Add new required method for finding filename property

Framework/API/inc/MantidAPI/NexusFileLoader.h

@@ -18,6 +18,8 @@ public:
   void
   exec() override final; // makes sure the NexusHDF5Descriptor is initialized
   virtual void execLoader() = 0; // what would normally be called exec
+  // the name of the property that the NexusHDF5Descriptor should be created against
+  virtual std::string getFilenamePropertyName() const = 0;
   boost::shared_ptr<Algorithm> createChildAlgorithm(
       const std::string &name, const double startProgress = -1.,
       const double endProgress = -1., const bool enableLogging = true,

Framework/API/src/NexusFileLoader.cpp

@@ -5,15 +5,12 @@
 //     & Institut Laue - Langevin
 // SPDX - License - Identifier: GPL - 3.0 +
 #include "MantidAPI/NexusFileLoader.h"
-//include "MantidDataHandling/Load.h"
 
 namespace Mantid::DataHandling {
 void NexusFileLoader::exec() {
   // make sure the descriptor is initialized
   if (!m_fileInfo) {
-    // TODO move this functionality elsewhere
-    const std::string filePropName = "Filename"; //Load::findFilenamePropertyName(this);
-    const std::string filename = this->getPropertyValue(filePropName);
+    const std::string filename = this->getPropertyValue(this->getFilenamePropertyName());
     m_fileInfo =
         std::make_shared<Mantid::Kernel::NexusHDF5Descriptor>(filename);
   }