Start computing channel instance derivations for multiple systems

These aren't stored yet, but this is a start.

guix-data-service/jobs/load-new-guix-revision.scm

@@ -714,14 +714,14 @@ WHERE job_id = $1"
        (build-derivations store (list derivation))))
     (derivation->output-path derivation)))
 
-(define (channel->derivation-file-name store channel)
+(define (channel->derivation-file-names-by-system store channel)
   (define use-container? (defined?
                            'open-inferior/container
                            (resolve-module '(guix inferior))))
 
-  (define inferior-code
+  (define (inferior-code channel-instance systems)
     `(lambda (store)
-       (let ((instances
+       (let* ((instances
                (list
                 (channel-instance
                  (channel (name ',(channel-name channel))
@@ -730,12 +730,70 @@ WHERE job_id = $1"
                           (commit ,(channel-commit channel)))
                  ,(channel-instance-commit channel-instance)
                  ,(channel-instance-checkout channel-instance)))))
+         (map
+          (lambda (system)
+            (log-time
+             (simple-format
+              #f "computing the derivation-file-name for ~A"
+              system)
+             (lambda ()
+               (with-store store
+                 ((set-current-system system) store)
+                 (let ((manifest
+                        (catch #t
+                          (lambda ()
+                            ((channel-instances->manifest instances) store))
+                          (lambda (key . args)
+                            (simple-format
+                             (current-error-port)
+                             "error: while computing manifest entry derivation for ~A\n"
+                             system)
+                            (simple-format
+                             (current-error-port)
+                             "error ~A: ~A\n" key args)
+                            #f))))
+                   `(,system
+                     .
+                     ((manifest-entry-item
+                       . ,(and manifest
+                               (derivation-file-name
+                                (manifest-entry-item
+                                 (first
+                                  (manifest-entries manifest))))))
+                      (profile
+                       . ,(catch #t
+                            (lambda ()
+                              (and manifest
+                                   (derivation-file-name
                                     (run-with-store store
-           (mlet* %store-monad ((manifest (channel-instances->manifest
+                                      (profile-derivation
-                                           instances))
+                                       manifest
-                                (derv (profile-derivation manifest)))
+                                       #:hooks %channel-profile-hooks)))))
-             (mbegin %store-monad
+                            (lambda (key . args)
-               (return (derivation-file-name derv))))))))
+                              (simple-format
+                               (current-error-port)
+                               "error: while computing profile derivation for ~A\n"
+                               system)
+                              (simple-format
+                               (current-error-port)
+                               "error ~A: ~A\n" key args)
+                              #f))))))))))
+          (list ,@systems)))))
+
+  (let ((inferior
+         (if use-container?
+             (open-inferior/container
+              store
+              (guix-store-path store)
+              #:extra-shared-directories
+              '("/gnu/store")
+              #:extra-environment-variables
+              (list (string-append
+                     "SSL_CERT_DIR=" (nss-certs-store-path store))))
+             (begin
+               (simple-format #t "debug: using open-inferior\n")
+               (open-inferior (guix-store-path store)
+                              #:error-port (real-error-port))))))
 
     (define (start-inferior-and-return-derivation-file-names)
       ;; /etc is only missing if open-inferior/container has been used
@@ -756,38 +814,30 @@ WHERE job_id = $1"
              (first
               (latest-channel-instances store
                                         (list channel)))))
-      (inferior-eval '(use-modules (guix channels)
+        (inferior-eval '(use-modules (srfi srfi-1)
+                                     (guix channels)
+                                     (guix grafts)
                                      (guix profiles))
                        inferior)
+        (inferior-eval '(when (defined? '%graft?) (%graft? #f))
+                       inferior)
         (inferior-eval '(define channel-instance
                           (@@ (guix channels) channel-instance))
                        inferior)
 
-      (let ((result
+        (let* ((systems
+                (inferior-eval '(@ (guix packages) %supported-systems)
+                               inferior))
+               (result
                 (inferior-eval-with-store
                  inferior
                  store
-              inferior-code)))
+                 (inferior-code channel-instance systems))))
 
           (close-inferior inferior)
 
           result)))
 
-  (let ((inferior
-         (if use-container?
-             (open-inferior/container
-              store
-              (guix-store-path store)
-              #:extra-shared-directories
-              '("/gnu/store")
-              #:extra-environment-variables
-              (list (string-append
-                     "SSL_CERT_DIR=" (nss-certs-store-path store))))
-             (begin
-               (simple-format #t "debug: using open-inferior\n")
-               (open-inferior (guix-store-path store)
-                              #:error-port (real-error-port))))))
-
     (catch
       #t
       (lambda ()
@@ -797,14 +847,14 @@ WHERE job_id = $1"
             (display (backtrace) (current-error-port))
             (display "\n" (current-error-port))
             (simple-format (current-error-port)
-                           "error: channel->derivation-file-name: ~A: ~A\n"
+                           "error: channel->derivation-file-names-by-system: ~A: ~A\n"
                            key parameters))))
       (lambda args
         (close-inferior inferior)
         #f))))
 
 (define (channel->manifest-store-item conn store channel)
-  (let* ((manifest-store-item-derivation-file-name
+  (let* ((derivation-file-names-by-system
           (log-time
            "computing the channel derivation"
            (lambda ()
@@ -814,12 +864,20 @@ WHERE job_id = $1"
               conn
               'channel->manifest-store-item
               (lambda ()
-                (channel->derivation-file-name store channel))))))
+                (channel->derivation-file-names-by-system store channel))))))
          (derivation
-          (read-derivation-from-file manifest-store-item-derivation-file-name)))
+          (read-derivation-from-file (assoc-ref
+                                      (assoc-ref derivation-file-names-by-system
+                                                 (%current-system))
+                                      'profile))))
+    (for-each
+     (match-lambda
+       ((system . derivation-file-name)
         (simple-format (current-error-port)
-                   "debug: channel dervation: ~A\n"
+                       "debug: ~A: channel dervation: ~A\n"
-                   manifest-store-item-derivation-file-name)
+                       system
+                       derivation-file-name)))
+     derivation-file-names-by-system)
     (log-time
      "building the channel derivation"
      (lambda ()