Use Datatype::UNDEFINED to indicate no dataset definition in template

Author: franzpoeschel

include/openPMD/Dataset.hpp

@@ -37,7 +37,7 @@ class Dataset
     friend class RecordComponent;
 
 public:
-    Dataset(Datatype, Extent, std::string options = "{}");
+    Dataset(Datatype, Extent = {1}, std::string options = "{}");
 
     /**
      * @brief Constructor that sets the datatype to undefined.

src/RecordComponent.cpp

@@ -88,18 +88,28 @@ RecordComponent &RecordComponent::resetDataset(Dataset d)
         rc.m_hasBeenExtended = true;
     }
 
-    if (d.dtype == Datatype::UNDEFINED)
-    {
-        throw error::WrongAPIUsage(
-            "[RecordComponent] Must set specific datatype.");
-    }
-    // if( d.extent.empty() )
-    //    throw std::runtime_error("Dataset extent must be at least 1D.");
+    // if (d.dtype == Datatype::UNDEFINED)
+    // {
+    //     throw error::WrongAPIUsage(
+    //         "[RecordComponent] Must set specific datatype.");
+    // }
+    if (d.extent.empty())
+        throw std::runtime_error("Dataset extent must be at least 1D.");
     if (std::any_of(
             d.extent.begin(), d.extent.end(), [](Extent::value_type const &i) {
                 return i == 0u;
             }))
-        return makeEmpty(std::move(d));
+    {
+        if (d.dtype != Datatype::UNDEFINED)
+        {
+            return makeEmpty(std::move(d));
+        }
+        else
+        {
+            rc.m_dataset = std::move(d);
+            return *this;
+        }
+    }
 
     rc.m_isEmpty = false;
     if (written())

src/backend/PatchRecordComponent.cpp

@@ -46,14 +46,17 @@ PatchRecordComponent &PatchRecordComponent::resetDataset(Dataset d)
         throw std::runtime_error(
             "A Records Dataset can not (yet) be changed after it has been "
             "written.");
-    if (d.extent.empty())
-        throw std::runtime_error("Dataset extent must be at least 1D.");
-    if (std::any_of(
-            d.extent.begin(), d.extent.end(), [](Extent::value_type const &i) {
-                return i == 0u;
-            }))
-        throw std::runtime_error(
-            "Dataset extent must not be zero in any dimension.");
+    if (d.dtype != Datatype::UNDEFINED)
+    {
+        if (d.extent.empty())
+            throw std::runtime_error("Dataset extent must be at least 1D.");
+        if (std::any_of(
+                d.extent.begin(),
+                d.extent.end(),
+                [](Extent::value_type const &i) { return i == 0u; }))
+            throw std::runtime_error(
+                "Dataset extent must not be zero in any dimension.");
+    }
 
     get().m_dataset = d;
     dirty() = true;