[gnome-software] appstream: Support loading appstream files from custom install prefix

[Philip Withnall <pwithnall src gnome org>]

commit 080b622a794e2f99dcfb7597704997ec3fb28c0a
Author: Philip Withnall <withnall endlessm com>
Date:   Tue Jun 2 10:58:05 2020 +0100

    appstream: Support loading appstream files from custom install prefix
    
    This is useful for when developing in a custom prefix, such as with
    JHBuild.
    
    In particular, it means that modifications to
    `org.gnome.software.Featured.xml` can be tested without installing to
    `/`.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 plugins/core/gs-plugin-appstream.c | 47 +++++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 8 deletions(-)
---
diff --git a/plugins/core/gs-plugin-appstream.c b/plugins/core/gs-plugin-appstream.c
index 96d189ec..743c0c61 100644
--- a/plugins/core/gs-plugin-appstream.c
+++ b/plugins/core/gs-plugin-appstream.c
@@ -499,21 +499,46 @@ gs_plugin_appstream_check_silo (GsPlugin *plugin,
        } else {
                /* add search paths */
                g_ptr_array_add (parent_appstream,
-                                g_build_filename ("/usr/share", "app-info", "xmls", NULL));
+                                g_build_filename (DATADIR, "app-info", "xmls", NULL));
                g_ptr_array_add (parent_appstream,
-                                g_build_filename ("/usr/share", "app-info", "yaml", NULL));
+                                g_build_filename (DATADIR, "app-info", "yaml", NULL));
                g_ptr_array_add (parent_appdata,
-                                g_build_filename ("/usr/share", "appdata", NULL));
+                                g_build_filename (DATADIR, "appdata", NULL));
                g_ptr_array_add (parent_appdata,
-                                g_build_filename ("/usr/share", "metainfo", NULL));
+                                g_build_filename (DATADIR, "metainfo", NULL));
                g_ptr_array_add (parent_appstream,
-                                g_build_filename ("/var/cache", "app-info", "xmls", NULL));
+                                g_build_filename (LOCALSTATEDIR, "cache", "app-info", "xmls", NULL));
                g_ptr_array_add (parent_appstream,
-                                g_build_filename ("/var/cache", "app-info", "yaml", NULL));
+                                g_build_filename (LOCALSTATEDIR, "cache", "app-info", "yaml", NULL));
                g_ptr_array_add (parent_appstream,
-                                g_build_filename ("/var/lib", "app-info", "xmls", NULL));
+                                g_build_filename (LOCALSTATEDIR, "lib", "app-info", "xmls", NULL));
                g_ptr_array_add (parent_appstream,
-                                g_build_filename ("/var/lib", "app-info", "yaml", NULL));
+                                g_build_filename (LOCALSTATEDIR, "lib", "app-info", "yaml", NULL));
+
+               /* Add the normal system directories if the installation prefix
+                * is different from normal — typically this happens when doing
+                * development builds. It’s useful to still list the system apps
+                * during development. */
+               if (g_strcmp0 (DATADIR, "/usr/share") != 0) {
+                       g_ptr_array_add (parent_appstream,
+                                        g_build_filename ("/usr/share", "app-info", "xmls", NULL));
+                       g_ptr_array_add (parent_appstream,
+                                        g_build_filename ("/usr/share", "app-info", "yaml", NULL));
+                       g_ptr_array_add (parent_appdata,
+                                        g_build_filename ("/usr/share", "appdata", NULL));
+                       g_ptr_array_add (parent_appdata,
+                                        g_build_filename ("/usr/share", "metainfo", NULL));
+               }
+               if (g_strcmp0 (LOCALSTATEDIR, "/var") != 0) {
+                       g_ptr_array_add (parent_appstream,
+                                        g_build_filename ("/var", "cache", "app-info", "xmls", NULL));
+                       g_ptr_array_add (parent_appstream,
+                                        g_build_filename ("/var", "cache", "app-info", "yaml", NULL));
+                       g_ptr_array_add (parent_appstream,
+                                        g_build_filename ("/var", "lib", "app-info", "xmls", NULL));
+                       g_ptr_array_add (parent_appstream,
+                                        g_build_filename ("/var", "lib", "app-info", "yaml", NULL));
+               }
 
                /* import all files */
                for (guint i = 0; i < parent_appstream->len; i++) {
@@ -529,6 +554,12 @@ gs_plugin_appstream_check_silo (GsPlugin *plugin,
                                return FALSE;
                }
                if (!gs_plugin_appstream_load_desktop (plugin, builder,
+                                                      DATADIR "/applications",
+                                                      cancellable, error)) {
+                       return FALSE;
+               }
+               if (g_strcmp0 (DATADIR, "/usr/share") != 0 &&
+                   !gs_plugin_appstream_load_desktop (plugin, builder,
                                                       "/usr/share/applications",
                                                       cancellable, error)) {
                        return FALSE;