[gjs/gjs-1-30: 1/3] object: Don't crash when given a GObject singleton

[Owen Taylor <otaylor src gnome org>]

commit 8f08e8f5f83703fb72db3c49348f9b68b89c56ec
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Thu Jan 12 13:36:48 2012 -0500

    object: Don't crash when given a GObject singleton
    
    Some GObject libraries, like IBus, implement singletons by adding a custom
    construct vfunc, from which they return an existing GObject. This means that
    g_object_newv may not always return a new object. In these cases, returning the
    existing wrapper JS object should be enough to help clients out.

 gi/object.c |   18 +++++++++++++++++-
 1 files changed, 17 insertions(+), 1 deletions(-)
---
diff --git a/gi/object.c b/gi/object.c
index 6fefc61..05988fe 100644
--- a/gi/object.c
+++ b/gi/object.c
@@ -693,6 +693,21 @@ GJS_NATIVE_CONSTRUCTOR_DECLARE(object_instance)
             priv->gobj = g_object_newv(gtype, n_params, params);
             free_g_params(params, n_params);
 
+            if (peek_js_obj(context, priv->gobj) != NULL) {
+                /* g_object_newv returned an object that's already tracked by a JS
+                 * object. Let's assume this is a singleton like IBus.IBus and return
+                 * the existing JS wrapper object.
+                 *
+                 * 'object' has a value that was originally created by
+                 * JS_NewObjectForConstructor in GJS_NATIVE_CONSTRUCTOR_PRELUDE, but
+                 * we're not actually using it, so just let it get collected. Avoiding
+                 * this would require a non-trivial amount of work.
+                 * */
+                object = peek_js_obj(context, priv->gobj);
+
+                goto out;
+            }
+
             g_type_query(gtype, &query);
             JS_updateMallocCounter(context, query.instance_size);
 
@@ -715,9 +730,9 @@ GJS_NATIVE_CONSTRUCTOR_DECLARE(object_instance)
             unthreadsafe_template_for_constructor.gobj = NULL;
 
             g_object_ref_sink(priv->gobj);
+            g_assert(peek_js_obj(context, priv->gobj) == NULL);
         }
 
-        g_assert(peek_js_obj(context, priv->gobj) == NULL);
         set_js_obj(context, priv->gobj, object);
 
 #if DEBUG_DISPOSE
@@ -760,6 +775,7 @@ GJS_NATIVE_CONSTRUCTOR_DECLARE(object_instance)
                                     g_base_info_get_name ( (GIBaseInfo*) priv->info) ));
     }
 
+ out:
     GJS_NATIVE_CONSTRUCTOR_FINISH(object_instance);
 
     return JS_TRUE;