shapeless.Coproduct is imported but not used

Generated code that uses Shapeless Coproduct includes this import:

import shapeless.{:+:, CNil, Coproduct}

Example.

However, it seems that the generated code doesn’t actually use shapeless.Coproduct, which causes the following compiler error (I think if you have both -Xfatal-warnings and -Ywarn-unused:imports):

[error] /Users/foo/bar/target/scala-2.12/src_managed/test/compiled_avro/com/foo/Bar.scala:4: Unused import
[error] import shapeless.{:+:, CNil, Coproduct}
[error]                              ^
[error] one error found

[zcox]

shapeless.Coproduct is used in the generated Scala file for default values.

    record RecordWithADefaultValue {
        union { int, string, boolean } isb = 0;
    }

case class RecordWithADefaultValue(isb: Int :+: String :+: Boolean :+: CNil = Coproduct[Int :+: String :+: Boolean :+: CNil](0))

It would be great if the shapeless.Coproduct import could just be omitted when it is not used in the generated Scala.

[rkorver]

Hi @julianpeeters

When using a union of more than 2 types, using sbt compile, (plugin version 2.0.0), I’m getting this “unused import” error in the parent generated class.

https://stackoverflow.com/questions/41478202/can-we-use-oneof-in-confluent-platform-schema-registry (the schema in the response works – also with 3 types in the union.)

The schema below doesn’t work, even though the avro schema is/seems valid:

{
 "name": "userBalance",
 "type": "record",
 "fields": [
   {
     "name": "currentBalance",
     "type": {
       "type": "record",
       "name": "CurrentBalance",
       "fields": [
         {
           "name": "userBalance",
           "type": [
             {
               "type": "record",
               "name": "userCashDeposit",
               "fields": [
                 {
                   "name": "id",
                   "type": "long"
                 },
                 {
                   "name": "amount",
                   "type": "float"
                 }
               ]
             },
             {
               "type": "record",
               "name": "userCashWithdraw",
               "fields": [
                 {
                   "name": "id",
                   "type": "long"
                 },
                 {
                   "name": "amount",
                   "type": "float"
                 }
               ]
             },
             {
               "type": "record",
               "name": "userBalanceCheck",
               "fields": [
                 {
                   "name": "id",
                   "type": "long"
                 },
                 {
                   "name": "amount",
                   "type": "float"
                 }
               ]
             }
           ]
         }
       ]
     }
   }
 ]
}

Yielding:

my_path/userBalance.scala:2:24: Unused import
[error] import shapeless.{:+:, CNil}

I’m probably missing something here… but if it’s a bug, might you have a fix / workaround for this?