From 51a9a6ea6615eef9ce66985bb1ad0c3ddec5c8d8 Mon Sep 17 00:00:00 2001
From: Tim Gesthuizen <address@hidden>
Date: Fri, 4 Jan 2019 22:34:36 +0100
Subject: [PATCH 4/5] gnu: Add package-elisp-from-package

Add a function to generate package definitions that packages single elisp
files from other packages.

* gnu/packages/emacs.scm (package-elisp-from-package): New function
---
 gnu/packages/emacs.scm | 64 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/emacs.scm b/gnu/packages/emacs.scm
index 52f4018c2..cdee59ce4 100644
--- a/gnu/packages/emacs.scm
+++ b/gnu/packages/emacs.scm
@@ -35,7 +35,7 @@
 ;;; Copyright © 2018 Sohom Bhattacharjee <address@hidden>
 ;;; Copyright © 2018 Mathieu Lirzin <address@hidden>
 ;;; Copyright © 2018 Pierre Neidhardt <address@hidden>
-;;; Copyright © 2018 Tim Gesthuizen <address@hidden>
+;;; Copyright © 2018, 2019 Tim Gesthuizen <address@hidden>
 ;;; Copyright © 2018 Jack Hill <address@hidden>
 ;;; Copyright © 2018 Pierre-Antoine Rouby <address@hidden>
 ;;; Copyright © 2018 Alex Branham <address@hidden>
@@ -333,6 +333,68 @@ editor (without an X toolkit)" )
              (lambda _
                (invoke "mkdir" "-p" "src/deps")))))))))
 
+;;; Returns a package definition that packages an emacs-lisp file from the
+;;; SRCPKG source. The package has the name PKGNAME and packages the file
+;;; SRC-FILE from the source in its root directory as TARGET-FILE or the
+;;; basename of SRC-FILE where INPUTS NATIVE-INPUTS and PROPAGATED-INPUTS are
+;;; added as package inputs and SUBSTITUTIONS substitutions will be performed
+;;; on the elisp file and SYNOPSIS and DESCRIPTION as the package synopsis and
+;;; description.
+(define* (package-elisp-from-package
+          srcpkg pkgname src-file
+          #:key (target-file #f)
+          (inputs '())
+          (native-inputs '())
+          (propagated-inputs '())
+          (substitutions '())
+          (synopsis #f)
+          (description #f))
+  (let ((real-target-file (if target-file
+                              target-file
+                              (basename src-file)))
+        (orig (package-source srcpkg)))
+    (package
+      (inherit srcpkg)
+      (name pkgname)
+      (source (origin
+                (method (origin-method orig))
+                (uri (origin-uri orig))
+                (sha256 (origin-sha256 orig))
+                (file-name (string-append pkgname "-" (package-version srcpkg)))
+                (modules '((guix build utils)
+                           (srfi srfi-1)
+                           (ice-9 ftw)))
+                (snippet
+                 `(begin
+                    ;; Copy target file to source root and delete all other files
+                    (copy-file ,src-file
+                               ,real-target-file)
+                    (map delete-file-recursively
+                         (fold delete
+                               (scandir ".")
+                               '("." ".." ,real-target-file)))
+                    #t))))
+      (build-system emacs-build-system)
+      (inputs inputs)
+      (native-inputs native-inputs)
+      (propagated-inputs propagated-inputs)
+      (arguments
+       `(#:phases
+         (modify-phases %standard-phases
+           (add-after 'unpack 'configure
+             (lambda* (#:key inputs #:allow-other-keys)
+               (emacs-substitute-variables ,real-target-file
+                 ,substitutions)
+               #t)))))
+      (synopsis (if synopsis
+                    synopsis
+                    (package-synopsis srcpkg)))
+      (description (if description
+                       description
+                       (package-description srcpkg))))))
+
+(export package-elisp-from-package)
+
 
 ;;;
 ;;; Emacs hacking.
-- 
2.20.1