profiles: Add 'manifest-transaction'.

* guix/profiles.scm (<manifest-transaction>): New record-type.
  (manifest-perform-transaction): New procedure.
  (manifest-show-transaction): New procedure.
* tests/profiles.scm ("manifest-perform-transaction"): New test.

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

guix/profiles.scm

@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
+;;; Copyright © 2014 Alex Kost <alezost@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -18,6 +19,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (guix profiles)
+  #:use-module (guix ui)
   #:use-module (guix utils)
   #:use-module (guix records)
   #:use-module (guix derivations)
@@ -26,6 +28,7 @@
   #:use-module (ice-9 match)
   #:use-module (ice-9 regex)
   #:use-module (ice-9 ftw)
+  #:use-module (ice-9 format)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-9)
   #:use-module (srfi srfi-19)
@@ -51,6 +54,13 @@
             manifest-installed?
             manifest-matching-entries
 
+            manifest-transaction
+            manifest-transaction?
+            manifest-transaction-install
+            manifest-transaction-remove
+            manifest-perform-transaction
+            manifest-show-transaction
+
             profile-manifest
             package->manifest-entry
             profile-derivation
@@ -242,6 +252,72 @@ Remove MANIFEST entries that have the same name and output as ENTRIES."
 
   (filter matches? (manifest-entries manifest)))
 
+
+;;;
+;;; Manifest transactions.
+;;;
+
+(define-record-type* <manifest-transaction> manifest-transaction
+  make-manifest-transaction
+  manifest-transaction?
+  (install manifest-transaction-install ; list of <manifest-entry>
+           (default '()))
+  (remove  manifest-transaction-remove  ; list of <manifest-pattern>
+           (default '())))
+
+(define (manifest-perform-transaction manifest transaction)
+  "Perform TRANSACTION on MANIFEST and return new manifest."
+  (let ((install (manifest-transaction-install transaction))
+        (remove  (manifest-transaction-remove transaction)))
+    (manifest-add (manifest-remove manifest remove)
+                  install)))
+
+(define* (manifest-show-transaction store manifest transaction
+                                    #:key dry-run?)
+  "Display what will/would be installed/removed from MANIFEST by TRANSACTION."
+  ;; TODO: Report upgrades more clearly.
+  (let ((install (manifest-transaction-install transaction))
+        (remove  (manifest-matching-entries
+                  manifest (manifest-transaction-remove transaction))))
+    (match remove
+      ((($ <manifest-entry> name version output path _) ..1)
+       (let ((len    (length name))
+             (remove (map (cut format #f "   ~a-~a\t~a\t~a" <> <> <> <>)
+                          name version output path)))
+         (if dry-run?
+             (format (current-error-port)
+                     (N_ "The following package would be removed:~%~{~a~%~}~%"
+                         "The following packages would be removed:~%~{~a~%~}~%"
+                         len)
+                     remove)
+             (format (current-error-port)
+                     (N_ "The following package will be removed:~%~{~a~%~}~%"
+                         "The following packages will be removed:~%~{~a~%~}~%"
+                         len)
+                     remove))))
+      (_ #f))
+    (match install
+      ((($ <manifest-entry> name version output item _) ..1)
+       (let ((len     (length name))
+             (install (map (lambda (name version output item)
+                             (format #f "   ~a-~a\t~a\t~a" name version output
+                                     (if (package? item)
+                                         (package-output store item output)
+                                         item)))
+                           name version output item)))
+         (if dry-run?
+             (format (current-error-port)
+                     (N_ "The following package would be installed:~%~{~a~%~}~%"
+                         "The following packages would be installed:~%~{~a~%~}~%"
+                         len)
+                     install)
+             (format (current-error-port)
+                     (N_ "The following package will be installed:~%~{~a~%~}~%"
+                         "The following packages will be installed:~%~{~a~%~}~%"
+                         len)
+                     install))))
+      (_ #f))))
+
 
 ;;;
 ;;; Profiles.

tests/profiles.scm

@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014 Alex Kost <alezost@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -26,7 +27,7 @@
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-64))
 
-;; Test the (guix profile) module.
+;; Test the (guix profiles) module.
 
 (define %store
   (open-connection))
@@ -122,6 +123,25 @@
            (_ #f))
          (equal? m3 m4))))
 
+(test-assert "manifest-perform-transaction"
+  (let* ((m0 (manifest (list guile-2.0.9 guile-2.0.9:debug)))
+         (t1 (manifest-transaction
+              (install (list guile-1.8.8))
+              (remove (list (manifest-pattern (name "guile")
+                                              (output "debug"))))))
+         (t2 (manifest-transaction
+              (remove (list (manifest-pattern (name "guile")
+                                              (version "2.0.9")
+                                              (output #f))))))
+         (m1 (manifest-perform-transaction m0 t1))
+         (m2 (manifest-perform-transaction m1 t2))
+         (m3 (manifest-perform-transaction m0 t2)))
+    (and (match (manifest-entries m1)
+           ((($ <manifest-entry> "guile" "1.8.8" "out")) #t)
+           (_ #f))
+         (equal? m1 m2)
+         (null? (manifest-entries m3)))))
+
 (test-assert "profile-derivation"
   (run-with-store %store
     (mlet* %store-monad