DATACMNS-1338 - Calculate defaulting mask count in Kotlin default con…

…structor resolution.

We now calculate the number of expected default masks to filter synthetic constructors that do not match the expected parameter count. A Kotlin constructor with argument defaulting generates a synthetic integer argument for every 32 constructor arguments. This is independent of the number of actual optional arguments.

Previously, we used an non-exact check to consider constructors as default ones if they had at least two additional arguments. This caused the wrong constructor being used if the non-synthetic types matched the types of the default constructor.

src/main/java/org/springframework/data/convert/KotlinClassGeneratingEntityInstantiator.java

@@ -112,13 +112,12 @@ private static Constructor<?> resolveDefaultConstructor(PersistentEntity<?, ?> e
 					continue;
 				}
 
-				// with a parameter count greater zero
-				if (constructor.getParameterCount() == 0) {
-					continue;
-				}
+				// candidates must contain at least two additional parameters (int, DefaultConstructorMarker).
+				// Number of defaulting masks derives from the original constructor arg count
+				int syntheticParameters = (constructor.getParameterCount() / Integer.SIZE) + 1
+						+ /* DefaultConstructorMarker */ 1;
 
-				// candidates must contain at least two additional parameters (int, DefaultConstructorMarker)
-				if (constructor.getParameterCount() + 2 > candidate.getParameterCount()) {
+				if (constructor.getParameterCount() + syntheticParameters != candidate.getParameterCount()) {
 					continue;
 				}
 

src/test/kotlin/org/springframework/data/convert/KotlinClassGeneratingEntityInstantiatorUnitTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@ import org.junit.Test
 import org.junit.runner.RunWith
 import org.mockito.Mock
 import org.mockito.junit.MockitoJUnitRunner
+import org.springframework.data.annotation.PersistenceConstructor
 import org.springframework.data.mapping.PersistentEntity
 import org.springframework.data.mapping.context.SamplePersistentProperty
 import org.springframework.data.mapping.model.MappingInstantiationException
@@ -117,6 +118,21 @@ class KotlinClassGeneratingEntityInstantiatorUnitTests {
 		Assertions.assertThat(instance.aBool).isTrue()
 	}
 
+	@Test // DATACMNS-1338
+	fun `should create instance using @PersistenceConstructor`() {
+
+		val entity = this.entity as PersistentEntity<CustomUser, SamplePersistentProperty>
+		val constructor = PreferredConstructorDiscoverer.discover<CustomUser, SamplePersistentProperty>(CustomUser::class.java)
+
+		doReturn("Walter").`when`(provider).getParameterValue<SamplePersistentProperty>(any())
+		doReturn(constructor).whenever(entity).persistenceConstructor
+		doReturn(constructor.constructor.declaringClass).whenever(entity).type
+
+		val instance: CustomUser = KotlinClassGeneratingEntityInstantiator().createInstance(entity, provider)
+
+		Assertions.assertThat(instance.id).isEqualTo("Walter")
+	}
+
 	data class Contact(val firstname: String, val lastname: String)
 
 	data class ContactWithDefaulting(val prop0: String, val prop1: String = "White", val prop2: String,
@@ -137,5 +153,22 @@ class KotlinClassGeneratingEntityInstantiatorUnitTests {
 
 	data class WithPrimitiveDefaulting(val aByte: Byte = 0, val aShort: Short = 0, val anInt: Int = 0, val aLong: Long = 0L,
 									   val aFloat: Float = 0.0f, val aDouble: Double = 0.0, val aChar: Char = 'a', val aBool: Boolean = true)
+
+	data class ContactWithPersistenceConstructor(val firstname: String, val lastname: String) {
+
+		@PersistenceConstructor
+		constructor(firstname: String) : this(firstname, "")
+	}
+
+	data class CustomUser(
+			var id: String? = null,
+
+			var organisations: MutableList<Organisation> = mutableListOf()
+	) {
+		@PersistenceConstructor
+		constructor(id: String?) : this(id, mutableListOf())
+	}
+
+	data class Organisation(var id: String? = null)
 }