feat: add NullableInputVariableSerializer (#557)

* feat: add NullableInputVariableSerializer

* fix reference of interface for input value serializer

* refactor: internalize serialize assignment

* fix nullable params

* remove unnecessary condition

* fix constructors

graphql-dgs-codegen-shared-core/src/main/kotlin/com/netflix/graphql/dgs/client/codegen/GraphQLQueryRequest.kt

@@ -26,16 +26,27 @@ import graphql.schema.Coercing
 class GraphQLQueryRequest @JvmOverloads constructor(
     val query: GraphQLQuery,
     val projection: BaseProjectionNode? = null,
-    scalars: Map<Class<*>, Coercing<*, *>>? = null
+    options: GraphQLQueryRequestOptions? = null
 ) {
 
     private var selectionSet: SelectionSet? = null
-
-    @JvmOverloads constructor(query: GraphQLQuery, selectionSet: SelectionSet, scalars: Map<Class<*>, Coercing<*, *>>? = null) : this(query = query, scalars = scalars) {
+    constructor(query: GraphQLQuery, projection: BaseProjectionNode, scalars: Map<Class<*>, Coercing<*, *>>) : this(query = query, projection = projection, options = GraphQLQueryRequestOptions(scalars = scalars))
+    constructor(query: GraphQLQuery, selectionSet: SelectionSet, scalars: Map<Class<*>, Coercing<*, *>>? = null) : this(query = query, projection = null, options = GraphQLQueryRequestOptions(scalars = scalars ?: emptyMap())) {
         this.selectionSet = selectionSet
     }
+    class GraphQLQueryRequestOptions(val scalars: Map<Class<*>, Coercing<*, *>> = emptyMap()) {
+        // When enabled, input values that are derived from properties
+        // whose values are null will be serialized in the query request
+        val allowNullablePropertyInputValues = false
+    }
+
+    val inputValueSerializer =
+        if (options?.allowNullablePropertyInputValues == true) {
+            NullableInputValueSerializer(options.scalars)
+        } else {
+            InputValueSerializer(options?.scalars ?: emptyMap())
+        }
 
-    val inputValueSerializer = InputValueSerializer(scalars ?: emptyMap())
     val projectionSerializer = ProjectionSerializer(inputValueSerializer)
 
     fun serialize(): String {

graphql-dgs-codegen-shared-core/src/main/kotlin/com/netflix/graphql/dgs/client/codegen/InputValueSerializer.kt

@@ -35,25 +35,15 @@ import java.time.LocalDate
 import java.time.LocalDateTime
 import java.time.LocalTime
 import java.time.OffsetDateTime
-import java.util.Currency
-import java.util.Date
-import java.util.TimeZone
+import java.util.*
+import kotlin.reflect.KClass
 import kotlin.reflect.full.allSuperclasses
 import kotlin.reflect.full.hasAnnotation
 import kotlin.reflect.full.memberProperties
 import kotlin.reflect.jvm.isAccessible
 
-/**
- * Marks this property invisible for input value serialization.
- */
-@Target(AnnotationTarget.PROPERTY)
-internal annotation class Transient
-
-interface InputValue {
-    fun inputValues(): List<Pair<String, Any?>>
-}
-
-class InputValueSerializer(private val scalars: Map<Class<*>, Coercing<*, *>> = emptyMap()) {
+open class InputValueSerializer(private val scalars: Map<Class<*>, Coercing<*, *>> = emptyMap()) :
+    InputValueSerializerInterface {
     companion object {
         private val toStringClasses = setOf(
             String::class,
@@ -68,84 +58,115 @@ class InputValueSerializer(private val scalars: Map<Class<*>, Coercing<*, *>> =
         )
     }
 
-    fun serialize(input: Any?): String {
+    override fun serialize(input: Any?): String {
         return AstPrinter.printAst(toValue(input))
     }
 
-    fun toValue(input: Any?): Value<*> {
+    override fun toValue(input: Any?): Value<*> {
         if (input == null) {
             return NullValue.newNullValue().build()
         }
 
