Regression in 2.0.3 preview: NullReferenceException in RelationalDataReader.Dispose() on Migrate()

[OronDF343]

The following simple case, which worked in 2.0.0, throws a NullReferenceException in the new preview:

var context = services.GetRequiredService<VolunteerDbContext>();
context.Database.Migrate();

Note that it happen with any of my DbContexts, not just the one shown above.
The exception is as follows:

Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Storage.RelationalDataReader.Dispose()
   at Microsoft.EntityFrameworkCore.Migrations.HistoryRepository.GetAppliedMigrations()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
   at Microsoft.EntityFrameworkCore.RelationalDatabaseFacadeExtensions.Migrate(DatabaseFacade databaseFacade)
   at TestAspNetCore.Program.Main(String[] args)

Additionally, when executing a CountAsync and a ToListAsync the following exceptions are thrown, respectively:

Microsoft.EntityFrameworkCore.Query: Error: An exception occurred in the database while iterating the results of a query for context type 'TestAspNetCore.Model.VolunteerDbContext'.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Storage.RelationalDataReader.Dispose()
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable`1.AsyncEnumerator.Dispose()
   at Microsoft.EntityFrameworkCore.Query.AsyncQueryMethodProvider.<GetResult>d__16`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.TaskResultAsyncEnumerable`1.Enumerator.<MoveNext>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()

Microsoft.EntityFrameworkCore.Query: Error: An exception occurred in the database while iterating the results of a query for context type 'TestAspNetCore.Model.VolunteerDbContext'.
System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'WrappedMySqlDataReader'.
   at Microsoft.EntityFrameworkCore.Storage.Internal.WrappedMySqlDataReader.GetReader()
   at Microsoft.EntityFrameworkCore.Storage.Internal.WrappedMySqlDataReader.get_RecordsAffected()
   at Microsoft.EntityFrameworkCore.Storage.RelationalDataReader.Dispose()
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncQueryingEnumerable`1.AsyncEnumerator.Dispose()
   at System.Linq.AsyncEnumerable.SelectEnumerableAsyncIterator`2.Dispose()
   at System.Linq.AsyncEnumerable.AsyncIterator`1.<MoveNext>d__10.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.EntityFrameworkCore.Query.Internal.AsyncLinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.<MoveNext>d__5.MoveNext()

Further technical details

EF Core version: 2.0.1-rtm-203
Database Provider: Pomelo.EntityFrameworkCore.MySql (version 2.0.0 as well as 2.0.1-preview-10072)
Operating system: Windows 7 x64
IDE: Visual Studio 2017 15.4.1

[ajcvickers]

@OronDF343 Can you post a project or code listing so we can try to reproduce this?

[ajcvickers]

@smitpatel Please investigate this per my email.

[ajcvickers]

Filed PomeloFoundation/Pomelo.EntityFrameworkCore.MySql#418 on MySQL.

[yukozh]

Hi @OronDF343, I am from pomelo, we are fixing this issue, but not finished. For now, you can use .AddDbContext instead of .AddDbContextPool will work.

[OronDF343]

Thanks, but unfortunately that workaround did not solve the issue (only one of the DbContext was using .AddDbContextPool and changing that produced the same exceptions). I guess I will downgrade to EF Core 2.0.0 for now (and use non-Async methods for now since 2.0.0 has a bug)

[ajcvickers]

@OronDF343 A fix for this issue is being included in the 2.0.1 (2.0.3 meta package) patch.