[gcab/wip/hughsie/future: 16/18] trivial: Return a proper GError if trying to write an unsupported file

[Richard Hughes <rhughes src gnome org>]

commit 2b6f24e1617346628472e282c8e6421a5dcae9d4
Author: Richard Hughes <richard hughsie com>
Date:   Wed Dec 13 21:42:16 2017 +0000

    trivial: Return a proper GError if trying to write an unsupported file

 libgcab/gcab-cabinet.c |   16 ++++++++++++++--
 1 files changed, 14 insertions(+), 2 deletions(-)
---
diff --git a/libgcab/gcab-cabinet.c b/libgcab/gcab-cabinet.c
index ebe486e..975d747 100644
--- a/libgcab/gcab-cabinet.c
+++ b/libgcab/gcab-cabinet.c
@@ -235,8 +235,20 @@ gcab_cabinet_write (GCabCabinet *self,
     g_return_val_if_fail (G_IS_SEEKABLE (out), FALSE);
     g_return_val_if_fail (!cancellable || G_IS_CANCELLABLE (cancellable), FALSE);
     g_return_val_if_fail (!error || *error == NULL, FALSE);
-    /* FIXME: current limitation of 1 folder */
-    g_return_val_if_fail (self->folders->len == 1, FALSE);
+
+    /* nothing to do */
+    if (self->folders->len == 0) {
+        g_set_error_literal (error, GCAB_ERROR, GCAB_ERROR_FAILED,
+                             "Cabinet has no added folders");
+        return FALSE;
+    }
+
+    /* unsupported */
+    if (self->folders->len > 1) {
+        g_set_error_literal (error, GCAB_ERROR, GCAB_ERROR_FAILED,
+                             "Cabinet has more than one added folder");
+        return FALSE;
+    }
 
     GCabFolder *cabfolder = g_ptr_array_index (self->folders, 0);
     gsize nfiles = gcab_folder_get_nfiles (cabfolder);