gnu: aspell: 'dict-dir' set to ~/.guix-profile/lib/aspell or $ASPELL_DICT_DIR.

See <https://bugs.gnu.org/25836> for background.

* gnu/packages/patches/aspell-default-dict-dir.patch: New file.
* gnu/packages/aspell.scm (aspell)[source](patches): New field.
[native-search-paths]: New field.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -501,6 +501,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/antiword-CVE-2014-8123.patch			\
   %D%/packages/patches/apr-skip-getservbyname-test.patch	\
   %D%/packages/patches/artanis-fix-Makefile.in.patch		\
+  %D%/packages/patches/aspell-default-dict-dir.patch		\
   %D%/packages/patches/ath9k-htc-firmware-binutils.patch	\
   %D%/packages/patches/ath9k-htc-firmware-gcc.patch		\
   %D%/packages/patches/ath9k-htc-firmware-objcopy.patch		\

gnu/packages/aspell.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015, 2016 Alex Kost <alezost@gmail.com>
 ;;; Copyright © 2016 John Darrington <jmd@gnu.org>
 ;;; Copyright © 2016 Efraim Flashner <efraim@flashner.co.il>
@@ -26,6 +26,7 @@
   #:use-module (guix download)
   #:use-module (guix build-system gnu)
   #:use-module (guix licenses)
+  #:use-module (gnu packages)
   #:use-module (gnu packages perl)
   #:use-module (gnu packages base))
 
@@ -40,7 +41,8 @@
                           version ".tar.gz"))
       (sha256
        (base32
-        "1qgn5psfyhbrnap275xjfrzppf5a83fb67gpql0kfqv37al869gm"))))
+        "1qgn5psfyhbrnap275xjfrzppf5a83fb67gpql0kfqv37al869gm"))
+      (patches (search-patches "aspell-default-dict-dir.patch"))))
     (build-system gnu-build-system)
     (arguments
      `(#:phases
@@ -53,6 +55,15 @@
                  '("ASPELL_CONF" "" =
                    ("${ASPELL_CONF:-\"dict-dir ${GUIX_PROFILE:-$HOME/.guix-profile}/lib/aspell\"}")))))))))
     (inputs `(("perl" ,perl)))
+
+    (native-search-paths
+     ;; This is a Guix-specific environment variable that takes a single
+     ;; entry, not an actual search path.
+     (list (search-path-specification
+            (variable "ASPELL_DICT_DIR")
+            (separator #f)
+            (files '("lib/aspell")))))
+
     (home-page "http://aspell.net/")
     (synopsis "Spell checker")
     (description
@@ -66,7 +77,8 @@ dictionaries, including personal ones.")
 ;;; Dictionaries.
 ;;;
 ;;; Use 'export ASPELL_CONF="dict-dir $HOME/.guix-profile/lib/aspell"' to use
-;;; them.
+;;; them, or set the Guix-specific 'ASPELL_DICT_DIR', or just do nothing (as
+;;; long as 'HOME' is set, that's fine!).
 ;;;
 
 (define* (aspell-dictionary dict-name full-name

gnu/packages/patches/aspell-default-dict-dir.patch

@@ -0,0 +1,20 @@
+This patch changes the default value of 'dict-dir' to correspond
+to ~/.guix-profile/lib/aspell rather than $prefix/lib/aspell-X.Y.
+
+This is not strictly necessary for the 'aspell' program itself since
+one can simply set "ASPELL_CONF=dict-dir $HOME/.guix-profile/lib/aspell".
+However it is necessary for applications that use libaspell since
+'ASPELL_CONF' is not honored in this case.  See <https://bugs.gnu.org/25836>.
+
+--- a/common/config.cpp
++++ b/common/config.cpp
+@@ -1349,6 +1349,9 @@ namespace acommon {
+ #  define REPL     ".aspell.<lang>.prepl"
+ #endif
+ 
++#undef DICT_DIR
++#define DICT_DIR "<$ASPELL_DICT_DIR|home-dir/.guix-profile/lib/aspell>"
++
+   static const KeyInfo config_keys[] = {
+     // the description should be under 50 chars
+     {"actual-dict-dir", KeyInfoString, "<dict-dir^master>", 0}