ZIO learning - playing with json - zio-json cheat sheet / published by https://github.com/dacr/code-examples-manager #862c2592-c58c-4541-817b-eaf9da4c762e/40cadbd8aa99c0c3de770cd58ab647a0f736e0b8

zio-learning-json-2-cheat-sheet.sc

// summary : ZIO learning - playing with json - zio-json cheat sheet
// keywords : scala, zio, learning, json, pure-functional, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// license-url :
// id : 862c2592-c58c-4541-817b-eaf9da4c762e
// created-on : 2021-12-30T10:57:55+01:00
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala  "3.3.1"
//> using dep "dev.zio::zio:2.0.21"
//> using dep "dev.zio::zio-test:2.0.21"
//> using dep "dev.zio::zio-json:0.6.2"
//> using options "-Yretain-trees" // When case classes are using default values
// ---------------------

import zio.*
import zio.json.*
import zio.json.ast.{Json, JsonCursor, JsonType}
import zio.json.ast.Json.*
import zio.json.ast.JsonCursor.*
import zio.test.*
import zio.test.TestAspect.*
import zio.test.Assertion.*
import scala.annotation.targetName

import java.time.{Instant, ZonedDateTime}
import java.util.UUID

case class A(
  message: String
) derives JsonCodec

case class B(
  value: Long
) derives JsonCodec

case class Something(
  a: Int,
  b: Int
) derives JsonCodec

case class MayHaveContent(
  id: String,
  content: Option[String]
) derives JsonCodec

case class SomethingComplex(
  a: Int,
  b: Int,
  c: MayHaveContent
) derives JsonCodec

case class DummyClassWithURIBasedPropertyName(
  @targetName("isIn") `http://elite.polito.it/ontologies/dogont.owl#isIn`: String,
  @targetName("isbn1") `URN:ISBN:0-395-36341-1`: Int
) derives JsonCodec

enum Gender(val code: Int) {
  case Male   extends Gender(51)
  case Female extends Gender(42)
}
object Gender              {
  given JsonEncoder[Gender] = JsonEncoder[String].contramap(p => p.toString)
  given JsonDecoder[Gender] = JsonDecoder[String].map(p => Gender.valueOf(p))
}

