Fix "Expression depends on non-NOTIFYable properties" regression

CONSTANT properties are by nature non-NOTIFYable.

The issue behind the regression is caused by the fact that we were
capturing a property regardless of whether or not it was const.
There were two states that captureRequired was expressing:

true: We're reading the property of a QObject, and we're not quite sure
where the QObject comes from or what it is. So, when reading that
property at run-time, make sure that we capture where we read that
property so that if it changes we can re-evaluate the entire
expression.

false: We're reading the property of a QObject, and we know that it's
the scope object or context object, which we know very well. Instead of
registering a property capture every time, we can do that ahead of time
and then register all those captures in one shot in
registerQmlDependencies().

There is a third state that is only relevant when captureRequired is
false: We're reading a property from the scope or context object, but
it's a CONSTANT property, so we don't need to register a dependency
at all.

This patch adds replaces captureRequired with the PropertyCapturePolicy
enum, which accounts for the third state and, as a bonus, makes the
code easier to understand.

Task-number: QTBUG-66361
Change-Id: I6cef1deb76538fbdacf1324b4467403dd40dd7de
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

2 files changed, 18 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlecmascript/data/nonNotifyableConstant.qml b/tests/auto/qml/qqmlecmascript/data/nonNotifyableConstant.qml
new file mode 100644
index 0000000000..424b3e8b07
--- /dev/null
+++ b/tests/auto/qml/qqmlecmascript/data/nonNotifyableConstant.qml
@@ -0,0 +1,5 @@
+import Qt.test 1.0
+
+MyQmlObject {
+    objectName: trueProperty ? "foo" : "bar"
+}
diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index b7d5db9914..5e752d124b 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -261,6 +261,7 @@ private slots:
     void doubleEvaluate();
     void forInLoop();
     void nonNotifyable();
+    void nonNotifyableConstant();
     void deleteWhileBindingRunning();
     void callQtInvokables();
     void resolveClashingProperties();
@@ -6889,6 +6890,18 @@ void tst_qqmlecmascript::nonNotifyable()
     delete object;
 }
 
+void tst_qqmlecmascript::nonNotifyableConstant()
+{
+    QQmlComponent component(&engine, testFileUrl("nonNotifyableConstant.qml"));
+    QQmlTestMessageHandler messageHandler;
+
+    // Shouldn't produce an error message about non-NOTIFYable properties,
+    // as the property has the CONSTANT attribute.
+    QScopedPointer<QObject> object(component.create());
+    QVERIFY(object);
+    QCOMPARE(messageHandler.messages().size(), 0);
+}
+
 void tst_qqmlecmascript::forInLoop()
 {
     QQmlComponent component(&engine, testFileUrl("forInLoop.qml"));