NDLRCOR009: Lazy references undiscovered type¶

Cause¶

A constructor parameter of type Lazy<T> references a type T that was not discovered by source generation.

Rule Description¶

When using source generation with [assembly: GenerateTypeRegistry], Needlr scans your codebase to discover injectable types. This analyzer detects when a Lazy<T> dependency references a type that wasn't found during that scan.

// ⚠️ NDLRCOR009: IUnknownService not discovered
public class OrderService(Lazy<IUnknownService> unknown)
{
    // ...
}

This is an informational diagnostic (not a warning or error) because:

The type may be registered via reflection at runtime
The type may come from a third-party library
The type may be registered manually in an IServiceCollectionPlugin

How to Fix¶

Option 1: Ensure the Type is Discoverable¶

Make sure the implementation is in a namespace matching your IncludeNamespacePrefixes:

[assembly: GenerateTypeRegistry(IncludeNamespacePrefixes = new[] { "MyApp" })]

namespace MyApp.Services
{
    public interface IUnknownService { }

    // ✅ This will be discovered
    public class UnknownService : IUnknownService { }
}

Option 2: Register Manually via Plugin¶

If the type is intentionally registered elsewhere:

public class MyPlugin : IServiceCollectionPlugin
{
    public void Configure(IServiceCollection services)
    {
        // Registered manually - Lazy<IExternalService> will work
        services.AddSingleton<IExternalService, ExternalService>();
    }
}

Option 3: Suppress the Diagnostic¶

If you know the type will be available at runtime:

#pragma warning disable NDLRCOR009
public class OrderService(Lazy<IExternalService> external)
#pragma warning restore NDLRCOR009
{
    // ...
}

Or suppress project-wide in .editorconfig:

# .editorconfig
[*.cs]
dotnet_diagnostic.NDLRCOR009.severity = none

When This Analyzer Activates¶

This analyzer only runs when [assembly: GenerateTypeRegistry] is present. In reflection-only projects, there's no type registry to validate against.

Severity Levels¶

Level	Meaning
`info` (default)	Informational hint in IDE
`warning`	Promote to build warning
`error`	Fail the build
`none`	Disable completely

Configure in .editorconfig:

# Promote to warning for stricter validation
dotnet_diagnostic.NDLRCOR009.severity = warning