When used inside Emacs with Reline, input is echoed

[dgutov]

Description

This issue is about using Pry as a Ruby REPL inside Emacs.

The effect looks very much like ruby/reline#616:

[1] pry(main)> [1] pry(main)> 2
[1] pry(main)> 2[1] pry(main)> 2=> 2
[2] pry(main)> [2] pry(main)> 3
[2] pry(main)> 3[2] pry(main)> 3=> 3
[3] pry(main)> [3] pry(main)> 

But there doesn't seem to be any interest in having this solved inside Reline (i.e. providing a "simple" io driver).

What are your expected behavior and actual behavior of your environment?

The expected behavior is that the input is not copied or otherwise reproduced in the output.

This problem will come up more often now than Ruby 3.3 defaults to Reline.

Terminal Emulator

Comint inside Emacs.

IRB has a workaround: when launched with --nosingleline --nomultiline, it switches to a different I/O implementation, which it calls StdioInputMethod.

Should Pry carry its own solution like that as well? The hackish patch below seems to do the trick. It can be a configuration option, a separate wrapper class, etc.

@@ -179,7 +179,10 @@
diff --git a/lib/pry/repl.rb b/lib/pry/repl.rb
index 9a58b827..2bfcad35 100644
--- a/lib/pry/repl.rb
+++ b/lib/pry/repl.rb
@@ -179,7 +179,10 @@ class Pry
           end
         end
 
-        if readline_available?
+        if ENV['TERM'] == 'dumb'
+          STDOUT.print(current_prompt)
+          STDIN.gets
+        elsif readline_available?
           set_readline_output
           input_readline(current_prompt, false) # false since we'll add it manually
         elsif coolline_available?

Downstream report: dgutov/robe#147 (comment)

[andrehjr]

Hi, thanks for the issue!

I'm trying to add proper support for reline on #2298, wondering if this also fixes the issue?

If not, I think pry should have a workaround for TERM/dumb too. I will investigate a bit more

[dgutov]

@andrehjr Hi! I've tried your branch (and also the nearby one-liner PR with "basic Readline support") - no difference.

It does seem like there needs to be a fix inside Reline, or special handling in consumers.

I'm currently preparing a small PR that uses the approach from my patch, I think it will be orthogonal to your work, comments welcome. But if you manage to find a more organic solution, that'd be even better.