[IPython-dev] IPython+libedit

[Andrea Riciputi]

Hi all,
I've been working for a couple of days on the issues regarding IPython  
and the libedit shipped with OSX Leopard, and I've got a little more  
insight in it. I'd like to share this stuff with you in order to get a  
better understanding of these issues and to make IPython working  
better under OSX.

Although I can understand that installing the readline egg build by  
Ludwig Schwardt makes everything work smoothly, I think making IPython  
behaves correctly also using libedit could be a plus not only to all  
OSX users, but to any other user using that library as well.

So let me start listing the issues I've found so far:

1) Multi-line commands in history get scrambled when recalled at the  
prompt
2) Autoindentation doesn't work
3) Key binding initialization it's not correct

Regarding multi-line commands, the problem is due to the way libedit  
write out its history file. Despite readline, libedit encodes all the  
white spaces, newline and tabs before writing the history (look at  
libedit source code and to man strvis under OSX). As a consequence a  
muli-line command in the libedit history looked like this:

for\040i\040in\040[1,2,3]:\012\040\040print\040i

appearing as a single line command (it's a single entry in the  
history). However, a simple patch to iplib.py fixes this:

% diff -u IPython/iplib.py.orig IPython/iplib.py
--- IPython/iplib.py.orig       2008-09-03 12:12:11.000000000 +0200
+++ IPython/iplib.py    2008-09-04 10:12:05.000000000 +0200
@@ -2170,7 +2174,7 @@
        if line.strip():
            if continue_prompt:
                self.input_hist_raw[-1] += '%s\n' % line
-                if self.has_readline: # and some config option is set?
+                if self.has_readline and not  
self.readline.uses_libedit: # and some config option is set?
                    try:
                        histlen =  
self.readline.get_current_history_length()
                        if histlen > 1:

Regarding the autoindentation problem seems more rooted in libedit/ 
readline compatibility, and haven't been able to fix it yet. Infact it  
turns out that using libedit the _ip.IP.readline_startup_hook function  
(i.e. pre_readline()) is never called. I can't understand why, but if  
someone could give me so hints on how to test the readline module,  
I'll try to investagete it a little further.

Finally, I need your help again regarding the readline/libedit key- 
binging. It seems that (when libedit are present) readline key-binding  
are set despite the if-clause in init_readline() (in ipylib.py):

          if not readline.uses_libedit:
               for rlcommand in self.rc.readline_parse_and_bind:
                   readline.parse_and_bind(rlcommand)

Which file is actually read between ipythonrc and ipy_user_conf.py to  
configure IPython? And where in the code the rc Struct is initialized?

I'm sorry for this long email, but I hope someone could help me to  
make IPython a little better.

TIA,
Andrea