sprits

💦 Type-safe concurrent pipeline for ambitious applications

Features

✅ Declarative definition

A step is an object containing an Effect and its inputs. When running a step, a dependency graph will be generated and the steps will be run as concurrently as possible.

const child = Step.make({
  title: "some-step",
  inputs: [parent],
  run: Effect.succeed(42),
});

This means that you don't need to think whether something should run concurrently, it will just happen.

🔒 Extreme type-safe and composability

Thanks to Effect.ts, we get extreme type-safe and composition so we can build resilient apps that can scale fearlessly:

Error propagation

Errors are propagated to Step.run and can be handled in a type safe manner, so we won't leak errors to customers.

Context-aware input reading

Reading a step's inputs is provided through an Effect.ts context, meaning that you can compose function easily and don't think about passing down the input arguments.

All you need is to yield* step.

Bonus: if you try to read from an input that wasn't defined in Step.make, you will get a type error to make sure you define all the inputs and the dependency graph is correct.

const parent = Step.make({
  title: "parent",
  inputs: [],
  run: Effect.succeed(42),
});

const child = Step.make({
  title: "child",
  inputs: [], // forgot to pass the parent

  // 👇 TypeScript error: undeclared step input "parent"
  run: Effect.gen(function* () {
    yield* parent;
  }),
});

[!NOTE] Other Effect.ts context services will be propagated as usual. It's only step outputs that behave differently to ensure the dependency graph is known before we execute the code. This means you can keep doing yield* Db and provide you services in the runtime level the way you know and love from Effect.ts.

🖌️ Generate a graph (dot notation)

Once you have your steps defined, you can call Step.toDot(step) to generate a nice dot notation graph of your steps. This can be fed to a graphviz renderer to visualize the steps into a picture.

Complete example

import { Step } from "../src/index.ts";
import { Config, Data, Effect } from "effect";
import Fs from "node:fs/promises";
import { spawn } from "node:child_process";

const RandomDirectory = {
  make: Effect.promise(() => Fs.mkdtemp("ci-")),
};

class ProcessFailed extends Data.TaggedError("ProcessFailed")<{
  code: null | number;
}> {}

const runShell = (command: string, opts?: { cwd: string }) =>
  Effect.async<void, ProcessFailed>((emit) => {
    const spawned = spawn(`bash`, ["-c", command], { cwd: opts?.cwd });
    spawned.on("close", (code) => {
      emit(code === 0 ? Effect.void : Effect.fail(new ProcessFailed({ code })));
    });
    return Effect.sync(() => spawned.kill());
  });

const clone = Step.make({
  title: "clone",
  inputs: [],
  run: Effect.gen(function* () {
    const cwd = yield* RandomDirectory.make;
    const repo = yield* Config.string("GIT_REPO");
    yield* runShell(`git clone ${repo} ${cwd}`);
    return cwd;
  }),
});

const install = Step.make({
  title: "install",
  inputs: [clone],
  run: Effect.gen(function* () {
    const cwd = yield* clone;
    yield* runShell(`pnpm install`, { cwd });
    return cwd;
  }),
});

const build = Step.make({
  title: "build",
  inputs: [install],
  run: Effect.gen(function* () {
    const cwd = yield* install;
    yield* runShell("pnpm run build", { cwd });
  }),
});

const test = Step.make({
  title: "test",
  inputs: [install],
  run: Effect.gen(function* () {
    const cwd = yield* install;
    yield* runShell(`pnpm run test`, { cwd });
  }),
});

const release = Step.make({
  title: "release",
  inputs: [install, test, build],
  run: Effect.gen(function* () {
    const cwd = yield* install;
    yield* runShell(`pnpm publish`, { cwd });
  }),
});

// Generate a dot notation
const dot = Step.toDot(release).pipe(Effect.runSync);
Fs.writeFile("file.dot", dot);

// Run the app
Step.run(release)
  .pipe(Effect.runPromise)
  .then(
    () => console.log("finished publishing"),
    (err) => console.error(`Error: ${err}`),
  );