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Effect Documentation

Effect 3.7 (Release)

Tim Smart
Tim Smart
Founding Engineer

Effect 3.7 has been released! This release includes a number of new features and improvements. Here’s a summary of what’s new:

HttpApi modules in @effect/platform

The HttpApi family of modules provide a declarative way to define HTTP APIs.

These modules are still experimental and subject to change, so give them a try and post your feedback on the Effect Discord.

For more infomation see the README for the @effect/platform package:
https://github.com/Effect-TS/effect/blob/main/packages/platform/README.md

Effect.bindAll

Effect.bindAll combines Effect.all with Effect.bind, to allow you to combine multiple effects inside of a do notation pipeline.

import { Effect } from "effect"


const result = Effect.Do.pipe(
  Effect.bind("x", () => Effect.succeed(2)),
  Effect.bindAll(
    ({ x }) => ({
      a: Effect.succeed(x + 1),
      b: Effect.succeed("foo"),
    }),
    { concurrency: 2 },
  ),
)
assert.deepStrictEqual(Effect.runSync(result), {
  x: 2,
  a: 3,
  b: "foo",
})

Stream.race

Stream.race takes two streams, and the first stream to emit an item will be elected as the winner and continue to emit items. The other stream will be interrupted.

import { Stream, Schedule, Console, Effect } from "effect"


const stream = Stream.fromSchedule(Schedule.spaced('2 millis')).pipe(
  Stream.race(Stream.fromSchedule(Schedule.spaced('1 millis'))),
  Stream.take(6),
  Stream.tap(n => Console.log(n))
)


Effect.runPromise(Stream.runDrain(stream))
// Output each millisecond from the first stream, the other stream is interrupted
// 0
// 1
// 2
// 3
// 4
// 5

Config.nonEmptyString

Use Config.nonEmptyString to create a Config that is guaranteed to be a non-empty string. If the config value is present but is empty, Config.withDefault can be used to provide a fallback value.

Add propagateInterruption option to FiberHandle/Set/Map

In the case you would like Fiber interrupts to be propogated to Fiber{Handle,Set,Map}.join, you can now use the propagateInterruption option.

import { Effect, FiberHandle } from "effect"


Effect.gen(function*() {
  const handle = yield* FiberHandle.make()


  // run a fiber and propagate interrupts
  yield* FiberHandle.run(handle, Effect.interrupt, {
    propagateInterruption: true
  })


  // this will now receive the interrupt
  yield* FiberHandle.join(handle)
})

Fiber.awaitAll now returns Exit values

Previously Fiber.awaitAll would return a void result.

Now Fiber.awaitAll will return an Array<Exit<A, E>>, so you can inspect the results of the completed fibers.

Preserve non-empty arrays in Array module

The following apis will now preserve non-empty array types:

  • Array.modify
  • Array.modifyOption
  • Array.replace
  • Array.replaceOption

Scope finalizer concurrency is no longer automatically propogated

Previously, when using apis like Effect.forEach with concurrency, the Scope finalizer concurrency would be automatically adjusted to match.

In some scenarios this could cause finalizers to leak, so now the behavior must be explicitly requested using the concurrentFinalizers option.

import { Effect } from "effect"


Effect.forEach([1, 2, 3], (n) => Effect.succeed(n), {
  concurrency: "unbounded",
  concurrentFinalizers: true
})

Other changes

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

Don’t forget to join our Discord Community to follow the last updates and discuss every tiny detail!

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