Configuration and Customization

• Attributes and Attribute Properties
  • Attributes and their Properties on Service Provider
  • DependencyAttribute
  • ConstructorAttribute
  • ImportAttribute
• Specific Attributes in Depth
  • Implementation Property
  • Named Services
  • Generic Services
• Implicit Configurations
  • Name, Namespace, Modifiers, Containing Types and Generic
  • Interface name, namespace, access modifier, containing types and generic
  • Overwriting default services
  • Custom Constructor
  • Custom Dispose
  • Struct Types and Native/Built-in Types
  • Default Values
• Workarounds for not supported Features
  • Async Constructor
  • Decoration
  • Nullable Service
• Remarks
  • IServiceProvider Interface
  • Error Handling

Attributes and Attribute Properties

There are 7 attributes that are used at your ServiceProvider class and 2 other attributes that are used at service classes:

• ServiceProviderAttribute
• ScopedProviderAttribute
  • SingletonAttribute
  • ScopedAttribute
  • TransientAttribute
  • DelegateAttribute
  • ImportAttribute
    
    
• DependencyAttribute
• ConstructorAttribute

Attributes and their Properties on Service Provider

The main usage of the ServiceProviderAttribute is to indicate that the class is a ServiceProvider, so the generator will generate code for that class.
The ScopedProviderAttribute without setting any properties does nothing.
The other 5 attributes are for registering services.
There are several properties that can be configured to change the generated code:

• InterfaceName:
  Together with the ServiceProvider an interface will be generated based on the ServiceProvider. This sets the name/identifier of the generated interface explicitly. When InterfaceName is explicitly set to an empty string, no interface will be generated.
  The default name is "I{classname}". An Exception is when the class name is "ServiceProvider", then the default interface name will be "IServiceprovider" and explicitly setting the interface name to "IServiceProvider" is not allowed, otherwise it will collide with System.IServiceProvider.
  There is also the option to set the interface properties based on a declared interface, see Interface name, namespace, access modifier, containing types and generic. When setting this property, you must not set property InterfaceType.

• InterfaceType:
  Sets the interface properties based on a declared interface, see Interface name, namespace, access modifier, containing types and generic. When setting this property, you must not set property InterfaceName.

• CreationTime:
  Sets when the instantiation of a service happens: at ServiceProvider instantiation (inside the constructor) or lazy (first time used). This option is available at the ServiceProviderAttribute to set all services, at the ScopedProviderAttribute to set all scoped services or at a registration attribute to set this option for that specific service. It is structured hierarchically: Specific service settings take priority over ScopedProvider settings and ScopedProvider settings take priority over ServiceProvider settings.
  Note that TransientAttribute and DelegateAttribute do not have a CreationTiming, this applies only for SingletonAttribute and ScopedAttribute services. If a Singleton/Scoped service with CreationTiming.Constructor has a dependency on a service with same Lifetime and CreationTiming.Lazy, the lazy instantiated service will automatically also become constructor instantiated. A Scoped service with CreationTiming.Constructor can have a dependency on a Singleton service with CreationTiming.Lazy, the other way around (Singleton has dependency on Scoped) is not allowed/possible.

• GetAccessor:
  The type of the member to access the service: tt can be either a get property or a parameterless method. This option is available at the ServiceProviderAttribute to set all services, at the ScopedProviderAttribute to set all scoped services or at a registration attribute to set this option for that specific service. It is structured hierarchically: Specific service settings take priority over ScopedProvider settings and ScopedProvider settings take priority over ServiceProvider settings.

• Implementation:
  If nothing is specified the constructor is used to create the service, but you can also use a field to provide an instance or a property/method to use a factory method instead. For in depth explanation see Implementation Property.

• Name:
  Sets the name/identifier of the service getter property/method explicitly. This can be used to avoid naming conflicts, configure named services or just for better naming. For in depth explanation see Named Services.

• GenerateDisposeMethods:
  If nothing is specified both Dispose() and DisposeAsync() methods are generated to implement IDisposable and IAsyncDisposable. You can configure this property to only generate one method or omit both.

• NoDispose:
  Skips the generation for disposing a specific service, regardless the service implements IDisposable or IAsyncDisposable. If the service does not implement IDisposable/IAsyncDisposable, this will have no effect.

• Generate (ScopeProvider):
  Toggles the generation off the Scope Class inside the ServiceProvider. If turned off, no Scope is generated and therefore ScopedAttribute has no effect.

