[Scala] Add enums to scala-http4s-server

[KatyaValik]

There is an example of correct openAPI specification:

info:
  title: TestApi
  version: latest

components:
  schemas:
    EnumType:
      type: string
      enum:
        - Fix
        - Max
paths:
  /test/method:
    post:
      responses:
        '200':
          description: "success answer"
          content:
            application/json:
              schema:
                type: object
                required:
                  - constraint
                properties:
                  constraint:
                    $ref: '#/components/schemas/EnumType'

For given OpenAPI specification generated not valid type for enum EnumType - empty case class:

case class EnumType()

I added enum handling for scala-http4s-server.
Trying to fix #9987 for scala-http4s-server.

[wing328]

thanks for the PR

cc
@clasnake (2017/07), @shijinkui (2018/01), @ramzimaalej (2018/03), @chameleon82 (2020/03), @Bouillie (2020/04) @Fish86 (2023/06)

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/15276044149/job/42973797933?pr=21320

please follow step 3 to update the samples so that the CI can verify the change

[wing328]

thanks for the PR. what exactly is another?

[KatyaValik]

I added this type to describe types that are not traits or enums. This is necessary to get into this branch in the mustache templates and generate case classes

[chameleon82]

will x-unsupported works better in this case?

[KatyaValik]

I doubt that "unsupported" is the right name for simple types, which generated to scala case classes. I think "another" better describes all types except traits and enums

[wing328]

let's go with what you've right now. we can always fine tune the extension naming later.

[wing328]

tested locally and the result is good

$ sbt compile
[info] welcome to sbt 1.10.11 (Eclipse Adoptium Java 17.0.10)
[info] loading settings for project global-plugins from gpg.sbt...
[info] loading global plugins from C:\Users\wing3\.sbt\1.0\plugins
[info] loading project definition from C:\Users\wing3\AppData\Local\Temp\enumserver\project
[info] loading settings for project enumserver from build.sbt...
[info] set current project to enumserver (in build file:/C:/Users/wing3/AppData/Local/Temp/enumserver/)
[info] Executing in batch mode. For better performance use sbt's shell
[info] compiling 1 Scala source to C:\Users\wing3\AppData\Local\Temp\enumserver\target\scala-2.13\classes ...
[info] done compiling
[info] compiling 1 Scala source to C:\Users\wing3\AppData\Local\Temp\enumserver\target\scala-2.13\classes ...
[info] done compiling
[success] Total time: 11 s, completed Jun 16, 2025, 11:36:45 AM

here is what the change looks like before and after applying this fix

diff --git a/src/main/scala/org/openapitools/models/types.scala b/src/main/scala/org/openapitools/models/types.scala
index 8247885..2075ca8 100644
--- a/src/main/scala/org/openapitools/models/types.scala
+++ b/src/main/scala/org/openapitools/models/types.scala
@@ -8,15 +8,17 @@ import io.circe.{ Decoder, Encoder }
 import io.circe.generic.semiauto.{ deriveDecoder, deriveEncoder }


+import org.openapitools.models.EnumType.EnumType
 /**
 *
 */

-case class EnumType(
-)
-object EnumType {
-  implicit val encoderEnumType: Encoder[EnumType] = deriveEncoder[EnumType].mapJson(_.dropNullValues)
-  implicit val decoderEnumType: Decoder[EnumType] = deriveDecoder[EnumType]
+object EnumType extends Enumeration {
+    type EnumType = Value
+    val Fix = Value
+    val Max = Value
+    implicit val decoder: Decoder[EnumType.Value] = Decoder.decodeEnumeration(EnumType)
+    implicit val encoder: Encoder[EnumType.Value] = Encoder.encodeEnumeration(EnumType)
 }

 /**