+        val optionalValue = getOptionalValue(input)
+
+        if (optionalValue.isPresent) {
+            return optionalValue.get()
+        }
+
+        val classes = (sequenceOf(input::class) + input::class.allSuperclasses.asSequence()) - Any::class
+        val propertyValues = getPropertyValues(classes, input)
+
+        val objectFields = propertyValues.asSequence()
+            .filter { (_, value) -> value != null }
+            .map { (name, value) -> ObjectField(name, toValue(value)) }
+            .toList()
+        return ObjectValue.newObjectValue()
+            .objectFields(objectFields)
+            .build()
+    }
+
+    protected fun getOptionalValue(input: Any): Optional<Value<*>> {
         if (input is Value<*>) {
-            return input
+            return Optional.of(input)
         }
 
         for (scalar in scalars.keys) {
             if (input::class.java == scalar || scalar.isAssignableFrom(input::class.java)) {
-                return scalars[scalar]!!.valueToLiteral(input)
+                return Optional.of(scalars[scalar]!!.valueToLiteral(input))
             }
         }
 
         if (input::class in toStringClasses) {
-            return StringValue.of(input.toString())
+            return Optional.of(StringValue.of(input.toString()))
         }
 
         if (input is String) {
-            return StringValue.of(input)
+            return Optional.of(StringValue.of(input))
         }
 
         if (input is Float) {
-            return FloatValue.of(input.toDouble())
+            return Optional.of(FloatValue.of(input.toDouble()))
         }
 
         if (input is Double) {
-            return FloatValue.of(input)
+            return Optional.of(FloatValue.of(input))
         }
 
         if (input is BigDecimal) {
-            return FloatValue.newFloatValue(input).build()
+            return Optional.of(FloatValue.newFloatValue(input).build())
         }
 
         if (input is BigInteger) {
-            return IntValue.newIntValue(input).build()
+            return Optional.of(IntValue.newIntValue(input).build())
         }
 
         if (input is Int) {
-            return IntValue.of(input)
+            return Optional.of(IntValue.of(input))
         }
 
         if (input is Number) {
-            return IntValue.newIntValue(BigInteger.valueOf(input.toLong())).build()
+            return Optional.of(IntValue.newIntValue(BigInteger.valueOf(input.toLong())).build())
         }
 
         if (input is Boolean) {
-            return BooleanValue.of(input)
+            return Optional.of(BooleanValue.of(input))
         }
 
         if (input is Enum<*>) {
-            return EnumValue.newEnumValue(input.name).build()
+            return Optional.of(EnumValue.newEnumValue(input.name).build())
         }
 
         if (input is Collection<*>) {
-            return ArrayValue.newArrayValue()
-                .values(input.map { toValue(it) })
-                .build()
+            return Optional.of(
+                ArrayValue.newArrayValue()
+                    .values(input.map { toValue(it) })
+                    .build()
+            )
         }
 
         if (input is Map<*, *>) {
-            return ObjectValue.newObjectValue()
-                .objectFields(input.map { (key, value) -> ObjectField(key.toString(), toValue(value)) })
-                .build()
+            return Optional.of(
+                ObjectValue.newObjectValue()
+                    .objectFields(input.map { (key, value) -> ObjectField(key.toString(), toValue(value)) })
+                    .build()
+            )
         }
 
         if (input is InputValue) {
-            return ObjectValue.newObjectValue()
-                .objectFields(input.inputValues().map { (name, value) -> ObjectField(name, toValue(value)) })
-                .build()
+            return Optional.of(
+                ObjectValue.newObjectValue()
+                    .objectFields(input.inputValues().map { (name, value) -> ObjectField(name, toValue(value)) })
+                    .build()
+            )
         }
 
-        val classes = sequenceOf(input::class) + input::class.allSuperclasses.asSequence() - Any::class
+        return Optional.empty()
+    }
+
+    protected fun getPropertyValues(
+        classes: Sequence<KClass<out Any>>,
+        input: Any?
+    ): MutableMap<String, Any?> {
         val propertyValues = mutableMapOf<String, Any?>()
 
         for (klass in classes) {
@@ -158,13 +179,6 @@ class InputValueSerializer(private val scalars: Map<Class<*>, Coercing<*, *>> =
                 propertyValues[property.name] = property.call(input)
             }
         }
-
-        val objectFields = propertyValues.asSequence()
-            .filter { (_, value) -> value != null }
-            .map { (name, value) -> ObjectField(name, toValue(value)) }
-            .toList()
-        return ObjectValue.newObjectValue()
-            .objectFields(objectFields)
-            .build()
+        return propertyValues
     }
 }

graphql-dgs-codegen-shared-core/src/main/kotlin/com/netflix/graphql/dgs/client/codegen/InputValueSerializerInterface.kt

