Allow nullable return types for onGeneric

Author: nhaarman

mockito-kotlin/src/main/kotlin/com/nhaarman/mockitokotlin2/Mockito.kt

@@ -193,7 +193,7 @@ inline fun <reified T : Any> mock(s: MockSettings): T = Mockito.mock(T::class.ja
 class KStubbing<out T>(private val mock: T) {
     fun <R> on(methodCall: R) = Mockito.`when`(methodCall)
 
-    fun <R : Any> onGeneric(methodCall: T.() -> R, c: KClass<R>): OngoingStubbing<R> {
+    fun <R : Any> onGeneric(methodCall: T.() -> R?, c: KClass<R>): OngoingStubbing<R> {
         val r = try {
             mock.methodCall()
         } catch (e: NullPointerException) {
@@ -207,7 +207,7 @@ class KStubbing<out T>(private val mock: T) {
         return Mockito.`when`(r)
     }
 
-    inline fun <reified R : Any> onGeneric(noinline methodCall: T.() -> R): OngoingStubbing<R> {
+    inline fun <reified R : Any> onGeneric(noinline methodCall: T.() -> R?): OngoingStubbing<R> {
         return onGeneric(methodCall, R::class)
     }
 

mockito-kotlin/src/test/kotlin/test/Classes.kt

@@ -77,6 +77,7 @@ abstract class ThrowingConstructor {
 
 interface GenericMethods<T> {
     fun genericMethod(): T
+    fun nullableReturnType(): T?
 }
 
 class ThrowableClass(cause: Throwable) : Throwable(cause)

mockito-kotlin/src/test/kotlin/test/MockitoTest.kt

@@ -1004,6 +1004,15 @@ class MockitoTest : TestBase() {
         expect(mock.genericMethod()).toBe(2)
     }
 
+    @Test
+    fun doReturn_withGenericNullableReturnType_onGeneric() {
+        val m = mock<GenericMethods<String>> {
+            onGeneric { nullableReturnType() } doReturn "Test"
+        }
+
+        expect(m.nullableReturnType()).toBe("Test")
+    }
+
     @Test
     fun isA_withNonNullableString() {
         mock<Methods>().apply {