effect-io-ai

Package: effect
Module: Effect

Effect.runSync

Executes an effect synchronously, running it immediately and returning the result.

Details

This function evaluates the provided effect synchronously, returning its result directly. It is ideal for effects that do not fail or include asynchronous operations. If the effect does fail or involves async tasks, it will throw an error. Execution stops at the point of failure or asynchronous operation, making it unsuitable for effects that require asynchronous handling.

Important: Attempting to run effects that involve asynchronous operations or failures will result in exceptions being thrown, so use this function with care for purely synchronous and error-free effects.

When to Use

Use this function when:

• You are sure that the effect will not fail or involve asynchronous operations.
• You need a direct, synchronous result from the effect.
• You are working within a context where asynchronous effects are not allowed.

Avoid using this function for effects that can fail or require asynchronous handling. For such cases, consider using runPromise or runSyncExit.

Example (Synchronous Logging)

import { Effect } from "effect"

const program = Effect.sync(() => {
  console.log("Hello, World!")
  return 1
})

const result = Effect.runSync(program)
// Output: Hello, World!

console.log(result)
// Output: 1

Example (Incorrect Usage with Failing or Async Effects)

import { Effect } from "effect"

try {
  // Attempt to run an effect that fails
  Effect.runSync(Effect.fail("my error"))
} catch (e) {
  console.error(e)
}
// Output:
// (FiberFailure) Error: my error

try {
  // Attempt to run an effect that involves async work
  Effect.runSync(Effect.promise(() => Promise.resolve(1)))
} catch (e) {
  console.error(e)
}
// Output:
// (FiberFailure) AsyncFiberException: Fiber #0 cannot be resolved synchronously. This is caused by using runSync on an effect that performs async work

See

• runSyncExit for a version that returns an Exit type instead of throwing an error.

Signature

declare const runSync: <A, E>(effect: Effect<A, E>) => A

Source

Since v2.0.0