effect-io-ai

Package: effect
Module: Runtime

Runtime.makeRunMain

Creates a platform-specific main program runner that handles Effect execution lifecycle.

When to use

Use when building a runtime adapter for a host platform.

Details

The runner executes Effect programs as main entry points. The provided function receives a forked fiber and a teardown callback so it can install platform-specific signal handling, fiber observers, and final exit behavior.

Most applications should use a platform-provided runner, such as NodeRuntime.runMain, rather than constructing one directly.

disableErrorReporting disables the automatic log emitted for unreported non-interruption failures. It does not change exit-code calculation or the custom teardown callback.

Gotchas

The setup function is responsible for observing the fiber and eventually invoking teardown. makeRunMain also tries to keep the host process alive with a long interval while the main fiber is running; if the host blocks timers, the runner still starts but cannot use that keep-alive fallback.

Example (Creating platform runners)

import { Effect, Fiber, Runtime } from "effect"

// Create a simple runner for a hypothetical platform
const runMain = Runtime.makeRunMain(({ fiber, teardown }) => {
  // Set up signal handling
  const handleSignal = () => {
    Effect.runSync(Fiber.interrupt(fiber))
  }

  // Add signal listeners (platform-specific)
  // process.on('SIGINT', handleSignal)
  // process.on('SIGTERM', handleSignal)

  // Handle fiber completion
  fiber.addObserver((exit) => {
    teardown(exit, (code) => {
      console.log(`Program finished with exit code: ${code}`)
      // process.exit(code)
    })
  })
})

// Use the runner
const program = Effect.gen(function*() {
  yield* Effect.log("Starting program")
  yield* Effect.sleep(1000)
  yield* Effect.log("Program completed")
  return "success"
})

// Run with default options
runMain(program)

// Run with custom teardown
runMain(program, {
  teardown: (exit, onExit) => {
    console.log("Custom teardown logic")
    Runtime.defaultTeardown(exit, onExit)
  }
})

Signature

declare const makeRunMain: (f: <E, A>(options: { readonly fiber: Fiber.Fiber<A, E>; readonly teardown: Teardown; }) => void) => { (options?: { readonly disableErrorReporting?: boolean | undefined; readonly teardown?: Teardown | undefined; }): <E, A>(effect: Effect.Effect<A, E>) => void; <E, A>(effect: Effect.Effect<A, E>, options?: { readonly disableErrorReporting?: boolean | undefined; readonly teardown?: Teardown | undefined; }): void; }

Source

Since v4.0.0