Schema Types

The following types are available in the kayan { schema { ... } } DSL:

DSL	Generated Kotlin type	Raw config shape
string	String	string
boolean	Boolean	boolean
int	Int	integer
long	Long	integer
double	Double	number
stringMap	Map<String, String>	object with string values
stringList	List<String>	array of strings
stringListMap	Map<String, List<String>>	object with array-of-string values
enumValue / enum	Generated enum	string
custom	Adapter-defined	raw kind selected by the adapter declaration

Modifiers

Every schema entry supports the same constraint flags:

Flag	Meaning
required = true	The final resolved value must exist for the selected flavor and optional target.
nullable = true	Config files may explicitly set the value to null.
preventOverride = true	The custom override file cannot set this key; only the base config file may define it.

required and nullable cannot both be true for the same entry.

schema {
    string(
        jsonKey = "bundle_id",
        propertyName = "BUNDLE_ID",
        required = true,
    )
    string(
        jsonKey = "internal_distribution_id",
        propertyName = "INTERNAL_DISTRIBUTION_ID",
        preventOverride = true,
    )
}

Names

jsonKey is the key Kayan reads from JSON or YAML. propertyName is the Kotlin property generated into the config object.

Generated property names must be valid Kotlin identifiers and must be unique. JSON keys must be unique and cannot use Kayan’s reserved keys: flavors and targets.

Enums

Use enumValue(...) or its alias enum(...) when config stores a string but generated Kotlin should expose an enum value:

schema {
    enum(
        jsonKey = "release_stage",
        propertyName = "RELEASE_STAGE",
        enumTypeName = "sample.ReleaseStage",
    )
}

Enum config values are normalized into enum constant names during generation. At Gradle configuration time, buildValue("release_stage").asEnumName() returns the normalized constant name as a String.

Custom types

For types that do not fit the built-in kinds, use custom(...) with an adapter:

custom(
    jsonKey = "launch_date",
    propertyName = "LAUNCH_DATE",
    rawKind = io.kayan.ConfigValueKind.STRING,
    adapter = "sample.buildlogic.LaunchDateAdapter",
    required = true,
)

The adapter converts the raw validated value into a consumer-owned type and renders the Kotlin expression used in generated source. See Custom Adapters for the full contract.