gh-134746: implement Ctrl+Alt+L clear display keymap in pyREPL

[sharmaigne]

Changes:

• added a clear_all() method to console files that does what clear() does + clears scrollback
• added the Ctrl+Alt+L keymap

Note:

• description of clear_display behavior: Clear the screen and, if possible, the terminal's scrollback buffer, then redraw the current line, leaving the current line at the top of the screen.

• Manually tested for unix but not yet tested for windows

• Issue: Ctrl+Alt+L is broken after upgrading to Python 3.13 #134746

[python-cla-bot]

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[StanFromIreland]

Please undo all of the unrelated changes.

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[sharmaigne]

Please undo all of the unrelated changes.

Done! Sorry, forgot to turn off the formatter.

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[sharmaigne]

cc @corona10

[corona10]

@ambv @pablogsal

• She asked me onsite whether she needs to add a test case for this.
• If there isn’t already such a test, would it be okay for her to open a new issue for it?

[corona10]

ERROR: test_multiline_edit (test.test_pyrepl.test_pyrepl.TestPyReplOutput.test_multiline_edit)

---

Traceback (most recent call last):
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/test/test_pyrepl/test_pyrepl.py", line 686, in test_multiline_edit
reader = self.prepare_reader(events)
File "/Users/admin/actions-runner/_work/cpython/cpython/Lib/test/test_pyrepl/test_pyrepl.py", line 624, in prepare_reader
console = FakeConsole(events)
TypeError: Can't instantiate abstract class FakeConsole without an implementation for abstract method 'clear_all'

[sharmaigne]

@corona10 reran the test suite, should be good now

[chris-eibl]

Suggested change

	CLEAR_ALL= "\x1b[3J\x1b[2J\x1b[H"
	CLEAR_ALL= "\x1b[H\x1b[3J\x1b[J"

Using this works for me in the new virtual console on Windows. Also more symmetric to the CLEAR above.

[chris-eibl]

Suggested change

	self.__write("\x1b[3J\x1b[2J\x1b[H")
	self.__write("\x1b[H\x1b[3J\x1b[2J")

Altough both worked for me on Ubuntu 24.0.4.3 LTS, maybe starting with \x1b[H is better?
Since it is used like so for clear

cpython/Lib/_pyrepl/terminfo.py

Line 176 in 1c984ba

"clear": b"\x1b[H\x1b[2J", # Clear screen and home cursor

cpython/Lib/_pyrepl/terminfo.py

Line 250 in 1c984ba

"clear": b"\x1b[H\x1b[J", # Clear screen and home cursor (different from ansi!)

And for symmetry with Windows (see below)?

[chris-eibl]

This writes another "clear" sequence to the terminal, which did not play nicely on Ubuntu 24.0.4.3 LTS for me.
Replacing this with

        self.__gone_tall = 1
        self.__move = self.__move_tall
        self.posxy = 0, 0
        self.screen = []

did work for me, though. But I suggest to extract that in a new method (maybe called _clear?) to avoid repetition. Can be used in

cpython/Lib/_pyrepl/unix_console.py

Lines 350 to 353 in 1c984ba

	self.posxy = 0, 0
	self.__gone_tall = 0
	self.__move = self.__move_short
	self.__offset = 0

and the self.screen = [] a few lines above, too.

[chris-eibl]

See my comments wrt to Unix above. Although on Windows this does no harm for me, I'd suggest to extract that, too. Please note that #138732 should be merged first, though, since this is the reason for self.screen = [""] here vs self.screen = [] in prepare (see #138732 (comment)).

[chris-eibl]

In the legacy console on Windows this command is not executed, because in

cpython/Lib/_pyrepl/windows_console.py

Lines 471 to 481 in 1c984ba

	elif key == "\x00":
	# Handle special keys like arrow keys and translate them into the appropriate command
	key = VK_MAP.get(key_event.wVirtualKeyCode)
	if key:
	if key_event.dwControlKeyState & CTRL_ACTIVE:
	key = f"ctrl {key}"
	elif key_event.dwControlKeyState & ALT_ACTIVE:
	# queue the key, return the meta command
	self.event_queue.insert(Event(evt="key", data=key))
	return Event(evt="key", data="\033") # keymap.py uses this for meta
	return Event(evt="key", data=key)

• VK_MAP is missing all regular keys (at least L 0x4C needs to be added, see here for all possible codes)
• the if - elif does not handle a key_event like this that has both CTRL_ACTIVE and ALT_ACTIVE set.

[chris-eibl]

To smoothly work on Windows in the virtual console (AKA Windows Terminal), #139263 is needed, too.