installer: Use UUIDs in the 'swap-devices' field.

Note: This change requires an updated 'guix' package that contains
Linux-swap support in (gnu build file-systems).

* gnu/installer/parted.scm (user-partitions->configuration): Use UUIDs
in the 'swap-devices' field.
* gnu/installer/newt/final.scm (run-final-page)[wait-for-clients]: New
procedure.   Use it.
* gnu/installer/tests.scm (choose-partitioning): Wait for
'starting-final-step' message and move configuration file dialog
handling to...
(conclude-installation): ... here.  Send over PORT the reply
corresponding to 'starting-final-step'.
* gnu/tests/install.scm (gui-test-program): When ENCRYPTED? is false,
invoke 'swaplabel' in the marionette.
(installation-target-os-for-gui-tests): When ENCRYPTED? is false, except
a fixed UUID.

gnu/installer/newt/final.scm

@@ -29,6 +29,7 @@
   #:use-module (srfi srfi-34)
   #:use-module (srfi srfi-35)
   #:use-module (ice-9 match)
+  #:use-module ((ice-9 rdelim) #:select (read-line))
   #:use-module (newt)
   #:export (run-final-page))
 
@@ -107,6 +108,19 @@ a specific step, or restart the installer."))
     install-ok?))
 
 (define (run-final-page result prev-steps)
+  (define (wait-for-clients)
+    (unless (null? (current-clients))
+      (syslog "waiting with clients before starting final step~%")
+      (send-to-clients '(starting-final-step))
+      (match (select (current-clients) '() '())
+        (((port _ ...) _ _)
+         (read-line port)))))
+
+  ;; Before generating the configuration file, give clients a chance to do
+  ;; things such as changing the swap partition label.
+  (wait-for-clients)
+
+  (syslog "proceeding with final step~%")
   (let* ((configuration   (format-configuration prev-steps result))
          (user-partitions (result-step result 'partition))
          (locale          (result-step result 'locale))

gnu/installer/parted.scm

@@ -1327,7 +1327,12 @@ USER-PARTITIONS, or return nothing."
       ,@(initrd-configuration user-partitions)
       ,@(if (null? swap-devices)
             '()
-            `((swap-devices (list ,@swap-devices))))
+            (let* ((uuids (map (lambda (file)
+                                 (uuid->string (read-partition-uuid file)))
+                               swap-devices)))
+              `((swap-devices (list ,@(map (lambda (uuid)
+                                             `(uuid ,uuid))
+                                           uuids))))))
       ,@(if (null? encrypted-partitions)
             '()
             `((mapped-devices

gnu/installer/tests.scm

@@ -286,8 +286,9 @@ instrumented for further testing."
                                edit-configuration-file))
   "Converse over PORT to choose the partitioning method.  When ENCRYPTED? is
 true, choose full-disk encryption with PASSPHRASE as the LUKS passphrase.
-This conversation goes past the final dialog box that shows the configuration
-file, actually starting the installation process."
+This conversation stops when the user partitions have been formatted, right
+before the installer generates the configuration file and shows it in a dialog
+box."
   (converse port
     ((list-selection (title "Partitioning method")
                      (multiple-choices? #f)
@@ -330,15 +331,29 @@ file, actually starting the installation process."
      #t)
     ((info (title "Preparing partitions") _ ...)
      (values))                                    ;nothing to return
+    ((starting-final-step)
+     ;; Do not return anything.  The reply will be sent by
+     ;; 'conclude-installation' and in the meantime the installer just waits
+     ;; for us, giving us a chance to do things such as changing partition
+     ;; UUIDs before it generates the configuration file.
+     (values))))
+
+(define (conclude-installation port)
+  "Conclude the installation by checking over PORT that we get the generated
+configuration file, accepting it and starting the installation, and then
+receiving the final messages once the 'guix system init' process has
+completed."
+  ;; Assume the previous message received was 'starting-final-step'; here we
+  ;; send the reply to that message, which lets the installer continue.
+  (write #t port)
+  (newline port)
+  (force-output port)
+
+  (converse port
     ((file-dialog (title "Configuration file")
                   (text _)
                   (file ,configuration-file))
-     (edit-configuration-file configuration-file))))
-
-(define (conclude-installation port)
-  "Conclude the installation by checking over PORT that we get the final
-messages once the 'guix system init' process has completed."
-  (converse port
+     (edit-configuration-file configuration-file))
     ((pause)                                      ;"Press Enter to continue."
      #t)
     ((installation-complete)                      ;congratulations!

gnu/tests/install.scm

@@ -1211,6 +1211,16 @@ build (current-guix) and then store a couple of full system images.")
                         #$marionette)
       (screenshot "installer-run.ppm")
 
+      (unless #$encrypted?
+        ;; At this point, user partitions are formatted and the installer is
+        ;; waiting for us to start the final step: generating the
+        ;; configuration file, etc.  Set a fixed UUID on the swap partition
+        ;; that matches what 'installation-target-os-for-gui-tests' expects.
+        (marionette-eval* '(invoke #$(file-append util-linux "/sbin/swaplabel")
+                                   "-U" "11111111-2222-3333-4444-123456789abc"
+                                   "/dev/vda2")
+                          #$marionette))
+
       (marionette-eval* '(conclude-installation installer-socket)
                         #$marionette)
 
@@ -1257,8 +1267,12 @@ build (current-guix) and then store a couple of full system images.")
                            '("wheel" "audio" "video"))))
                    %base-user-accounts))
     ;; The installer does not create a swap device in guided mode with
-    ;; encryption support.
-    (swap-devices (if encrypted? '() '("/dev/vda2")))
+    ;; encryption support.  The installer produces a UUID for the partition;
+    ;; this "UUID" is explicitly set in 'gui-test-program' to the value shown
+    ;; below.
+    (swap-devices (if encrypted?
+                      '()
+                      (list (uuid "11111111-2222-3333-4444-123456789abc"))))
     (services (cons (service dhcp-client-service-type)
                     (operating-system-user-services %minimal-os-on-vda)))))