Autodetect Kotlin nullability for optional injection points (analogous to java.util.Optional)

Built-in support in MethodParameter and DependencyDescriptor supersedes our separate KotlinUtils helper.

Issue: SPR-14951

spring-core/src/test/kotlin/org/springframework/core/KotlinMethodParameterTests.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core
+
+import java.lang.reflect.Method
+
+import org.junit.Before
+import org.junit.Test
+
+import org.junit.Assert.*
+
+/**
+ * Tests for Kotlin support in [MethodParameter].
+ *
+ * @author Raman Gupta
+ * @author Sebastien Deleuze
+ * @author Juergen Hoeller
+ */
+class KotlinMethodParameterTests {
+
+	lateinit var nullableMethod: Method
+
+	lateinit var nonNullableMethod: Method
+
+
+	@Before
+	@Throws(NoSuchMethodException::class)
+	fun setup() {
+		nullableMethod = javaClass.getMethod("nullable", String::class.java)
+		nonNullableMethod = javaClass.getMethod("nonNullable", String::class.java)
+	}
+
+
+	@Test
+	fun `Method parameter nullability`() {
+		assertTrue(MethodParameter(nullableMethod, 0).isOptional())
+		assertFalse(MethodParameter(nonNullableMethod, 0).isOptional())
+	}
+
+	@Test
+	fun `Method return type nullability`() {
+		assertTrue(MethodParameter(nullableMethod, -1).isOptional())
+		assertFalse(MethodParameter(nonNullableMethod, -1).isOptional())
+	}
+
+
+	@Suppress("unused", "unused_parameter")
+	fun nullable(p1: String?): Int? = 42
+
+	@Suppress("unused", "unused_parameter")
+	fun nonNullable(p1: String): Int = 42
+
+}

spring-core/src/test/kotlin/org/springframework/util/KotlinUtilsTests.kt

@@ -1,62 +0,0 @@
-package org.springframework.util
-
-import org.junit.Before
-import org.junit.Test
-
-import java.lang.reflect.Method
-
-import org.junit.Assert.assertFalse
-import org.junit.Assert.assertTrue
-import org.springframework.core.MethodParameter
-import org.springframework.util.KotlinUtils.*
-
-/**
- * Test fixture for [KotlinUtils].
- *
- * @author Raman Gupta
- * @author Sebastien Deleuze
- */
-class KotlinUtilsTests {
-
-	lateinit var nullableMethod: Method
-
-	lateinit var nonNullableMethod: Method
-
-	@Before
-	@Throws(NoSuchMethodException::class)
-	fun setup() {
-		nullableMethod = javaClass.getMethod("nullable", String::class.java)
-		nonNullableMethod = javaClass.getMethod("nonNullable", String::class.java)
-	}
-
-	@Test
-	fun `Is kotlin present`() {
-		// we'd have to change the build to test the opposite
-		assertTrue(isKotlinPresent())
-	}
-
-	@Test
-	fun `Are kotlin classes detected`() {
-		assertFalse(isKotlinClass(MethodParameter::class.java))
-		assertTrue(isKotlinClass(javaClass))
-	}
-
-	@Test
-	fun `Obtains method return type nullability`() {
-		assertTrue(isNullable(MethodParameter(nullableMethod, -1)))
-		assertFalse(isNullable(MethodParameter(nonNullableMethod, -1)))
-	}
-
-	@Test
-	fun `Obtains method parameter nullability`() {
-		assertTrue(isNullable(MethodParameter(nullableMethod, 0)))
-		assertFalse(isNullable(MethodParameter(nonNullableMethod, 0)))
-	}
-
-	@Suppress("unused", "unused_parameter")
-	fun nullable(p1: String?): Int? = 42
-
-	@Suppress("unused", "unused_parameter")
-	fun nonNullable(p1: String): Int = 42
-
-}