Missing Support for ComposedModels

[irishshagua]

Swagger documents which contain model definitions which use inheritance via the allOf property (as documented here ) fail to generate server/client stubs due to a Match Error as per the stack trace:

`Exception in thread "main" scala.MatchError: io.swagger.models.ComposedModel@99ff0ebf (of class io.swagger.models.ComposedModel)
at com.twilio.swagger.codegen.SwaggerUtil$.modelMetaType(SwaggerUtil.scala:113)
at com.twilio.swagger.codegen.generators.CirceProtocolGenerator$ProtocolSupportTermInterp$.$anonfun$apply$49(CirceProtocolGenerator.scala:279)
at cats.instances.ListInstances$$anon$1.$anonfun$traverse$2(list.scala:73)
at cats.instances.ListInstances$$anon$1.loop$2(list.scala:63)
at cats.instances.ListInstances$$anon$1.$anonfun$foldRight$1(list.scala:63)
at cats.Eval$$anon$11.$anonfun$start$3(Eval.scala:276)
at cats.Eval$.loop$1(Eval.scala:338)
at cats.Eval$.cats$Eval$$evaluate(Eval.scala:372)
at cats.Eval$Defer.value(Eval.scala:258)
at cats.instances.ListInstances$$anon$1.traverse(list.scala:72)
at cats.instances.ListInstances$$anon$1.traverse(list.scala:12)
at cats.Traverse$Ops.traverse(Traverse.scala:19)
at cats.Traverse$Ops.traverse$(Traverse.scala:19)
at cats.Traverse$ToTraverseOps$$anon$3.traverse(Traverse.scala:19)
at com.twilio.swagger.codegen.generators.CirceProtocolGenerator$ProtocolSupportTermInterp$.apply(CirceProtocolGenerator.scala:275)
at com.twilio.swagger.codegen.generators.CirceProtocolGenerator$ProtocolSupportTermInterp$.apply(CirceProtocolGenerator.scala:271)
at cats.data.EitherK.$anonfun$fold$1(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:189)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.data.EitherK.$anonfun$fold$2(EitherK.scala:87)
at scala.util.Either.fold(Either.scala:188)
at cats.data.EitherK.fold(EitherK.scala:87)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at cats.arrow.FunctionK$$anon$2.apply(FunctionK.scala:47)
at com.twilio.swagger.codegen.generators.AkkaHttp$.apply(AkkaHttp.scala:24)
at com.twilio.swagger.codegen.generators.AkkaHttp$.apply(AkkaHttp.scala:14)
at cats.free.Free.$anonfun$foldMap$1(Free.scala:155)
at cats.data.EitherTMonad.$anonfun$tailRecM$1(EitherT.scala:581)
at cats.data.WriterTFlatMap1.step$1(WriterT.scala:329)
at cats.data.WriterTFlatMap1.$anonfun$tailRecM$2(WriterT.scala:340)
at cats.package$$anon$1.tailRecM(package.scala:42)
at cats.data.WriterTFlatMap1.tailRecM(WriterT.scala:340)
at cats.data.WriterTFlatMap1.tailRecM$(WriterT.scala:326)
at cats.data.WriterTInstances3$$anon$4.tailRecM(WriterT.scala:185)
at cats.data.WriterTInstances3$$anon$4.tailRecM(WriterT.scala:185)
at cats.data.EitherTMonad.tailRecM(EitherT.scala:581)
at cats.data.EitherTMonad.tailRecM$(EitherT.scala:580)
at cats.data.EitherTInstances1$$anon$1.tailRecM(EitherT.scala:507)
at cats.data.EitherTInstances1$$anon$1.tailRecM(EitherT.scala:507)
at cats.free.Free.foldMap(Free.scala:153)
at cats.free.Free.$anonfun$foldMap$1(Free.scala:156)
at cats.data.EitherTMonad.$anonfun$tailRecM$1(EitherT.scala:581)
at cats.data.WriterTFlatMap1.step$1(WriterT.scala:329)
at cats.data.WriterTFlatMap1.$anonfun$tailRecM$2(WriterT.scala:340)
at cats.package$$anon$1.tailRecM(package.scala:42)
at cats.data.WriterTFlatMap1.tailRecM(WriterT.scala:340)
at cats.data.WriterTFlatMap1.tailRecM$(WriterT.scala:326)
at cats.data.WriterTInstances3$$anon$4.tailRecM(WriterT.scala:185)
at cats.data.WriterTInstances3$$anon$4.tailRecM(WriterT.scala:185)
at cats.data.EitherTMonad.tailRecM(EitherT.scala:581)
at cats.data.EitherTMonad.tailRecM$(EitherT.scala:580)
at cats.data.EitherTInstances1$$anon$1.tailRecM(EitherT.scala:507)
at cats.data.EitherTInstances1$$anon$1.tailRecM(EitherT.scala:507)
at cats.free.Free.foldMap(Free.scala:153)
at com.twilio.swagger.codegen.core.CoreTermInterp$.$anonfun$apply$36(CoreInterp.scala:98)
at com.twilio.swagger.codegen.ReadSwagger$.$anonfun$unsafeReadSwagger$3(ReadSwagger.scala:16)
at scala.Option.map(Option.scala:146)
at com.twilio.swagger.codegen.ReadSwagger$.$anonfun$unsafeReadSwagger$2(ReadSwagger.scala:15)
at scala.Option.flatMap(Option.scala:171)
at com.twilio.swagger.codegen.ReadSwagger$.unsafeReadSwagger(ReadSwagger.scala:14)
at com.twilio.swagger.codegen.CLICommon$.$anonfun$run$8(CLI.scala:63)
at scala.collection.immutable.List.map(List.scala:283)
at com.twilio.swagger.codegen.CLICommon$.run(CLI.scala:62)
at com.twilio.swagger.codegen.CLICommon.main(CLI.scala:114)
at com.twilio.swagger.codegen.CLICommon.main$(CLI.scala:113)
at com.twilio.swagger.codegen.CLI$.main(CLI.scala:118)
at com.twilio.swagger.codegen.CLI.main(CLI.scala)`

