[gen] fix for codegen of sumtypes with reusable fields (#2850)

* [gen] sum types (enums) are now generated with cases in companion that actually extend the sealed trait.
      Sum types abstract members generation by reusable components in the schema, as an opt-in, configurable feature.
      Only generating sealed trait body if all subtypes include same reusable component, with it's fields as the abstract trait's members.
      Redundant duplicate classes for each case is now omitted.
      Validate fields in case classes and traits does not contain duplicates that cannot be reconciled.
      Existing tests has been amended to reflect the fix.
      New tests were added.
      Some utilities were added.

* Update zio-http-gen/src/main/scala/zio/http/gen/openapi/Config.scala

* Update zio-http-gen/src/main/scala/zio/http/gen/openapi/Config.scala

* fmt

---------

Co-authored-by: Nabil Abdel-Hafeez <7283535+987Nabil@users.noreply.github.com>

build.sbt

@@ -293,6 +293,7 @@ lazy val zioHttpGen = (project in file("zio-http-gen"))
       `zio-test-sbt`,
       scalafmt.cross(CrossVersion.for3Use2_13),
       scalametaParsers.cross(CrossVersion.for3Use2_13).exclude("org.scala-lang.modules", "scala-collection-compat_2.13"),
+      `zio-json-yaml` % Test
     ),
   )
   .settings(

project/Dependencies.scala

@@ -7,6 +7,7 @@ object Dependencies {
   val ScalaCompactCollectionVersion = "2.12.0"
   val ZioVersion                    = "2.1.1"
   val ZioCliVersion                 = "0.5.0"
+  val ZioJsonVersion                = "0.6.2"
   val ZioSchemaVersion              = "1.1.1"
   val SttpVersion                   = "3.3.18"
   val ZioConfigVersion              = "4.0.2"
@@ -35,6 +36,7 @@ object Dependencies {
 
   val zio                   = "dev.zio" %% "zio"                 % ZioVersion
   val `zio-cli`             = "dev.zio" %% "zio-cli"             % ZioCliVersion
+  val `zio-json-yaml`       = "dev.zio" %% "zio-json-yaml"       % ZioJsonVersion
   val `zio-streams`         = "dev.zio" %% "zio-streams"         % ZioVersion
   val `zio-schema`          = "dev.zio" %% "zio-schema"          % ZioSchemaVersion
   val `zio-schema-json`     = "dev.zio" %% "zio-schema-json"     % ZioSchemaVersion

zio-http-gen/src/main/scala/zio/http/gen/openapi/Config.scala

@@ -0,0 +1,15 @@
+package zio.http.gen.openapi
+
+final case class Config(commonFieldsOnSuperType: Boolean)
+object Config {
+
+  val default: Config = Config(
+    commonFieldsOnSuperType = false,
+  )
+
+  lazy val config: zio.Config[Config] =
+    zio.Config
+      .boolean("common-fields-on-super-type")
+      .withDefault(Config.default.commonFieldsOnSuperType)
+      .map(Config.apply)
+}

zio-http-gen/src/main/scala/zio/http/gen/scala/Code.scala

@@ -62,10 +62,11 @@ object Code {
       Object(name, schema = false, endpoints, Nil, Nil, Nil)
   }
 
-  final case class CaseClass(name: String, fields: List[Field], companionObject: Option[Object]) extends ScalaType
+  final case class CaseClass(name: String, fields: List[Field], companionObject: Option[Object], mixins: List[String])
+      extends ScalaType
 
   object CaseClass {
-    def apply(name: String): CaseClass = CaseClass(name, Nil, None)
+    def apply(name: String, mixins: List[String]): CaseClass = CaseClass(name, Nil, None, mixins)
   }
 
   final case class Enum(
@@ -75,6 +76,7 @@ object Code {
     discriminator: Option[String] = None,
     noDiscriminator: Boolean = false,
     schema: Boolean = true,
+    abstractMembers: List[Field] = Nil,
   ) extends ScalaType
 
   sealed abstract case class Field private (name: String, fieldType: ScalaType) extends Code {

zio-http-gen/src/main/scala/zio/http/gen/scala/CodeGen.scala

@@ -86,20 +86,24 @@ object CodeGen {
           "\n}"
       Nil -> content
 
-    case Code.CaseClass(name, fields, companionObject) =>
+    case Code.CaseClass(name, fields, companionObject, mixins) =>
       val (imports, contents)    = fields.map(render(basePackage)).unzip
       val (coImports, coContent) =
         companionObject.map { co =>
           val (coImports, coContent) = render(basePackage)(co)
           (coImports, s"\n$coContent")
         }.getOrElse(Nil -> "")
+      val mixinsString           = mixins match {
+        case Nil => ""
+        case _   => mixins.mkString(" extends ", " with ", "")
+      }
       val content                =
         s"case class $name(\n" +
           contents.mkString(",\n").replace("val ", " ") +
-          "\n)" + coContent
+          "\n)" + mixinsString + coContent
       (imports.flatten ++ coImports).distinct -> content
 
