Reline::Terminfo::TerminfoError in Reline, but no error in Readline.

[rubyFeedback]

Hey there reline-devs,

Following hsbt's proposal to replace readline with reline, I started to
look at how I can replace the old readline code in my own projects.

(On that note, it may be useful to provide some standalone .rb files
somewhere associated with the project here or elsewhere; I had to
learn by trial-and-error, and re-use my old readline code and adapt
it. For instance, Reline::HISTORY exists, like Readline::HISTORY, but
I did not see any .rb file or documentation that mentions this.)

Anyway.

As I am in the process of replacing the old readline code, or at the
least make reline an additional option, I ran into a situation where
the last output (it should print the current working directory, in
colours) gets swallowed away. I looked at my ruby code but the ruby
code was working fine, so the problem must have originated from
elsewhere.

So, during my investigation I thought that my ENV variables messed
up something.

I started a clean version of bash via:

env -i bash --noprofile --norc

So I had basically no ENV variables there.

Interestingly, if you are in such an environment, and start irb,
and then try to do this:

require 'reline'

The following error shows up:

reline/terminfo.rb:108:in `setupterm': The terminfo database could not be found. (Reline::Terminfo::TerminfoError)

However had when I do:

require 'readline'

No such error shows up.

Now you may argue which behaviour is better of course. Reline tells
us about a problem; readline on the other hand simply continues
as-is.

I don't really care about which variant is better, but it is clear
that reline is NOT behaving like readline in this case.

On a more general design philosophy, I think it is not a good idea
to insta-die upon require time, based on external conditions (in
this context that reline relies on the terminfo database, which
can not be found because of missing ENV variables). I don't think
an exception should be raised in this case, so I consider readline's
behaviour more standard, idiomatic ruby. But, as stated, I don't
care either way - I am only here to report that, since it surprised
me - now I have to put the require 'reline' into begin/rescue clauses
just for that error alone. (In the shell I am working on, users can
then switch between $stdin.gets, reline and readline; so I already
rescue readline anyway, since it is external, and will do for reline
as well, so it does not really affect me. It only surprised me.)

PS: I think it may also be useful IF there is a difference in behaviour
between reline and Readline, to document it. I do not know how much
compatibility you guys aim for, but some text-file or something
that could mention differences, could be useful. Right now I am
primarily tinkering, but there is very little documentation out there
for reline, so switching to reline is not so trivial for casual
users/developers. Adding more documentation here for reline would
be great; it could also help motivate more people to transition into
reline. (I'll continue with my investigation of that odd thing where
the last input is swallowed; I first noticed this already via readline
on windows, and the prompt is shown briefly but then vanishes. Will
have to track it down, but this is a separate issue - the issue here
is primarily about the terminfo-situation, which appears to be
different between reline and readline.)

[Greg-Myers-SB]

I encountered the same error-message as this issue but with a different cause. I resolved my issue with brew install readline gem pristine reline

[tompng]

Related to, or maybe same to #447

[Greg-Myers-SB]

If it makes a difference, I do not use Overmind or tmux.

$ brew list | grep tmux
$

[tompng]

Fixed by #673