• ThreadSafe:
  Toggle for generating lock()-statements to make the ServiceProvider thread safe or omitting those for better performance. This option should be set to false, if the ServiceProvider is used in a single threaded scenario or only accessed by one thread at a time. Default is generating lock()-statements.

DependencyAttribute

This attribute can be used on parameters and properties. You can mark a non-required property as dependency by decorating it with this attribute.

using CircleDIAttributes;

namespace MySpace;

public sealed class MyServiceImplementation {
    [Dependency]
    public OtherService otherService { get; set; } = OtherService.Default;
}

It is also used to mark dependency parameters in the constructor of the ScopedProvider.

When the [SetsRequiredMembers] attribute is present on the constructor, the required keyword on properties is ignored and only [Dependency] marked properties are registered.

Another usage is for Named Services. When at the DependencyAttribute the Name-property is specified, the service will be injected by name instead by service type. For in depth explanation see Named Services.

ConstructorAttribute

This attribute is only needed if a service implementation has 2 or more constructors and the service is not constructed via Implementation (Only constructors with accessibility public or internal are considered, others are ignored). In this case you have to specify one constructor which should be used to create the service. This is done by marking the constructor with this attribute.

using CircleDIAttributes;

namespace MySpace;

// marks the primary constructor for creating this service
[method: Constructor]
public sealed class MyServiceImplementation(string name, int age) {
    public MyServiceImplementation(string name) : this(name, -1) { }
}

using CircleDIAttributes;

namespace MySpace;

public sealed class MyServiceImplementation(string name, int age) {
    // marks this constructor for creating this service
    [Constructor]
    public MyServiceImplementation(string name) : this(name, -1) { }
}

ImportAttribute

This attribute registers all services listed on the specified type. The specified type (also referred as module) can be a class, struct or interface.

using CircleDIAttributes;

[ServiceProvider]
[Import<IMyModule>] // includes services "IService" and "Service"
public sealed partial class MyProvider;

[Singleton<IService, Service>(Name = "IService")]
[Singleton<Service>]
public interface IMyModule;

public interface IService;
public sealed class Service : IService;

You can also include the services listed on another ServiceProvider.

using CircleDIAttributes;

[ServiceProvider]
[Import<MyTopLevelProvider>] // includes services "IService" and "Service"
public sealed partial class MyProvider;

[ServiceProvider]
[Singleton<IService, Service>(Name = "IService")]
[Singleton<Service>]
public partial class MyTopLevelProvider;

public interface IService;
public sealed class Service : IService;

There are 4 different ImportModes to handle the implementation members of a module:

• Static

If the module has only static members or no members at all, it can be imported with ImportMode.Static. This means, no instance of the module is created and service instantiation can be done by constructors and static members.

using CircleDIAttributes;

[ServiceProvider]
[Import<MyModule>(ImportMode.Static)] // includes services "IService" and "Service" without instantiating "MyModule"
public sealed partial class MyProvider;

[Singleton<IService, Service>(Name = "IService")]
[Singleton<Service>]
public class MyModule;

public interface IService;
public sealed class Service : IService;

• Service

The module is registered as singleton service and the instance of that service is used to construct services that need object members for creation.

using CircleDIAttributes;

[ServiceProvider]
[Import<MyModule>(ImportMode.Service)] // includes services "IService" and "Service" and registers "MyModule" as singleton
public sealed partial class MyProvider;

[Singleton<IService, Service>(Name = "IService")]
[Singleton<Service>]
public class MyModule;

public interface IService;
public sealed class Service : IService;

• Parameter

An instance of the module is given by constructor parameter to construct services that need object members for creation.

using CircleDIAttributes;

[ServiceProvider]
[Import<MyModule>(ImportMode.Parameter)] // includes services "IService" and "Service" and adds "MyModule" as constructor parameter
public sealed partial class MyProvider;

[Singleton<IService, Service>(Name = "IService")]
[Singleton<Service>]
public class MyModule;

public interface IService;
public sealed class Service : IService;

• Auto

This mode is the default and it chooses automatically one of these three modes:
Static -> If the given type is an interface Service -> If the given type is constructed with a parameterless constructor Parameter -> otherwise

using CircleDIAttributes;

[ServiceProvider]
[Import<MyModule1>] // defaults to ImportMode.Static -> does not instantiate "MyModule1"
[Import<MyModule2>] // defaults to ImportMode.Service -> registers "MyModule2" as singleton
[Import<MyModule3>] // defaults to ImportMode.Parameter -> adds "MyModule3" as constructor parameter
public sealed partial class MyProvider;

public interface MyModule1;
public class MyModule2;
public class MyModule3(string connectionString);

public interface IService;
public sealed class Service : IService;

If possible, a module should be declared as interface, so it will be automatically imported with ImportMode.Static. A static class also defaults to ImportMode.Static, but should not be used because it cannot be used as generic parameter.