-    case Code.Enum(name, cases, caseNames, discriminator, noDiscriminator, schema) =>
+    case Code.Enum(name, cases, caseNames, discriminator, noDiscriminator, schema, abstractMembers) =>
       val discriminatorAnnotation      =
         if (noDiscriminator) "@noDiscriminator\n" else ""
       val discriminatorNameAnnotation  =
@@ -118,15 +122,40 @@ object CodeGen {
           imports -> contents.mkString("\n")
         }
 
+      val (traitBodyImports, traitBody) = {
+        val traitBodyBuilder = new StringBuilder().append(' ')
+        var pre              = '{'
+        val imports          = abstractMembers.foldLeft(List.empty[Code.Import]) {
+          case (importsAcc, Code.Field(name, fieldType)) =>
+            val (imports, tpe) = render(basePackage)(fieldType)
+            if (tpe.isEmpty) importsAcc
+            else {
+              traitBodyBuilder += pre
+              pre = '\n'
+              traitBodyBuilder ++= "def "
+              traitBodyBuilder ++= name
+              traitBodyBuilder ++= ": "
+              traitBodyBuilder ++= tpe
+
+              imports ::: importsAcc
+            }
+        }
+        val body             =
+          if (pre == '{') "\n"
+          else traitBodyBuilder.append("\n}\n").result()
+
+        imports -> body
+      }
+
       val content =
         discriminatorAnnotation +
           discriminatorNameAnnotation +
-          s"sealed trait $name\n" +
+          s"sealed trait $name" + traitBody +
           s"object $name {\n" +
           (if (schema) s"\n\n implicit val codec: Schema[$name] = DeriveSchema.gen[$name]\n" else "") +
           casesContent +
           "\n}"
-      casesImports.flatten.distinct -> content
+      casesImports.foldRight(traitBodyImports)(_ ::: _).distinct -> content
 
     case col: Code.Collection =>
       col match {

zio-http-gen/src/test/resources/ComponentAnimal.scala

@@ -0,0 +1,31 @@
+package test.component
+
+import zio.schema._
+import zio.schema.annotation._
+
+@noDiscriminator
+sealed trait Animal
+object Animal {
+
+  implicit val codec: Schema[Animal] = DeriveSchema.gen[Animal]
+  case class Alligator(
+    age: Int,
+    weight: Float,
+    num_teeth: Int,
+  ) extends Animal
+  object Alligator {
+
+    implicit val codec: Schema[Alligator] = DeriveSchema.gen[Alligator]
+
+  }
+  case class Zebra(
+    age: Int,
+    weight: Float,
+    num_stripes: Int,
+  ) extends Animal
+  object Zebra {
+
+    implicit val codec: Schema[Zebra] = DeriveSchema.gen[Zebra]
+
+  }
+}

zio-http-gen/src/test/resources/ComponentAnimalWithAbstractMembers.scala

@@ -0,0 +1,34 @@
+package test.component
+
+import zio.schema._
+import zio.schema.annotation._
+
+@noDiscriminator
+sealed trait Animal {
+  def age: Int
+  def weight: Float
+}
+object Animal       {
+
+  implicit val codec: Schema[Animal] = DeriveSchema.gen[Animal]
+  case class Alligator(
+    age: Int,
+    weight: Float,
+    num_teeth: Int,
+  ) extends Animal
+  object Alligator {
+
+    implicit val codec: Schema[Alligator] = DeriveSchema.gen[Alligator]
+
+  }
+  case class Zebra(
+    age: Int,
+    weight: Float,
+    num_stripes: Int,
+  ) extends Animal
+  object Zebra {
+
+    implicit val codec: Schema[Zebra] = DeriveSchema.gen[Zebra]
+
+  }
+}

