Deepstaging — Roslyn code generation for LanguageExt effects

[trbngr]

I've been building a code generation toolkit on top of LanguageExt for the last year or so and it's at a point worth sharing.

The core idea is simple: everything fans out from a Runtime composed of EffectsModules.

[EffectsModule(typeof(IEmailService))]
public sealed partial class EmailModule;

[Runtime]
[Uses(typeof(EmailModule))]
public sealed partial class ScribeRuntime;

That's it. The generator sees your Runtime, sees what it [Uses], and generates the capability interfaces, the DI wiring, and OpenTelemetry instrumentation for every effect method. Your handlers work with Eff<ScribeRuntime, A> and the compiler enforces that you only touch capabilities you declared.

The testing story is where it gets interesting. Drop [TestRuntime] on a class and you get generated stubs, builders, and in-memory implementations for every capability. No mocking frameworks, no DI containers, no ceremony:

[TestRuntime<ScribeRuntime>]
public partial class TestScribeRuntime;

var runtime = TestScribeRuntime.Create()
    .WithStubEmailService(stub => stub
        .OnSendAsync(_ => unit));

var result = await ArticleCommands.Handle(cmd).Run(runtime);
await Assert.That(result).IsSucc();

Set INTEGRATION=true and the same tests run against real Postgres/Redis/whatever via Testcontainers. Same assertions, same test code — just a different runtime configuration.

There's a bunch of other stuff built on top: [DataStore] for persistence with generated CRUD effects, [DispatchModule] for typed CQRS where method overload resolution IS the dispatch (no runtime routing), [TypedId] for strongly-typed IDs, [ConfigProvider] for typed configuration with JSON Schema, [EventQueue] for Channel-backed async workflows. 50+ analyzers catch mistakes at compile time with one-click fixes.

Not open source yet but getting close. Docs site and NuGet packages attached below.

Full Docs: https://deepstaging.github.io/

[micmarsh]

Very interesting! I don't know when I'll have time to look into this deeply, but it seems to address a very important need to drive language-ext adoption. Maybe too premature to compare to Rails for Ruby adoption, but that general idea.

[trbngr]

It's definitely shaping up to be a super rails!

I really had no intention of any of that. I simply went coding my way into understanding the Roslyn APIs with the intention of cleaning up a horribly implemented source generator I made for a previous project...

Then I started to realize what I created was insanely powerful. https://deepstaging.github.io/roslyn/index.html

Which resulted in many experiments, and ultimately this. https://deepstaging.github.io/deepstaging/index.html

Do take a look when you get a chance. I'm really underselling it in the OP.

[micmarsh]

Looks very promising indeed! A couple of points of feedback

• I've found the pattern of "Eff with a runtime containing 'more traditional' OO services" to be very viable in my limited experimentation, so it's interesting and reassuring to see you're taking the same approach for the actual business logic here
• The main thing I was thinking as I was skimming the tutorial was "where is all of this actually getting stored?", and the only mention of non in-memory services was in the "Integration Testing" section
  • Related to this, it'd be really great to have a SQLite storage layer like the Postgres one that's used in testing, since it would suit both my own preferences and add a "get up and running quickly" element to the guide, being so low-maintainence.

Anyway, all I've been able to do is read so far, but I'm excited to try this out for some of my own projects and see where it goes from here (especially once the source is open!)

[trbngr]

Thanks for the feedback.

"Eff with a runtime containing 'more traditional' OO services" really shines a light how insane coding has become!

SQLite support should be a dead simple task and I will put it on the backlog -- right on top!

I will work on getting my packages publishing again tonight or tomorrow.

[micmarsh]

Haha, I wasn't even referring to that pattern as negative thing, but maybe I'm just like this guy https://www.youtube.com/watch?v=Uo3cL4nrGOk in regards to hybrid OO-FP C#, describing the mess and then saying "I love it".

Thanks for prioritizing SQLite! I think time on my end is the main obstacle to getting up and running, so no rush.