[gnome-music] grltrackerwrapper: Retrieve MusicBrainz album ids to get cover art

[Jean Felder <jfelder src gnome org>]

commit d5c96d4ef3745d433aea9fe4fa9ecf63251b90d0
Author: Jean Felder <jfelder src gnome org>
Date:   Mon Sep 2 12:29:08 2019 +0200

    grltrackerwrapper: Retrieve MusicBrainz album ids to get cover art
    
    There are two MusicBrainz identifiers associated with an album:
    Release and Release_Group. These tags are supported by Tracker since
    version 2.3.
    
    By updating the queries of `_get_album_for_song_id` and
    `_get_album_for_album_id` to retrieve those identifiers, it is now
    possible to use grl-musicbrainz-coverart plugin to download an album's
    cover art from https://coverartarchive.org/ website.
    
    This change also depends on grilo-plugins version 0.3.10 which adds
    support for tracker:ExternalReference in the Tracker plugin.
    
    This work (Tracker and grilo-plugins support) was done by Sumaid Syed
    as part as a Google Summer of Code project.
    
    Closes: #205

 gnomemusic/coregrilo.py                       |  3 ++-
 gnomemusic/grilowrappers/grltrackerwrapper.py | 26 ++++++++++++++++++++++++++
 meson.build                                   |  2 +-
 3 files changed, 29 insertions(+), 2 deletions(-)
---
diff --git a/gnomemusic/coregrilo.py b/gnomemusic/coregrilo.py
index e2001bf2..0d34dc34 100644
--- a/gnomemusic/coregrilo.py
+++ b/gnomemusic/coregrilo.py
@@ -43,7 +43,8 @@ class CoreGrilo(GObject.GObject):
         'grl-spotify-cover'
     ]
 
-    _grl_plugin_ranks = ("grl-lastfm-cover:2,"
+    _grl_plugin_ranks = ("grl-musicbrainz-coverart:3,"
+                         "grl-lastfm-cover:2,"
                          "grl-theaudiodb-cover:1")
 
     _theaudiodb_api_key = "195003"
diff --git a/gnomemusic/grilowrappers/grltrackerwrapper.py b/gnomemusic/grilowrappers/grltrackerwrapper.py
index ace4bb61..ceb8242e 100644
--- a/gnomemusic/grilowrappers/grltrackerwrapper.py
+++ b/gnomemusic/grilowrappers/grltrackerwrapper.py
@@ -834,6 +834,9 @@ class GrlTrackerWrapper(GObject.GObject):
         SELECT DISTINCT
             rdf:type(?album)
             tracker:id(?album) AS ?id
+            tracker:referenceIdentifier(?release_group_id)
+                AS ?mb_release_group_id
+            tracker:referenceIdentifier(?release_id) AS ?mb_release_id
             tracker:coalesce(nmm:artistName(?album_artist),
                              nmm:artistName(?song_artist)) AS ?artist
             nie:title(?album) AS ?album
@@ -842,6 +845,16 @@ class GrlTrackerWrapper(GObject.GObject):
             ?song a nmm:MusicPiece ;
                     nmm:musicAlbum ?album ;
                     nmm:performer ?song_artist .
+            OPTIONAL {
+                ?album tracker:hasExternalReference ?release_group_id .
+                ?release_group_id tracker:referenceSource
+                    "https://musicbrainz.org/doc/Release_Group"; .
+            }
+            OPTIONAL {
+                ?album tracker:hasExternalReference ?release_id .
+                ?release_id tracker:referenceSource
+                    "https://musicbrainz.org/doc/Release"; .
+            }
             OPTIONAL { ?album nmm:albumArtist ?album_artist . }
             FILTER (
                 tracker:id(?album) = %(album_id)s
@@ -861,6 +874,9 @@ class GrlTrackerWrapper(GObject.GObject):
         SELECT DISTINCT
             rdf:type(?album)
             tracker:id(?album) AS ?id
+            tracker:referenceIdentifier(?release_group_id)
+                AS ?mb_release_group_id
+            tracker:referenceIdentifier(?release_id) AS ?mb_release_id
             tracker:coalesce(nmm:artistName(?album_artist),
                              nmm:artistName(?song_artist)) AS ?artist
             nie:title(?album) AS ?album
@@ -868,6 +884,16 @@ class GrlTrackerWrapper(GObject.GObject):
             ?song a nmm:MusicPiece ;
                     nmm:musicAlbum ?album ;
                     nmm:performer ?song_artist .
+            OPTIONAL {
+                ?album tracker:hasExternalReference ?release_group_id .
+                ?release_group_id tracker:referenceSource
+                    "https://musicbrainz.org/doc/Release_Group"; .
+            }
+            OPTIONAL {
+                ?album tracker:hasExternalReference ?release_id .
+                ?release_id tracker:referenceSource
+                    "https://musicbrainz.org/doc/Release"; .
+            }
             OPTIONAL { ?album nmm:albumArtist ?album_artist . }
             FILTER (
                 tracker:id(?song) = %(song_id)s
diff --git a/meson.build b/meson.build
index 23aa7612..bb147bdc 100644
--- a/meson.build
+++ b/meson.build
@@ -46,7 +46,7 @@ dependency('tracker-sparql-2.0', version: '>= 2.3.0')
 dependency('pygobject-3.0', version: '>= 3.29.1')
 dependency('py3cairo', version: '>= 1.14.0')
 dependency('grilo-0.3', version: '>= 0.3.9')
-dependency('grilo-plugins-0.3', version: '>= 0.3.9')
+dependency('grilo-plugins-0.3', version: '>= 0.3.10')
 
 subproject('libgd',
     default_options: [