Define and plug Polymorphic annotation PolymorphicAdapterFactory class

Author: macisamuele

gradle-plugin/plugin/src/main/java/com/yelp/codegen/KotlinGenerator.kt

@@ -125,6 +125,8 @@ open class KotlinGenerator : SharedCodegen() {
                 "CollectionFormats.kt",
                 "EnumToValueConverterFactory.kt",
                 "GeneratedCodeConverters.kt",
+                "OptimisticHashCode.kt",
+                "PolymorphicAdapterFactory.kt",
                 "TypesAdapters.kt",
                 "WrapperConverterFactory.kt",
                 "XNullable.kt",

gradle-plugin/plugin/src/main/resources/kotlin/tools/OptimisticHashCode.kt.mustache

@@ -0,0 +1,4 @@
+package {{packageName}}.tools
+
+@Suppress("NOTHING_TO_INLINE")
+internal inline fun <T> T.optimisticHashCode(): Int = this?.hashCode() ?: 0

gradle-plugin/plugin/src/main/resources/kotlin/tools/PolymorphicAdapterFactory.kt.mustache

@@ -0,0 +1,40 @@
+package {{packageName}}.tools
+
+import com.squareup.moshi.JsonAdapter
+import com.squareup.moshi.Moshi
+import com.squareup.moshi.Types
+import com.squareup.moshi.adapters.PolymorphicJsonAdapterFactory
+import java.lang.reflect.Type
+import kotlin.reflect.KClass
+
+@Target(AnnotationTarget.CLASS)
+@Retention(AnnotationRetention.RUNTIME)
+internal annotation class Polymorphic(
+    val discriminatorField: String,
+    val discriminatedValues: Array<String>,
+    val discriminatedClasses: Array<KClass<*>>
+)
+
+internal class PolymorphicAdapterFactory : JsonAdapter.Factory {
+    override fun create(type: Type, annotations: MutableSet<out Annotation>, moshi: Moshi): JsonAdapter<*>? {
+        val rawType = Types.getRawType(type)
+        return rawType.getAnnotation(Polymorphic::class.java)?.let { annotation ->
+            @Suppress("UNCHECKED_CAST")
+            val polymorphicJsonAdapterFactory: PolymorphicJsonAdapterFactory<Any> = PolymorphicJsonAdapterFactory.of(
+                    rawType, annotation.discriminatorField
+            ) as? PolymorphicJsonAdapterFactory<Any> ?: return@let null
+
+            return annotation.discriminatedClasses.zip(annotation.discriminatedValues).fold(
+            initial = polymorphicJsonAdapterFactory.withFallbackJsonAdapter(
+                moshi.nextAdapter<Any>(
+                    this@PolymorphicAdapterFactory,
+                    type,
+                    annotations
+                )
+            )
+            ) { jsonAdapterFactory, (klass, label) ->
+                jsonAdapterFactory.withSubtype(klass.java, label)
+            }.create(type, annotations, moshi)
+        }
+    }
+}

samples/junit-tests/src/main/java/com/yelp/codegen/generatecodesamples/tools/OptimisticHashCode.kt

@@ -0,0 +1,4 @@
+package com.yelp.codegen.generatecodesamples.tools
+
+@Suppress("NOTHING_TO_INLINE")
+internal inline fun <T> T.optimisticHashCode(): Int = this?.hashCode() ?: 0

samples/junit-tests/src/main/java/com/yelp/codegen/generatecodesamples/tools/PolymorphicAdapterFactory.kt

@@ -0,0 +1,40 @@
+package com.yelp.codegen.generatecodesamples.tools
+
+import com.squareup.moshi.JsonAdapter
+import com.squareup.moshi.Moshi
+import com.squareup.moshi.Types
+import com.squareup.moshi.adapters.PolymorphicJsonAdapterFactory
+import java.lang.reflect.Type
+import kotlin.reflect.KClass
+
+@Target(AnnotationTarget.CLASS)
+@Retention(AnnotationRetention.RUNTIME)
+internal annotation class Polymorphic(
+    val discriminatorField: String,
+    val discriminatedValues: Array<String>,
+    val discriminatedClasses: Array<KClass<*>>
+)
+
+internal class PolymorphicAdapterFactory : JsonAdapter.Factory {
+    override fun create(type: Type, annotations: MutableSet<out Annotation>, moshi: Moshi): JsonAdapter<*>? {
+        val rawType = Types.getRawType(type)
+        return rawType.getAnnotation(Polymorphic::class.java)?.let { annotation ->
+            @Suppress("UNCHECKED_CAST")
+            val polymorphicJsonAdapterFactory: PolymorphicJsonAdapterFactory<Any> = PolymorphicJsonAdapterFactory.of(
+                    rawType, annotation.discriminatorField
+            ) as? PolymorphicJsonAdapterFactory<Any> ?: return@let null
+
+            return annotation.discriminatedClasses.zip(annotation.discriminatedValues).fold(
+            initial = polymorphicJsonAdapterFactory.withFallbackJsonAdapter(
+                moshi.nextAdapter<Any>(
+                    this@PolymorphicAdapterFactory,
+                    type,
+                    annotations
+                )
+            )
+            ) { jsonAdapterFactory, (klass, label) ->
+                jsonAdapterFactory.withSubtype(klass.java, label)
+            }.create(type, annotations, moshi)
+        }
+    }
+}