gh-122273: Support PyREPL history in Windows

[devdanzin]

This PR aims to add support for recording and loading command history in Windows, using _pyrepl.readline to support handling the history file.

• Issue: Support command history in PyREPL on Windows #122273

[JeffersGlass]

Gave this a try, and it does appear to work as expected, at least on a stock Windows 10 build:

[vstinner]

@devdanzin: There is now a merge conflict after my latest site change. Would you mind to update your PR?

[vstinner]

You should not import if PYTHON_BASIC_REPL is set.

[devdanzin]

This part replaces an unconditional import of readline:

 import atexit
try:
- import readline+ try:+ import readline+ real_readline = True+ except ImportError:+ import _pyrepl.readline as readline+ real_readline = False
import rlcompleter # noqa: F401

Then readline is used in a couple places without checking it's a valid module. Should I set readline = None for the PYTHON_BASIC_REPL case and check against it being falsy where needed?

Should look something like:

diff --git a/Lib/site.py b/Lib/site.py
index 9d3352c70e3..a27373000fa 100644
--- a/Lib/site.py+++ b/Lib/site.py@@ -502,12 +502,13 @@ def register_readline():
import readline
real_readline = True
except ImportError:
- import _pyrepl.readline as readline+ readline = None
real_readline = False
import rlcompleter # noqa: F401
if PYTHON_BASIC_REPL:
CAN_USE_PYREPL = False
else:
+ import _pyrepl.readline as readline
from _pyrepl.main import CAN_USE_PYREPL
if real_readline:
import _pyrepl.unix_console
@@ -521,9 +522,10 @@ def register_readline():
# Reading the initialization (config) file may not be enough to set a
# completion key, so we set one first and then read the file.
- if getattr(readline, "backend", None) == 'editline':+ backend = getattr(readline, "backend", None)+ if backend == 'editline':
readline.parse_and_bind('bind ^I rl_complete')
- else:+ elif backend:
readline.parse_and_bind('tab: complete')
try:
@@ -536,7 +538,7 @@ def register_readline():
# want to ignore the exception.
pass
- if readline.get_current_history_length() == 0:+ if readline and readline.get_current_history_length() == 0:
# If no history was loaded, default to .python_history,
# or PYTHON_HISTORY.
# The guard is necessary to avoid doubling history size at
@@ -553,13 +555,15 @@ def register_readline():
exceptions = OSError
try:
- readline_module.read_history_file(history)+ if readline:+ readline_module.read_history_file(history)
except exceptions:
pass
def write_history():
try:
- readline_module.write_history_file(history)+ if readline:+ readline_module.write_history_file(history)
except (FileNotFoundError, PermissionError):
# home directory does not exist or is not writable
# https://bugs.python.org/issue19891

[devdanzin]

I've committed a version of the approach above.

[vstinner]

I'm not fully satisfied by proposed change, so I proposed a PR based somehow on this one: PR gh-127141.

[devdanzin]

Closing in favor of PR #127141, which does it better.