From eb859e7866e38b8fb19b1aa14ccd85c5375feff0 Mon Sep 17 00:00:00 2001
From: Christopher Baines <address@hidden>
Date: Fri, 23 Jun 2017 20:53:10 +0100
Subject: [PATCH] gnu: packages: Support subdirectories in GUIX_PACKAGE_PATH

* gnu/packages.scm (%package-module-path): Treat anything after ^ within each
  element of the GUIX_PACKAGE_PATH as a subdirectory.
---
 gnu/packages.scm | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/gnu/packages.scm b/gnu/packages.scm
index 562906178..25be89c87 100644
--- a/gnu/packages.scm
+++ b/gnu/packages.scm
@@ -117,18 +117,35 @@ for system '~a'")
   ;; Search path for package modules.  Each item must be either a directory
   ;; name or a pair whose car is a directory and whose cdr is a sub-directory
   ;; to narrow the search.
-  (let* ((not-colon   (char-set-complement (char-set #\:)))
-         (environment (string-tokenize (or (getenv "GUIX_PACKAGE_PATH") "")
-                                       not-colon)))
+  (let* ((not-colon (char-set-complement (char-set #\:)))
+         (not-caret (char-set-complement (char-set #\^)))
+         (path-elements-from-environment
+          (map
+           (lambda (path-element)
+             (match (string-tokenize path-element not-caret)
+                    ((dir) dir)
+                    ((dir sub) (cons dir sub))
+                    ((dir sub rest ...)
+                     (leave
+                      (G_ "%package-module-path: GUIX_PACKAGE_PATH element \"~A\"
+ does not match form \"directory[^sub-directory]\".")
+                      path-element))))
+           (string-tokenize (or (getenv "GUIX_PACKAGE_PATH") "")
+                            not-colon))))
+
     ;; Automatically add items from $GUIX_PACKAGE_PATH to Guile's search path.
     (for-each (lambda (directory)
                 (set! %load-path (cons directory %load-path))
                 (set! %load-compiled-path
                       (cons directory %load-compiled-path)))
-              environment)
+              (map (match-lambda
+                    (directory directory)
+                    ((directory sub-directory) directory))
+                   path-elements-from-environment))
 
     (make-parameter
-     (append environment `((,%distro-root-directory . "gnu/packages"))))))
+     `(,@path-elements-from-environment
+       (,%distro-root-directory . "gnu/packages")))))
 
 (define %patch-path
   ;; Define it after '%package-module-path' so that '%load-path' contains user
-- 
2.13.1