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Effect Documentation

Effect 3.1 (Release)

Tim Smart
Tim Smart
Founding Engineer

Effect 3.1.0 has been released! This release includes a number of new features and improvements. Here’s a summary of what’s new:

Stream.fromEventListener

This new api allows you to create a Stream from an EventTarget:

import { Stream } from "effect/Stream"


Stream.fromEventListener(window, "click")

@effect/platform-browser/BrowserStream has also been added, with fromEventListenerWindow & fromEventListenerDocument apis.

Effect.timeoutOption

A new timeout api has been added, which returns the result of the wrapped Effect as an Option.

If the wrapped Effect times out, a Option.None is returned - otherwise the result is wrapped with Option.Some.

”kind” field has been added to spans

Tracing spans now include a kind field, which is used to indicate the type of system that generated the span.

For example, @effect/platform/HttpServer will generate spans with a kind of server. While @effect/platform/HttpClient will generate spans with a kind of client.

@effect/platform/Http/Multipart schema changes

  • Http.multipart.filesSchema has been renamed to Http.multipart.FilesSchema
  • Http.multipart.FileSchema is now exported
  • Http.multipart.SingleFileSchema has been added

Effect.annotateLogsScoped

A new api has been added to Effect which allows you to annotate logs during the lifetime of a Scope.

import { Effect } from "effect"


Effect.gen(function* () {
  yield* Effect.log("no annotations")
  yield* Effect.annotateLogsScoped({ foo: "bar" })
  yield* Effect.log("annotated with foo=bar")
}).pipe(Effect.scoped, Effect.andThen(Effect.log("no annotations again")))

Data.TaggedEnum helpers

$is & $match helpers have been added to Data.TaggedEnum constructors.

import { Data } from "effect"


type HttpError = Data.TaggedEnum<{
  NotFound: {}
  InternalServerError: { reason: string }
}>
const { $is, $match, InternalServerError, NotFound } =
  Data.taggedEnum<HttpError>()


// create a matcher
const matcher = $match({
  NotFound: () => 0,
  InternalServerError: () => 1
})


// use the guard
$is("NotFound")(NotFound()) // true
$is("NotFound")(InternalServerError({ reason: "fail" })) // false

Types.DeepMutable

A type helper has been added, which transforms a type into a deeply mutable version.

import { Types } from "effect"


type Values<A> = {
  readonly _tag: string
  readonly value: ReadonlyArray<A>
}


// { _tag: string, value: Array<A> }
type MutableValues<A> = Types.DeepMutable<Values<A>>

New SortedMap APIs

  • SortedMap.lastOption has been added
  • SortedMap.partition has been added

Other changes

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

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