ProjectExplorer: Allow a device to declare that empty commands are fine

Docker allows to run a container "by itself", not needing an explicit
command line.

Change-Id: I4f3992410f7f7bbcce1897a7400628ef9354043d
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/projectexplorer/applicationlauncher.cpp

@@ -419,7 +419,7 @@ void ApplicationLauncherPrivate::start(const Runnable &runnable, const IDevice::
             return;
         }
 
-        if (runnable.executable.isEmpty()) {
+        if (!device->isEmptyCommandAllowed() && runnable.executable.isEmpty()) {
             doReportError(ApplicationLauncher::tr("Cannot run: No command given."));
             setFinished();
             return;

src/plugins/projectexplorer/devicesupport/idevice.cpp

@@ -152,6 +152,7 @@ public:
     Utils::PortList freePorts;
     QString debugServerPath;
     QString qmlsceneCommand;
+    bool emptyCommandAllowed = false;
 
     QList<Utils::Icon> deviceIcons;
     QList<IDevice::DeviceAction> deviceActions;
@@ -189,6 +190,16 @@ void IDevice::openTerminal(const Utils::Environment &env, const QString &working
     d->openTerminal(env, workingDir);
 }
 
+bool IDevice::isEmptyCommandAllowed() const
+{
+    return d->emptyCommandAllowed;
+}
+
+void IDevice::setAllowEmptyCommand(bool allow)
+{
+    d->emptyCommandAllowed = allow;
+}
+
 IDevice::~IDevice() = default;
 
 /*!

src/plugins/projectexplorer/devicesupport/idevice.h

@@ -221,6 +221,9 @@ public:
     bool canOpenTerminal() const;
     void openTerminal(const Utils::Environment &env, const QString &workingDir) const;
 
+    bool isEmptyCommandAllowed() const;
+    void setAllowEmptyCommand(bool allow);
+
 protected:
     IDevice();