core: Restart find_object on container update

Before asynchronously descending in the hierarchy, we connect to the
updated signal of this container. If the container is updated, it might
be that this.children changed while we're iterating over it. If that
happens, we restart the foreach loop, but only 10 times. If we still
are interrupted, we give up.

diff --git a/src/rygel/rygel-simple-container.vala b/src/rygel/rygel-simple-container.vala
index 1030882..79fcafd 100644 (file)
--- a/src/rygel/rygel-simple-container.vala
+++ b/src/rygel/rygel-simple-container.vala
@@ -135,21 +135,51 @@ public class Rygel.SimpleContainer : Rygel.MediaContainer,
                                                     Cancellable? cancellable)
                                                     throws Error {
         MediaObject media_object = null;
+        var restart_count = 0;
+        var restart = false;
 
-        foreach (var child in this.children) {
-            if (child.id == id) {
-                media_object = child;
+        do {
+            restart = false;
+            ulong updated_id = 0;
 
-                break;
-            } else if (child is MediaContainer) {
-                var container = child as MediaContainer;
+            foreach (var child in this.children) {
+                if (child.id == id) {
+                    media_object = child;
 
-                media_object = yield container.find_object (id, cancellable);
-                if (media_object != null) {
                     break;
+                } else if (child is MediaContainer) {
+                    updated_id = this.container_updated.connect ( (_, updated) => {
+                        if (updated == this) {
+                            restart = true;
+                            restart_count++;
+
+                            // bail out on first update
+                            this.disconnect (updated_id);
+                            updated_id = 0;
+                        }
+                    });
+
+                    var container = child as MediaContainer;
+                    media_object = yield container.find_object (id, cancellable);
+
+                    if (media_object != null) {
+                        // no need to loop when we've found what we were looking
+                        // for
+                        restart = false;
+
+                        break;
+                    }
+
+                    if (restart) {
+                        break;
+                    }
+
+                    if (updated_id != 0) {
+                        this.disconnect (updated_id);
+                    }
                 }
             }
-        }
+        } while (restart && restart_count < 10);
 
         return media_object;
     }