When imported with ImportMode.Service or ImportMode.Parameter, the serviceName/parameterName will always be the name of the module type. In case of a naming conflicts, you have to rename a module or import a module with ImportMode.Static.
Consequently, the diamond problem also leads to a naming conflict.

ImportMode applies always to both ServiceProvider and ScopedProvider, different ImportModes for ServiceProvider and ScopedProvider is not supported.

If the module implements IDisposable/IAsyncDisposable it will only be disposed when it is imported as service.
When it is imported as parameter, the function/object that creates the module should also handle the disposing.
A static import creates no object, so nothing to dispose.

Specific Attributes in Depth

Implementation Property

The Implementation property can contain the name/identifier of a field, property or method, typically supplied with nameof(). If this property is not used, the constructor is used to create an implementation.

If a field is provided, that instance of the field is used. (for singleton/scoped services only)

[ServiceProvider]
[Singleton<IService, Service>(Implementation = nameof(_service))]
public sealed partial class MyProvider {
    private readonly Service _service;

    public MyProvider(Service service) {
        _service = service;
        InitServices();
    }
}

public interface IService;
public sealed class Service : IService;

If a property or method is provided, that factory method is executed to create an implementation.

[ServiceProvider]
[Singleton<IService, Service>(Implementation = nameof(CreateService))]
public sealed partial class MyProvider {
    private Service CreateService => new Service();
}

public interface IService;
public sealed class Service : IService;

If a method is provided and the method has parameters, these parameters will be dependency injected.

[ServiceProvider]
[Singleton<IService, Service>(Implementation = nameof(CreateService))]
[Singleton<INameProvider, NameProvider>]
public sealed partial class MyProvider {
    private Service CreateService(INameProvider nameProvider) => new Service(nameProvider.Name);
}

public interface IService;
public sealed class Service(string name) : IService {
    public string Name => name;
}

public interface INameProvider {
    string Name { get; }
}
public sealed class NameProvider : INameProvider {
    public string Name => "BlackWhiteYoshi";
}

Note:
Do not use the ServiceProvider itself as dependency to resolve your dependencies with that parameter, otherwise there will be no guarantee of order correctness, so the services might not be initialized at that point.

The special keyword "this" is also supported and is treated like a field, see Overwriting default services for an example.

Named Services

The default name/identifier of a service is the name of the implementation class.

[ServiceProvider]
[Singleton<IService, Service1>]     // has name "Service1"
[Singleton<IService, Service2>]     // has name "Service2"
internal sealed partial class MyProvider;

public interface IService;
public sealed class Service1 : IService;
public sealed class Service2 : IService;

The name can be set explicitly by using the Name property. This can be used to avoid naming conflicts.

[ServiceProvider]
[Singleton<IService, Service>(Name = "Service1")]
[Singleton<IService2, Service>(Name = "Service2")]
internal sealed partial class MyProvider;

public interface IService;
public interface IService2;
public sealed class Service : IService, IService2;

When you have multiple services with the same service type, the normal approach injecting the service by service type is ambiguous and will fail in a compile error. In that case you must inject the service by name using the DependencyAttribute.

[ServiceProvider]
[Singleton<IService, Service>]                      // has default name "Service"
[Singleton<IService, Service>(Name = "Service2")]   // explicitly named "Service2"
[Transient<MyService>]
internal sealed partial class MyProvider;

public interface IService;
public sealed class Service : IService;

public sealed class MyService([Dependency(Name = "Service")] IService firstService) {
    [Dependency(Name = "Service2")]
    public required IService SecondService { private get; init; }
}

Generic Services

You can register open/unbound generic services to create automatically all kinds of closed generic services out of it.

namespace MySpace;

[ServiceProvider]
[Singleton(typeof(ILogger<>), typeof(Logger<>))]
public partial class MyProvider;

public class Service1(ILogger<Service1> logger);
public class Service2(ILogger<Service2> logger);

Open generic services are treated differently than non-generic or closed generic services. Behind the scenes they get registered in a separate list. Each time a service cannot be resolved/found in the normal registration list, the open generic list is searched for a match. If a match can be found, the open generic service is taken as template to create a closed service out of it.
Consequently, if a closed generic service and an open generic service are registered and both would match, the already existing closed generic service is taken.
The other take away is, that open generic services are only for generating closed generic services. They do not generate anything on their own. That means, if you want to request a closed generic Service directly from the provider, you must explicitly register that closed version first.

