Confusion between unix-word-rubout and backward-kill-word

[vfaronov]

GNU Readline has commands:

• unix-word-rubout (bound to C-w = Ctrl+W by default) kills the word before point, using white space as a word boundary;
• backward-kill-word (bound to M-DEL = Alt+Bksp by default) kills the word before point, using “not a letter nor a digit” as a word boundary.

The difference between these two commands is very useful. For example, suppose I have typed:

some-command --some-option /some/very/long/path

then realize that the path is wrong. I can then erase the entire path by pressing Ctrl+W, or erase it part-by-part by pressing Alt+Bksp.

However, prompt_toolkit binds both unix-word-rubout and backward-kill-word to the same action, which behaves more like backward-kill-word but not exactly (e.g. considers underscores as parts of words), and then binds both Ctrl+W and Alt+Bksp to unix-word-rubout by default.

Is there any specific reason for this divergence from Readline? Would you consider making prompt_toolkit behave the same as Readline here?

[jonathanslenders]

Hi @vfaronov,

Thanks a lot for pointing this out! This was indeed not yet implemented. It should be fixed in this commit: https://github.com/jonathanslenders/python-prompt-toolkit/commit/44e571b68e84d5007c6f5ab416771e7abbf25a64

Could you try with the latest "master" commit, and let me know whether it now works correctly? Whenever possible, we should follow GNU readline by default.

Thanks, Jonathan

[vfaronov]

This is great, thank you!

It’s still not quite the same as Readline, though. Readline’s backward-kill-word deletes any non-word characters after a word, so if you’re at the end of /foo/bar/ and press Alt+Bksp, you get /foo/. Whereas with your commit the result is /foo/bar.

Also, as I mentioned earlier, Readline does not consider the underscore _ as part of a word.

But for me personally, this is not a big deal. What’s important is that now I can delete back to whitespace with a single keystroke.