Parsing key value maps from Java properties file with Hoplite

Question

I want to load a list of structured objects from configuration using Hoplite.

propertyName: <complex object 1>, <complex object 2>, ...

What is the correct syntax for a list of structured objects in the Java properties file?

I tried variations of the following with no success:

application.properties:

lookupValues={key: a, value: 1}, {key: b, value: 2}

AppConfig.kt:

data class ApplicationConfig(
    val lookupValues: List<LookupPair>
)

data class LookupPair(val key: String, val value: String)
...
  val configLoader = ConfigLoaderBuilder.default()
       .addResourceSource("/application.properties")
  val config = configLoader.build().loadConfigOrThrow<ApplicationConfig>()
...

It does appear to attempt to parse lookupValues as a list, but then it doesn't successfully parse each element of the list as an instance of LookupPair:

   - Could not instantiate 'ApplicationConfig' because:

        - 'lookupValues': Collection element decode failure (classpath:/application.properties):

                - Could not instantiate 'LookupPair' because:

                    - 'key': Missing from config
               
                    - 'value': Missing from config