emacs-build-system: Add set-emacs-load-path phase.

This generalizes the mechanism by which the Emacs dependencies are made visible,
so that any build phase can make use of them.

* guix/build/emacs-build-system.scm (%legacy-install-suffix): New variable.
(%install-suffix): Redefine in terms of %legacy-install-suffix.
(set-emacs-load-path): Add new phase used for dependency resolution.
(build): Remove ad-hoc dependency discovery mechanism.
(emacs-input->el-directory): Add new procedure.
(emacs-inputs-el-directories): Use it.
(package-name-version->elpa-name-version): Fix typo.
(%standard-phases): Include the new `set-emacs-load-path' phase. Refactor to
make the ordering of the phases clearer.
* guix/build/emacs-utils.scm (emacs-byte-compile-directory): Remove the
optional `dependency-dirs' argument, which is now obsoleted by the
`set-emacs-load-path' phase.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

guix/build/emacs-build-system.scm

@@ -2,6 +2,7 @@
 ;;; Copyright © 2015 Federico Beffa <beffa@fbengineering.ch>
 ;;; Copyright © 2016 David Thompson <davet@gnu.org>
 ;;; Copyright © 2016 Alex Kost <alezost@gmail.com>
+;;; Copyright © 2018 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -42,7 +43,8 @@
 ;; Directory suffix where we install ELPA packages.  We avoid ".../elpa" as
 ;; Emacs expects to find the ELPA repository 'archive-contents' file and the
 ;; archive signature.
-(define %install-suffix "/share/emacs/site-lisp/guix.d")
+(define %legacy-install-suffix "/share/emacs/site-lisp")
+(define %install-suffix (string-append %legacy-install-suffix "/guix.d"))
 
 ;; These are the default inclusion/exclusion regexps for the install phase.
 (define %default-include '("^[^/]*\\.el$" "^[^/]*\\.info$" "^doc/.*\\.info$"))
@@ -72,17 +74,25 @@ archive, a directory, or an Emacs Lisp file."
         #t)
       (gnu:unpack #:source source)))
 
+(define* (set-emacs-load-path #:key inputs #:allow-other-keys)
+  "Set the EMACSLOADPATH environment variable so that dependencies are found."
+  (let* ((input-elisp-dirs (emacs-inputs-el-directories
+                            (emacs-inputs-directories inputs)))
+         (emacs-load-path-value (string-join
+                                 input-elisp-dirs ":" 'suffix)))
+    (setenv "EMACSLOADPATH" emacs-load-path-value)
+    (format #t "environment variable `EMACSLOADPATH' set to ~a\n"
+            emacs-load-path-value)))
+
 (define* (build #:key outputs inputs #:allow-other-keys)
   "Compile .el files."
   (let* ((emacs (string-append (assoc-ref inputs "emacs") "/bin/emacs"))
          (out (assoc-ref outputs "out"))
          (elpa-name-ver (store-directory->elpa-name-version out))
-         (el-dir (string-append out %install-suffix "/" elpa-name-ver))
-         (deps-dirs (emacs-inputs-directories inputs)))
+         (el-dir (string-append out %install-suffix "/" elpa-name-ver)))
     (setenv "SHELL" "sh")
     (parameterize ((%emacs emacs))
-      (emacs-byte-compile-directory el-dir
-                                    (emacs-inputs-el-directories deps-dirs)))))
+      (emacs-byte-compile-directory el-dir))))
 
 (define* (patch-el-files #:key outputs #:allow-other-keys)
   "Substitute the absolute \"/bin/\" directory with the right location in the
@@ -199,18 +209,27 @@ store in '.el' files."
     (match inputs
       (((names . directories) ...) directories))))
 
+(define (emacs-input->el-directory emacs-input)
+  "Return the correct Elisp directory location of EMACS-INPUT or #f if none."
+  (let ((legacy-elisp-dir (string-append emacs-input %legacy-install-suffix))
+        (guix-elisp-dir (string-append
+                         emacs-input %install-suffix "/"
+                         (store-directory->elpa-name-version emacs-input))))
+    (cond
+     ((file-exists? guix-elisp-dir) guix-elisp-dir)
+     ((file-exists? legacy-elisp-dir) legacy-elisp-dir)
+     (else (format #t "warning: could not locate elisp directory under `~a'\n"
+                   emacs-input)
+           #f))))
+
 (define (emacs-inputs-el-directories dirs)
   "Build the list of Emacs Lisp directories from the Emacs package directory
 DIRS."
-  (append-map (lambda (d)
-                (list (string-append d "/share/emacs/site-lisp")
-                      (string-append d %install-suffix "/"
-                                     (store-directory->elpa-name-version d))))
-              dirs))
+  (filter-map emacs-input->el-directory dirs))
 
 (define (package-name-version->elpa-name-version name-ver)
   "Convert the Guix package NAME-VER to the corresponding ELPA name-version
-format.  Essnetially drop the prefix used in Guix."
+format.  Essentially drop the prefix used in Guix."
   (if (emacs-package? name-ver)  ; checks for "emacs-" prefix
       (string-drop name-ver (string-length "emacs-"))
       name-ver))
@@ -224,12 +243,15 @@ second hyphen.  This corresponds to 'name-version' as used in ELPA packages."
 
 (define %standard-phases
   (modify-phases gnu:%standard-phases
+    (add-after 'set-paths 'set-emacs-load-path set-emacs-load-path)
     (replace 'unpack unpack)
     (delete 'configure)
     (delete 'check)
-    (delete 'install)
-    (replace 'build build)
-    (add-before 'build 'install install)
+    ;; Move the build phase after install: the .el files are byte compiled
+    ;; directly in the store.
+    (delete 'build)
+    (replace 'install install)
+    (add-after 'install 'build build)
     (add-after 'install 'make-autoloads make-autoloads)
     (add-after 'make-autoloads 'patch-el-files patch-el-files)
     (add-after 'make-autoloads 'move-doc move-doc)))

guix/build/emacs-utils.scm

@@ -58,14 +58,9 @@
                   (update-directory-autoloads ,directory))))
     (emacs-batch-eval expr)))
 
-(define* (emacs-byte-compile-directory dir #:optional (dependency-dirs '()))
-  "Byte compile all files in DIR and its sub-directories.  Before compiling
-the files, add DIR and all directories in DEPENDENCY-DIRS to 'load-path'."
-  (let ((expr `(progn
-                (add-to-list 'load-path ,dir)
-                (when ',dependency-dirs
-                  (setq load-path (append ',dependency-dirs load-path)))
-                (byte-recompile-directory (file-name-as-directory ,dir) 0))))
+(define* (emacs-byte-compile-directory dir)
+  "Byte compile all files in DIR and its sub-directories."
+  (let ((expr `(byte-recompile-directory (file-name-as-directory ,dir) 0)))
     (emacs-batch-eval expr)))
 
 (define-syntax emacs-substitute-sexps