When registering an open generic delegate or provide an implementation method for an open generic service, the number of type parameters of the method and of the service must match. Therefore, fields and properties cannot be used as implementation for open generic services, since they cannot have type parameters.

Implicit Configurations

Name, Namespace, Modifiers, Containing Types and Generic

The class name, type, namespace, containing types and type parameters are given with partial class under the ServiceProviderAttribute. The modifiers are also inferred from the class definition.

namespace MySpace;

public partial class Wrapper {
    [ServiceProvider]
    internal sealed partial record class MyProvider<T>;
}

// generated ServiceProvider will have:
//   name: "MyProvider"
//   type: "record class"
//   namespace: "MySpace"
//   modifier: "internal", "sealed", "partial"
//   containing types: "class Wrapper"
//   type parameter: "T"

Interface name, namespace, access modifier, containing types and generic

When using ServiceProviderAttribute<TInterface> the interface specified as type parameter is used for inferring the properties for the generated interface. The generated interface will have the same name, access modifiers, type parameters, will be in the same namespace and will be nested in the same types.

namespace MySpace {
    [ServiceProvider<Interface.IWrapper.IProvider>]
    internal sealed partial class MyProvider<T> {
        public sealed partial class Scope<U>;
    }
}

namespace MySpace.Interface {
    public partial interface IWrapper {
        internal partial interface IProvider {
            public partial interface IScope<U>;
        }
    }
}


// generated interface will have:
//   name: "IProvider"
//   namespace: "MySpace.Interface"
//   access modifier: "internal", Scope -> "public"
//   containing types: "interface IWrapper"
//   type parameter: Scope -> "U"

For a generic interface set the property InterfaceType with an unbound generic.

namespace MySpace {
    [ServiceProvider(InterfaceType = typeof(Interface.IWrapper.IProvider<>))]
    internal sealed partial class MyProvider<T> {
        public sealed partial class Scope<U>;
    }
}

namespace MySpace.Interface {
    public partial interface IWrapper {
        internal partial interface IProvider<T> {
            public partial interface IScope<U>;
        }
    }
}


// generated interface will have:
//   name: "IProvider"
//   namespace: "MySpace.Interface"
//   access modifier: "internal", Scope -> "public"
//   containing types: "interface IWrapper"
//   type parameter: "T", Scope -> "U"

Overwriting default services

There are always 2 services registered by default: A singleton service returning the ServiceProvider itself and scoped service returning the ScopedProvider itself. If a service is registered that matches the service type and lifetime of a default service, the default service is not registered and the manual registered service is used instead.

Note:
The service types of the ServiceProvider and ScopedProvider are the auto-generated interfaces. You can use them without getting a syntax error, however, at the point of generation the interfaces do not exist yet and therefore the generator will accept these types, but puts them in the global namespace. To solve this issue, you can correct the namespace by just declaring the interface type in the same namespace.
If no interfaces are generated, then the service types are the ServiceProvider and ScopedProvider classes itself.

namespace MySpace;

[ServiceProvider]
// overrides default singleton service => default is identifier "Self", now it is identifier "Me"
[Singleton<IMyProvider, MyProvider>(Name = "Me", Implementation = "this")]
// overrides default scoped service => default is identifier "SelfScope", now it is identifier "MeScope"
[Scoped<IMyProvider.IScope, MyProvider.Scope>(Name = "MeScope", Implementation = "this")]
public sealed partial class MyProvider {
    public sealed partial class Scope;
}

// declaring the interface type in the same namespace
public partial interface IMyProvider {
    public partial interface IScope;
}

Custom Constructor

The generator implements a constructor to initialize Singleton/Scoped services. When you declare a constructor in the ServiceProvider/ScopedProvider, the generator will generate a private InitServices() method instead. This method should be called at the end of your constructor to initialize the services. In the ScopeProvider the generated constructor takes as parameter a reference of the ServiceProvider, so the InitServices() method will also take this parameter.