zio-http-gen/src/test/resources/ComponentHttpError.scala

@@ -0,0 +1,12 @@
+package test.component
+
+import zio.schema._
+
+case class HttpError(
+  messages: Option[String],
+)
+object HttpError {
+
+  implicit val codec: Schema[HttpError] = DeriveSchema.gen[HttpError]
+
+}

zio-http-gen/src/test/resources/EndpointForZoo.scala

@@ -0,0 +1,15 @@
+package test.api.v1.zoo
+
+import test.component._
+import zio.Chunk
+
+object Animal {
+  import zio.http._
+  import zio.http.endpoint._
+  import zio.http.codec._
+  val get_animal = Endpoint(Method.GET / "api" / "v1" / "zoo" / string("animal"))
+    .in[Unit]
+    .out[Chunk[Animal]](status = Status.Ok)
+    .outError[HttpError](status = Status.InternalServerError)
+
+}

zio-http-gen/src/test/resources/EndpointForZooNoError.scala

@@ -0,0 +1,14 @@
+package test.api.v1.zoo
+
+import test.component._
+import zio.Chunk
+
+object Animal {
+  import zio.http._
+  import zio.http.endpoint._
+  import zio.http.codec._
+  val get_animal = Endpoint(Method.GET / "api" / "v1" / "zoo" / string("animal"))
+    .in[Unit]
+    .out[Chunk[Animal]](status = Status.Ok)
+
+}

zio-http-gen/src/test/resources/GeneratedPaymentNamedDiscriminator.scala

@@ -12,7 +12,7 @@ object PaymentNamedDiscriminator {
   case class Card(
     number: String,
     cvv: String,
-  )
+  ) extends PaymentNamedDiscriminator
   object Card {
 
     implicit val codec: Schema[Card] = DeriveSchema.gen[Card]
@@ -21,7 +21,7 @@ object PaymentNamedDiscriminator {
   @caseName("cash")
   case class Cash(
     amount: Int,
-  )
+  ) extends PaymentNamedDiscriminator
   object Cash {
 
     implicit val codec: Schema[Cash] = DeriveSchema.gen[Cash]

zio-http-gen/src/test/resources/GeneratedPaymentNoDiscriminator.scala

@@ -11,15 +11,15 @@ object PaymentNoDiscriminator {
   case class Card(
     number: String,
     cvv: String,
-  )
+  ) extends PaymentNoDiscriminator
   object Card {
 
     implicit val codec: Schema[Card] = DeriveSchema.gen[Card]
 
   }
   case class Cash(
     amount: Int,
-  )
+  ) extends PaymentNoDiscriminator
   object Cash {
 
     implicit val codec: Schema[Cash] = DeriveSchema.gen[Cash]

zio-http-gen/src/test/resources/inline_schema_sumtype_with_multiple_contradicting_reusable_fields.yaml

@@ -0,0 +1,80 @@
+info:
+  title: Animals Service
+  version: 0.0.1
+tags:
+  - name: Animals_API
+paths:
+  /api/v1/zoo/{animal}:
+    get:
+      operationId: get_animal
+      parameters:
+        - in: path
+          name: animal
+          schema:
+            type: string
+          required: true
+      tags:
+        - Animals_API
+      description: Get animals by species name
+      responses:
+        "200":
+          content:
+            application/json:
+              schema:
+                type: array
+                items:
+                  $ref: '#/components/schemas/Animal'
+          description: OK
+openapi: 3.0.3
+components:
+  schemas:
+    Animal:
+      oneOf:
+        - $ref: '#/components/schemas/Alligator'
+        - $ref: '#/components/schemas/Zebra'
+    HasAgeAndWeight:
+      type: object
+      required:
+        - age
+      properties:
+        age:
+          type: integer
+          format: int32
+          minimum: 0
+        weight:
+          type: number
+          format: float
+          minimum: 0
+    HasWeight:
+      type: object
+      required:
+        - weight
+      properties:
+        weight:
+          type: number
+          format: double
+          minimum: 0
+    Alligator:
+      allOf:
+        - $ref: '#/components/schemas/HasAgeAndWeight'
+        - $ref: '#/components/schemas/HasWeight'
+        - type: object
+          required:
+            - num_teeth
+          properties:
+            num_teeth:
+              type: integer
+              format: int32
+              minimum: 0
+    Zebra:
+      allOf:
+        - $ref: '#/components/schemas/HasAgeAndWeight'
+        - $ref: '#/components/schemas/HasWeight'
+        - type: object
+          required:
+            - num_stripes
+          properties:
+            num_stripes:
+              type: integer
+              format: int32
+              minimum: 0