guix package: '--search-paths' can report combined search paths.

Partly fixes <http://bugs.gnu.org/20255>.

* guix/scripts/package.scm (search-path-environment-variables): Change
  'profile' to 'profiles'; expect it to be a list.
  (display-search-paths): Likewise.
  (%default-options): Remove 'profile' entry.
  (%options) <--profile>: Keep previous values associated with 'profile'
  in RESULT.
  (guix-package)[process-actions, process-query]: Handle the possible
  lack of 'profile' pair in OPTS.

doc/guix.texi

@@ -1347,6 +1347,20 @@ meaning that the returned environment variable definitions will either
 be exact settings, or prefixes or suffixes of the current value of these
 variables.  When omitted, @var{kind} defaults to @code{exact}.
 
+This option can also be used to compute the @emph{combined} search paths
+of several profiles.  Consider this example:
+
+@example
+$ guix package -p foo -i guile
+$ guix package -p bar -i guile-json
+$ guix package -p foo -p bar --search-paths
+@end example
+
+The last command above reports about the @code{GUILE_LOAD_PATH}
+variable, even though, taken individually, neither @file{foo} nor
+@file{bar} would lead to that recommendation.
+
+
 @item --profile=@var{profile}
 @itemx -p @var{profile}
 Use @var{profile} instead of the user's default profile.

guix/scripts/package.scm

@@ -186,11 +186,11 @@ an output path different than CURRENT-PATH."
 ;;; Search paths.
 ;;;
 
-(define* (search-path-environment-variables entries profile
+(define* (search-path-environment-variables entries profiles
                                             #:optional (getenv getenv)
                                             #:key (kind 'exact))
   "Return environment variable definitions that may be needed for the use of
-ENTRIES, a list of manifest entries, in PROFILE.  Use GETENV to determine the
+ENTRIES, a list of manifest entries, in PROFILES.  Use GETENV to determine the
 current settings and report only settings not already effective.  KIND
 must be one of 'exact, 'prefix, or 'suffix, depending on the kind of search
 path definition to be returned."
@@ -205,15 +205,15 @@ path definition to be returned."
                      (environment-variable-definition variable value
                                                       #:separator sep
                                                       #:kind kind))))
-                (evaluate-search-paths search-paths (list profile)
+                (evaluate-search-paths search-paths profiles
                                        getenv))))
 
-(define* (display-search-paths entries profile
+(define* (display-search-paths entries profiles
                                #:key (kind 'exact))
   "Display the search path environment variables that may need to be set for
 ENTRIES, a list of manifest entries, in the context of PROFILE."
-  (let* ((profile  (user-friendly-profile profile))
+  (let* ((profiles (map user-friendly-profile profiles))
-         (settings (search-path-environment-variables entries profile
+         (settings (search-path-environment-variables entries profiles
                                                       #:kind kind)))
     (unless (null? settings)
       (format #t (_ "The following environment variable definitions may be needed:~%"))
@@ -226,8 +226,7 @@ ENTRIES, a list of manifest entries, in the context of PROFILE."
 
 (define %default-options
   ;; Alist of default option values.
-  `((profile . ,%current-profile)
+  `((max-silent-time . 3600)
-    (max-silent-time . 3600)
     (verbosity . 0)
     (substitutes? . #t)))
 
@@ -386,7 +385,7 @@ kind of search path~%")
          (option '(#\p "profile") #t #f
                  (lambda (opt name arg result arg-handler)
                    (values (alist-cons 'profile (canonicalize-profile arg)
-                                       (alist-delete 'profile result))
+                                       result)
                            #f)))
          (option '(#\n "dry-run") #f #f
                  (lambda (opt name arg result arg-handler)
@@ -601,7 +600,7 @@ more information.~%"))
     ;; Process any install/remove/upgrade action from OPTS.
 
     (define dry-run? (assoc-ref opts 'dry-run?))
-    (define profile  (assoc-ref opts 'profile))
+    (define profile  (or (assoc-ref opts 'profile) %current-profile))
 
     (define (build-and-use-profile manifest)
       (let* ((bootstrap?  (assoc-ref opts 'bootstrap?)))
@@ -645,7 +644,7 @@ more information.~%"))
                                     "~a packages in profile~%"
                                     count)
                              count)
-                     (display-search-paths entries profile)))))))))
+                     (display-search-paths entries (list profile))))))))))
 
     ;; First roll back if asked to.
     (cond ((and (assoc-ref opts 'roll-back?)
@@ -709,7 +708,14 @@ more information.~%"))
   (define (process-query opts)
     ;; Process any query specified by OPTS.  Return #t when a query was
     ;; actually processed, #f otherwise.
-    (let ((profile  (assoc-ref opts 'profile)))
+    (let* ((profiles (match (filter-map (match-lambda
+                                          (('profile . p) p)
+                                          (_              #f))
+                                        opts)
+                       (() (list %current-profile))
+                       (lst lst)))
+           (profile  (match profiles
+                       ((head tail ...) head))))
       (match (assoc-ref opts 'query)
         (('list-generations pattern)
          (define (list-generation number)
@@ -793,10 +799,10 @@ more information.~%"))
            #t))
 
         (('search-paths kind)
-         (let* ((manifest (profile-manifest profile))
+         (let* ((manifests (map profile-manifest profiles))
-                (entries  (manifest-entries manifest))
+                (entries   (append-map manifest-entries manifests))
-                (profile  (user-friendly-profile profile))
+                (profiles  (map user-friendly-profile profiles))
-                (settings (search-path-environment-variables entries profile
+                (settings  (search-path-environment-variables entries profiles
                                                               (const #f)
                                                               #:kind kind)))
            (format #t "~{~a~%~}" settings)

tests/guix-package-net.sh

@@ -46,9 +46,10 @@ fi
 
 
 profile="t-profile-$$"
+profile_alt="t-profile-alt-$$"
 rm -f "$profile"
 
-trap 'rm -f "$profile" "$profile-"[0-9]* ; rm -rf t-home-'"$$" EXIT
+trap 'rm -f "$profile" "$profile_alt" "$profile-"[0-9]* ; rm -rf t-home-'"$$" EXIT
 
 
 guix package --bootstrap -p "$profile" -i guile-bootstrap
@@ -156,6 +157,15 @@ guix package -p "$profile" --switch-generation=2
 guix package -p "$profile" --delete-generations=3
 test -z "`guix package -p "$profile" -l 3`"
 
+# Search path of combined profiles.  'LIBRARY_PATH' should show up only in the
+# combination, not in the individual profiles.
+rm "$profile"
+guix package --bootstrap -p "$profile" -i guile-bootstrap
+guix package --bootstrap -p "$profile_alt" -i gcc-bootstrap
+if guix package -p "$profile" --search-paths | grep LIBRARY_PATH
+then false; fi
+guix package -p "$profile" -p "$profile_alt" --search-paths \
+     | grep "LIBRARY_PATH.*$profile/lib"
 
 #
 # Try with the default profile.