@@ -0,0 +1,36 @@
+/*
+ *
+ *  Copyright 2020 Netflix, Inc.
+ *
+ *  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 com.netflix.graphql.dgs.client.codegen
+
+import graphql.language.Value
+
+/**
+ * Marks this property invisible for input value serialization.
+ */
+@Target(AnnotationTarget.PROPERTY)
+internal annotation class Transient
+
+interface InputValueSerializerInterface {
+    fun serialize(input: Any?): String
+    fun toValue(input: Any?): Value<*>
+}
+
+interface InputValue {
+    fun inputValues(): List<Pair<String, Any?>>
+}

graphql-dgs-codegen-shared-core/src/main/kotlin/com/netflix/graphql/dgs/client/codegen/NullableInputValueSerializer.kt

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2021 Netflix, Inc.
+ *
+ * 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 com.netflix.graphql.dgs.client.codegen
+
+import graphql.language.NullValue
+import graphql.language.ObjectField
+import graphql.language.ObjectValue
+import graphql.language.Value
+import graphql.schema.Coercing
+import kotlin.reflect.full.allSuperclasses
+
+class NullableInputValueSerializer(scalars: Map<Class<*>, Coercing<*, *>> = emptyMap()) :
+    InputValueSerializer(scalars) {
+
+    override fun toValue(input: Any?): Value<*> {
+        if (input == null) {
+            return NullValue.newNullValue().build()
+        }
+
+        val optionalValue = getOptionalValue(input)
+
+        if (optionalValue.isPresent) {
+            return optionalValue.get()
+        }
+
+        val classes = (sequenceOf(input::class) + input::class.allSuperclasses.asSequence()) - Any::class
+        val propertyValues = getPropertyValues(classes, input)
+
+        val objectFields = propertyValues.asSequence()
+            .map { (name, value) -> ObjectField(name, toValue(value)) }
+            .toList()
+        return ObjectValue.newObjectValue()
+            .objectFields(objectFields)
+            .build()
+    }
+}

graphql-dgs-codegen-shared-core/src/main/kotlin/com/netflix/graphql/dgs/client/codegen/ProjectionSerializer.kt

@@ -23,7 +23,7 @@ import graphql.language.InlineFragment
 import graphql.language.SelectionSet
 import graphql.language.TypeName
 
-class ProjectionSerializer(private val inputValueSerializer: InputValueSerializer) {
+class ProjectionSerializer(private val inputValueSerializer: InputValueSerializerInterface) {
 
     fun toSelectionSet(projection: BaseProjectionNode): SelectionSet {
         val selectionSet = SelectionSet.newSelectionSet()

graphql-dgs-codegen-shared-core/src/test/kotlin/com/netflix/graphql/dgs/client/codegen/InputValueSerializerTest.kt

@@ -60,11 +60,27 @@ class InputValueSerializerTest {
     }
 
     @Test
-    fun `Null values should be skipped`() {
-        val movieInput = MovieInput(1)
+    fun `Null values should be serialized except when properties of a POJO`() {
+        class ExamplePojo {
+            private val movieId: String? = null
+            private val movieTitle: String = "Bojack Horseman"
+        }
 
-        val serialize = InputValueSerializer(mapOf(DateRange::class.java to DateRangeScalar())).serialize(movieInput)
-        assertThat(serialize).isEqualTo("{movieId : 1}")
+        assertThat(InputValueSerializer(mapOf()).serialize(null)).isEqualTo("null")
+        assertThat(InputValueSerializer(mapOf()).serialize(mapOf("hello" to null))).isEqualTo("{hello : null}")
+        assertThat(InputValueSerializer(mapOf()).serialize(ExamplePojo())).isEqualTo("{movieTitle : \"Bojack Horseman\"}")
+    }
+
+    @Test
+    fun `NullableInputValueSerializer allows null values from POJO`() {
+        class ExamplePojo {
+            private val movieId: String? = null
+            private val movieTitle: String = "Bojack Horseman"
+        }
+
+        assertThat(NullableInputValueSerializer(mapOf()).serialize(null)).isEqualTo("null")
+        assertThat(NullableInputValueSerializer(mapOf()).serialize(mapOf("hello" to null))).isEqualTo("{hello : null}")
+        assertThat(NullableInputValueSerializer(mapOf()).serialize(ExamplePojo())).isEqualTo("{movieId : null, movieTitle : \"Bojack Horseman\"}")
     }
 
     @Test