[gnome-software] Fix installation of external appstream files

[Joaquim Manuel Pereira Rocha <jrocha src gnome org>]

commit 52c1afd8f5a9adfb85a4f0ceca8d0bec8b39c2c9
Author: Joaquim Rocha <jrocha endlessm com>
Date:   Wed Nov 23 14:49:34 2016 +0100

    Fix installation of external appstream files
    
    The files were being installed with a random prefix which meant they
    were never replaced as every download would have a different name.

 src/plugins/gs-plugin-external-appstream.c |   49 +++++++++++++++++----------
 1 files changed, 31 insertions(+), 18 deletions(-)
---
diff --git a/src/plugins/gs-plugin-external-appstream.c b/src/plugins/gs-plugin-external-appstream.c
index 5827a98..658ea1a 100644
--- a/src/plugins/gs-plugin-external-appstream.c
+++ b/src/plugins/gs-plugin-external-appstream.c
@@ -161,14 +161,27 @@ gs_plugin_external_appstream_refresh_url (GsPlugin *plugin,
                return FALSE;
        }
 
-       /* write the download contents into a temporary file that will be
-        * copied into the system */
-       tmp_file_tmpl = g_strdup_printf ("XXXXXX_%s", file_name);
-       tmp_file = g_file_new_tmp (tmp_file_tmpl, &iostream, error);
-       if (tmp_file == NULL)
+       /* write the download contents into a file that will be copied into
+        * the system */
+       tmp_file_path = gs_utils_get_cache_filename ("external-appstream",
+                                                    file_name,
+                                                    GS_UTILS_CACHE_FLAG_WRITEABLE,
+                                                    error);
+       if (tmp_file_path == NULL)
                return FALSE;
 
-       tmp_file_path = g_file_get_path (tmp_file);
+       tmp_file = g_file_new_for_path (tmp_file_path);
+
+       /* ensure the file doesn't exist */
+       if (g_file_query_exists (tmp_file, cancellable) &&
+           !g_file_delete (tmp_file, cancellable, error))
+               return FALSE;
+
+       iostream = g_file_create_readwrite (tmp_file, G_FILE_CREATE_NONE,
+                                           cancellable, error);
+
+       if (iostream == NULL)
+               return FALSE;
 
        g_debug ("Downloaded appstream file %s", tmp_file_path);
 
@@ -182,20 +195,20 @@ gs_plugin_external_appstream_refresh_url (GsPlugin *plugin,
        /* close the file */
        g_output_stream_close (outstream, cancellable, NULL);
 
-       if (!file_written) {
-               /* clean up the temporary file if we could not write */
-               g_file_delete (tmp_file, NULL, NULL);
-               return FALSE;
-       }
-
        /* install file systemwide */
-       if (!gs_plugin_external_appstream_install (tmp_file_path,
-                                                  cancellable,
-                                                  error))
-               return FALSE;
-       g_debug ("Installed appstream file %s", tmp_file_path);
+       if (file_written) {
+               if (gs_plugin_external_appstream_install (tmp_file_path,
+                                                         cancellable,
+                                                         error)) {
+                       g_debug ("Installed appstream file %s", tmp_file_path);
+               } else {
+                       file_written = FALSE;
+               }
+       }
 
-       return TRUE;
+       /* clean up the temporary file */
+       g_file_delete (tmp_file, cancellable, NULL);
+       return file_written;
 }
 
 gboolean