Mazboot (previously called Validated)

Companion to the Scala std lib, providing newtypes + validations. It has usefull types out of the box (like PositiveInt or MatchesRegex), as well as the ability to define your own custom validated types.

"mazboot" (مظبوط) is an Egyptian Arabic word that could mean "correct", "proper", or "valid".

Example:

scala> import mazboot.strings.NonEmptyString

scala> NonEmptyString.validate("") // Error messages out of the box                   
val res0: NonEmptyString.Error | NonEmptyString.Valid = NonEmptyString.Error: '' doesn't pass the predicate: not equals

scala> val input: NonEmptyString = NonEmptyString.validate("input-from-user").getOrThrow
val input: NonEmptyString.Valid = input-from-user

scala> val itIsAlsoString: String = input // isA relationship (subtyping)
val itIsAlsoString: String = input-from-user

scala> val butNotTheOtherWayAround: NonEmptyString = "lol" // Doesn't compile, must validate to get instance of NonEmptyString
1 |val butNotTheOtherWayAround: NonEmptyString = "lol"
  |                                              ^^^^^
  |            Found:    ("lol" : String)
  |            Required: mazboot.strings.NonEmptyString

You can also make your own types

import mazboot.validations.strings.StartsWith
import mazboot.net.Ipv4

val StartsWith127 = StartsWith("127")
type StartsWith127 = StartsWith127.Valid

val LocalHost = Ipv4 and StartsWith127 // Combine newtypes to make new ones
type LocalHost = LocalHost.Valid

val x: LocalHost = LocalHost.validate("127.0.0.1").getOrThrow

// isA relationships work as you expect
val mustBeIpV4: Ipv4 = x
val mustBeStartsWith: StartsWith127 = x

// Composes Error messages out of the box
println(LocalHost.validate("loll").toEither.left.map(_.getMessage))
// Left('loll' doesn't pass the predicate: match pattern '^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$' and start with '127')

Also, it works out of the box with Scala 3' Main methods syntax

import mazboot.net.{Ipv4, PortNumber}

@main def myCmdLineApp(host: Ipv4, port: PortNumber): Unit = 
  println(s"host = $host, port = $port")

$ sbt run 127.0.0.1 99999
Illegal command line after first argument: java.lang.IllegalArgumentException: '99999' doesn't pass the predicate: greater than 0 or equals 0 and less than 65535 or equals 65535

Getting started

Add the following to your build.sbt

libraryDependencies += "com.abdulradi" %% "mazboot-types" % "0.5.0"

Integrations

Happypath

Did you notice we have been calling toEither and getOrThrow on a union type? This functionality comes from happypath. Allowing union types to behave like Either/Try without any implicits imports at the use site.

import mazboot.ints.{GreaterThanOrEqualsOne, Positive}

val res = // ValidationError | Int
    for
      a <- GreaterThanOrEqualsOne.validate(1)
      b <- Positive.validate(1)
    yield a + b

Positive.validate(-1).fold(e => s"Error!! $e", n =>  s"Res = $n")
// val res2: String = Error!! mazboot.validations.Validation$Error: '-1' doesn't pass the predicate: greater than 0

Note: this integration is part of the core module, so nothing needs to be added to build.sbt

Cats Parse

Add this your build.sbt

libraryDependencies += "com.abdulradi" %% "mazboot-cats-parse" % "0.5.0"

This module will allow you to easily extend cats parsers with a validation step

import cats.parse.Parser
import mazboot.cats.parse.syntax.*
import mazboot.net.*

val parser = Parser.anyChar.rep.string.validateAs(Ipv4)
val a: Ipv4 = parser.parse("127.0.0.1").fold(_ => ???, _._2)
parser.parse("lol").fold(e => println(e.expected), _ => ???) 
// Error(3,NonEmptyList(FailWith(3,'lol' doesn't pass the predicate: match pattern '^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$')))

Ciris

Add this your build.sbt

libraryDependencies += "com.abdulradi" %% "mazboot-ciris" % "0.5.0"

This module provides ConfigDecoder instance for all Validated types

import mazboot.net.*
import mazboot.ciris.given
import cats.effect.*
import cats.implicits.*
import ciris.*

case class Config(host: Ipv4, port: PortNumber)

object App extends IOApp.Simple:
  val run = 
    (
      env("HOST").as[Ipv4],
      env("PORT").as[PortNumber]
    ).parMapN(Config.apply).load[IO].flatMap(IO.println)

Acknowledgements

This library is inspired by Refined and tries to provide similar functionality using Scala 3 constructs.

tabdulradi / mazboot 0.5.0