[Feature request] allow to override default printer

[wahtique]

Hi !

I am confronted with a case where the default diff printer for iterable is less than helpful. Specifically, I have a case class ( a product ) wrapping a ByteVector ( an iterable ). When comparing two instances, the resulting diff look like this :

which is not very helpful as I do not actually want to compar byte by byte. The root cause seem to be

• values are different => munit will try to print the diff https://github.com/scalameta/munit/blob/main/munit/shared/src/main/scala/munit/Assertions.scala#L309 by using munit.internal.console.Printers
• it finds a case class which is a product and recursively try to print each field https://github.com/scalameta/munit/blob/main/munit/shared/src/main/scala/munit/internal/console/Printers.scala#L102
• the ByteVector is an iterable => compare element wise https://github.com/scalameta/munit/blob/main/munit/shared/src/main/scala/munit/internal/console/Printers.scala#L83

Rough expected behaviour would be :

• Given a case class wrapping an scodecs ByteVector https://github.com/scodec/scodec-bits/blob/main/core/shared/src/main/scala/scodec/bits/ByteVector.scala

//> using scala "3.2.2"
//> using dep  "org.scodec::scodec-bits:1.1.37"

import scodec.bits.ByteVector

final case class Wrapped(bv: ByteVector) {
  val stringValue: String = s"0x${bv.toHex}"
  override def toString: String = stringValue
}

• When I compare two instances

//> using dep "org.scalameta::munit0.7.29"

import munit.FunSuite

class Example extends FunSuite {
  test("This will fail") {
    val a = Wrapped(ByteVector.fromValidHex("0x1")
    val b = Wrapped(ByteVector.fromValidHex("0x2")
    assertEquals(a, b)
  }
}

• Then the diff should be

- Wrapped(0x1)
+ Wrapped(0x2)

Would it be possible to :

• use traits instead of an object for printers so that users could override them when needed ?
• use implicits for printers to allow more fine grained control over diffs for specific types ?

[wahtique]

Nvm foud the custom printer param :)