Cannot cast a spec to data class (in general issue in casting)

[Animeshz]

1. To reproduce the error run the following code.:
Main.kt

val config = Config { addSpec(ConfigurationSpec) }.enable(Feature.OPTIONAL_SOURCE_BY_DEFAULT)
	.from.json.file("config.json")
	.from.properties.file("config.prop")
	.from.properties.file("config.properties")
	.from.hocon.file("config.conf")
	.validateRequired()
	.toValue<Configuration>()

ConfigurationSpec.kt:

package io.github.xyz.xyz

import com.uchuhimo.konf.*
import io.github.animeshz.air_bent.*
import java.io.*
import java.nio.file.*

object ConfigurationSpec : ConfigSpec("configuration") {
	object Server : ConfigSpec("server") {
		val port by optional(80)
		val dbFile by optional("${Paths.get("").toAbsolutePath().toString().trimEnd(File.separatorChar) + File.separator}data.db", "database file")
	}

	object Hardware : ConfigSpec("hardware") {
		val A0 by required<Configuration.SerialAddressConfiguration>()
		val A1 by required<Configuration.SerialAddressConfiguration>()

		val rShunt by required<Double>("resistor shunt")
		val maxExpectedCurrent by optional(10.0, "max expected current")
	}
}

Confguration.kt:

package io.github.xyz.xyz

data class Configuration (val server: Server, val hardware: Hardware){
	enum class SerialAddressConfiguration(val value: Int) {
		GND(0),
		VS(1),
		SDA(2),
		SCL(3)
	}

	data class Server(val port: Int, val dbFile: String)
	data class Hardware(val A0: SerialAddressConfiguration, val A1: SerialAddressConfiguration, val rShunt: Double, val maxExpectedCurrent: Double)
}

Sample hocon file:

configuration = {
  server = {
    port = 80
    database file = "data.db"
  }

  hardware = {
    resistor shunt = 0.005
    max expected current = 10.0

    A0 = "GND"
    A1 = "GND"
  }
}

2. Error occurred:

Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: com.uchuhimo.konf.NameConflictException: item root cannot be added
	at com.uchuhimo.konf.BaseConfig.addItem(BaseConfig.kt:530)
	at com.uchuhimo.konf.RequiredConfigProperty.provideDelegate(Config.kt:399)
	at io.github.xyz.xyz.MainKt.<clinit>(Main.kt:53)

3. Expected behavior:
Should cast the spec to the Configuration data class. I did not cast to data class directly because configuration hocon file has spaces in between the keys which cannot be casted to standard kotlin as variables with spaces donot exist :(

[uchuhimo]

@Animeshz You cannot cast a spec to a data class and you don't have to.

Spec is used as a schema for your HOCON source. We cannot use two schema to explain the same source. When you use config.toValue<Configuration>(), konf will implictly add a new spec, which will conflict with ConfigurationSpec. Thus cast a config with an existed spec to a data class will fail.

Fortunately, there is a much simpler solution for your case. Konf use Jackson to support data class, thus you can use Jackson annotation to cast your key names. Add @JsonProperty annotation to Configuration:

import com.fasterxml.jackson.annotation.JsonProperty

data class Configuration (val server: Server, val hardware: Hardware){
    enum class SerialAddressConfiguration(val value: Int) {
        GND(0),
        VS(1),
        SDA(2),
        SCL(3)
    }

    data class Server(val port: Int, @JsonProperty("database file") val dbFile: String)
    data class Hardware(
        val A0: SerialAddressConfiguration, 
        val A1: SerialAddressConfiguration, 
        @JsonProperty("resistor shunt") val rShunt: Double, 
        @JsonProperty("max expected current") val maxExpectedCurrent: Double)
}

And then you can cast the config to the data class directly:

val configuration = config.at("configuration").toValue<Configuration>()

[P1NG2WIN]

Omg, why this moment is not in readme ... I spent several hours trying to understand why my config cause error. Please mark that you must write 'at' and why

[P1NG2WIN]

@uchuhimo also what i should write in 'at' if my config is this and i want to cast it to ApiConfig data class

[P1NG2WIN]

@uchuhimo For some reason i also get error item root cannot be added

    val apiConfig =
        Config {
            addSpec(ApiConfigSpec)
        }
            .from.json.watchFile("/home/config.json")
            .validateRequired()
            .at("")
            .toValue<ApiConfig>()

object ApiConfigSpec : ConfigSpec("") {
    val updatePass by required<String>("update_pass")
    val androidConfig by required<AndroidConfig>("android_config")
    val remoteUpdateConf by required<RemoteUpdateConf>("remote_update_config")

//    object AndroidConfigSpec : ConfigSpec("android_config") {
//        val suspendApp by required<Boolean>("suspend_app")
//    }
//
//    object RemoteUpdateConfSpec : ConfigSpec("remote_update_config") {
//        val remoteUpdateEnabled by required<Boolean>("remote_update_enabled")
//        val newAppVersion by required<String>("new_app_version")
//        val newAppStoreUrl by required<String>("new_app_store_url")
//        val requestClearData by required<Boolean>("request_clear_data")
//        val testMode by required<Boolean>("test_mode")
//        val testTokes by required<List<String>>("test_tokens")
//    }
}

data class ApiConfig(
    @SerializedName("update_pass")
    @JsonProperty("update_pass")
    val updatePass: String = "",
    @SerializedName("android_config")
    @JsonProperty("android_config")
    val androidConfig: AndroidConfig,
    @SerializedName("remote_update_config")
    @JsonProperty("remote_update_config")
    val remoteUpdateConf: RemoteUpdateConf
)

data class AndroidConfig(
    @SerializedName("suspend_app")
    @JsonProperty("suspend_app")
    val suspendApp: Boolean = false
)

data class RemoteUpdateConf(
    @SerializedName("remote_update_enabled")
    @JsonProperty("remote_update_enabled")
    val remoteUpdateEnabled: Boolean = true,
    @SerializedName("new_app_version")
    @JsonProperty("new_app_version")
    val newAppVersion: String = "",
    @SerializedName("new_app_store_url")
    @JsonProperty("new_app_store_url")
    val newAppStoreUrl: String = "",
    @SerializedName("request_clear_data")
    @JsonProperty("request_clear_data")
    val requestClearData: Boolean = false,
    @SerializedName("test_mode")
    @JsonProperty("test_mode")
    val testMode: Boolean = false,
    @SerializedName("test_tokens")
    @JsonProperty("test_tokens")
    val testTokes: List<String> = emptyList()
)

config.json:

{
    
    "update_pass": "",

    "android_config": {
        "suspend_app": false
    },

    "remote_update_config": {
        "remote_update_enabled":true,

        "new_app_version":"1.2553",
        "new_app_store_url":"",
        "request_clear_data":true,

        "test_mode": false,
        "test_tokens": [
            "asd",
            "asd",
            "asd"
        ]
    }

}