Create NullInputException and test for null input deser

Author: dinomite

src/main/kotlin/com/fasterxml/jackson/module/kotlin/Exceptions.kt

@@ -20,3 +20,5 @@ class MissingKotlinParameterException(val parameter: KParameter,
             msg: String
     ) : this(parameter, processor as JsonParser, msg)
 }
+
+class NullInputException(msg: String) : MismatchedInputException(null, msg)

src/main/kotlin/com/fasterxml/jackson/module/kotlin/Extensions.kt

@@ -3,14 +3,9 @@ package com.fasterxml.jackson.module.kotlin
 import com.fasterxml.jackson.core.JsonParser
 import com.fasterxml.jackson.core.TreeNode
 import com.fasterxml.jackson.core.type.TypeReference
-import com.fasterxml.jackson.databind.JsonMappingException
-import com.fasterxml.jackson.databind.MappingIterator
-import com.fasterxml.jackson.databind.ObjectMapper
-import com.fasterxml.jackson.databind.ObjectReader
-import com.fasterxml.jackson.databind.module.SimpleModule
-import com.fasterxml.jackson.databind.JsonDeserializer
-import com.fasterxml.jackson.databind.JsonSerializer
+import com.fasterxml.jackson.databind.*
 import com.fasterxml.jackson.databind.json.JsonMapper
+import com.fasterxml.jackson.databind.module.SimpleModule
 import java.io.File
 import java.io.InputStream
 import java.io.Reader
@@ -68,7 +63,7 @@ inline fun <reified T : Any> SimpleModule.addDeserializer(kClass: KClass<T>, des
 
 inline fun <reified T> T.throwIfNullableTypeIsNull(): T {
     if (null !is T && this == null) {
-        throw Exception()
+        throw NullInputException(msg = "Cannot deserialize null into non-null object of type ${T::class.java.name}")
     }
     return this
-}
+}

src/test/kotlin/com/fasterxml/jackson/module/kotlin/test/ExtensionMethodsTests.kt

@@ -2,17 +2,22 @@ package com.fasterxml.jackson.module.kotlin.test
 
 import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.databind.SerializationFeature
-import com.fasterxml.jackson.module.kotlin.*
+import com.fasterxml.jackson.module.kotlin.NullInputException
+import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.readValue
 import org.hamcrest.CoreMatchers.equalTo
 import org.hamcrest.MatcherAssert.assertThat
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertThrows
 import org.junit.Test
 
 class TestExtensionMethods {
     val mapper: ObjectMapper = jacksonObjectMapper().configure(SerializationFeature.INDENT_OUTPUT, false)
 
-    data class BasicPerson(val name: String, val age: Int)
+    @Test
+    fun testAllInferenceForms() {
+        data class BasicPerson(val name: String, val age: Int)
 
-    @Test fun testAllInferenceForms() {
         val json = """{"name":"John Smith","age":30}"""
 
         val inferRightSide = mapper.readValue<BasicPerson>(json)
@@ -26,11 +31,25 @@ class TestExtensionMethods {
         assertThat(person, equalTo(expectedPerson))
     }
 
-    data class MyData(val a: String, val b: Int)
+    /**
+     * https://stackoverflow.com/questions/33368328/how-to-use-jackson-to-deserialize-to-kotlin-collections
+     */
+    @Test
+    fun testStackOverflow33368328() {
+        data class MyData(val a: String, val b: Int)
 
-    @Test fun testStackOverflow33368328() {
         val jsonStr = """[{"a": "value1", "b": 1}, {"a": "value2", "b": 2}]"""
         val myList: List<MyData> = mapper.readValue(jsonStr)
         assertThat(myList, equalTo(listOf(MyData("value1", 1), MyData("value2", 2))))
     }
-}
+
+    enum class Options { ONE, TWO }
+
+    @Test
+    fun testNullEnumThrows() {
+        assertThrows(NullInputException::class.java) {
+            val foo: Options = mapper.readValue("null")
+            assertNull(foo)
+        }
+    }
+}