async-disposable-scope.md

Async disposable scope

interface IDependency
{
    bool IsDisposed { get; }
}

class Dependency : IDependency, IAsyncDisposable
{
    public bool IsDisposed { get; private set; }

    public ValueTask DisposeAsync()
    {
        IsDisposed = true;
        return ValueTask.CompletedTask;
    }
}

interface IService
{
    IDependency Dependency { get; }
}

class Service(IDependency dependency) : IService
{
    public IDependency Dependency => dependency;
}

// Implements a session
class Session(Composition composition) : Composition(composition);

class Program(Func<Session> sessionFactory)
{
    public Session CreateSession() => sessionFactory();
}

partial class Composition
{
    static void Setup() =>
        DI.Setup()
            // This hint indicates to not generate methods such as Resolve
            .Hint(Hint.Resolve, "Off")
            .Bind().As(Scoped).To<Dependency>()
            .Bind().To<Service>()

            // Session composition root
            .Root<IService>("SessionRoot")

            // Program composition root
            .Root<Program>("ProgramRoot");
}

var composition = new Composition();
var program = composition.ProgramRoot;

// Creates session #1
var session1 = program.CreateSession();
var dependency1 = session1.SessionRoot.Dependency;
var dependency12 = session1.SessionRoot.Dependency;

// Checks the identity of scoped instances in the same session
dependency1.ShouldBe(dependency12);

// Creates session #2
var session2 = program.CreateSession();
var dependency2 = session2.SessionRoot.Dependency;

// Checks that the scoped instances are not identical in different sessions
dependency1.ShouldNotBe(dependency2);

// Disposes of session #1
await session1.DisposeAsync();
// Checks that the scoped instance is finalized
dependency1.IsDisposed.ShouldBeTrue();

// Disposes of session #2
await session2.DisposeAsync();
// Checks that the scoped instance is finalized
dependency2.IsDisposed.ShouldBeTrue();

The following partial class will be generated:

partial class Composition: IDisposable, IAsyncDisposable
{
  private readonly Composition _root;
  private readonly Lock _lock;
  private object[] _disposables;
  private int _disposeIndex;

  private Dependency? _scopedDependency41;

  [OrdinalAttribute(20)]
  public Composition()
  {
    _root = this;
    _lock = new Lock();
    _disposables = new object[1];
  }

  internal Composition(Composition parentScope)
  {
    _root = (parentScope ?? throw new ArgumentNullException(nameof(parentScope)))._root;
    _lock = _root._lock;
    _disposables = new object[1];
  }

  public IService SessionRoot
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      if (_scopedDependency41 is null)
      {
        using (_lock.EnterScope())
        {
          if (_scopedDependency41 is null)
          {
            _scopedDependency41 = new Dependency();
            _disposables[_disposeIndex++] = _scopedDependency41;
          }
        }
      }

      return new Service(_scopedDependency41!);
    }
  }

  public Program ProgramRoot
  {
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    get
    {
      Func<Session> perBlockFunc1 = new Func<Session>([MethodImpl(MethodImplOptions.AggressiveInlining)] () =>
      {
        Composition transientComposition3 = this;
        Session localValue78 = new Session(transientComposition3);
        return localValue78;
      });
      return new Program(perBlockFunc1);
    }
  }

  public void Dispose()
  {
    int disposeIndex;
    object[] disposables;
    using (_lock.EnterScope())
    {
      disposeIndex = _disposeIndex;
      _disposeIndex = 0;
      disposables = _disposables;
      _disposables = new object[1];
      _scopedDependency41 = null;
    }

    while (disposeIndex-- > 0)
    {
      switch (disposables[disposeIndex])
      {
        case IAsyncDisposable asyncDisposableInstance:
          try
          {
            var valueTask = asyncDisposableInstance.DisposeAsync();
            if (!valueTask.IsCompleted)
            {
              valueTask.AsTask().Wait();
            }
          }
          catch (Exception exception)
          {
            OnDisposeAsyncException(asyncDisposableInstance, exception);
          }
          break;
      }
    }
  }

  partial void OnDisposeException<T>(T disposableInstance, Exception exception) where T : IDisposable;

  public async ValueTask DisposeAsync()
  {
    int disposeIndex;
    object[] disposables;
    _lock.Enter();
    try
    {
      disposeIndex = _disposeIndex;
      _disposeIndex = 0;
      disposables = _disposables;
      _disposables = new object[1];
      _scopedDependency41 = null;
    }
    finally
    {
      _lock.Exit();
    }

    while (disposeIndex-- > 0)
    {
      switch (disposables[disposeIndex])
      {
        case IAsyncDisposable asyncDisposableInstance:
          try
          {
            await asyncDisposableInstance.DisposeAsync();
          }
          catch (Exception exception)
          {
            OnDisposeAsyncException(asyncDisposableInstance, exception);
          }
          break;
      }
    }
  }

  partial void OnDisposeAsyncException<T>(T asyncDisposableInstance, Exception exception) where T : IAsyncDisposable;
}

Class diagram:

classDiagram
	class Composition {
		<<partial>>
		+Program ProgramRoot
		+IService SessionRoot
	}
	Composition --|> IDisposable
	Composition --|> IAsyncDisposable
	Service --|> IService
	class Service {
		+Service(IDependency dependency)
	}
	class FuncᐸSessionᐳ
	Dependency --|> IDependency
	Dependency --|> IAsyncDisposable
	class Dependency {
		+Dependency()
	}
	class Session {
		+Session(Composition composition)
	}
	class Composition
	class IService {
		<<interface>>
	}
	class IDependency {
		<<interface>>
	}
	class IAsyncDisposable {
		<<interface>>
	}
	Composition ..> Program : Program ProgramRoot
	Composition ..> Service : IService SessionRoot
	Program o-- "PerBlock" FuncᐸSessionᐳ : FuncᐸSessionᐳ
	Service o-- "Scoped" Dependency : IDependency
	FuncᐸSessionᐳ *--  Session : Session
	Session *--  Composition : Composition

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