Open up ValidationBuilder for extension

api/konform.api

@@ -33,8 +33,10 @@ public final class io/konform/validation/Invalid : io/konform/validation/Validat
 	public fun getErrors ()Ljava/util/List;
 	public fun hashCode ()I
 	public fun isValid ()Z
-	public synthetic fun prependPath$konform (Lio/konform/validation/path/PathSegment;)Lio/konform/validation/ValidationResult;
-	public synthetic fun prependPath$konform (Lio/konform/validation/path/ValidationPath;)Lio/konform/validation/ValidationResult;
+	public fun prependPath (Lio/konform/validation/path/PathSegment;)Lio/konform/validation/Invalid;
+	public synthetic fun prependPath (Lio/konform/validation/path/PathSegment;)Lio/konform/validation/ValidationResult;
+	public fun prependPath (Lio/konform/validation/path/ValidationPath;)Lio/konform/validation/Invalid;
+	public synthetic fun prependPath (Lio/konform/validation/path/ValidationPath;)Lio/konform/validation/ValidationResult;
 	public fun toString ()Ljava/lang/String;
 }
 
@@ -52,6 +54,8 @@ public final class io/konform/validation/Valid : io/konform/validation/Validatio
 	public final fun getValue ()Ljava/lang/Object;
 	public fun hashCode ()I
 	public fun isValid ()Z
+	public fun prependPath (Lio/konform/validation/path/PathSegment;)Lio/konform/validation/ValidationResult;
+	public fun prependPath (Lio/konform/validation/path/ValidationPath;)Lio/konform/validation/ValidationResult;
 	public fun toString ()Ljava/lang/String;
 }
 
@@ -73,7 +77,7 @@ public final class io/konform/validation/Validation$DefaultImpls {
 	public static fun prependPath (Lio/konform/validation/Validation;Lio/konform/validation/path/ValidationPath;)Lio/konform/validation/Validation;
 }
 
-public final class io/konform/validation/ValidationBuilder {
+public class io/konform/validation/ValidationBuilder {
 	public static final field Companion Lio/konform/validation/ValidationBuilder$Companion;
 	public fun <init> ()V
 	public final fun addConstraint (Ljava/lang/String;[Ljava/lang/String;Lkotlin/jvm/functions/Function1;)Lio/konform/validation/Constraint;
@@ -154,6 +158,8 @@ public abstract class io/konform/validation/ValidationResult {
 	public abstract fun isValid ()Z
 	public final fun map (Lkotlin/jvm/functions/Function1;)Lio/konform/validation/ValidationResult;
 	public final fun plus (Lio/konform/validation/ValidationResult;)Lio/konform/validation/ValidationResult;
+	public abstract fun prependPath (Lio/konform/validation/path/PathSegment;)Lio/konform/validation/ValidationResult;
+	public abstract fun prependPath (Lio/konform/validation/path/ValidationPath;)Lio/konform/validation/ValidationResult;
 }
 
 public final class io/konform/validation/ValidationResultKt {

src/commonMain/kotlin/io/konform/validation/ValidationBuilder.kt

@@ -20,7 +20,8 @@ import kotlin.reflect.KProperty1
 private annotation class ValidationScope
 
 @ValidationScope
-public class ValidationBuilder<T> {
+// Class is open to users can define their extra local extension methods
+public open class ValidationBuilder<T> {
     private val constraints = mutableListOf<Constraint<T>>()
     private val subValidations = mutableListOf<Validation<T>>()
 

src/commonMain/kotlin/io/konform/validation/ValidationResult.kt

@@ -35,9 +35,9 @@ public sealed class ValidationResult<out T> {
                 }
         }
 
-    internal abstract fun prependPath(pathSegment: PathSegment): ValidationResult<T>
+    public abstract fun prependPath(pathSegment: PathSegment): ValidationResult<T>
 
-    internal abstract fun prependPath(path: ValidationPath): ValidationResult<T>
+    public abstract fun prependPath(path: ValidationPath): ValidationResult<T>
 }
 
 public data class Invalid(

src/commonTest/kotlin/io/konform/validation/validationbuilder/ExtendingValidationBuilderTest.kt

@@ -0,0 +1,53 @@
+package io.konform.validation.validationbuilder
+
+import io.konform.validation.Validation
+import io.konform.validation.ValidationBuilder
+import io.konform.validation.ValidationError
+import io.konform.validation.constraints.minLength
+import io.konform.validation.path.ValidationPath
+import io.kotest.assertions.konform.shouldBeInvalid
+import io.kotest.assertions.konform.shouldBeValid
+import io.kotest.assertions.konform.shouldContainExactlyErrors
+import kotlin.reflect.KProperty1
+import kotlin.test.Test
+
+class ExtendingValidationBuilderTest {
+    @Test
+    fun allowsExtending() {
+        val validation =
+            MyValidationBuilder<User> {
+                User::name trimmed {
+                    minLength(1)
+                }
+            }
+
+        validation shouldBeValid User("John")
+        (validation shouldBeInvalid User("")).shouldContainExactlyErrors(
+            ValidationError.of(User::name, "must have at least 1 characters"),
+        )
+        (validation shouldBeInvalid User("\t")).shouldContainExactlyErrors(
+            ValidationError.of(User::name, "must have at least 1 characters"),
+        )
+    }
+}
+
+data class User(
+    val name: String,
+)
+
+class MyValidationBuilder<T> : ValidationBuilder<T>() {
+    infix fun KProperty1<T, String>.trimmed(init: ValidationBuilder<String>.() -> Unit): Unit =
+        this {
+            validate(ValidationPath.EMPTY, { it.trim() }) {
+                run(buildWithNew(init))
+            }
+        }
+
+    companion object {
+        operator fun <T> invoke(init: MyValidationBuilder<T>.() -> Unit): Validation<T> {
+            val builder = MyValidationBuilder<T>()
+            init(builder)
+            return builder.build()
+        }
+    }
+}