Hide singleton support

release-notes/CREDITS-2.x

@@ -36,3 +36,8 @@ Vladimir Petrakovich (frost13it@github)
 * Contributed fix for #279: 2.10 introduces another binary compatibility issue in
   `KotlinModule` constructor
  (2.10.2)
+
+Drew Stephens (dinomite@github)
+* Contributed fix for #281: KotlinObjectSingletonDeserializer fails to deserialize
+    previously serialized JSON as it doesn't delegate deserializeWithType
+  (2.11.0)

release-notes/VERSION-2.x

@@ -8,6 +8,8 @@ Project: jackson-module-kotlin
 
 #284: Use `AnnotationIntrospector.findRenameByField()` to support "is properties"
 - Add Builder for KotlinModule
+#281: Hide singleton deserialization support behind a setting on the module,
+    `singletonSupport` and enum `SingletonSupport`.  Defaults to pre-2.10 behavior.
 
 Kotlin updated to 1.3.61
 

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

@@ -2,6 +2,8 @@ package com.fasterxml.jackson.module.kotlin
 
 import com.fasterxml.jackson.databind.MapperFeature
 import com.fasterxml.jackson.databind.module.SimpleModule
+import com.fasterxml.jackson.module.kotlin.SingletonSupport.CANONICALIZE
+import com.fasterxml.jackson.module.kotlin.SingletonSupport.DISABLED
 import kotlin.reflect.KClass
 
 private val metadataFqName = "kotlin.Metadata"
@@ -14,7 +16,8 @@ class KotlinModule constructor (
     val reflectionCacheSize: Int = 512,
     val nullToEmptyCollection: Boolean = false,
     val nullToEmptyMap: Boolean = false,
-    val nullIsSameAsDefault: Boolean = false
+    val nullIsSameAsDefault: Boolean = false,
+    val singletonSupport: SingletonSupport = DISABLED
 ) : SimpleModule(PackageVersion.VERSION) {
     @Deprecated(level = DeprecationLevel.HIDDEN, message = "For ABI compatibility")
     constructor(
@@ -27,7 +30,8 @@ class KotlinModule constructor (
         builder.reflectionCacheSize,
         builder.nullToEmptyCollection,
         builder.nullToEmptyMap,
-        builder.nullIsSameAsDefault
+        builder.nullIsSameAsDefault,
+        builder.singletonSupport
     )
 
     companion object {
@@ -47,8 +51,12 @@ class KotlinModule constructor (
 
         context.addValueInstantiators(KotlinInstantiators(cache, nullToEmptyCollection, nullToEmptyMap, nullIsSameAsDefault))
 
-        // [module-kotlin#225]: keep Kotlin singletons as singletons
-        context.addBeanDeserializerModifier(KotlinBeanDeserializerModifier)
+        when(singletonSupport) {
+            DISABLED -> Unit
+            CANONICALIZE -> {
+                context.addBeanDeserializerModifier(KotlinBeanDeserializerModifier)
+            }
+        }
 
         context.insertAnnotationIntrospector(KotlinAnnotationIntrospector(context, cache, nullToEmptyCollection, nullToEmptyMap, nullIsSameAsDefault))
         context.appendAnnotationIntrospector(KotlinNamesAnnotationIntrospector(this, cache, ignoredClassesForImplyingJsonCreator))
@@ -80,14 +88,21 @@ class KotlinModule constructor (
         var nullIsSameAsDefault: Boolean = false
             private set
 
+        var singletonSupport = DISABLED
+            private set
+
         fun reflectionCacheSize(reflectionCacheSize: Int) = apply { this.reflectionCacheSize = reflectionCacheSize }
 
-        fun nullToEmptyCollection(nullToEmptyCollection: Boolean) = apply { this.nullToEmptyCollection = nullToEmptyCollection }
+        fun nullToEmptyCollection(nullToEmptyCollection: Boolean) =
+            apply { this.nullToEmptyCollection = nullToEmptyCollection }
 
         fun nullToEmptyMap(nullToEmptyMap: Boolean) = apply { this.nullToEmptyMap = nullToEmptyMap }
 
         fun nullIsSameAsDefault(nullIsSameAsDefault: Boolean) = apply { this.nullIsSameAsDefault = nullIsSameAsDefault }
 
+        fun singletonSupport(singletonSupport: SingletonSupport) =
+            apply { this.singletonSupport = singletonSupport }
+
         fun build() = KotlinModule(this)
     }
 }

