Add a hack to block calls to certain introspected functions

This is useful for keeping people from using methods that only fail in
certain circumstances, by making them fail in all circumstances
instead.

https://bugzilla.gnome.org/show_bug.cgi?id=618918

src/shell-global.c

@@ -1327,3 +1327,68 @@ shell_global_create_app_launch_context (ShellGlobal *global)
 
   return (GAppLaunchContext *)context;
 }
+
+/**
+ * shell_global_set_property_mutable:
+ * @global: the #ShellGlobal
+ * @object: the "path" to a JS object, starting from the root object.
+ *  (Eg, "global.stage" or "imports.gi.Gtk.Window.prototype")
+ * @property: a property on @object
+ * @mutable: %TRUE or %FALSE
+ *
+ * If @mutable is %TRUE, this clears the "permanent" and "readonly" flags
+ * on @property of @object. If @mutable is %FALSE, it sets them.
+ *
+ * You can use this to make it possible to modify properties that
+ * would otherwise be read-only from JavaScript.
+ *
+ * Return value: success or failure.
+ */
+gboolean
+shell_global_set_property_mutable (ShellGlobal *global,
+                                   const char  *object,
+                                   const char  *property,
+                                   gboolean     mutable)
+{
+  JSContext *context = gjs_context_get_native_context (global->js_context);
+  char **parts;
+  JSObject *obj;
+  jsval val = JSVAL_VOID;
+  int i;
+  jsuint attrs;
+  JSBool found;
+
+  JS_AddRoot (context, &val);
+
+  parts = g_strsplit (object, ".", -1);
+  obj = JS_GetGlobalObject (context);
+  for (i = 0; parts[i]; i++)
+    {
+      if (!JS_GetProperty (context, obj, parts[i], &val))
+        {
+          g_strfreev (parts);
+          JS_RemoveRoot (context, &val);
+          gjs_log_exception (context, NULL);
+          return FALSE;
+        }
+      obj = JSVAL_TO_OBJECT (val);
+    }
+  g_strfreev (parts);
+
+  if (!JS_GetPropertyAttributes (context, obj, property, &attrs, &found) || !found)
+    {
+      JS_RemoveRoot (context, &val);
+      gjs_log_exception (context, NULL);
+      return FALSE;
+    }
+
+  if (mutable)
+    attrs &= ~(JSPROP_PERMANENT | JSPROP_READONLY);
+  else
+    attrs |= (JSPROP_PERMANENT | JSPROP_READONLY);
+
+  JS_SetPropertyAttributes (context, obj, property, attrs, &found);
+
+  JS_RemoveRoot (context, &val);
+  return !gjs_log_exception (context, NULL);
+}

src/shell-global.h

@@ -96,6 +96,11 @@ guint32 shell_global_get_current_time (ShellGlobal *global);
 
 GAppLaunchContext *shell_global_create_app_launch_context (ShellGlobal *global);
 
+gboolean shell_global_set_property_mutable (ShellGlobal *global,
+                                            const char  *object,
+                                            const char  *property,
+                                            gboolean     mutable);
+
 G_END_DECLS
 
 #endif /* __SHELL_GLOBAL_H__ */