Remove flush-time check for populized components

Moved to finalize(), degraded to warning

Author: franzpoeschel

src/backend/BaseRecord.cpp

@@ -813,10 +813,10 @@ inline void BaseRecord<T_elem>::flush(
     }
 
     if (!this->written() && this->empty() && !this->datasetDefined())
-        throw std::runtime_error(
-            "A Record can not be written without any contained "
-            "RecordComponents: " +
-            name);
+        // Verify upon ScientificDefaults::finalize() that the Record has been
+        // populized. For now, we will assume that data will come later; ignore
+        // this Record at the moment.
+        return;
 
     /*
      * Defensive programming. Normally, this error should yield as soon as

src/backend/ScientificDefaults.cpp

@@ -169,6 +169,24 @@ void ScientificDefaults<Child>::addDefaults()
     std::cout << "Adding defaults for '" << asChild().myPath().openPMDPath()
               << "'" << std::endl;
 
+    // First some verifications
+    if constexpr (auxiliary::IsTemplateBaseOf_v<BaseRecord, Child>)
+    {
+        if (asChild().empty() && !asChild().datasetDefined())
+        {
+            std::cerr
+                << "Cannot flush Record without any contained components: '"
+                << asChild().myPath().openPMDPath() << "'. Will ignore.";
+            if (asChild().written())
+            {
+                std::cerr << "\n(Note: The Record seems to have been written "
+                             "previously?)";
+            }
+            std::cerr << std::endl;
+            return;
+        }
+    }
+
     if constexpr (std::is_same_v<Child, Iteration>)
     {
         addDefaultFor("time", 0., &Iteration::setTime);
@@ -267,11 +285,6 @@ void ScientificDefaults<Child>::addDefaults()
     {
         addParentDefaults<BaseRecord<PatchRecordComponent>>();
     }
-    else if constexpr (auxiliary::IsTemplateBaseOf_v<BaseRecord, Child>)
-    {
-        addDefaultFor<unit_representations::AsArray const &>(
-            "unitDimension", unit_representations::AsArray{});
-    }
     else if constexpr (std::is_same_v<Child, RecordComponent>)
     {
         addDefaultFor("unitSI", 1.0, &RecordComponent::setUnitSI);
@@ -299,6 +312,11 @@ void ScientificDefaults<Child>::addDefaults()
     {
         addParentDefaults<RecordComponent>();
     }
+    else if constexpr (auxiliary::IsTemplateBaseOf_v<BaseRecord, Child>)
+    {
+        addDefaultFor<unit_representations::AsArray const &>(
+            "unitDimension", unit_representations::AsArray{});
+    }
 }
 
 template class ScientificDefaults<Iteration>;

test/CoreTest.cpp

@@ -1299,16 +1299,14 @@ TEST_CASE("empty_record_test", "[core]")
 
     o.iterations[1].meshes["E"].setComment(
         "No assumption about contained RecordComponents will be made");
-    REQUIRE_THROWS_WITH(
-        o.flush(),
-        Catch::Equals(
-            "A Record can not be written without any contained "
-            "RecordComponents: E"));
-    o.iterations[1].meshes["E"][RecordComponent::SCALAR].resetDataset(
-        Dataset(Datatype::DOUBLE, {1}));
     auto B = o.iterations[1].meshes["B"];
     B.resetDataset(Dataset(Datatype::DOUBLE, {1}));
-    o.flush();
+    auto sneakily_keep_meshes_alive = o.iterations[1].meshes;
+    o.close();
+#if openPMD_USE_INVASIVE_TESTS
+    REQUIRE(!sneakily_keep_meshes_alive["E"].written());
+    REQUIRE(sneakily_keep_meshes_alive["B"].written());
+#endif
 }
 
 TEST_CASE("zero_extent_component", "[core]")