upstream: Add new GNOME updater.

Partly fixes <https://bugs.gnu.org/28159>.
Reported by Hartmut Goebel <h.goebel@crazy-compilers.com>.

* guix/import/gnome.scm: New file.
* Makefile.am (MODULES): Add it.
* guix/gnu-maintenance.scm (latest-gnome-release)
(%gnome-updater): Remove.

Makefile.am

@@ -151,6 +151,7 @@ MODULES =					\
   guix/import/hackage.scm			\
   guix/import/elpa.scm   			\
   guix/import/texlive.scm   			\
+  guix/import/gnome.scm				\
   guix/scripts.scm				\
   guix/scripts/download.scm			\
   guix/scripts/perform-download.scm		\

guix/gnu-maintenance.scm

@@ -61,7 +61,6 @@
 
             %gnu-updater
             %gnu-ftp-updater
-            %gnome-updater
             %kde-updater
             %xorg-updater
             %kernel.org-updater))
@@ -512,6 +511,9 @@ list available from %GNU-FILE-LIST-URI over HTTP(S)."
         (values name+version #f)
         (values (match:substring match 1) (match:substring match 2)))))
 
+(define gnome-package?
+  (url-prefix-predicate "mirror://gnome/"))
+
 (define (pure-gnu-package? package)
   "Return true if PACKAGE is a non-Emacs and non-GNOME GNU package.  This
 excludes AucTeX, for instance, whose releases are now uploaded to
@@ -525,49 +527,6 @@ releases are on gnu.org."
 (define gnu-hosted?
   (url-prefix-predicate "mirror://gnu/"))
 
-(define gnome-package?
-  (url-prefix-predicate "mirror://gnome/"))
-
-(define (latest-gnome-release package)
-  "Return the latest release of PACKAGE, the name of a GNOME package."
-  (define %not-dot
-    (char-set-complement (char-set #\.)))
-
-  (define (even-minor-version? version)
-    (match (string-tokenize version %not-dot)
-      (((= string->number major) (= string->number minor) . rest)
-       (and minor (even? minor)))
-      (_
-       #t)))                                      ;cross fingers
-
-  (define (even-numbered? file)
-    ;; Return true if FILE somehow denotes an even-numbered file name.  The
-    ;; trick here is that we want this to match both directories such as
-    ;; "3.18.6" and actual file names such as "gtk+-3.18.6.tar.bz2".
-    (let-values (((name version) (package-name->name+version file)))
-      (even-minor-version? (or version name))))
-
-  (define upstream-name
-    ;; Some packages like "NetworkManager" have camel-case names.
-    (package-upstream-name package))
-
-  (false-if-ftp-error
-   (latest-ftp-release upstream-name
-                       #:server "ftp.gnome.org"
-                       #:directory (string-append "/pub/gnome/sources/"
-                                                  upstream-name)
-
-
-                       ;; <https://www.gnome.org/gnome-3/source/> explains
-                       ;; that odd minor version numbers represent development
-                       ;; releases, which we are usually not interested in.
-                       #:keep-file? even-numbered?
-
-                       ;; ftp.gnome.org provides no signatures, only
-                       ;; checksums.
-                       #:file->signature (const #f))))
-
-
 (define (latest-kde-release package)
   "Return the latest release of PACKAGE, the name of an KDE.org package."
   (let ((uri (string->uri (origin-uri (package-source package)))))
@@ -624,13 +583,6 @@ releases are on gnu.org."
                 (pure-gnu-package? package))))
    (latest latest-release*)))
 
-(define %gnome-updater
-  (upstream-updater
-   (name 'gnome)
-   (description "Updater for GNOME packages")
-   (pred gnome-package?)
-   (latest latest-gnome-release)))
-
 (define %kde-updater
   (upstream-updater
     (name 'kde)

guix/import/gnome.scm

@@ -0,0 +1,112 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2017 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix import gnome)
+  #:use-module (guix upstream)
+  #:use-module (guix utils)
+  #:use-module (guix packages)
+  #:use-module (guix http-client)
+  #:use-module (json)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-11)
+  #:use-module (srfi srfi-34)
+  #:use-module (web uri)
+  #:use-module (ice-9 match)
+  #:export (%gnome-updater))
+
+;;; Commentary:
+;;;
+;;; This package provides not an actual importer but simply an updater for
+;;; GNOME packages.  It grabs package meta-data from 'cache.json' files
+;;; available on ftp.gnome.org.
+;;;
+;;; Code:
+
+(define (jsonish->upstream-source name jsonish)
+  "Return an <upstream-source> object for package NAME, using JSONISH as the
+source for metadata."
+  (match jsonish
+    ((version . dictionary)
+     (upstream-source
+      (package name)
+      (version version)
+      (urls (filter-map (lambda (extension)
+                          (match (hash-ref dictionary extension)
+                            (#f
+                             #f)
+                            ((? string? relative-url)
+                             (string-append "mirror://gnome/sources/"
+                                            name "/" relative-url))))
+                        '("tar.lz" "tar.xz" "tar.bz2" "tar.gz")))))))
+
+(define (latest-gnome-release package)
+  "Return the latest release of PACKAGE, a GNOME package, or #f if it could
+not be determined."
+  (define %not-dot
+    (char-set-complement (char-set #\.)))
+
+  (define (even-minor-version? version)
+    (match (string-tokenize version %not-dot)
+      (((= string->number major) (= string->number minor) . rest)
+       (and minor (even? minor)))
+      (_
+       #t)))                                      ;cross fingers
+
+  (define upstream-name
+    ;; Some packages like "NetworkManager" have camel-case names.
+    (package-upstream-name package))
+
+  (guard (c ((http-get-error? c)
+             (if (= 404 (http-get-error-code c))
+                 #f
+                 (raise c))))
+    (let* ((port (http-fetch/cached
+                  (string->uri (string-append
+                                "https://ftp.gnome.org/pub/gnome/sources/"
+                                upstream-name "/cache.json"))
+
+                  ;; ftp.gnome.org supports 'if-Modified-Since', so the local
+                  ;; cache can expire early.
+                  #:ttl (* 60 10)))
+           (json (json->scm port)))
+      (close-port port)
+      (match json
+        ((4 (? hash-table? releases) _ ...)
+         (let* ((releases (hash-ref releases upstream-name))
+                (latest   (hash-fold (lambda (key value result)
+                                       (cond ((even-minor-version? key)
+                                              (match result
+                                                (#f
+                                                 (cons key value))
+                                                ((newest . _)
+                                                 (if (version>? key newest)
+                                                     (cons key value)
+                                                     result))))
+                                             (else
+                                              result)))
+                                     #f
+                                     releases)))
+           (and latest
+                (jsonish->upstream-source upstream-name latest))))))))
+
+(define %gnome-updater
+  (upstream-updater
+   (name 'gnome)
+   (description "Updater for GNOME packages")
+   (pred (url-prefix-predicate "mirror://gnome/"))
+   (latest latest-gnome-release)))