zlick

Slick ZIO bindings for Scala 3.

Getting Started

zlick-core

Core module providing ZIO integration for Slick's DBIO actions.

libraryDependencies += "dev.hshn" %% "zlick-core" % "<version>"

zlick-prelude

Optional module adding ZIO Prelude Newtype column type support.

libraryDependencies += "dev.hshn" %% "zlick-prelude" % "<version>"

Setup

Mix zlick traits into your Slick profile:

import slick.jdbc.PostgresProfile
import zlick.*

object MyProfile extends PostgresProfile
  with ZioApiComponent
  with OptionDBIOComponent
  with EitherDBIOComponent {

  object MyApi extends JdbcAPI
    with ZioApi
    with OptionDBIOApi
    with EitherDBIOApi
}

import MyProfile.MyApi.*

Usage

Running DBIO as ZIO

// Expose database exceptions as ZIO failures
val result: Task[Int] =
  db.runZIO.attempt(DBIO.successful(42))

// Database exceptions become ZIO defects (for infallible queries)
val result: ZIO[Any, Nothing, Int] =
  db.runZIO.succeed(DBIO.successful(42))

// Map Either: Left becomes ZIO failure, Right becomes success
// Requires a transactional DBIO
val result: ZIO[Any, String, Int] =
  db.runZIO.fromEither {
    myTransactionalQuery.transactionally
  }

Embedding ZIO into DBIO

val dbio: DBIO[Int] = ZIO.succeed(42).unsafeToDBIO

Option Combinators

Extension methods on DBIO[Option[A]]:

// Apply f on Some, short-circuit on None
findById(id).semiFlatMap(user => updateLastLogin(user))

// Fallback if None
findById(id).orElseF(findByEmail(email))

// Convert to Either: Some → Right, None → Left
findById(id).someOrLeft(UserNotFound(id))

// Extract Some or fail with exception
findById(id).someOrFail(new NoSuchElementException("not found"))

Either Combinators

Extension methods on DBIO[Either[L, R]]:

// Apply f on Right, short-circuit on Left
validate(input).semiflatMap(data => save(data))

// Apply pure function returning Either
validate(input).subflatMap(data => refine(data))

// Chain with another DBIO[Either[...]]
validate(input).flatMapF(data => checkUniqueness(data))

// Extract Right when Left is Nothing
DBIO.successful(Right(42): Either[Nothing, Int]).right

Transactional Rollback on Left

Tag an Either action with .rollbackOnLeft to roll back the transaction when the result is Left, while still returning the Left value (instead of throwing):

val result: DBIO[Either[String, Int]] =
  insertRecord(data)
    .flatMap(_ => validate(data))
    .rollbackOnLeft
    .transactionally
// Right → committed, Left → rolled back (Left value preserved)

Newtype Column Types (zlick-prelude)

Map ZIO Prelude Newtype values to Slick columns:

import zlick.NewtypeColumnTypesComponent

object MyProfile extends PostgresProfile with NewtypeColumnTypesComponent {
  object MyApi extends JdbcAPI with NewtypeColumnTypesApi
}
import MyProfile.MyApi.*

object UserId extends Newtype[String]
type UserId = UserId.Type

// No validation on read
given BaseColumnType[UserId] = MappedColumnType.newtypeWrap(UserId)

// Validates assertions on read
given BaseColumnType[UserId] = MappedColumnType.newtypeMake(UserId)

Requirements

• Scala 3
• Slick 3.6.x
• ZIO 2.x

License

Apache License 2.0