object JsonTests extends ZIOSpecDefault:
  def spec = suite("learning zio json through tests")(
    // -----------------------------------------------------------------------
    test("literal types")(
      assertTrue(
        "42".fromJson[Int] == Right(42),
        "42.0".fromJson[Double] == Right(42d),
        """"hello"""".fromJson[String] == Right("hello")
      )
    ),
    // -----------------------------------------------------------------------
    test("object types")(
      assertTrue(
        """{"a":42,"b":24}""".fromJson[Map[String, Int]] == Right(Map("a" -> 42, "b" -> 24)),
        """{"a":42,"b":24}""".fromJson[Something] == Right(Something(42, 24))
      )
    ),
    // -----------------------------------------------------------------------
    test("collection types")(
      assertTrue(
        // "[1,2,3]".fromJson[Array[Int]] == Right(Array(1, 2, 3)), // TAKE CARE WITH JAVA ARRAY => THIS TEST FAILS
        "[1,2,3]".fromJson[List[Int]] == Right(List(1, 2, 3)),
        "[1,2,3]".fromJson[Vector[Int]] == Right(Vector(1, 2, 3)),
        """[{"a":42,"b":24}, {"a":52,"b":34}]""".fromJson[List[Something]] == Right(List(Something(42, 24), Something(52, 34)))
      )
    ),
    // -----------------------------------------------------------------------
    test("date/time types")(
      // assert(""""2021-12-30T10:57:55+01:00"""".fromJson[Instant])(isRight(equalTo(Instant.parse("2021-12-30T10:57:55+01:00"))))
      assertTrue(
        """"2021-12-30T09:57:55Z"""".fromJson[Instant] == Right(Instant.parse("2021-12-30T10:57:55+01:00")),
        """"2021-12-30T10:57:55+01:00"""".fromJson[ZonedDateTime] == Right(ZonedDateTime.parse("2021-12-30T10:57:55+01:00"))
      )
    ),
    // -----------------------------------------------------------------------
    test("advanced types")(
      assertTrue(""""da0214d8-88fe-4d3f-8fc4-bd1ac19758c1"""".fromJson[UUID] == Right(UUID.fromString("da0214d8-88fe-4d3f-8fc4-bd1ac19758c1")))
    ),
    // -----------------------------------------------------------------------
    test("enumeration types")(
      assertTrue(
        "\"Male\"".fromJson[Gender] == Right(Gender.Male),
        Gender.Female.toJson == "\"Female\""
      )
    ),
    // -----------------------------------------------------------------------
      test ("jsonify") {
        val result     = """{"a":42,"b":24}"""
        val collection = Map("a" -> 42, "b" -> 24)
        assertTrue(
          collection.toJson == result,
          Something(42, 24).toJson == result
        )
      },
    test("jsonify complex") {
      val result     = """{"a":42,"b":24,"c":{"id":"aa-bb","content":"hello"}}"""
      val collection = Map("a" -> Num(42), "b" -> Num(24), "c" -> Obj("id" -> Str("aa-bb"), "content" -> Str("hello")))
      assertTrue(
        collection.toJson == result,
        SomethingComplex(42, 24, MayHaveContent("aa-bb", Some("hello"))).toJson == result
      )
    },
    test("jsonify complex property name") {
      val result = """{"http://elite.polito.it/ontologies/dogont.owl#isIn":"room","URN:ISBN:0-395-36341-1":42}"""
      assertTrue(
        DummyClassWithURIBasedPropertyName("room", 42).toJson == result
      )
    },
    test("jsonify map") {
      val result = """{"a":42,"b":24.0,"c":"hello"}"""
      type GenericValue = Int | Double | String
      type GenericMap   = Map[String, GenericValue]
      given JsonEncoder[GenericMap]             = JsonEncoder[Map[String, Json]].contramap { initialMap =>
        initialMap.map {
          case (key, x: Int)    => key -> Num(x)
          case (key, x: Double) => key -> Num(x)
          case (key, x: String) => key -> Str(x)
        }
      }
      val collection: Map[String, GenericValue] = Map("a" -> 42, "b" -> 24d, "c" -> "hello")
      assertTrue(collection.toJson == result)
    },
    test("jsonify map 2") {
      case class Dummy(x: Int, y: String) derives JsonCodec
      type GenericValue = Int | Double | String | Dummy
      type GenericMap   = Map[String, GenericValue]

      given JsonEncoder[GenericMap] = JsonEncoder[Map[String, Json]].contramap { initialMap =>
        initialMap.map {
          case (key, x: Int)    => key -> Num(x)
          case (key, x: Double) => key -> Num(x)
          case (key, x: String) => key -> Str(x)
          case (key, x: Dummy)  =>
            key ->
              x.toJsonAST.toOption.get
          // OF COURSE VERY BAD CODE HERE
          // AND : the type test for Dummy cannot be checked at runtime
        }
      }

      val result                                = """{"a":42,"b":24.0,"c":"hello"}"""
      val collection: Map[String, GenericValue] = Map("a" -> 42, "b" -> 24d, "c" -> "hello")
      assertTrue(collection.toJson == result)
    },
    // -----------------------------------------------------------------------
    test("jsonify option") {
      val json1 = """{"id":"42"}"""
      val json2 = """{"id":"42","content":"the response"}"""
      val inst1 = MayHaveContent("42", None)
      val inst2 = MayHaveContent("42", Some("the response"))
      for {
        parsedInst1    <- ZIO.from(json1.fromJson[MayHaveContent])
        parsedInst2    <- ZIO.from(json2.fromJson[MayHaveContent])
        astJson1       <- ZIO.from(json1.fromJson[Json])
        astJson2       <- ZIO.from(json2.fromJson[Json])
        // convertedInst1 <- ZIO.from(astJson1.as[MayHaveContent])
        convertedInst2 <- ZIO.from(astJson2.as[MayHaveContent])
      } yield assertTrue(
        inst1.toJson == json1,
        inst2.toJson == json2,
        parsedInst1 == inst1,
        parsedInst2 == inst2,
        // convertedInst1 == inst1,
        convertedInst2 == inst2
      )
    },
    // -----------------------------------------------------------------------
    test("jsonify JWT example") {
      val jwtId           = UUID.randomUUID().toString
      val nowEpochSeconds = Instant.now.getEpochSecond

