Pomelo with EFCore.FSharp - Cannot create further migrations after Option types are included once

[GunnerGuyven]

Steps to reproduce

git clone https://github.com/GunnerGuyven/ef-pomelo-fsharp-migrate-failure
cd .\ef-pomelo-fsharp-migrate-failure\
dotnet tool restore
dotnet restore
dotnet ef migrations add test4

The issue

There is no actual database involved, this issue merely pertains to the creation of migrations. Using the dotnet-ef tool with EntityFrameworkCore.FSharp alongside Pomelo to create database migrations for MySql from a code-first model, works in almost all cases until the introduction of FSharp.Core.Option types in the model. EFCore.FSharp uses these types to model the nullable/required nature of a field.

The first migration with these types present succeeds, but subsequent migrations (regardless of change) fail. The migration being staged in the example project linked above is a no-change migration. It appears to fail when the existing model is being diffed.

It is unclear which project between Pomelo or EFCore.FSharp is to blame for this failure, and I am opening tickets with both projects as a result (relevant bug report for EFCore.FSharp here). EFCore.FSharp supports this scenario with other connectors such as Microsoft.EntityFrameworkCore.Sqlite without this issue.

The failure message and stacktrace appear as:

# dotnet ef migrations add test4
Build started...
Build succeeded.
System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Initialize(ColumnOperation columnOperation, IColumn column, RelationalTypeMapping typeMapping, Boolean isNullable, IEnumerable`1 migrationsAnnotations, Boolean inline)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Diff(IColumn 
source, IColumn target, DiffContext diffContext)+MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.DiffCollection[T](IEnumerable`1 sources, IEnumerable`1 targets, DiffContext diffContext, Func`4 diff, Func`3 add, Func`3 remove, Func`4[] predicates)+MoveNext()
   at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Diff(ITable source, ITable target, DiffContext diffContext)+MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.DiffCollection[T](IEnumerable`1 sources, IEnumerable`1 targets, DiffContext diffContext, Func`4 diff, Func`3 add, Func`3 remove, Func`4[] predicates)+MoveNext()
   at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Sort(IEnumerable`1 operations, DiffContext diffContext)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetDifferences(IRelationalModel source, IRelationalModel target)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language)        
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, 
String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Object reference not set to an instance of an object.

Further technical details

MySQL version: 10.8.3
Operating system: Windows
Pomelo.EntityFrameworkCore.MySql version: 6.0.2
Microsoft.AspNetCore.App 6.0.7

Other details about my project setup:
dotnet-cli 6.0.302
FSharp net6.0
EntityFrameworkCore.FSharp 6.0.7