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Effect Documentation

Effect 3.12 (Release)

Tim Smart
Tim Smart
Founding Engineer

Effect 3.12 has been released! This release includes a number of new features and improvements. Here’s a summary of what’s new:

Effect.fn improvements

  • Stack traces will now include the location where the function was defined, not just where it was called.
  • A variant has been added that allows you to directly pass the function body.
  • Effect.fnUntraced has been added which allows you to create a function that is not traced, for when performance is critical.
import { NodeRuntime } from "@effect/platform-node"
import { Effect } from "effect"


const boomFunction = Effect.fn(function*(n: number) { // line 4
  yield* Effect.annotateCurrentSpan("n", n)
  yield* Effect.fail(new Error("boom")) // line 6
})


boomFunction(42).pipe( // line 9
  Effect.catchAllCause(Effect.logError),
  NodeRuntime.runMain
)


/*
Output:


[09:33:00.998] ERROR (#0):
  Error: boom
      at <anonymous> (/Volumes/Code/effect/effect/scratchpad/fn.ts:6:22)
      at <anonymous> (/Volumes/Code/effect/effect/scratchpad/fn.ts:4:29)
      at <anonymous> (/Volumes/Code/effect/effect/scratchpad/fn.ts:9:1)
*/

Runtime.Context type extractor

You can now easily extract the R (requirements) type from a Runtime.

import { Runtime } from "effect"


declare const runtime: Runtime<"ServiceA" | "ServiceB">


// "ServiceA" | "ServiceB"
type Extracted = Runtime.Runtime.Context<typeof runtime>

Context.mergeAll

This API allows you to merge multiple Context instances into a single one.

import { Context } from "effect"


declare const contextA: Context.Context<"A">
declare const contextB: Context.Context<"B">
declare const contextC: Context.Context<"C">


// Context.Context<"A" | "B" | "C">
const merged = Context.mergeAll(contextA, contextB, contextC)

Cron improvements

  • Cron expressions now support second granularity.
  • Added Cron.unsafeParse which throws an error if the expression is invalid
import { Cron } from "effect"


// At 04:00:30 on every day-of-month from 8 through 14.
const cron = Cron.unsafeParse("30 0 4 8-14 * 0-6")
const either = Cron.parse("30 0 4 8-14 * 0-6")


// `cron` is a `Cron` instance instead of an `Either` type

Schema additions

Some new schema types & combinators have been added:

  • DateTimeUtcFromDate - Transform a Date to a DateTime.Utc.
  • StringFromUriComponent - Transform a URI component encoded string to a regular string.
  • headNonEmpty - Get the first element of a non-empty array.

Other changes

There were several other smaller changes made. Take a look through the CHANGELOG to see them all: CHANGELOG.

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