Fix edge case in signal emission semantics

Signal emission triggered by property changes during an onDestruction
handler was previously not well tested.  This commit adds several
unit tests to ensure correct behaviour in that situation.

Those unit tests showed a problem in signal emission related to when
children objects are cleaned up.  This commit also ensures that if
such children own their own context, their onDestruction handlers
are called prior to marking the child as deleted.

Change-Id: Ibf84ae56ba1134e5d6402b742aee1bdc0e5e4e15
Reviewed-by: Matthew Vogt <matthew.vogt@nokia.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlecmascript/data/signalEmitted.3.qml b/tests/auto/qml/qqmlecmascript/data/signalEmitted.3.qml
new file mode 100644
index 0000000000..0cae5c02d8
--- /dev/null
+++ b/tests/auto/qml/qqmlecmascript/data/signalEmitted.3.qml
@@ -0,0 +1,34 @@
+import QtQuick 2.0
+import Qt.test 1.0 as ModApi
+
+Item {
+    id: root
+
+    property bool success: false
+    property bool c1HasBeenDestroyed: false
+
+    property Item c1 // not a js reference, so won't keep it alive
+
+    SignalEmittedComponent {
+        id: c2
+        property int c1a: if (root.c1) root.c1.a; else 0; // will change during onDestruction handler of c1.
+        function c1aChangedHandler() {
+            // this should still be called, after c1 has been destroyed by gc,
+            // because the onDestruction handler of c1 will be triggered prior
+            // to when c1 will be invalidated.
+            if (root.c1HasBeenDestroyed && c1a == 20) root.c1.setSuccessPropertyOf(root, true);
+        }
+    }
+
+    Component.onCompleted: {
+        // dynamically construct sibling.  When it goes out of scope, it should be gc'd.
+        // note that the gc() will call weakqobjectcallback which will set queued for
+        // deletion flag -- thus QQmlData::wasDeleted() will return true for that object..
+        var c = Qt.createComponent("SignalEmittedComponent.qml", root);
+        var o = c.createObject(null); // JS ownership
+        o.onAChanged.connect(c2.c1aChangedHandler);
+        c1 = o;
+        c1HasBeenDestroyed = true;
+        // return to event loop.
+    }
+}