bug EFCore: Error when saving an entity without specifying a default value

Author: KirillKurdyukov

src/EFCore.Ydb/src/Metadata/Conventions/YdbConventionSetBuilder.cs

@@ -13,6 +13,7 @@ public override ConventionSet CreateConventionSet()
     {
         var coreConventions = base.CreateConventionSet();
         coreConventions.Add(new YdbStringAttributeConvention(Dependencies));
+        coreConventions.Add(new YdbValueGenerationConvention(Dependencies, RelationalDependencies));
         return coreConventions;
     }
 }

src/EFCore.Ydb/src/Metadata/Conventions/YdbValueGenerationConvention.cs

@@ -0,0 +1,38 @@
+using System.Linq;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions;
+using Microsoft.EntityFrameworkCore.Metadata.Conventions.Infrastructure;
+using Microsoft.EntityFrameworkCore.Metadata.Internal;
+
+namespace EntityFrameworkCore.Ydb.Metadata.Conventions;
+
+public class YdbValueGenerationConvention(
+    ProviderConventionSetBuilderDependencies dependencies,
+    RelationalConventionSetBuilderDependencies relationalDependencies)
+    : RelationalValueGenerationConvention(dependencies, relationalDependencies)
+{
+    protected override ValueGenerated? GetValueGenerated(IConventionProperty property)
+    {
+        if (property.DeclaringType.IsMappedToJson()
+#pragma warning disable EF1001 // Internal EF Core API usage.
+            && property.IsOrdinalKeyProperty()
+#pragma warning restore EF1001 // Internal EF Core API usage.
+            && (property.DeclaringType as IReadOnlyEntityType)?.FindOwnership()!.IsUnique == false)
+        {
+            return ValueGenerated.OnAdd;
+        }
+
+        var declaringTable = property.GetMappedStoreObjects(StoreObjectType.Table).FirstOrDefault();
+        if (declaringTable.Name == null)
+        {
+            return null;
+        }
+
+        return property.GetComputedColumnSql(declaringTable) != null
+            ? ValueGenerated.OnAddOrUpdate
+            : property.GetDefaultValueSql(declaringTable) != null
+                ? ValueGenerated.OnAdd
+                : null;
+    }
+}