Fallback for undefined gridUnitSI

Author: franzpoeschel

src/Mesh.cpp

@@ -209,14 +209,10 @@ namespace
 {
     uint64_t retrieveMeshDimensionality(Mesh const &m)
     {
-        try
+        if (m.containsAttribute("axisLabels"))
         {
             return m.axisLabels().size();
         }
-        catch (no_such_attribute_error const &)
-        {
-            // no-op, continue with fallback below
-        }
 
         // maybe we have record components and can ask them
         if (auto it = m.begin(); it != m.end())
@@ -233,7 +229,27 @@ namespace
 
 std::vector<double> Mesh::gridUnitSIPerDimension() const
 {
-    return getAttribute("gridUnitSI").get<std::vector<double>>();
+    if (containsAttribute("gridUnitSI"))
+    {
+        if (auto series_opt = retrieveSeries_optional(); series_opt.has_value())
+        {
+            if (auto version = series_opt->openPMD(); version < "2.")
+            {
+                // If the openPMD version is lower than 2.0, the gridUnitSI is a
+                // scalar interpreted for all axes. Copy it d times.
+                return std::vector<double>(
+                    retrieveMeshDimensionality(*this),
+                    getAttribute("gridUnitSI").get<double>());
+            }
+        }
+        return getAttribute("gridUnitSI").get<std::vector<double>>();
+    }
+    else
+    {
+        // gridUnitSI is an optional attribute
+        // if it is missing, the mesh is interpreted as unscaled
+        return std::vector<double>(retrieveMeshDimensionality(*this), 1.);
+    }
 }
 
 Mesh &Mesh::setGridUnitSIPerDimension(std::vector<double> gridUnitSI)
@@ -328,7 +344,7 @@ std::vector<std::array<double, 7>> Mesh::gridUnitDimension() const
     }
     else
     {
-        // gridUnitSI is an optional attribute
+        // gridUnitDimension is an optional attribute
         // if it is missing, the mesh is interpreted as spatial
         std::array<double, 7> spatialMesh;
         fromMapOfUnitDimension(spatialMesh.begin(), {{UnitDimension::L, 1}});

test/SerialIOTest.cpp

@@ -947,10 +947,15 @@ inline void constant_scalar(std::string const &file_ending)
         E_mesh.setDataOrder(dataOrder);
         E_mesh.setGridSpacing(gridSpacing);
         E_mesh.setGridGlobalOffset(gridGlobalOffset);
-        E_mesh.setGridUnitSI(std::vector(3, gridUnitSI));
         E_mesh.setAxisLabels(axisLabels);
         E_mesh.setUnitDimension(unitDimensions);
         E_mesh.setTimeOffset(timeOffset);
+        REQUIRE(
+            E_mesh.gridUnitSIPerDimension() == std::vector<double>{1., 1., 1.});
+        E_mesh.setGridUnitSI(std::vector(3, gridUnitSI));
+        REQUIRE(
+            E_mesh.gridUnitSIPerDimension() ==
+            std::vector<double>{gridUnitSI, gridUnitSI, gridUnitSI});
 
         // constant scalar
         auto pos =