Log errors in QQmlComponent

Add logging to QQmlComponent::create(). For instance, this handles
cases when errors (non-logged) occur before the QQmlObjectCreator.
What would typically be written is
"QQmlComponent: Component is not ready", which is, well, not helpful

Change-Id: Ia7aabe68d8f42f64b00528a3559830f54a3821d8
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index d1aa2a09db..7d9261604e 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -64,12 +64,15 @@
 #include <QStringList>
 #include <QThreadStorage>
 #include <QtCore/qdebug.h>
+#include <QtCore/qloggingcategory.h>
 #include <qqmlinfo.h>
 
 namespace {
     QThreadStorage<int> creationDepth;
 }
 
+Q_LOGGING_CATEGORY(lcQmlComponentGeneral, "qt.qml.qmlcomponent")
+
 QT_BEGIN_NAMESPACE
 
 class QQmlComponentExtension : public QV4::ExecutionEngine::Deletable
@@ -890,6 +893,12 @@ QObject *QQmlComponent::beginCreate(QQmlContext *publicContext)
 QObject *QQmlComponentPrivate::beginCreate(QQmlRefPointer<QQmlContextData> context)
 {
     Q_Q(QQmlComponent);
+    auto cleanup = qScopeGuard([this] {
+        if (!state.errors.isEmpty()) {
+            for (const auto &e : qAsConst(state.errors))
+                qCDebug(lcQmlComponentGeneral) << "QQmlComponent: " << e.toString();
+        }
+    });
     if (!context) {
         qWarning("QQmlComponent: Cannot create a component in a null context");
         return nullptr;