[PATCH] emacs: Fix converting scheme into elisp expression.

[Alex Kost <alezost@gmail.com>]

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There is a bug in "scheme → elisp" conversion in the emacs interface.
It can be seen with the following recipe:

1. M-x guix-licenses

2. Move to "FreeBSD" license and press "i" to describe it.

3. In the *Guix License Info* buffer you can see:

  https://www.gnu.org/licenses/license-listnilreeBSD

while it should be:

  https://www.gnu.org/licenses/license-list#FreeBSD

As you can see, "#F" is replaced with "nil".  The problem is: we receive
a string with scheme expression from geiser, and it should be converted
into elisp expression.  I don't see how to do it other than just to
replace scheme specific things (#t, #f, #<unspecified>) with elisp
analogs in this raw string.

The attached patch improves this conversion process, but it is still
ugly.  Are there better ideas how to perform this conversion?


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From f127fc2ac741334340b650736b98ed15879a3be1 Mon Sep 17 00:00:00 2001
From: Alex Kost <alezost@gmail.com>
Date: Sun, 24 Jan 2016 11:16:44 +0300
Subject: [PATCH] emacs: Fix converting scheme into elisp expression.

* emacs/guix-geiser.el (guix-geiser-eval-read): Replace #f/#t with nil/t
  only when they follow "(" or " ".
---
 emacs/guix-geiser.el | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/emacs/guix-geiser.el b/emacs/guix-geiser.el
index 0e6cc03..833f5bb 100644
--- a/emacs/guix-geiser.el
+++ b/emacs/guix-geiser.el
@@ -46,11 +46,23 @@ Return a list of strings with result values of evaluation."
 (defun guix-geiser-eval-read (str &optional repl)
   "Evaluate STR with guile expression using Geiser REPL.
 Return elisp expression of the first result value of evaluation."
-  ;; Parsing scheme code with elisp `read' is probably not the best idea.
-  (read (replace-regexp-in-string
-         "#f\\|#<unspecified>" "nil"
-         (replace-regexp-in-string
-          "#t" "t" (car (guix-geiser-eval str repl))))))
+  ;; The goal is to convert a string with scheme expression into elisp
+  ;; expression.
+  (let ((result (car (guix-geiser-eval str repl))))
+    (cond
+     ((or (string= result "#f")
+          (string= result "#<unspecified>"))
+      nil)
+     ((string= result "#t")
+      t)
+     (t
+      (read (replace-regexp-in-string
+             "[ (]\\(#f\\)" "nil"
+             (replace-regexp-in-string
+              "[ (]\\(#t\\)" "t"
+              result
+              nil nil 1)
+             nil nil 1))))))
 
 (defun guix-repl-send (cmd &optional save-history)
   "Send CMD input string to the current REPL buffer.
-- 
2.6.3