1 files changed, 38 insertions, 2 deletions
diff --git a/gnu/services.scm b/gnu/services.scm
index 8ef1ae7c77..329b7b1513 100644
--- a/gnu/services.scm
+++ b/gnu/services.scm
@@ -23,6 +23,7 @@
   #:use-module (guix store)
   #:use-module (guix records)
   #:use-module (guix profiles)
+  #:use-module (guix discovery)
   #:use-module (guix sets)
   #:use-module (guix ui)
   #:use-module ((guix utils) #:select (source-properties->location))
@@ -49,6 +50,11 @@
             service-type-compose
             service-type-extend
             service-type-default-value
+            service-type-description
+            service-type-location
+
+            %service-type-path
+            fold-service-types
 
             service
             service?
@@ -91,7 +97,8 @@
             %activation-service
             etc-service
 
-            file-union))                      ;XXX: for lack of a better place
+            file-union                        ;XXX: for lack of a better place
+            directory-union))
 
 ;;; Comment:
 ;;;
@@ -145,7 +152,15 @@
 
   ;; Optional default value for instances of this type.
   (default-value service-type-default-value       ;Any
-                 (default &no-default-value)))
+                 (default &no-default-value))
+
+  ;; Meta-data.
+  (description  service-type-description          ;string
+                (default #f))
+  (location     service-type-location             ;<location>
+                (default (and=> (current-source-location)
+                                source-properties->location))
+                (innate)))
 
 (define (write-service-type type port)
   (format port "#<service-type ~a ~a>"
@@ -154,6 +169,27 @@
 
 (set-record-type-printer! <service-type> write-service-type)
 
+(define %distro-root-directory
+  ;; Absolute file name of the module hierarchy.
+  (dirname (search-path %load-path "guix.scm")))
+
+(define %service-type-path
+  ;; Search path for service types.
+  (make-parameter `((,%distro-root-directory . "gnu/services")
+                    (,%distro-root-directory . "gnu/system"))))
+
+(define* (fold-service-types proc seed
+                             #:optional
+                             (modules (all-modules (%service-type-path))))
+  "For each service type exported by one of MODULES, call (PROC RESULT).  SEED
+is used as the initial value of RESULT."
+  (fold-module-public-variables (lambda (object result)
+                                  (if (service-type? object)
+                                      (proc object result)
+                                      result))
+                                '()
+                                modules))
+
 ;; Services of a given type.
 (define-record-type <service>
   (make-service type value)