feat: Support custom metadata property

akkurate-arrow/src/commonMain/kotlin/dev/nesk/akkurate/arrow/Arrow.kt

@@ -23,8 +23,10 @@ import arrow.core.raise.either
 import dev.nesk.akkurate.ValidationResult
 import dev.nesk.akkurate.constraints.ConstraintViolation
 import dev.nesk.akkurate.constraints.ConstraintViolationSet
+import dev.nesk.akkurate.constraints.GenericConstraintViolation
+import dev.nesk.akkurate.constraints.GenericConstraintViolationSet
 
-private fun ConstraintViolationSet.toNonEmptySet(): NonEmptySet<ConstraintViolation> =
+private fun <E> GenericConstraintViolationSet<E>.toNonEmptySet(): NonEmptySet<GenericConstraintViolation<E>> =
     nonEmptySetOf(this.first(), *this.drop(1).toTypedArray())
 
 /**
@@ -52,7 +54,7 @@ private fun ConstraintViolationSet.toNonEmptySet(): NonEmptySet<ConstraintViolat
  * normalizeBookName("  ") // Returns: "<error: Must not be blank>"
  * ```
  */
-public fun <T> ValidationResult<T>.toEither(): Either<NonEmptySet<ConstraintViolation>, T> = when (this) {
+public fun <E, T> ValidationResult<E, T>.toEither(): Either<NonEmptySet<GenericConstraintViolation<E>>, T> = when (this) {
     is ValidationResult.Failure -> violations.toNonEmptySet().left()
     is ValidationResult.Success -> value.right()
 }
@@ -85,7 +87,7 @@ public fun <T> ValidationResult<T>.toEither(): Either<NonEmptySet<ConstraintViol
  *
  * @return The validated value on successful result.
  */
-public fun <T> Raise<NonEmptySet<ConstraintViolation>>.bind(validationResult: ValidationResult<T>): T = when (validationResult) {
+public fun <E, T> Raise<NonEmptySet<GenericConstraintViolation<E>>>.bind(validationResult: ValidationResult<E, T>): T = when (validationResult) {
     is ValidationResult.Failure -> raise(validationResult.violations.toNonEmptySet())
     is ValidationResult.Success -> validationResult.value
 }

akkurate-arrow/src/commonTest/kotlin/dev/nesk/akkurate/arrow/ArrowKtTest.kt

@@ -24,6 +24,7 @@ import dev.nesk.akkurate.ValidationResult
 import dev.nesk.akkurate.Validator
 import dev.nesk.akkurate.constraints.ConstraintViolation
 import dev.nesk.akkurate.constraints.builders.isIdenticalTo
+import dev.nesk.akkurate.validatables.DefaultMetadataType
 import kotlin.test.Test
 import kotlin.test.assertIs
 import kotlin.test.assertSame
@@ -59,7 +60,7 @@ class ArrowKtTest {
         val validationResult = validate(SomeSealedClass.Invalid)
         val validationEither = validationResult.toEither()
 
-        assertIs<ValidationResult.Failure>(validationResult)
+        assertIs<ValidationResult.Failure<DefaultMetadataType>>(validationResult)
         assertIs<Either.Left<NonEmptySet<ConstraintViolation>>>(validationEither, "The `Either` instance is a `Left` type")
         assertSame(
             validationResult.violations.single(),
@@ -87,7 +88,7 @@ class ArrowKtTest {
         val validationResult = validate(SomeSealedClass.Invalid)
         val validationEither = either { bind(validationResult) }
 
-        assertIs<ValidationResult.Failure>(validationResult)
+        assertIs<ValidationResult.Failure<DefaultMetadataType>>(validationResult)
         assertIs<Either.Left<NonEmptySet<ConstraintViolation>>>(validationEither, "The `Either` instance is a `Left` type")
         assertSame(
             validationResult.violations.single(),

akkurate-core/src/commonMain/kotlin/dev/nesk/akkurate/AkkurateScratch.kt

@@ -17,6 +17,7 @@
 
 package dev.nesk.akkurate
 
+import dev.nesk.akkurate.validatables.DefaultMetadataType
 import dev.nesk.akkurate.validatables.Validatable
 
 /**
@@ -62,13 +63,13 @@ internal class AkkurateScratch {
         public fun <ValueType> Validator(
             configuration: Configuration = Configuration(),
             block: Validatable<ValueType>.() -> Unit,
-        ): Validator.Runner<ValueType> = ValidatorWrapper(dev.nesk.akkurate.Validator(configuration, block))
+        ): Validator.Runner<ValueType, DefaultMetadataType> = ValidatorWrapper(dev.nesk.akkurate.Validator(configuration, block))
     }
 
     public class ValidatorWrapper<ValueType>(
-        private val delegate: Validator.Runner<ValueType>,
-    ) : Validator.Runner<ValueType> by delegate {
-        override fun invoke(value: ValueType): ValidationResult<ValueType> {
+        private val delegate: Validator.Runner<ValueType, DefaultMetadataType>,
+    ) : Validator.Runner<ValueType, DefaultMetadataType> by delegate {
