Nestia

What is Nestia?

Nestia turns a plain TypeScript type into everything a NestJS server usually needs to wire by hand. You write one interface, and you get:

Runtime validation of requests and responses — typically 30–100× faster than class-validator and up to 20,000× on pathological cases.
A typed client SDK — like tRPC, but over plain REST.
An OpenAPI 3.1 / 3.0 / 2.0 document.
An end-to-end test suite generated for every endpoint.
A mockup simulator so a frontend can call your API before the server exists.

No decorator triplets. No separate schema files. No codegen round-trip. Just types.

The vanilla NestJS problem

NestJS DTOs need to be declared three times:


class CreateArticle {
  @ApiProperty({ description: "Title", minLength: 3, maxLength: 50 })   // ← Swagger
  @IsString() @MinLength(3) @MaxLength(50)                              // ← validator
  title!: string;
  // ...and the TypeScript type itself
}

Three sources of truth. Any drift — and there is always drift — becomes a runtime bug.

Nestia replaces all of that with one TypeScript type. The validation, the schema, and the SDK function signature all derive from the same declaration:


interface ICreateArticle {
  title: string & tags.MinLength<3> & tags.MaxLength<50>;
}

That’s it. The rest is generated.

How it works (in three lines)

You decorate routes with @TypedRoute.* and parameters with @TypedBody, @TypedParam, @TypedQuery — same shape as vanilla NestJS, type-aware.
At build time, ttsc (a Go-based TypeScript compiler) runs Nestia’s transformer. It reads your TypeScript types and inlines a hand-written validator and serializer for each call site.
The nestia CLI reads the same types to generate an SDK, a Swagger document, and an e2e suite into files you commit.

The packages

Nestia is a small family. The two you’ll see most are bold:

@nestia/core — typed request / response decorators for NestJS controllers.
@nestia/sdk — generators: SDK, Swagger document, mockup simulator, e2e suite.
@nestia/fetcher — the typed fetch runtime the generated SDK is built on.
@nestia/e2e — discoverer and helpers for the generated e2e suite.
@nestia/benchmark — runs the same e2e functions as a load test.
@nestia/migrate — turns an existing Swagger document into a NestJS project.
@nestia/editor — Swagger UI with an embedded TypeScript playground.
nestia — the CLI that drives @nestia/sdk.