Do not store instantiation errors in QQmlComponent

QQmlComponent::createWithInitialProperties() allows to pass non-existent
properties to create the object with. In this case, we still return a
valid pointer (pre-existing), however, the state of the component is
affected: there are errors internally that fail repeated calls even with
valid properties specified. Fix this, aligning to the behavior of
QQmlComponent::createObject() which is a QML counterpart of the same
function (to a degree)

Additionally, make required properties warnings also not break the
component state: if a required property is not set, we return nullptr
instead of object. The error state is affected but it gets cleaned
on the next creation call, allowing one to set the missing required
properties

Unify the logic (with slight deviations) between create() (the
non-incubator-accepting version), createWithInitialProperties() and
createObject() as all they all should do roughly equivalent things

[ChangeLog][QQmlComponent][Important Behavior Changes] Setting properties
via createWithInitialProperties() and setInitialProperties() no longer
affects the QQmlComponent's error state unless there are unset required
properties. A warning is issued when a property could not be set.

Fixes: QTBUG-101439
Change-Id: I814c00bc3715d7a54004c3fcd0af6ee6d50b0726
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 29 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlcomponent_p.h b/src/qml/qml/qqmlcomponent_p.h
index 3edd330ee8..d4a1e10f12 100644
--- a/src/qml/qml/qqmlcomponent_p.h
+++ b/src/qml/qml/qqmlcomponent_p.h
@@ -75,10 +75,31 @@ public:
     bool hadTopLevelRequiredProperties() const;
     QQmlRefPointer<QV4::ExecutableCompilationUnit> compilationUnit;
 
+    struct AnnotatedQmlError
+    {
+        AnnotatedQmlError() = default;
+        AnnotatedQmlError(const QQmlError &error) // convenience ctor
+            : error(error)
+        {
+        }
+        AnnotatedQmlError(const QQmlError &error, bool transient)
+            : error(error), isTransient(transient)
+        {
+        }
+        QQmlError error;
+        bool isTransient = false; // tells if the error is temporary (e.g. unset required property)
+    };
+
     struct ConstructionState {
         std::unique_ptr<QQmlObjectCreator> creator;
-        QList<QQmlError> errors;
+        QList<AnnotatedQmlError> errors;
         bool completePending = false;
+
+        void appendErrors(const QList<QQmlError> &qmlErrors)
+        {
+            for (const QQmlError &e : qmlErrors)
+                errors.emplaceBack(e);
+        }
     };
     ConstructionState state;
 
@@ -103,6 +124,13 @@ public:
     QObject *doBeginCreate(QQmlComponent *q, QQmlContext *context);
     bool setInitialProperty(QObject *component, const QString &name, const QVariant& value);
 
+    enum CreateBehavior {
+        CreateDefault,
+        CreateWarnAboutRequiredProperties,
+    };
+    QObject *createWithProperties(QObject *parent, const QVariantMap &properties,
+                                  QQmlContext *context, CreateBehavior behavior = CreateDefault);
+
     bool isBound() const {
         return compilationUnit->unitData()->flags & QV4::CompiledData::Unit::ComponentsBound;
     }