Re: Bug#443439: emacs: run-octave captures the shell directory tracker

[Francesco Potorti` <pot@gnu.org>]

Shell mode is unusable together with octave inferior mode, because it
often loses the notion of current directory.  Appended is a patch.

Apparently there are two problems.

The facts: shell mode adds a directory tracker to comint input filters,
but only locally:

|  comint-input-filter-functions is a variable defined in `comint.el'.
|  Its value is
|  (shell-directory-tracker t)
|
|  Permanently local in buffer *shell*; global value is nil

However, octave-inf mode changes it also globally, and in fact, after
running M-x run-octave RET, one gets this in the shell buffer:

|  comint-input-filter-functions is a variable defined in `comint.el'.
|  Its value is
|  (shell-directory-tracker t)
|
|  Permanently local in buffer *shell*; global value is
|  (inferior-octave-directory-tracker)

My interpretation:

The first problem is that inferior-octave-mode sets
comint-input-filter-functions globally rather than locally only.

The second problem is that shell-mode uses the global value of
comint-input-filter-functions rather than the local one.

This patch solves (or hides?) the first problem and removes the
symptoms.  The second problem, if I diagnosed it correctly, is more
serious and I will not touch upon it.

2007-09-21  Francesco Potortì  <pot@gnu.org>

	* progmodes/octave-inf.el (inferior-octave-mode): make local the
	comint-input-filter-functions variable before setting it.


--- /usr/share/emacs/22.1/lisp/progmodes/octave-inf.el~	2007-01-21 04:20:44.000000000 +0100
+++ /usr/share/emacs/22.1/lisp/progmodes/octave-inf.el	2007-09-21 12:11:09.000000000 +0200
@@ -153,8 +153,9 @@ Entry to this mode successively runs the
 
   (setq comint-input-ring-file-name
 	(or (getenv "OCTAVE_HISTFILE") "~/.octave_hist")
-	comint-input-ring-size (or (getenv "OCTAVE_HISTSIZE") 1024)
-	comint-input-filter-functions '(inferior-octave-directory-tracker))
+	comint-input-ring-size (or (getenv "OCTAVE_HISTSIZE") 1024))
+  (set (make-local-variable 'comint-input-filter-functions)
+       '(inferior-octave-directory-tracker))
   (set (make-local-variable 'comint-dynamic-complete-functions)
        inferior-octave-dynamic-complete-functions)
   (comint-read-input-ring t)

If this patch is good, I can install it in the Emacs CVS.

-- 
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