Add Effect.transposeFlatMapOption

[vinassefranche]

Type

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

This adds Effect.transposeFlatMapOption:

import { Effect, Option, pipe } from "effect"
//          ┌─── Effect<Option<number>, never, never>>
//          ▼
const noneResult = pipe(
  Option.none(),
  Effect.transposeFlatMapOption(() => Effect.succeedSome(42)) // will not be executed
)
console.log(Effect.runSync(noneResult))
// Output: { _id: 'Option', _tag: 'None' }
//          ┌─── Effect<Option<number>, never, never>>
//          ▼
const someSuccessResult = pipe(
  Option.some(42),
  Effect.transposeMapOption((value) => Effect.succeedSome(value 2))
)
console.log(Effect.runSync(someSuccessResult))
// Output: { _id: 'Option', _tag: 'Some', value: 84 }
//          ┌─── Effect<Option<number>, never, never>>
//          ▼
const someSuccessResult = pipe(
  Option.some(42),
  Effect.transposeMapOption((value) => Effect.succeedNone())
)
console.log(Effect.runSync(someSuccessResult))
// Output: { _id: 'Option', _tag: 'None' }

Related

• Related Issue #
• Closes #

[changeset-bot]

🦋 Changeset detected

Latest commit: d0fba6d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 32 packages

Name	Type
effect	Minor
@effect/cli	Major
@effect/cluster	Major
@effect/experimental	Major
@effect/opentelemetry	Major
@effect/platform-browser	Major
@effect/platform-bun	Major
@effect/platform-node-shared	Major
@effect/platform-node	Major
@effect/platform	Major
@effect/printer-ansi	Major
@effect/printer	Major
@effect/rpc	Major
@effect/sql-clickhouse	Major
@effect/sql-d1	Major
@effect/sql-drizzle	Major
@effect/sql-kysely	Major
@effect/sql-libsql	Major
@effect/sql-mssql	Major
@effect/sql-mysql2	Major
@effect/sql-pg	Major
@effect/sql-sqlite-bun	Major
@effect/sql-sqlite-do	Major
@effect/sql-sqlite-node	Major
@effect/sql-sqlite-react-native	Major
@effect/sql-sqlite-wasm	Major
@effect/sql	Major
@effect/typeclass	Major
@effect/vitest	Major
@effect/ai	Major
@effect/ai-anthropic	Major
@effect/ai-openai	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[tim-smart]

Not sure about this, we are trying to get away from auto flattening now.

[gcanti]

Yeah, automatic flattening is almost always an unexpected behavior and should be avoided.

[vinassefranche]

Ok. I get the point.
@tim-smart or @gcanti would you be ok with a transposeFlatMapOption then or is it not an option?

[vinassefranche]

@tim-smart and @gcanti I did the change to Effect.transposeFlatMapOption. Tell me if you think it's a good idea or if I should discard the pull request completely

[gcanti]

@vinassefranche I'm not sure this is a common enough use case to justify a dedicated API

import { Effect, Option, pipe } from "effect"

//     ┌─── Effect<Option<number>, never, never>>
//     ▼
const res = pipe(
  Option.some(2),
  Effect.transposeMapOption((n) => Effect.succeedSome(n * 3)),
  Effect.map(Option.flatten)                                   
)

[vinassefranche]

@vinassefranche I'm not sure this is a common enough use case to justify a dedicated API

import { Effect, Option, pipe } from "effect"

//     ┌─── Effect<Option<number>, never, never>>
//     ▼
const res = pipe(
  Option.some(2),
  Effect.transposeMapOption((n) => Effect.succeedSome(n * 3)),
  Effect.map(Option.flatten)                                   
)

Alright. We have this helper in our code base anyway. This is something we do pretty often so it's worth for us but I know you want to limit the api surface so I won't push it :-)