+        override fun invoke(value: ValueType): ValidationResult<DefaultMetadataType, ValueType> {
             return delegate(value).also { result ->
                 when (result) {
                     is ValidationResult.Success -> println("Success")

akkurate-core/src/commonMain/kotlin/dev/nesk/akkurate/Path.kt

@@ -17,11 +17,12 @@
 
 package dev.nesk.akkurate
 
+import dev.nesk.akkurate.validatables.GenericValidatable
 import dev.nesk.akkurate.validatables.Validatable
 
 public typealias Path = List<String>
 
-public class PathBuilder(private val validatable: Validatable<*>) {
+public class PathBuilder<MetadataType>(private val validatable: GenericValidatable<*, MetadataType>) {
     public fun absolute(vararg pathSegments: String): Path = pathSegments.toList()
 
     public fun relative(vararg pathSegments: String): Path {
@@ -32,4 +33,4 @@ public class PathBuilder(private val validatable: Validatable<*>) {
     public fun appended(vararg pathSegments: String): Path = validatable.path() + pathSegments.toList()
 }
 
-public fun Validatable<*>.path(block: PathBuilder.() -> Path): Path = PathBuilder(this).block()
+public fun <MetadataType> GenericValidatable<*, MetadataType>.path(block: PathBuilder<MetadataType>.() -> Path): Path = PathBuilder(this).block()

akkurate-core/src/commonMain/kotlin/dev/nesk/akkurate/ValidationResult.kt

@@ -20,16 +20,20 @@ package dev.nesk.akkurate
 import dev.nesk.akkurate.ValidationResult.Failure
 import dev.nesk.akkurate.ValidationResult.Success
 import dev.nesk.akkurate.constraints.ConstraintViolationSet
+import dev.nesk.akkurate.constraints.GenericConstraintViolationSet
+import dev.nesk.akkurate.validatables.DefaultMetadataType
 
 /**
  * The result of a validation. Can be [a successful outcome][Success] with the validated value, or [a failure][Failure] with a violation list.
  */
-public sealed interface ValidationResult<out T> {
+public sealed interface ValidationResult<out E, out T> {
     /**
      * Throws an [Exception] if the result is a failure.
      */
     public fun orThrow()
 
+    public fun orThrow(toDefaultMetadata: (E) -> DefaultMetadataType)
+
     /**
      * A successful outcome to the validation, with [the validated value][value].
      */
@@ -38,13 +42,14 @@ public sealed interface ValidationResult<out T> {
          * The subject of the validation result.
          */
         public val value: T,
-    ) : ValidationResult<T> {
+    ) : ValidationResult<Nothing, T> {
         /**
          * Returns the [value].
          */
         public operator fun component1(): T = value
 
         override fun orThrow(): Unit = Unit
+        override fun orThrow(toDefaultMetadata: (Nothing) -> DefaultMetadataType): Unit = Unit
 
         override fun equals(other: Any?): Boolean {
             if (this === other) return true
@@ -64,30 +69,36 @@ public sealed interface ValidationResult<out T> {
     /**
      * A failed outcome to the validation, with a violation list describing what went wrong.
      */
-    public class Failure internal constructor(
+    public class Failure<E> internal constructor(
         /**
          * A list of failed constraint violations.
          */
-        public val violations: ConstraintViolationSet,
-    ) : ValidationResult<Nothing> {
+        public val violations: GenericConstraintViolationSet<E>,
+    ) : ValidationResult<E, Nothing> {
         /**
          * Returns the [violations].
          */
-        public operator fun component1(): ConstraintViolationSet = violations
+        public operator fun component1(): GenericConstraintViolationSet<E> = violations
+
+        override fun orThrow(): Nothing = orThrow { emptyMap() }
+        override fun orThrow(toDefaultMetadata: (E) -> DefaultMetadataType): Nothing =
+            throw Exception(
+                ConstraintViolationSet(violations.map { it.copy(metadata = toDefaultMetadata(it.metadata)) }.toSet())
+            )
 
-        override fun orThrow(): Nothing = throw Exception(violations)
 
         override fun equals(other: Any?): Boolean {
             if (this === other) return true
             if (other == null || this::class != other::class) return false
 
-            other as Failure
+            other as Failure<E>
 
             return violations == other.violations
         }
 
         override fun hashCode(): Int = violations.hashCode()
         override fun toString(): String = "ValidationResult.Failure(violations=$violations)"
+
     }
 
     /**