Skip to main content

Cheatsheet

Basic imports​

import difflicious.*
import difflicious.implicits.*

Summoning Differ instances​

val intListDiffer = Differ[List[Int]]

Deriving instances for case class and sealed traits (Scala 3 enums)​

val differ = Differ.derived[Person]

Use Differ.derivedDeep when you want Difflicious to recursively derive missing field instances at that call site. Existing instances in scope still take priority.

case class Address(city: String)
case class Employee(name: String, address: Address)

val differ = Differ.derivedDeep[Employee]

For classes with generic fields, Differ.derived needs you to also ask for the Differ instance of the field type (not just the generic type).

case class Box[A](
  content: List[A]
)

case class Factory[A](
  boxes: List[Box[A]]
)

implicit def boxDiffer[A](implicit listDiffer: Differ[List[A]]): Differ[Box[A]] = Differ.derived[Box[A]]
implicit def factoryDiffer[A](implicit boxesDiffer: Differ[List[Box[A]]]): Differ[Factory[A]]  = Differ.derived[Factory[A]]

val differ = Differ[Factory[Int]]

If you do not need to name those intermediate instances, derivedDeep can derive the missing instances recursively:

val differ = Differ.derivedDeep[Factory[Int]]

Configuring Differs​

val differ = Differ[Map[String, List[Person]]]

differ.configure(_.each)(_.pairBy(_.name))
differ.configure(_.each)(_.pairByIndex)

differ.ignoreAt(_.each.each.name)
// Equivalent to differ.configure(_.each.each.name)(_.ignore)

// Replacing a differ at path
val anotherPersonListDiffer: Differ[List[Person]] = ???
differ.replace(_.each)(anotherPersonListDiffer)