QML: Let IDs in outer context override bound components' properties

This is necessary to make the usage of such IDs actually safe. If we let
local properties override outer IDs, then adding local properties in
later versions invalidates the ID lookups.

[ChangeLog][QtQml][Important Behavior Changes] In QML documents with
bound components, IDs defined in outer contexts override properties
defined in inner contexts now. This is how qmlcachegen has always
interpreted bound components when generating C++ code, and it is
required to make access to outer IDs actually safe. The interpreter and
JIT have previously preferred inner properties over outer IDs.

Pick-to: 6.6 6.5
Fixes: QTBUG-119162
Change-Id: Ic5d3cc3342b4518d3fde1b800efe1b95d8e8b210
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 26 insertions, 2 deletions

diff --git a/src/qml/jsruntime/qv4qmlcontext.cpp b/src/qml/jsruntime/qv4qmlcontext.cpp
index f032e953b9..7b4e5e7387 100644
--- a/src/qml/jsruntime/qv4qmlcontext.cpp
+++ b/src/qml/jsruntime/qv4qmlcontext.cpp
@@ -269,9 +269,33 @@ ReturnedValue QQmlContextWrapper::getPropertyAndBase(const QQmlContextWrapper *r
         contextGetterFunction = QQmlContextWrapper::lookupScopeObjectProperty;
     }
 
+    QQmlRefPointer<QQmlContextData> outer = context;
     while (context) {
-        if (auto property = searchContextProperties(v4, context, name, hasProperty, base, lookup, originalLookup, ep))
-            return *property;
+        if (outer == context) {
+            if (auto property = searchContextProperties(
+                        v4, context, name, hasProperty, base, lookup, originalLookup, ep)) {
+                return *property;
+            }
+
+            outer = outer->parent();
+
+            if (const auto cu = context->typeCompilationUnit(); cu && cu->componentsAreBound()) {
+                // If components are bound in this CU, we can search the whole context hierarchy
+                // of the file. Bound components' contexts override their local properties.
+                // You also can't instantiate bound components outside of their creation
+                // context. Therefore this is safe.
+
+                for (;
+                     outer && outer->typeCompilationUnit() == cu;
+                     outer = outer->parent()) {
+                    if (auto property = searchContextProperties(
+                                v4, outer, name, hasProperty, base,
+                                nullptr, originalLookup, ep)) {
+                        return *property;
+                    }
+                }
+            }
+        }
 
         // Search scope object
         if (scopeObject) {