Incremental search overlaps long PS1

[nisbet-hubbard]

When PS1 is long enough, launching an incremental search doesn’t dismiss the prompt:

[root@longhostname root]# 
(i-search)`': name root]# 

The prompt goes away entirely only after the length of the search terms exceeds it.

Sometimes, it can linger on like this:

oils-for-unix-0.23.0]# lr _build/oils.shnix-0.23.0]# 

[andychu]

Thanks for the report, I reproduced this ... I'm not sure why this is happening since we are basically just calling GNU readline with a prompt string

Maybe we are calling it the wrong way, or maybe it doesn't calculate the width correctly

[andychu]

Hm this happens in both Python and C++ - bin/osh and _bin/cxx-asan/osh

the former calls line_input() directly

But it doesn't happen in demo/cpython/readline_mod.py , which also ends up calling raw_input(), in frontend/py_readline.py

that is odd

[andychu]

Oh man I tracked this down to

core/comp_ui.py:    readline.parse_and_bind('set horizontal-scroll-mode on') 

disabling that restores the bash-like behavior

I added that in order to fix an issue with line wrapping, and our custom completion UI

Gah

we are trying to complete in a nicer way than bash, by not re-printing the prompt all the time, but it appears that GNU readline may not support that without bugs

I guess we could change the default back to something bash-like, and provide the current behavior as an option (which I like better)

[andychu]

@melvinw Thanks for finding this bug! I am not sure what to do about this, other than downgrade to the bash-like experience, which doesn't use "reuse the prompt line"

i.e. zsh and OSH reuse the prompt line, by printing ANSI sequences to go up, whereas bash doesn't

I feel that is nicer, but it causes this bug in OSH. (zsh has their own line editor of course; they don't use GNU readline)

---

It could be that GNU readline only correctly supports the bash-like behavior, and that's my suspicion, although I didn't look into it that deeply

https://oilshell.zulipchat.com/#narrow/channel/121539-oil-dev/topic/incremental.20search.20bug

[andychu]

Related issues

• Detect when the user types past the last column in the terminal #257 - this is the main one, which caused horizontal-scroll-mode. The root cause is our zsh-like behavior, as opposed to bash-like
• Figure out what the default completion UI should be #1078

not sure if this is still desirable

• complete across multi-line commands #1094

[andychu]

So I think the problem is that if we try to do the zsh-like thing, we have either

• bug Detect when the user types past the last column in the terminal #257 - with horizontal scroll mode off
• bug Incremental search overlaps long PS1 #2081 with it on

I'm not sure if there is a way to solve both at once, within the constraints of GNU readline, but it would sure be nice !!

If we can't solve both, then I guess we fall back to a bash-like experience as the default?