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.