Pasting zero-width characters into PyREPL results in incorrect cursor position

[grayjk]

Bug report

Bug description:

To reproduce

Tested with Python 3.14 rc3 on Linux

1. Open the new REPL
2. Paste: ééééé

The paste-able string above is five letter 'e's each followed by \u0301. To create it use:

print('e\u0301' * 5)

The \u0301 is a combining mark with zero-width display length

Current behavior

The cursor position is five spaces after the pasted string

Expected behavior

The cursor position is immediately after the pasted string

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Linked PRs

• gh-139246: zero-width word paste can be wrong in default repl #139254

[grayjk]

The root cause seems to be related to pyrepl wlen miscalculating the length of the zero-width combining mark

wlen('e\u0301') is 2 instead of 1

[StanFromIreland]

Possibly related: #130273

>>> ééééé/0
Traceback (most recent call last):
  File "<python-input-6>", line 1, in <module>
    ééééé/0
    ~~~~~~~~~~^~
ZeroDivisionError: division by zero

[grayjk]

@StanFromIreland It does look like traceback has a similar mishandling of zero-width characters in _display_width

[yihong0618]

something like
seems width is wrong here

é
ȩ

[yihong0618]

I create a draft patch maybe can fix this can you help test?
cc @grayjk

[grayjk]

Also affects Python 3.13