Decoding fields with common prefix and dash does not work

Hello, I’ve run into peculiar issue. Imagine the following code:

package com.github.mypackage

case class A(text: String)
case class B(`a-ha`: String, a: A)


import io.circe.parser._
import io.circe.generic.auto._

val msg =
  """
     { "a-ha": "foo", "a": {"text": "foofoo" } }
  """
println(decode[B](msg))

When running this, I got the following exception (the code was run in scala-test so line numbers don’t fit):

class java.lang.String cannot be cast to class com.github.mypackage.A (java.lang.String is in module java.base of loader 'bootstrap'; com.github.mypackage.A is in unnamed module of loader 'app')
java.lang.ClassCastException: class java.lang.String cannot be cast to class com.github.mypackage.A (java.lang.String is in module java.base of loader 'bootstrap'; com.github.mypackage.A is in unnamed module of loader 'app')
	at com.github.mypackage.B.<init>(ParsingSpec.scala:11)
	at com.github.mypackage.ParsingSpec$anon$importedDecoder$macro$15$1$anon$macro$7$1.from(ParsingSpec.scala:25)
	at com.github.mypackage.ParsingSpec$anon$importedDecoder$macro$15$1$anon$macro$7$1.from(ParsingSpec.scala:25)
	at shapeless.LabelledGeneric$$anon$1.from(generic.scala:229)
	at shapeless.LabelledGeneric$$anon$1.from(generic.scala:226)
	at io.circe.generic.decoding.DerivedDecoder$$anon$1.apply(DerivedDecoder.scala:15)
	at io.circe.Decoder.decodeJson(Decoder.scala:86)
	at io.circe.Decoder.decodeJson$(Decoder.scala:86)
	at io.circe.generic.decoding.DerivedDecoder.decodeJson(DerivedDecoder.scala:6)
	at io.circe.Parser.finishDecode(Parser.scala:13)
	at io.circe.Parser.finishDecode$(Parser.scala:9)
	at io.circe.parser.package$.finishDecode(package.scala:5)
	at io.circe.Parser.decode(Parser.scala:29)
	at io.circe.Parser.decode$(Parser.scala:28)
	at io.circe.parser.package$.decode(package.scala:5)
...

The problem is when there are fields with common prefix and the suffix of the longer one starts with dash. This means, for example, that if we had these case classes:

case class A(text: String)
case class B(`aha`: String, a: A)

(note field aha without dash) - then decoding works as expected.

[travisbrown]

Sure! Thanks for reminding me of this ridiculous bug. 😃

[vbmacher]

It works, thanks again. I suggest to close the ticket now…