ['37275']
hgrepos = []
issue_num = 22940
keywords = ['patch']
message_count = 3.0
messages = ['231661', '231726', '231730']
nosy_count = 2.0
nosy_names = ['python-dev', 'bru']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue22940'
versions = ['Python 3.5']

[bru]

The "readline" module offers "write_history_file" from readline/history.h "write_history", but there's no "append_history_file" that would invoke "append_history" from the C header.

This causes inconveniences when saving history to a file (like shown there: https://docs.python.org/3.5/library/readline.html?highlight=readline#example). Indeed, say you have 2 interpreters (A) and (B) open.

• (A) and (B) load the history, composed of (z) lines
• you work on both, writing (a) lines in (A) and (b) lines in (b)
• you close (A), the history file now has (z)+(a)
• you close (B), the history file now has (z)+(b)
  Therefore (A) history (the (a) lines) is lost. Offering "append_history_file" would be a nice way to fix this problem: having (z)+(a)+(b) in the end would be easy.

This is exactly what the attached patch does. With it are tests, doc and an example. I've not updated Misc/NEWS yet though (no issue #).

[python-dev]

New changeset ff00588791be by Benjamin Peterson in branch 'default':
add readline.append_history_file (closes bpo-22940)
https://hg.python.org/cpython/rev/ff00588791be

[python-dev]

New changeset c8bcede1b37a by Ned Deily in branch 'default':
bpo-22940: fixes to editline support
https://hg.python.org/cpython/rev/c8bcede1b37a