For constructing the Scope you can make use of the CreateScope() method. Every dependency of the ScopeProvider will be a parameter in CreateScope() or if the dependency has a [Dependency]-attribute, the dependency will be injected from the ServiceProvider instead.

Note:
The service types of the ServiceProvider and ScopedProvider are the auto-generated interfaces. You can use them without getting a syntax error, however, at the point of generation the interfaces do not exist yet and therefore the generator will accept these types, but puts them in the global namespace. To solve this issue, you can correct the namespace by just declaring the interface type in the same namespace.
If no interfaces are generated, then the service types are the ServiceProvider and ScopedProvider classes itself.

[ServiceProvider]
public sealed partial class MyProvider {
    private readonly string _dbConnection;

    public MyProvider(string dbConnection) {
        _dbConnection = dbConnection;
        InitServices();
    }

    public sealed partial class Scope {
        private readonly string _dbConnectionScoped;

        public Scope([Dependency] IMyProvider myProvider, string dbConnectionScoped) {
            _dbConnectionScoped = dbConnectionScoped;
            InitServices(myProvider);
        }
    }
}

// declaring the interface type in the same namespace
public partial interface IMyProvider;

/**
 * generated CreateScope() method:
 *
 * public global::IMyProvider.IScope CreateScope(global::System.String dbConnectionScoped) => new global::MyProvider.Scope(Self, dbConnectionScoped);
 **/

If you have nullable reference types enabled and forgot to call InitServices(), you get "Non-nullable field '{name}' must contain a non-null value when exiting constructor" warning for each reference type service. These warnings vanish when you call InitServices().
You can define multiple constructors in your ScopedProvider, but then you must mark one of them with the ConstructorAttribute.
Primary constructors are not supported and will not be detected as constructor. Since you must call InitServices() at the end of your constructor logic, primary constructors are not suited anyway.

Custom Dispose

The generator implements Dispose() and DisposeAsync() methods when not disabled. When you declare your own Dispose() or DisposeAsync() method in the ServiceProvider/ScopedProvider, the generator will generate a private Dispose()/DisposeAsync() method instead. This method should be called in your Dispose()/DisposeAsync() method to dispose the services.

[ServiceProvider]
public sealed partial class MyProvider {
    // Does the same as not providing this method
    public void Dispose() {
        DisposeServices();
    }

    // Does the same as not providing this method
    public async ValueTask DisposeAsync() {
        await DisposeServicesAsync();
    }

    public sealed partial class Scope {
        // Does the same as not providing this method
        public void Dispose() {
            DisposeServices();
        }

        // Does the same as not providing this method
        public async ValueTask DisposeAsync() {
            await DisposeServicesAsync();
        }
    }
}

Struct Types and Native/Built-in Types

It is also possible to register struct types or native/built-in types as service. If structs are passed by value, they get copied when retrieving the service. So, make sure the registered struct is trivially copyable.

Passing a struct by reference is only possible in certain conditions. First of all, only singleton and scoped services can be passed by reference, transient services have no field where the reference could point to. Additionally service type and implementation type must be the same and the ServiceProvider must be a class.
To pass by reference just use ref, ref readonly, in or out on a dependency parameter.

[ServiceProvider]
[Singleton<IService, Service>]
[Singleton<StructService>]
public sealed partial class MyProvider;


public interface IService;
public sealed class Service(ref StructService structService) : IService;

public struct StructService;

Default Values

If no matching service is registered and a dependency has a default value specified, it will take that value.
An Exception are named services. If a dependency is requested with a specific service, that service must be available and the default value is not taken as fallback.

The parameter default value can be any expression and is not evaluated. Instead, that expression is taken as is with no further checks. So, make sure when using any members (e.g. a method call) as default Value, that these members are accessible and fully qualified, so that the expression is also a valid expression in the dependency container.

[ServiceProvider]
[Singleton<IService, Service>]
public sealed partial class MyProvider;

public interface IService;
public sealed class Service(string optionalKey = "") : IService {
    public required int Number { private get; init; } = 0;
}

Workarounds for not supported Features

Async Constructor

A special feature for constructing services asynchronous or the ServiceProvider itself asynchronous does not exist. However, you can just use common practices to deal with asynchronous operations.

