A menagerie of macro utilities and extensions for Scala 3.
"io.github.kitlangton" %% "quotidian" % "0.0.14"Currently, this library supports FromExpr and ToExpr derivation. It also contains an opinionated set of
extensions and extractors for working with scala.quoted; these are brought into scope with import quotidian.syntax.*.
- Add
FromExprderivation - Add
ToExprderivation - Support Parameterized Types
- Add support for leaving out default values
Writing FromExpr instances is a boilerplate-heavy task. Wouldn't it be better if it were derivable?
How boring! How trite! 😭
import quotidian.*
import scala.quoted.*
final case class Person(name: String, age: Int, pet: Pet)
object Person:
given FromExpr[Person] with
def unapply(expr: Expr[Person])(using Quotes): Option[Person] =
import quotes.reflect.*
expr match
case '{ Person(${ Expr(name) }, ${ Expr(age) }, ${ Expr(pet) }) } =>
Some(Person(name, age, pet))
case _ => None
given ToExpr[Person] with
def apply(person: Person)(using Quotes): Expr[Person] =
import quotes.reflect.*
'{ Person(${ Expr(person.name) }, ${ Expr(person.age) }, ${ Expr(person.pet) }) }
final case class Pet(name: String, hasBone: Boolean, favoritePerson: Option[Person])
object Pet:
given FromExpr[Pet] with
def unapply(expr: Expr[Pet])(using Quotes): Option[Pet] =
import quotes.reflect.*
expr match
case '{ Pet(${ Expr(name) }, ${ Expr(hasBone) }, ${ Expr(favoritePerson) }) } =>
Some(Pet(name, hasBone, favoritePerson))
case _ => None
given ToExpr[Pet] with
def apply(pet: Pet)(using Quotes): Expr[Pet] =
import quotes.reflect.*
'{ Pet(${ Expr(pet.name) }, ${ Expr(pet.hasBone) }, ${ Expr(pet.favoritePerson) }) }
enum Fruit:
case Apple(variety: String)
case Orange(juiciness: Int)
case Banana(isYellow: Boolean)
object Fruit:
given FromExpr[Fruit] with
def unapply(expr: Expr[Fruit])(using Quotes): Option[Fruit] =
import quotes.reflect.*
expr match
case '{ Fruit.Apple(${ Expr(variety) }) } => Some(Fruit.Apple(variety))
case '{ Fruit.Orange(${ Expr(juiciness) }) } => Some(Fruit.Orange(juiciness))
case '{ Fruit.Banana(${ Expr(isYellow) }) } => Some(Fruit.Banana(isYellow))
case _ => None
given ToExpr[Fruit] with
def apply(fruit: Fruit)(using Quotes): Expr[Fruit] =
import quotes.reflect.*
fruit match
case Fruit.Apple(variety) => '{ Fruit.Apple(${ Expr(variety) }) }
case Fruit.Orange(juiciness) => '{ Fruit.Orange(${ Expr(juiciness) }) }
case Fruit.Banana(isYellow) => '{ Fruit.Banana(${ Expr(isYellow) }) }Much better! Much more concise! 😍
import quotidian.*
import scala.quoted.*
case class Person(name: String, age: Int, pet: Pet) derives FromExpr, ToExpr
case class Pet(name: String, hasBone: Boolean, favoritePerson: Option[Person]) derives FromExpr, ToExpr
enum Fruit derives FromExpr, ToExpr:
case Apple(variety: String)
case Orange(juiciness: Int)
case Banana(isYellow: Boolean)