      val result =
        s"""{
           |  "jti" : "$jwtId",
           |  "iss" : "this-app",
           |  "iat" : $nowEpochSeconds,
           |  "exp" : ${nowEpochSeconds + 60L},
           |  "nbf" : ${nowEpochSeconds + 2L},
           |  "sub" : "userlogin@example.com",
           |  "user" : 1
           |}""".stripMargin

      val claim = Map(
        "jti"  -> Str(jwtId),                   // JTW ID
        "iss"  -> Str("this-app"),              // Issuer
        "iat"  -> Num(nowEpochSeconds),         // Issued at
        "exp"  -> Num(nowEpochSeconds + 60L),   // Expiration time
        "nbf"  -> Num(nowEpochSeconds + 2L),    // Not before
        "sub"  -> Str("userlogin@example.com"), // The subject
        "user" -> Num(1)
      )
      for {
        claimAST  <- ZIO.from(claim.toJsonAST)
        resultAST <- ZIO.from(result.fromJson[Json])
      } yield assertTrue(claimAST == resultAST)
    },
    // -----------------------------------------------------------------------
    test("json AST") {
      val reference = """{"a":42,"b":24}"""
      for {
        result <- ZIO.from(reference.fromJson[Json])
      } yield {
        assertTrue(result.toJson == reference) &&
        assertTrue(result.as[Something] == Right(Something(42, 24))) &&
        assert(result.as[Something])(isRight(equalTo(Something(42, 24)))) &&
        assertTrue(result.as[Map[String, Int]] == Right(Map("a" -> 42, "b" -> 24))) &&
        assert(result.as[Map[String, Int]])(isRight(equalTo(Map("a" -> 42, "b" -> 24))))
      }
    },
    // -----------------------------------------------------------------------
    test("build json from scratch") {
      val json: Json = Obj("a" -> Num(42), "b" -> Num(24))
      val payload    = json.merge(Obj("c" -> Str("424")))
      assertTrue(payload.toJson == """{"a":42,"b":24,"c":"424"}""")
    },
    // -----------------------------------------------------------------------
    test("build json from scala data structures simple case") {
      val json = Map("a" -> 42, "b" -> 24)
      for {
        payload <- ZIO.from(json.toJsonAST) // initially Either[String,Json]
      } yield assertTrue(payload.toJson == """{"a":42,"b":24}""")
    },
    // -----------------------------------------------------------------------
//    test("build json from scala data structures complex case") {
//      val json = Map("a" -> 42, "b" -> 24, "c" -> "424", "d" -> Map("x" -> 42))
//      // Map[String, Any] => No codec for Any of course !
//      for {
//        payload <- ZIO.from(json.toJsonAST)
//      } yield assertTrue(payload.toJson == """{"a":42,"b":24,"c":"424","d":{"x":42}}""")
//    },
    // -----------------------------------------------------------------------
    test("build json from scala data structures limitations") {
      // use Json instead of AnyRef As it encapsulate types
      val json: Map[String, Json] = Map(
        "a" -> Num(42),
        "b" -> Num(24),
        "c" -> Str("424"),
        "d" -> Obj("x" -> Num(42))
      )
      for {
        payload <- ZIO.from(json.toJsonAST)
      } yield assertTrue(payload.toJson == """{"a":42,"b":24,"c":"424","d":{"x":42}}""")
    },
    // -----------------------------------------------------------------------
    test("build json from scala data structures limitations alternative ?") {
//      type JMap = Map[String, JVal]   // Cyclic reference !
//      type JVal = String | Int | Double | JMap
//      val json: JMap = Map(
//        "a" -> 42,
//        "b" -> 24,
//        "c" -> "424",
//        "d" -> Map("x" -> 42d)
//      )
      // case class is the only solution
      case class D(x: Double) derives JsonCodec
      case class O(a: Int, b: Int, c: String, d: D) derives JsonCodec
