Shallow copy field data from input to output in ghost cells generator

This ensures field data is passed through
vtkPUnstructuredGridGhostCellsGenerator.

Modify test to check that field data is passed to output.

Filters/ParallelGeometry/Testing/Cxx/TestPUnstructuredGridGhostCellsGenerator.cxx

@@ -84,6 +84,18 @@ private:
 
 vtkStandardNewMacro(vtkRTAnalyticSource2);
 
+bool CheckFieldData(vtkFieldData* fd)
+{
+  vtkUnsignedCharArray* fdArray = vtkUnsignedCharArray::SafeDownCast(fd->GetArray("FieldData"));
+  if (!fdArray || fdArray->GetValue(0) != 2)
+  {
+    cerr << "Field data array value is not the same as the input" << endl;
+    return false;
+  }
+
+  return true;
+}
+
 } // anonymous namespace
 
 //------------------------------------------------------------------------------
@@ -106,7 +118,17 @@ int TestPUnstructuredGridGhostCellsGenerator(int argc, char* argv[])
   tetrahedralize->SetInputConnection(wavelet->GetOutputPort());
   tetrahedralize->UpdatePiece(myRank, nbRanks, 0);
 
-  vtkUnstructuredGrid* initialGrid = tetrahedralize->GetOutput();
+  vtkNew<vtkUnstructuredGrid> initialGrid;
+  initialGrid->ShallowCopy(tetrahedralize->GetOutput());
+
+  // Add field data
+  vtkNew<vtkUnsignedCharArray> fdArray;
+  fdArray->SetNumberOfTuples(1);
+  fdArray->SetName("FieldData");
+  fdArray->SetValue(0, 2);
+  vtkNew<vtkFieldData> fd;
+  fd->AddArray(fdArray);
+  initialGrid->SetFieldData(fd);
 
   // Prepare the ghost cells generator
   vtkNew<vtkPUnstructuredGridGhostCellsGenerator> ghostGenerator;
@@ -135,6 +157,14 @@ int TestPUnstructuredGridGhostCellsGenerator(int argc, char* argv[])
     ret = EXIT_FAILURE;
   }
 
+  // Check that field data is copied
+  ghostGenerator->Update();
+  if (!CheckFieldData(ghostGenerator->GetOutput()->GetFieldData()))
+  {
+    cerr << "Field data was not copied correctly" << std::endl;
+    ret = EXIT_FAILURE;
+  }
+
   // Check if algorithm works with empty input on all nodes except first one
   vtkNew<vtkUnstructuredGrid> emptyGrid;
   ghostGenerator->SetInputData(myRank == 0 ? initialGrid : emptyGrid);
@@ -164,6 +194,12 @@ int TestPUnstructuredGridGhostCellsGenerator(int argc, char* argv[])
       // Save the grid for further analysis
       outGrids[step] = ghostGenerator->GetOutput();
 
+      if (!CheckFieldData(outGrids[step]->GetFieldData()))
+      {
+        cerr << "Field data was not copied" << std::endl;
+        ret = EXIT_FAILURE;
+      }
+
       double elapsed = timer->GetElapsedTime();
 
       // get some performance statistics

Filters/ParallelGeometry/vtkPUnstructuredGridGhostCellsGenerator.cxx

@@ -366,6 +366,14 @@ int vtkPUnstructuredGridGhostCellsGenerator::RequestData(vtkInformation* vtkNotU
   output->ShallowCopy(this->Internals->CurrentGrid);
   output->GetInformation()->Set(vtkDataObject::DATA_NUMBER_OF_GHOST_LEVELS(), maxGhostLevel);
 
+  // copy field data
+  if (cleanedInput && cleanedInput->GetFieldData())
+  {
+    vtkNew<vtkFieldData> fd;
+    fd->ShallowCopy(cleanedInput->GetFieldData());
+    output->SetFieldData(fd);
+  }
+
   vtkDebugMacro("Produced " << maxGhostLevel << " ghost levels.");
 
   delete this->Internals;