ProjectExplorer: Fix qmlRunCommand caching

Previously the value set by the user was lost when
the settings dialog is opened again.

Change-Id: Ic6e977e2287671b460a4115d88580a44d4b10b74
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/projectexplorer/devicesupport/idevice.cpp

@@ -141,8 +141,7 @@ public:
     PortList freePorts;
     FilePath debugServerPath;
     FilePath debugDumperPath = Core::ICore::resourcePath("debugger/");
-    FilePath qmlRunCommand;
+    std::optional<FilePath> qmlRunCommand;
-    bool qmlRunCommandChecked = false;
     bool emptyCommandAllowed = false;
 
     QList<Icon> deviceIcons;
@@ -482,7 +481,9 @@ void IDevice::fromMap(const QVariantMap &map)
     d->version = map.value(QLatin1String(VersionKey), 0).toInt();
 
     d->debugServerPath = FilePath::fromSettings(map.value(QLatin1String(DebugServerKey)));
-    d->qmlRunCommand = FilePath::fromSettings(map.value(QLatin1String(QmlRuntimeKey)));
+    const FilePath qmlRunCmd = FilePath::fromSettings(map.value(QLatin1String(QmlRuntimeKey)));
+    if (!qmlRunCmd.isEmpty())
+        d->qmlRunCommand = qmlRunCmd;
     d->extraData = map.value(ExtraDataKey).toMap();
 }
 
@@ -515,7 +516,9 @@ QVariantMap IDevice::toMap() const
     map.insert(QLatin1String(VersionKey), d->version);
 
     map.insert(QLatin1String(DebugServerKey), d->debugServerPath.toSettings());
-    map.insert(QLatin1String(QmlRuntimeKey), d->qmlRunCommand.toSettings());
+    map.insert(QLatin1String(QmlRuntimeKey),
+               d->qmlRunCommand ? d->qmlRunCommand->toSettings() : FilePath().toSettings());
+
     map.insert(ExtraDataKey, d->extraData);
 
     return map;
@@ -604,20 +607,23 @@ void IDevice::setDebugServerPath(const FilePath &path)
 
 FilePath IDevice::qmlRunCommand() const
 {
-    if (!d->qmlRunCommandChecked) {
+    if (d->qmlRunCommand)
-        d->qmlRunCommandChecked = true;
+        return *d->qmlRunCommand;
-        QString runtime = d->qmlRunCommand.path();
+
-        if (runtime.isEmpty())
+    const FilePath newPath = searchExecutableInPath("qml");
-           runtime = "qml";
+    if (newPath.isEmpty())
-        d->qmlRunCommand = searchExecutableInPath(runtime);
+        return {};
-    }
+
-    return d->qmlRunCommand;
+    d->qmlRunCommand = newPath;
+    return *d->qmlRunCommand;
 }
 
 void IDevice::setQmlRunCommand(const FilePath &path)
 {
-    d->qmlRunCommand = path;
+    if (path.isEmpty())
-    d->qmlRunCommandChecked = false;
+        d->qmlRunCommand.reset();
+    else
+        d->qmlRunCommand = path;
 }
 
 void IDevice::setExtraData(Id kind, const QVariant &data)