[PATCH 1/2] packages: Merge like search path specifications.

[David Thompson]

>From 3f72a5d1cfe6d65f54c50c2ac8a8dd31f1a0691f Mon Sep 17 00:00:00 2001
From: David Thompson <address@hidden>
Date: Mon, 23 Feb 2015 20:36:59 -0500
Subject: [PATCH 1/2] packages: Merge like search path specifications.

* guix/packages.scm (merge-search-path-specifications): New procedure.
* guix/scripts/packages.scm (search-path-environment-variables): Merge search
  paths before displaying them.
---
 guix/packages.scm        | 28 ++++++++++++++++++++++++++++
 guix/scripts/package.scm |  7 ++++---
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/guix/packages.scm b/guix/packages.scm
index 5b686a1..3e0574a 100644
--- a/guix/packages.scm
+++ b/guix/packages.scm
@@ -54,6 +54,7 @@
             search-path-specification
             search-path-specification?
             search-path-specification->sexp
+            merge-search-path-specifications
 
             package
             package?
@@ -203,6 +204,33 @@ corresponds to the arguments expected by 
`set-path-environment-variable'."
     (($ <search-path-specification> variable files separator type pattern)
      `(,variable ,files ,separator ,type ,pattern))))
 
+(define (merge-search-path-specifications specs)
+  "Merge the elements of SPECS, a list of search path specifications, by
+combining the ones that represent the same environment variable."
+  (match specs
+    (() '())
+    (((? search-path-specification? spec) . tail)
+     (let-values (((dupes others)
+                   ;; Separate duplicate variables from the remainder of
+                   ;; the list.
+                   (partition
+                    (lambda (other-spec)
+                      (string=?
+                       (search-path-specification-variable spec)
+                       (search-path-specification-variable other-spec)))
+                    tail)))
+       (cons (fold (lambda (dupe memo)
+                     ;; Assuming separator, type, and pattern are the same
+                     ;; since the environment variable names match.
+                     (search-path-specification (inherit memo)
+                      (files (delete-duplicates
+                              (append
+                               (search-path-specification-files memo)
+                               (search-path-specification-files dupe))))))
+                   spec
+                   dupes)
+             (merge-search-path-specifications others))))))
+
 (define %supported-systems
   ;; This is the list of system types that are supported.  By default, we
   ;; expect all packages to build successfully here.
diff --git a/guix/scripts/package.scm b/guix/scripts/package.scm
index fc116d8..da95d45 100644
--- a/guix/scripts/package.scm
+++ b/guix/scripts/package.scm
@@ -393,9 +393,10 @@ current settings and report only settings not already 
effective."
                       (string-join path separator)))))))
 
     (let* ((packages     (filter-map manifest-entry->package entries))
-           (search-paths (delete-duplicates
-                          (append-map package-native-search-paths
-                                      packages))))
+           (search-paths (merge-search-path-specifications
+                          (delete-duplicates
+                           (append-map package-native-search-paths
+                                       packages)))))
       (filter-map search-path-definition search-paths))))
 
 (define (display-search-paths entries profile)
-- 
2.1.4

-- 
David Thompson
Web Developer - Free Software Foundation - http://fsf.org
GPG Key: 0FF1D807
Support the FSF: https://fsf.org/donate