DependencyModules.SourceGenerator.Impl 1.0.0-RC9059

DependencyModules

DependencyModules is a C# source generator package that uses attributes to create dependency injection registration modules. These modules can then be used to populate an IServiceCollection instance.

Installation

dotnet add package DependencyModules.Runtime
dotnet add package DependencyModules.SourceGenerator

Service Attributes

• [DependencyModule] - used to attribute class that will become dependency module (must be partial)
• [SingletonService] - registers service as AddSingleton
• [ScopedService] - registers service as AdddScoped
• [TransientService] - registers service as AddTransient

// Registration example
[DependencyModule]
public partial class MyModule { }

// registers SomeClass implementation for ISomeService
[SingletonService]
public class SomeClass : ISomeService 
{
  public string SomeProp => "SomeString";
}

// registers OtherSerice implementation
[TransientService]
public class OtherService
{
  public OtherService(ISomeService service)
  { 
    SomeProp = service.SomeProp;
  }
  public string SomeProp { get; }
}

Container Instantiation

AddModule - method adds modules to service collection

var serviceCollection = new ServiceCollection();

serviceCollection.AddModule<MyModule>();

var provider = serviceCollection.BuildServiceProvider();

var service = provider.GetService<OtherService>();

Module Re-use

DependencyModules creates an Attribute class that can be used to apply sub dependencies.

// Modules can be re-used with the generated attributes
[DependencyModule]
[MyModule.Attribute]
public partial class AnotherModule { }

Parameters

Sometimes you want to provide extra registration for your module. This can be achieved by adding a constructor to your module or optional properties. Note these parameters and properties will be correspondingly implemented in the module attribute.

[DependencyModule]
public partial class SomeModule : IServiceCollectionConfiguration 
{
  private bool _someFlag;
  public SomeModule(bool someFlag = false)
  {
    _someFlag = someFlag;
  }
  
  public string OptionalString { get; set; } = "";
  
  public void ConfigureServices(IServiceCollection services) 
  {
    if (_someFlag) 
    {
      // custom registration
    } 
  }
}

[DependencyModule]
[SomeModule.Attribute(true, OptionalString = "otherString")]
public partial class SomeOtherModule 
{

}

Managing duplicate registration

By default a module will only be loaded once, assuming attributes are used or the modules are specified in the same AddModules call. Seperate calls to AddModule will result in modules being loaded multiple times. If a module uses parameters it can be useful to load a module more than once. That can be accompilished by overriding the Equals and GetHashcode methods to allow for multiple loads.

In addition by default services will be registered with using an Add method. This can be controlled using the With property on individual service or at the DepedencyModule level.

[SingletonService(With = Registration.Type)]
public class SomeService { }

[DependencyModule(With = RegistrationType.Try)]
public partial class SomeModule { }

Realm

By default, all dependencies are registered in all modules within the same assembly. The realm allows the developer to scope down the registration within a given module.

// register only dependencies specifically marked for this realm
[DependencyModule(OnlyRealm = true)]
public partial class AnotherModule { }

[SingletonService(ServiceType = typeof(ISomeInterface), 
  Realm = typeof(AnotherModule))]
public class SomeDep : ISomeInterface { }

Unit testing & Mocking

DependencyModules provides an xUnit extension to make testing much easier. It handles the population and construction of a service provider using specified modules.

> dotnet add package DependencyModules.xUnit
> dotnet add package DependencyModules.xUnit.NSubstitute

// applies module & nsubstitute support to all tests.
// test attributes can be applied at the assembly, class, and test method level
[assemlby: MyModule.Attribute]
[assembly: NSubstituteSupport]

public class OtherServiceTests 
{
  [ModuleTest]
  public void SomeTest(OtherService test, [Mock]ISomeService service)
  {
     service.SomeProp.Returns("some mock value");
     Assert.Equals("some mock value", test.SomeProp);
  }
}

Implementation

Behind the scenes the library generates registration code that can be used with any IServiceCollection compatible DI container.

Example generated code for SutModule.cs

    // SutModule.Dependencies.g.cs
    public partial class SutModule
    {
        private static int moduleField = DependencyRegistry<SutModule>.Add(ModuleDependencies);

        private static void ModuleDependencies(IServiceCollection services)
        {
            services.AddTransient(typeof(IDependencyOne), typeof(DependencyOne));
            services.AddSingleton(typeof(IGenericInterface<>), typeof(GenericClass<>));
            services.AddScoped(typeof(IScopedService), typeof(ScopedService));
            services.AddSingleton(typeof(ISingletonService), typeof(SingletonService));
            services.AddSingleton(typeof(IGenericInterface<string>), typeof(StringGeneric));
        }
    }

    // SutModule.Modules.g.cs
    public partial class SutModule : IDependencyModule
    {
        static SutModule()
        {
        }

        // this method loads all dependencies into IServiceCollection.
        public void PopulateServiceCollection(IServiceCollection services)
        {
            DependencyRegistry<SutModule>.LoadModules(services, this);
        }

        void IDependencyModule.InternalApplyServices(IServiceCollection services)
        {
            DependencyRegistry<SutModule>.ApplyServices(services);
        }

        // this method returns any modules that are attached using attributes
        IEnumerable<object> IDependencyModule.InternalGetModules()
        {
            yield break;
        }

        public override bool Equals(object? obj)
        {
            return obj is SutModule;
        }

        public override int GetHashCode()
        {
            return HashCode.Combine(base.GetHashCode());
        }

        public class ModuleAttribute : Attribute, IDependencyModuleProvider
        {
            public IDependencyModule GetModule()
            {
                var newModule = new SutModule();
                return newModule;
            }
        }
    }