ServiceProvider

If constructing of the ServiceProvider needs a asynchronous operation, just set the constructor private and expose a static async method for constructing the ServiceProvider

[ServiceProvider]
public sealed partial class MyProvider {
    private readonly string _fileContent;

    private MyProvider(string fileContent) {
        _fileContent = fileContent;
        InitServices();
    }

    public static async Task<MyProvider> Create() {
        string fileContent = await File.ReadAllTextAsync("secret.json");
        return new MyProvider(fileContent);
    }
}

Service

If the construction of a service needs asynchronous operations, you can either move the problem to the outside by registering Task<Service> instead of Service:

[ServiceProvider]
[Singleton<Task<MyService>>(Implementation = nameof(CreateMyService))]
public sealed partial class MyProvider {
    public static Task<MyService> CreateMyService => MyService.Create();
}

public class MyService {
    private readonly string _fileContent;

    private MyService(string fileContent) {
        _fileContent = fileContent;
    }

    public static async Task<MyService> Create() {
        string fileContent = await File.ReadAllTextAsync("secret.json");
        return new MyService(fileContent);
    }
}

Or you move the problem to the inside and all methods using the resource become asynchronous operations:

[ServiceProvider]
[Singleton<MyService>]
public sealed partial class MyProvider;

public class MyService {
    private readonly Task<string> _fileContent;

    public MyService() {
        _fileContent = File.ReadAllTextAsync("secret.json");
    }

    public async ValueTask<string> GetSecret() {
        return await _fileContent;
    }
}

Decoration

Sometimes you have a base class and want to extend that class via Composition. The extensions have a dependency to the base class, so you have to register the base class in order to be able to construct the extensions. But then nothing stops other services to (accidentally) get this service as well. To solve this problem you could not register the base class and instead construct the base and each extension by yourself:

[ServiceProvider]
[Singleton<Service1>(Implementation = nameof(CreateService1))]
[Singleton<Service2>(Implementation = nameof(CreateService2))]
public sealed partial class MyProvider {
    private readonly ServiceBase _serviceBase;

    private Service1 CreateService1 => new Service1(_serviceBase);
    private Service2 CreateService2 => new Service2(_serviceBase);

    public MyProvider() {
        _serviceBase = new();
        InitServices();
    }
}

public class ServiceBase;
public class Service1(ServiceBase serviceBase);
public class Service2(ServiceBase serviceBase);

Nullable Service

If you need a service that can be null and you want to decide at runtime if that service is available or not, you have to write that functionality by yourself. The easiest way to achieve this is by using the Nullable<T> type. However, there are some issues with this approach.

• It only works for value types, if you have a reference type service, you have to wrap it in a struct.
• You need to supply an Implementation, because Nullable<T> has multiple constructors and since you do not own the type, you cannot add a [Constructor]-attribute.
• The default name will be "Nullable", so you probably want to set it explicitly.
• If the service implements IDisposable/IAsyncDisposable, it will not be disposed. If the service needs to be disposed, you have to write your own Nullable type that forwards the disposing.

[ServiceProvider]
// MyServiceWrapper? is a shorthand for Nullable<MyServiceWrapper>
[Singleton<MyServiceWrapper?>(Name = "MyValueService", Implementation = nameof(CreateMyService))]
public sealed partial class MyProvider {
    private static MyServiceWrapper? CreateMyService() => SomeRuntimeDecision() ? new() : null;
}

public class MyService;
public record struct MyServiceWrapper(MyService MyService);

Remarks

IServiceProvider Interface

The generated ServiceProvider also implements System.IServiceProvider, but it is not recommended to use it. The interface is implemented explicitly, so you need a IServiceProvider reference to call the GetService(Type) method. The method can return null, an object of the given type or an Array of the given type, depending if the given type is registered zero, one or many times.

Error Handling

The source generator will emit descriptive errors when something is wrong. The location of the error is always at the corresponding attribute to make clear the error originate from a ServiceProvider, even if the error itself is in the interface or implementation. So reading the error message will certainly help to figure out the problem.

However, not all errors are emitted by the source generator, some are just natural syntax errors. e.g. when there are 2 services with the same name/identifier, the generator will generate the source code without issues, but the generated code is just not legal C# code, because the class contains 2 properties/methods with the same name/identifier. It is intended that the generated code can contain errors and do not be afraid of reading and understanding the generated code, it is intended to be read.

Note:
When the generator emits an error, it does not generate the ServiceProvider class. In most cases this results in additional errors and these errors are listed first and the source generator errors are usually at the bottom. So take care of the errors starting with id 'CDI' first and then look at the remaining ones (if any).