grid_read_mapping: set default name for CDI_KEY_GRIDMAP_VARNAME.

src/grid_read.cc

@@ -256,6 +256,7 @@ grid_read_data(size_t ikv, size_t nkv, KVMap *kvmap, GridDesciption &grid, size_
 static void
 grid_read_mapping(size_t igmap, size_t nkv, KVMap *kvmap, int gridID)
 {
+  bool hasGridmapVarname = false;
   for (size_t ik = igmap; ik < nkv; ++ik)
     {
       if (!kvmap[ik].isValid) continue;
@@ -269,14 +270,25 @@ grid_read_mapping(size_t igmap, size_t nkv, KVMap *kvmap, int gridID)
 
       if (key == "grid_mapping")
         {
+          hasGridmapVarname = true;
           cdiDefKeyString(gridID, CDI_GLOBAL, CDI_KEY_GRIDMAP_VARNAME, value.c_str());
           continue;
         }
 
-      if (key == "grid_mapping_name") cdiDefKeyString(gridID, CDI_GLOBAL, CDI_KEY_GRIDMAP_NAME, value.c_str());
+      if (key == "grid_mapping_name")
+        {
+          if (!hasGridmapVarname)
+            {
+              if (value == "rotated_latitude_longitude")
+                cdiDefKeyString(gridID, CDI_GLOBAL, CDI_KEY_GRIDMAP_VARNAME, "rotated_pole");
+              else
+                cdiDefKeyString(gridID, CDI_GLOBAL, CDI_KEY_GRIDMAP_VARNAME, "crs");
+            }
 
-      const auto dtype = literalsFindDatatype(nvalues, values);
+          cdiDefKeyString(gridID, CDI_GLOBAL, CDI_KEY_GRIDMAP_NAME, value.c_str());
+        }
 
+      const auto dtype = literalsFindDatatype(nvalues, values);
       if (dtype == CDI_DATATYPE_INT8 || dtype == CDI_DATATYPE_INT16 || dtype == CDI_DATATYPE_INT32)
         {
           std::vector<int> ivals(nvalues);