A sample swagger document to reproduce this issue is attached:

 swagger: '2.0'
 info:
   title: Parsing Error Sample
   version: 1.0.0
 paths:
   /pet/{name}:
     get:
       parameters:
         - $ref: '#/parameters/PetNamePathParam'
       responses:
         200:
           description: Return the details about the pet
           schema:
             $ref: '#/definitions/Pet'
 parameters:
   PetNamePathParam:
     name: name
     description: Unique name of the pet
     in: path
     type: string
     required: true
 definitions:
   Pet:
     type: object
     discriminator: petType
     properties:
       name:
         type: string
       petType:
         type: string
     required:
     - name
     - petType
   Cat:
     description: A representation of a cat
     allOf:
     - $ref: '#/definitions/Pet'
     - type: object
       properties:
         huntingSkill:
           type: string
           description: The measured skill for hunting
           default: lazy
           enum:
           - clueless
           - lazy
           - adventurous
           - aggressive
       required:
       - huntingSkill
   Dog:
     description: A representation of a dog
     allOf:
     - $ref: '#/definitions/Pet'
     - type: object
       properties:
         packSize:
           type: integer
           format: int32
           description: the size of the pack the dog is from
           default: 0
           minimum: 0
       required:
       - packSize

It looks like the swagger ComposedModel is not supported at the moment. Are there plans to support model definitions that use inheritance?

[trane]

I'd like to take a stab at this, but beforehand I'd like to put some thoughts.

According to the schema definition, polymorphism is only supported iff the discriminator field is used. So we need could/should support two modes of code generation here:

1. When discriminator is present, we do a sealed trait hierarchy with the discriminator linked to the class name itself -- in the case of circe, we configure the decoders/encoders to use the discriminator field value (https://circe.github.io/circe/api/io/circe/generic/extras/Configuration.html); in play json we can either used the https://github.com/julienrf/play-json-derived-codecs macros or hard code this. it's probably trivially easy to just generate these discriminators manually though, so maybe adding library dependencies is kind of pointless.

2. When it isn't present, we create separate objects but namespaces together.

For (2), this could be something like:

object Pet {
  case class Dog(....)
  case class Cat(...)
}

[blast-hardcheese]

One additional note is it would be a good idea to define an x-scala- extension that allows explicitly setting a more convenient class name, in the case of integrating with services that provide unpleasant definitions names. Other than that, this is a solid approach.

Something we're still missing is definition literals, like

 paths:
   /pet/{name}:
     get:
       responses:
         200:
           schema:
             type: object
             properties:
               name:
                 type: string
               age:
                 type: integer
                 format: int32

which is tangentially related to this.