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

@@ -0,0 +1,12 @@
+package com.fasterxml.jackson.module.kotlin
+
+/**
+ * Special handling for singletons.
+ */
+enum class SingletonSupport {
+    // No special handling of singletons (pre-2.10 behavior)
+    DISABLED,
+    // Deserialize then canonicalize (was the default in 2.10)
+    //     [jackson-module-kotlin#225]: keep Kotlin singletons as singletons
+    CANONICALIZE
+}

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

@@ -1,9 +1,30 @@
 package com.fasterxml.jackson.module.kotlin
 
+import com.fasterxml.jackson.module.kotlin.SingletonSupport.CANONICALIZE
+import com.fasterxml.jackson.module.kotlin.SingletonSupport.DISABLED
 import org.junit.Assert.*
 import org.junit.Test
+import kotlin.reflect.full.memberProperties
+import kotlin.reflect.full.primaryConstructor
 
 class KotlinModuleTest {
+    /**
+     * Ensure that the main constructor and the Builder have the same default settings.
+     */
+    @Test
+    fun constructorAndBuilderCreateSameDefaultObject() {
+        val constructorModule = KotlinModule()
+        val builderModule = KotlinModule.Builder().build()
+
+
+        assertEquals(KotlinModule::class.primaryConstructor?.parameters?.size, KotlinModule.Builder::class.memberProperties.size)
+        assertEquals(constructorModule.reflectionCacheSize, builderModule.reflectionCacheSize)
+        assertEquals(constructorModule.nullToEmptyCollection, builderModule.nullToEmptyCollection)
+        assertEquals(constructorModule.nullToEmptyMap, builderModule.nullToEmptyMap)
+        assertEquals(constructorModule.nullIsSameAsDefault, builderModule.nullIsSameAsDefault)
+        assertEquals(constructorModule.singletonSupport, builderModule.singletonSupport)
+    }
+
     @Test
     fun builder_Defaults() {
         val module = KotlinModule.Builder().build()
@@ -12,6 +33,7 @@ class KotlinModuleTest {
         assertFalse(module.nullToEmptyCollection)
         assertFalse(module.nullToEmptyMap)
         assertFalse(module.nullIsSameAsDefault)
+        assertEquals(DISABLED, module.singletonSupport)
     }
 
     @Test
@@ -64,4 +86,17 @@ class KotlinModuleTest {
         assertFalse(module.nullToEmptyMap)
         assertTrue(module.nullIsSameAsDefault)
     }
+
+    @Test
+    fun builder_EnableCanonicalSingletonSupport() {
+        val module = KotlinModule.Builder().apply {
+            singletonSupport(CANONICALIZE)
+        }.build()
+
+        assertEquals(512, module.reflectionCacheSize)
+        assertFalse(module.nullToEmptyCollection)
+        assertFalse(module.nullToEmptyMap)
+        assertFalse(module.nullIsSameAsDefault)
+        assertEquals(CANONICALIZE, module.singletonSupport)
+    }
 }

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

@@ -1,18 +1,18 @@
 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.jacksonObjectMapper
+import com.fasterxml.jackson.module.kotlin.KotlinModule
+import com.fasterxml.jackson.module.kotlin.SingletonSupport
+import com.fasterxml.jackson.module.kotlin.SingletonSupport.CANONICALIZE
 import com.fasterxml.jackson.module.kotlin.readValue
 import org.hamcrest.CoreMatchers.equalTo
-import org.hamcrest.CoreMatchers.not
 import org.hamcrest.MatcherAssert.assertThat
 import org.junit.Test
 
 // [module-kotlin#225]: keep Kotlin singletons as singletons
 class TestObjectSingleton {
-
-    val mapper: ObjectMapper = jacksonObjectMapper()
+    val mapper: ObjectMapper = ObjectMapper()
+        .registerModule(KotlinModule(singletonSupport = CANONICALIZE))
 
     object Singleton {
         var content = 1 // mutable state
@@ -49,9 +49,8 @@ class TestObjectSingleton {
         val newSingleton = mapper.readValue<Singleton>(js)
         assertThat(newSingleton.content, equalTo(Singleton.content))
 
-        newSingleton.content += 1;
+        newSingleton.content += 1
 
         assertThat(Singleton.content, equalTo(newSingleton.content))
     }
-
-}
+}