      val json = O(a = 42, b = 24, c = "424", d = D(x = 42d))
      for {
        payload <- ZIO.from(json.toJsonAST)
      } yield assertTrue(payload.toJson == """{"a":42,"b":24,"c":"424","d":{"x":42.0}}""")
    },
    // -----------------------------------------------------------------------
    test("json AST content extraction") {
      val reference  = """{"a":42,"b":24,"items":[42,24]}"""
      val jsonEither = reference.fromJson[Json]
      for {
        result    <- ZIO.from(jsonEither)
        itemsJson <- ZIO.from(result.get(field("items").isArray))
        items     <- ZIO.from(itemsJson.as[List[Int]])
      } yield {
        assertTrue(items == List(42, 24))
      }
    },
    // -----------------------------------------------------------------------
    test("json AST default values for missing fields") {
      val reference = """{"a":42,"b":24,"c":{"c1":142,"c2":124}}"""
      for {
        result     <- ZIO.from(reference.fromJson[Json])
        rawArr1    <- ZIO.from(result.get(field("arr").isArray)).option.map(_.getOrElse(Arr()))
        emptyArray <- ZIO.from(rawArr1.as[List[Int]])
      } yield {
        assertTrue(emptyArray.isEmpty)
      }
    },
    // -----------------------------------------------------------------------
    test("json AST content array field extraction") {
      val reference =
        """{
          |  "name":"joe",
          |  "age":42,
          |  "address":{"town":"there", "country":"france"},
          |  "phones":[{"kind":"mobile","num":"+330600000000"}, {"kind":"fix"}]
          |}""".stripMargin
      for {
        json      <- ZIO.from(JsonDecoder[Json].decodeJson(reference))
        cursor     = field("phones").isArray.element(0).isObject.field("num").isString
        phoneJson <- ZIO.from(json.get(cursor))
        // Str(phone)  <- ZIO.from(json.get(cursor)).mapError(err => Exception(err))
        // Str(phone2) <- ZIO.attempt(json.get(cursor)).absolve
      } yield {
        assertTrue(
          phoneJson.value == "+330600000000"
          // assertTrue(phone == "+330600000000"
          // assertTrue(phone2 == "+330600000000"
        )
      }
    },
    // -----------------------------------------------------------------------
    test("json AST equality corner cases") {
      val a = """{"a":42}"""
      val b = """{"a":42.0}"""
      for {
        astA <- ZIO.from(a.fromJson[Json])
        astB <- ZIO.from(b.fromJson[Json])
      } yield assertTrue(astA == astB)
    } @@ ignore,
    // -----------------------------------------------------------------------
    test("json encoding/decoding either type") {
      type MyEither = Either[String, Long]
      val a: MyEither = Right(42L)
      val b: MyEither = Left("Hello")
      for {
        // _       <- Console.printLine(s"a=${a.toJson} b=${b.toJson}")
        resultA <- ZIO.from(a.toJson.fromJson[MyEither])
        resultB <- ZIO.from(b.toJson.fromJson[MyEither])
      } yield assertTrue(
        resultA == a,
        resultB == b
      )
    },
    // -----------------------------------------------------------------------
    test("json encoding/decoding either type with case classes") {
      type MyEither = Either[A, B]
      val a: MyEither = Right(B(42L))
      val b: MyEither = Left(A("Hello"))
      for {
        // _       <- Console.printLine(s"a=${a.toJson} b=${b.toJson}")
        resultA <- ZIO.from(a.toJson.fromJson[MyEither])
        resultB <- ZIO.from(b.toJson.fromJson[MyEither])
      } yield assertTrue(
        resultA == a,
        resultB == b
      )
    }
  )

JsonTests.main(Array.empty)

Hey thanks for the cheatsheet. I used it to get more familiar with the ast cursor functionality.