Allow checking for and catching errors from QJSEngine

As you can manually throw an error, you should be able to catch it
again, too.

Change-Id: I82475df1969a1fd76f4cf5fc0a8d921dfafaef89
Reviewed-by: Maximilian Goldstein <max.goldstein@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 43 insertions, 0 deletions

diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index 96fcd99de4..a0e2cb2c3a 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -927,6 +927,33 @@ void QJSEngine::throwError(QJSValue::ErrorType errorType, const QString &message
 }
 
 /*!
+ * Returns \c true if the last JavaScript execution resulted in an exception or
+ * if throwError() was called. Otherwise returns \c false. Mind that evaluate()
+ * catches any exceptions thrown in the evaluated code.
+ *
+ * \since Qt 6.1
+ */
+bool QJSEngine::hasError() const
+{
+    return m_v4Engine->hasException;
+}
+
+/*!
+ * If an exception is currently pending, catches it and returns it as a
+ * QJSValue. Otherwise returns undefined as QJSValue. After calling this method
+ * hasError() returns \c false.
+ *
+ * \since Qt 6.1
+ */
+QJSValue QJSEngine::catchError()
+{
+    if (m_v4Engine->hasException)
+        return QJSValuePrivate::fromReturnedValue(m_v4Engine->catchException());
+    else
+        return QJSValue();
+}
+
+/*!
   \property QJSEngine::uiLanguage
   \brief the language to be used for translating user interface strings
   \since 5.15
diff --git a/src/qml/jsapi/qjsengine.h b/src/qml/jsapi/qjsengine.h
index 775f9e658a..c480a77599 100644
--- a/src/qml/jsapi/qjsengine.h
+++ b/src/qml/jsapi/qjsengine.h
@@ -121,6 +121,8 @@ public:
 
     void throwError(const QString &message);
     void throwError(QJSValue::ErrorType errorType, const QString &message = QString());
+    bool hasError() const;
+    QJSValue catchError();
 
     QString uiLanguage() const;
     void setUiLanguage(const QString &language);
diff --git a/tests/auto/qml/qjsengine/tst_qjsengine.cpp b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
index 4f2e6f1866..a5316dce21 100644
--- a/tests/auto/qml/qjsengine/tst_qjsengine.cpp
+++ b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
@@ -243,6 +243,7 @@ private slots:
     void throwError();
     void throwErrorObject();
     void returnError();
+    void catchError();
     void mathMinMax();
 
     void importModule();
@@ -4810,6 +4811,19 @@ void tst_QJSEngine::returnError()
     QVERIFY(!result.property("stack").isUndefined());
 }
 
+void tst_QJSEngine::catchError()
+{
+    QJSEngine engine;
+    QVERIFY(!engine.hasError());
+    engine.throwError(QJSValue::GenericError, "some error");
+    QVERIFY(engine.hasError());
+    const QJSValue error = engine.catchError();
+    QVERIFY(error.isError());
+    QCOMPARE(error.errorType(), QJSValue::GenericError);
+    QCOMPARE(error.property("message").toString(), "some error");
+    QVERIFY(!engine.hasError());
+}
+
 QJSValue tst_QJSEngine::throwingCppMethod1()
 {
     qjsEngine(this)->throwError("blub");