Support mapping PostgreSQL arrays to List<T>

[MarcosAndre]

Hi,
I got an exception when I'm trying to create a new migration.

Version: 2.1.0 RC1 version

Error:

`System.ArgumentNullException: Value cannot be null.
   at System.RuntimeType.MakeGenericType(Type[] instantiation)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.Mapping.NpgsqlArrayTypeMapping.CreateComparer(RelationalTypeMapping elementMapping, Type arrayType) in /home/roji/projects/EFCore.PG/src/EFCore.PG/Storage/Internal/Mapping/NpgsqlArrayTypeMapping.cs:line 99
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.Mapping.NpgsqlArrayTypeMapping..ctor(String storeType, RelationalTypeMapping elementMapping, Type arrayType) in /home/roji/projects/EFCore.PG/src/EFCore.PG/Storage/Internal/Mapping/NpgsqlArrayTypeMapping.cs:line 53
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlTypeMappingSource.FindArrayMapping(RelationalTypeMappingInfo mappingInfo) in /home/roji/projects/EFCore.PG/src/EFCore.PG/Storage/InternalNpgsqlTypeMappingSource.cs:line 391
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlTypeMappingSource.FindMapping(RelationalTypeMappingInfo& mappingInfo) in /home/roji/projects/EFCore.PG/src/EFCore.PG/Storage/Internal/NpgsqlTypeMappingSource.cs:line 323
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.<FindMappingWithConversion>b__7_0(ValueTuple`3 k)
   at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindMappingWithConversion(RelationalTypeMappingInfo& mappingInfo, IReadOnlyList`1 principals)
   at Microsoft.EntityFrameworkCore.Storage.RelationalTypeMappingSource.FindMapping(MemberInfo member)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.PropertyDiscoveryConvention.IsCandidatePrimitiveProperty(PropertyInfo propertyInfo)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.PropertyDiscoveryConvention.Apply(InternalEntityTypeBuilder entityTypeBuilder)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.PropertyDiscoveryConvention.Apply(InternalEntityTypeBuilder entityTypeBuilder, EntityType oldBaseType)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.ImmediateConventionScope.OnBaseEntityTypeChanged(InternalEntityTypeBuilder entityTypeBuilder, EntityType previousBaseType)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.RunVisitor.VisitOnBaseEntityTypeChanged(OnBaseEntityTypeChangedNode node)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.ConventionVisitor.VisitConventionScope(ConventionScope node)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.ConventionBatch.Run()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalEntityTypeBuilder.HasBaseType(EntityType baseEntityType, ConfigurationSource configurationSource)
   at Microsoft.EntityFrameworkCore.Metadata.Conventions.Internal.ConventionDispatcher.ImmediateConventionScope.OnEntityTypeAdded(InternalEntityTypeBuilder entityTypeBuilder)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Model.AddEntityType(EntityType entityType)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalModelBuilder.Entity(TypeIdentity& type, ConfigurationSource configurationSource, Boolean throwOnQuery)
   at Microsoft.EntityFrameworkCore.Metadata.Internal.InternalModelBuilder.Entity(Type type, ConfigurationSource configurationSource, Boolean throwOnQuery)
   at Microsoft.EntityFrameworkCore.ModelBuilder.Entity(Type type)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelCustomizer.FindSets(ModelBuilder modelBuilder, DbContext context)
   at Microsoft.EntityFrameworkCore.Infrastructure.RelationalModelCustomizer.FindSets(ModelBuilder modelBuilder, DbContext context)
   at Microsoft.EntityFrameworkCore.Infrastructure.RelationalModelCustomizer.Customize(ModelBuilder modelBuilder, DbContext context)
   at Microsoft.EntityFrameworkCore.Infrastructure.ModelSource.CreateModel(DbContext context, IConventionSetBuilder conventionSetBuilder, IModelValidator validator)
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.CreateModel()
   at Microsoft.EntityFrameworkCore.Internal.DbContextServices.get_Model()
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitScoped(ScopedCallSite scopedCallSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.EntityFrameworkCore.DbContext.get_DbContextDependencies()
   at Microsoft.EntityFrameworkCore.DbContext.get_InternalServiceProvider()
   at Microsoft.EntityFrameworkCore.Internal.InternalAccessorExtensions.GetService[TService](IInfrastructure`1 accessor)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(Func`1 factory)
   at Microsoft.EntityFrameworkCore.Design.Internal.DbContextOperations.CreateContext(String contextType)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)`

I think this is related to the commit: 2d0e595

Best regards,
Marcos André

[roji]

Any chance you can post the relevant parts of your model so I know what triggers this?

[MarcosAndre]

I can't, sorry. I have the new value converts, it helps?

[roji]

OK, I think I figured it out - you probably have a List<T> of something somewhere in your model, this triggers the error for me. For the moment, change it to an array T[] which should work, I'll look into it.

[MarcosAndre]

Yes I have that.

Thank you ;)

Cheers!

[gary-holland]

HI Roji. Just a quick note, I don't have List, I have ICollection which I suspect is the cause of the issue for me. Hopefully you're fix will cover this also.

Thanks
Cheers,

[roji]

Mapping a PostgreSQL array type to an ICollection isn't supported - only array or list. Note that I'm referring to the Npgsql-specific mapping of arrays of primitive types (array of int, array of string) to a single column in PostgreSQL. Otherwise EF Core handles mapping collections of entities as relations, i.e. via a foreign key to another table.

You may want to take a look at your model again to understand where this is coming from, and possibly post part of it (or all of it) here.