Subject: [bug#28832] [PATCH 1/3] gnu: Add emacs-json-reformat.

From: Oleg Pykhalov <[email-masked]>
Date: Wed, 13 Dec 2017 07:55:22 +0300

Hello Alex and Ludovic,

Alex Kost <[email-masked]> writes:

[...]

>> If ‘emacs-build-system’ sets ‘EMACSLOADPATH’ automatically, then
>> individual package definitions won’t need those -L flags.  Dunno if
>> there are good reasons not to do so.  Maybe Alex has an opinion?
>
> I would rather ask Federico who wrote ‘emacs-build-system’ :)

Do you mean Federico Beffa <[email-masked]>?  He is quite in
Guix git repository for 9 months as I see.  Is it a good idea to CC him?

> Yeah, maybe ‘emacs-build-system’ could benefit from using EMACSLOADPATH,
> I don't know, someone should probably give it a try ;-)

I succeeded to implement this, but the patch needs some more love.  The
biggest issue is how to get an Emacs version in setup-environment.

You could test it on emacs-git-messenger or emacs-json-reformat.

diff --git a/guix/build/emacs-build-system.scm b/guix/build/emacs-build-system.scm
index bd0d2e026..269038744 100644
--- a/guix/build/emacs-build-system.scm
+++ b/guix/build/emacs-build-system.scm
@@ -183,6 +183,10 @@ store in '.el' files."
   "Check if NAME correspond to the name of an Emacs package."
   (string-prefix? "emacs-" name))
 
+(define (string-drop-emacs x)
+  "Drops `emacs-' from a string."
+  (string-drop x 6))
+
 (define (emacs-inputs inputs)
   "Retrieve the list of Emacs packages from INPUTS."
   (filter (match-lambda
@@ -222,6 +226,38 @@ second hyphen.  This corresponds to 'name-version' as used in ELPA packages."
             strip-store-file-name)
    store-dir))
 
+;; Copied from haskell-build-system.scm
+(define (package-name-version store-dir)
+  "Given a store directory STORE-DIR return 'name-version' of the package."
+  (let* ((base (basename store-dir)))
+    (string-drop base (+ 1 (string-index base #\-)))))
+
+(define* (setup-environment #:key inputs outputs #:allow-other-keys)
+  "Export the variable EMACSLOADPATH, which are based on INPUTS and OUTPUTS,
+respectively."
+  (let ((out (assoc-ref outputs "out")))
+    ;; EMACSLOADPATH is where Emacs looks for the source code of the build's
+    ;; dependencies.
+    (set-path-environment-variable
+     "EMACSLOADPATH"
+     ;; XXX Matching "." hints that we could do
+     ;; something simpler here...
+     (list ".")
+     (cons (let ((store-item (cdr (assoc "emacs" (emacs-inputs inputs)))))
+             ;; TODO: Get a version from inputs
+             (string-append store-item "/share/emacs/25.3/lisp"))
+           (map
+            (lambda (foobar)
+              (let ((store-item (cdr foobar)))
+                (string-append store-item
+                               %install-suffix "/"
+                               (string-drop-emacs
+                                (package-name-version store-item)))))
+            (alist-delete "emacs"
+                          (alist-delete "source"
+                                        (emacs-inputs inputs))))))
+    #t))
+
 (define %standard-phases
   (modify-phases gnu:%standard-phases
     (replace 'unpack unpack)
@@ -229,6 +265,7 @@ second hyphen.  This corresponds to 'name-version' as used in ELPA packages."
     (delete 'check)
     (delete 'install)
     (replace 'build build)
+    (add-before 'build 'setup-environment setup-environment)
     (add-before 'build 'install install)
     (add-after 'install 'make-autoloads make-autoloads)
     (add-after 'make-autoloads 'patch-el-files patch-el-files)

> BTW, Oleg, did you try to use 'ert-runner' instead of running emacs for
> tests manually?  Perhaps, it will work; look at commit
> 8505d34829b99744a36d72dd583768f1e49210a6 for example.

Nope, but I will.  Thank you for notice this!

Thanks,
Oleg.