[gnome-maps/gnome-3-14] Add MAPS_SERVICE environment override

[Jonas Danielsson <jonasdn src gnome org>]

commit 8363ddd8fe6fad6f32c709c96b360bf8fc7f44f4
Author: Jonas Danielsson <jonas threetimestwo org>
Date:   Sat Aug 20 20:36:31 2016 +0200

    Add MAPS_SERVICE environment override

 src/mapSource.js |   18 ++++++++++++++++--
 1 files changed, 16 insertions(+), 2 deletions(-)
---
diff --git a/src/mapSource.js b/src/mapSource.js
index 39323b3..3a0b982 100644
--- a/src/mapSource.js
+++ b/src/mapSource.js
@@ -25,6 +25,7 @@ const Gtk = imports.gi.Gtk;
 const GtkClutter = imports.gi.GtkClutter;
 const Lang = imports.lang;
 const Soup = imports.gi.Soup;
+const System = imports.system;
 
 const Config = imports.config;
 const Path = imports.path;
@@ -87,17 +88,30 @@ function _updateAttributionImage(source) {
     _attributionImage.pixbuf = GdkPixbuf.Pixbuf.new_from_stream(stream, null);
  }
 
+function _getServiceFromFile(filename) {
+    let data = Utils.readFile(filename);
+    if (!data) {
+        log('Failed to open service file: ' + filename);
+        System.exit(1);
+    }
+    _tileService = JSON.parse(data).tiles;
+    return _tileService;
+}
+
 function _createDefaultService() {
     let filename = GLib.build_filenamev([Path.RESOURCE_DIR,
                                          _DEFAULT_SERVICE_FILE]);
-    let data = Utils.readFile(filename);
-    return JSON.parse(data);
+    return _getServiceFromFile(filename);
 }
 
 function _getTileService() {
     if (_tileService)
         return _tileService;
 
+    let serviceOverride = GLib.getenv('MAPS_SERVICE');
+    if (serviceOverride)
+        return _getServiceFromFile(serviceOverride);
+
     let user_agent = 'gnome-maps/' +  Config.PACKAGE_VERSION;
     let session = new Soup.Session({ user_agent : user_agent });
     let msg = Soup.Message.new('GET', _TILE_SERVICE_URL);