JasperFx.SourceGenerator

Roslyn source generators for JasperFx, all reflection-free for fast cold start and trim/AOT-friendly builds. This single analyzer package bundles five generators:

Renamed from JasperFx.SourceGeneration. The command-discovery and input-parser generators previously shipped in the JasperFx.SourceGeneration (noun) package, which is now retired. Reference JasperFx.SourceGenerator (singular) instead — its version tracks the JasperFx package.

Install

<PackageReference Include="JasperFx.SourceGenerator"
                  PrivateAssets="all"
                  OutputItemType="Analyzer"
                  ReferenceOutputAssembly="false" />

Reference it as an analyzer/source-generator only — there's no runtime API. For OptionsDescription, apply the [GenerateDescription] attribute to a partial class that implements IDescribeMyself and a ToDescription() method is generated. The command-discovery and input-parser output is consumed transparently by JasperFx.CommandLine.

Service registrations

Annotate a concrete class with [JasperFxService(typeof(TService), ServiceLifetime)] to have the generator emit a real DI registration for it. The generator produces a per-assembly JasperFx.Generated.GeneratedServiceRegistrations.Register(IServiceCollection) method of plain services.Add(new ServiceDescriptor(...)) calls — no reflection, trim/AOT-clean.

[JasperFxService(typeof(IWolverineExtension), ServiceLifetime.Singleton)]
public class MyExtension : IWolverineExtension { }

// Open generic service types are closed from the implemented interface (=> IValidator<Foo>):
[JasperFxService(typeof(IValidator<>), ServiceLifetime.Scoped)]
public class FooValidator : IValidator<Foo> { }

Apply the attribute multiple times to register one implementation against several service types. At startup, apply everything discovered across the loaded assemblies (reflection-free on the generated side; a no-op when the generator wasn't run, so a reflective fallback still applies):

JasperFx.GeneratedExtensionManifest.RegisterAllDiscoveredServices(services);

Only assemblies that are eligible emit a manifest — those carrying a [JasperFxAssembly]-derived attribute, or executable (entry) assemblies — matching the ExtensionDiscoveryGenerator gate.

Performance

The generators replace runtime reflection with code emitted at compile time. Measured against the reflection fallback with BenchmarkDotNet (src/CommandLineBenchmarks, Apple M5 Max, .NET 9):

The win is eliminating reflection (PropertyInfo.SetValue, converter lookups, assembly scanning), not eliminating allocation — the generated parser still allocates its handler list and delegates. Earlier "thousands of times faster / zero allocation" figures were a measurement artifact: the generators were emitting nothing, so the benchmark compared reflection against a no-op. The numbers above reflect the generators actually running.

Documentation

Full docs at https://jasperfx.net.

Repo: github.com/JasperFx/jasperfx.