Don't suppress <log> tags with missing or bad expr

Rather, output an empty string as message in this case. Ignoring log
instructions is highly confusing.

Change-Id: Iebb30ffd3ade33f1277f3073f015127a99170e40
Task-number: QTBUG-71746
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

4 files changed, 33 insertions, 10 deletions

diff --git a/src/scxml/qscxmlexecutablecontent.cpp b/src/scxml/qscxmlexecutablecontent.cpp
index 206809c..45079d7 100644
--- a/src/scxml/qscxmlexecutablecontent.cpp
+++ b/src/scxml/qscxmlexecutablecontent.cpp
@@ -434,18 +434,20 @@ const InstructionId *QScxmlExecutionEngine::step(const InstructionId *ip, bool *
         qCDebug(qscxmlLog) << stateMachine << "Executing log step";
         const Log *log = reinterpret_cast<const Log *>(instr);
         ip += log->size();
+        QString str;
         if (log->expr != NoEvaluator) {
-            const QString str = dataModel->evaluateToString(log->expr, ok);
-            if (*ok) {
-                const QString label = tableData->string(log->label);
-                qCDebug(scxmlLog) << label << ":" << str;
-                QMetaObject::invokeMethod(stateMachine,
-                                          "log",
-                                          Qt::QueuedConnection,
-                                          Q_ARG(QString, label),
-                                          Q_ARG(QString, str));
-            }
+            str = dataModel->evaluateToString(log->expr, ok);
+            if (!*ok)
+                qCWarning(qscxmlLog) << stateMachine << "Could not evaluate <log> expr to string.";
         }
+
+        const QString label = tableData->string(log->label);
+        qCDebug(scxmlLog) << label << ":" << str;
+        QMetaObject::invokeMethod(stateMachine,
+                                  "log",
+                                  Qt::QueuedConnection,
+                                  Q_ARG(QString, label),
+                                  Q_ARG(QString, str));
         return ip;
     }
 
diff --git a/tests/auto/statemachine/emptylog.scxml b/tests/auto/statemachine/emptylog.scxml
new file mode 100644
index 0000000..e31f925
--- /dev/null
+++ b/tests/auto/statemachine/emptylog.scxml
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<scxml xmlns="http://www.w3.org/2005/07/scxml" version="1.0" name="qtbug71746.scxml">
+    <state id="failing">
+        <onentry>
+            <log label="Hi2"/>
+        </onentry>
+    </state>
+</scxml>
diff --git a/tests/auto/statemachine/tst_statemachine.cpp b/tests/auto/statemachine/tst_statemachine.cpp
index 94b1d6f..4bd4ef2 100644
--- a/tests/auto/statemachine/tst_statemachine.cpp
+++ b/tests/auto/statemachine/tst_statemachine.cpp
@@ -56,6 +56,7 @@ private Q_SLOTS:
     void invokeStateMachine();
 
     void multipleInvokableServices(); // QTBUG-61484
+    void logWithoutExpr();
 };
 
 void tst_StateMachine::stateNames_data()
@@ -443,6 +444,17 @@ void tst_StateMachine::multipleInvokableServices()
     QVERIFY(stateMachine->activeStateNames(true).contains(QLatin1String("success")));
 }
 
+void tst_StateMachine::logWithoutExpr()
+{
+    QScopedPointer<QScxmlStateMachine> stateMachine(
+                QScxmlStateMachine::fromFile(QString(":/tst_statemachine/emptylog.scxml")));
+    QVERIFY(!stateMachine.isNull());
+    QTest::ignoreMessage(QtDebugMsg, "\"Hi2\" : \"\"");
+    stateMachine->start();
+    QSignalSpy logSpy(stateMachine.data(), SIGNAL(log(QString,QString)));
+    QTRY_COMPARE(logSpy.count(), 1);
+}
+
 QTEST_MAIN(tst_StateMachine)
 
 #include "tst_statemachine.moc"
diff --git a/tests/auto/statemachine/tst_statemachine.qrc b/tests/auto/statemachine/tst_statemachine.qrc
index 0bd68ff..599ba29 100644
--- a/tests/auto/statemachine/tst_statemachine.qrc
+++ b/tests/auto/statemachine/tst_statemachine.qrc
@@ -8,5 +8,6 @@
         <file>invoke.scxml</file>
         <file>historystate.scxml</file>
         <file>multipleinvokableservices.scxml</file>
+        <file>emptylog.scxml</file>
     </qresource>
 </RCC>