services: cuirass: Improve simple-cuirass-services.

Instead of returning multiple services in simple-cuirass-services, rely on the
instantiate-missing-services procedure to instantiate postgresql and
postgresql-role-service-type when missing.

Turn simple-cuirass-services procedure into
simple-cuirass-configuration->specs, that takes a simple-cuirass-configuration
record and returns a Cuirass specification.

Suggested-by: Ludovic Courtès <ludo@gnu.org>

* gnu/services/cuirass.scm (%default-cuirass-config): Remove it.
(simple-cuirass-services): Rename it to ...
(simple-cuirass-configuration->specs): ... this procedure.
* gnu/tests/cuirass.scm (cuirass-services): Remove postgresql and
postgresql-role services that are automatically instantiated.
(simple-cuirass-service): New variable.
(%cuirass-simple-test): Adapt it to use simple-cuirass-configuration->specs
instead of simple-cuirass-services.
* doc/guix.texi (Simple Cuirass): Update it.

doc/guix.texi

@@ -27145,11 +27145,15 @@ The Cuirass package to use.
 @subsubheading Simple Cuirass
 
 The Cuirass service configuration described above can be a little
-intimidating.  The @code{simple-cuirass-services} procedure offers a way
+intimidating.  In particular, getting the right @code{specifications}
-to setup a continuous integration server more readily.
+can prove difficult.  The @code{simple-cuirass-configuration->specs}
+procedure offers a way to generate those @code{specifications} and thus
+setup a continuous integration server more readily.
 
-It takes a @code{simple-cuirass-configuration} record as its first
+@deffn {Scheme Procedure} simple-cuirass-configuration->specs @var{configuration}
-argument.
+This procedure takes a @code{simple-cuirass-configuration} record as
+argument and returns the corresponding Cuirass specifications gexp.
+@end deffn
 
 @deftp {Data Type} simple-cuirass-configuration
 Data type representing the configuration of a simple Cuirass instance.
@@ -27195,13 +27199,16 @@ is re-evaluated each time a commit is pushed in one of the declared
 channels.
 
 @lisp
-(simple-cuirass-services
+(service cuirass-service-type
+         (cuirass-configuration
+          (specifications
+           (simple-cuirass-configuration->specs
             (simple-cuirass-configuration
              (build 'all)
              (channels (cons (channel
                               (name 'my-guix)
                               (url "https://my-git-repo/guix.git"))
-                  %default-channels))))
+                             %default-channels)))))))
 @end lisp
 
 In the same spirit, this builds all the packages that are part of the
@@ -27209,7 +27216,10 @@ In the same spirit, this builds all the packages that are part of the
 located in the @code{conf} channel.
 
 @lisp
-(simple-cuirass-services
+(service cuirass-service-type
+         (cuirass-configuration
+          (specifications
+           (simple-cuirass-configuration->specs
             (simple-cuirass-configuration
              (build (list
                      (build-manifest
@@ -27222,7 +27232,7 @@ located in the @code{conf} channel.
                                (name 'conf)
                                (url "https://my-git-repo/conf.git"))
                               %default-channels))
-  (non-package-channels '(conf))))
+             (non-package-channels '(conf)))))))
 @end lisp
 
 Finally, @code{simple-cuirass-services} takes as a second optional

gnu/services/cuirass.scm

@@ -60,8 +60,7 @@
             simple-cuirass-configuration
             simple-cuirass-configuration?
 
-            %default-cuirass-config
+            simple-cuirass-configuration->specs))
-            simple-cuirass-services))
 
 ;;;; Commentary:
 ;;;
@@ -419,13 +418,7 @@ CONFIG."
   (systems               simple-cuirass-configuration-systems
                          (default (list (%current-system))))) ;list of strings
 
-(define %default-cuirass-config
+(define* (simple-cuirass-configuration->specs config)
-  (cuirass-configuration
-   (specifications #~())))
-
-(define* (simple-cuirass-services config
-                                  #:optional
-                                  (cuirass %default-cuirass-config))
   (define (format-name name)
     (if (string? name)
         name
@@ -475,13 +468,4 @@ CONFIG."
         (#:build-outputs . ())
         (#:priority . 1))))
 
-  (list
+  #~(list '#$(config->spec config)))
-   (service cuirass-service-type
-            (cuirass-configuration
-             (inherit cuirass)
-             (specifications #~(list
-                                '#$(config->spec config)))))
-   (service postgresql-service-type
-            (postgresql-configuration
-             (postgresql postgresql-10)))
-   (service postgresql-role-service-type)))

gnu/tests/cuirass.scm

@@ -132,11 +132,7 @@
              (remote-server (and remote-build?
                                  (cuirass-remote-server-configuration)))
              (host "0.0.0.0")
-             (use-substitutes? #t)))
+             (use-substitutes? #t)))))
-   (service postgresql-service-type
-            (postgresql-configuration
-             (postgresql postgresql-10)))
-   (service postgresql-role-service-type)))
 
 (define (run-cuirass-test name os)
   (define os*
@@ -286,6 +282,20 @@
      (description "Connect to a Cuirass server with remote build.")
      (value (run-cuirass-test name os)))))
 
+(define simple-cuirass-service
+  (service cuirass-service-type
+           (cuirass-configuration
+            (specifications
+             (simple-cuirass-configuration->specs
+              (simple-cuirass-configuration
+               (build 'all)
+               (channels
+                (list (channel
+                       (name 'guix)
+                       (url "file:///tmp/cuirass-main/")))))))
+            (host "0.0.0.0")
+            (use-substitutes? #t))))
+
 (define %cuirass-simple-test
   (let ((os (operating-system
               (inherit %simple-os)
@@ -293,17 +303,8 @@
                (append
                 (list cow-service
                       (service dhcp-client-service-type)
-                      git-service)
+                      git-service
-                (simple-cuirass-services
+                      simple-cuirass-service)
-                 (simple-cuirass-configuration
-                  (build 'all)
-                  (channels (list (channel
-                                   (name 'guix)
-                                   (url "file:///tmp/cuirass-main/")))))
-                 (cuirass-configuration
-                  (inherit %default-cuirass-config)
-                  (host "0.0.0.0")
-                  (use-substitutes? #t)))
                 (operating-system-user-services %simple-os))))))
     (system-test
      (name "cuirass-simple")