fix(kotlin): support non-discriminator oneOf/anyOf model and array types with kotlinx_serialization

.github/workflows/samples-kotlin-client.yaml

@@ -11,6 +11,7 @@ on:
       - 'samples/client/petstore/kotlin*/**'
       - 'samples/client/others/kotlin-jvm-okhttp-parameter-tests/**'
       - samples/client/others/kotlin-integer-enum/**
+      - samples/client/others/kotlin-oneOf-anyOf-kotlinx-serialization/**
 
 jobs:
   build:
@@ -70,6 +71,7 @@ jobs:
           - samples/client/others/kotlin-integer-enum
           - samples/client/petstore/kotlin-allOf-discriminator-kotlinx-serialization
           - samples/client/others/kotlin-oneOf-discriminator-kotlinx-serialization
+          - samples/client/others/kotlin-oneOf-anyOf-kotlinx-serialization
     steps:
       - uses: actions/checkout@v5
       - uses: actions/setup-java@v5

bin/configs/kotlin-oneOf-anyOf-kotlinx-serialization.yaml

@@ -0,0 +1,12 @@
+generatorName: kotlin
+outputDir: samples/client/others/kotlin-oneOf-anyOf-kotlinx-serialization
+inputSpec: modules/openapi-generator/src/test/resources/3_0/kotlin/oneof-anyof-non-discriminator.yaml
+templateDir: modules/openapi-generator/src/main/resources/kotlin-client
+additionalProperties:
+  artifactId: kotlin-oneOf-anyOf-kotlinx-serialization
+  serializableModel: "false"
+  dateLibrary: java8
+  library: jvm-retrofit2
+  enumUnknownDefaultCase: true
+  serializationLibrary: kotlinx_serialization
+  generateOneOfAnyOfWrappers: true

docs/generators/kotlin.md

@@ -27,7 +27,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |enumPropertyNaming|Naming convention for enum properties: 'camelCase', 'PascalCase', 'snake_case', 'UPPERCASE', and 'original'| |original|
 |explicitApi|Generates code with explicit access modifiers to comply with Kotlin Explicit API Mode.| |false|
 |failOnUnknownProperties|Fail Jackson de-serialization on unknown properties| |false|
-|generateOneOfAnyOfWrappers|Generate oneOf, anyOf schemas as wrappers. Only `jvm-retrofit2`(library), `gson`(serializationLibrary) support this option.| |false|
+|generateOneOfAnyOfWrappers|Generate oneOf, anyOf schemas as wrappers. Only `jvm-retrofit2`(library) with `gson` or `kotlinx_serialization`(serializationLibrary) support this option.| |false|
 |generateRoomModels|Generate Android Room database models in addition to API models (JVM Volley library only)| |false|
 |groupId|Generated artifact package's organization (i.e. maven groupId).| |org.openapitools|
 |idea|Add IntelliJ Idea plugin and mark Kotlin main and test folders as source folders.| |false|

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinClientCodegen.java

@@ -286,7 +286,7 @@ public KotlinClientCodegen() {
 
         cliOptions.add(new CliOption(MAP_FILE_BINARY_TO_BYTE_ARRAY, "Map File and Binary to ByteArray (default: false)").defaultValue(Boolean.FALSE.toString()));
 
-        cliOptions.add(CliOption.newBoolean(GENERATE_ONEOF_ANYOF_WRAPPERS, "Generate oneOf, anyOf schemas as wrappers. Only `jvm-retrofit2`(library), `gson`(serializationLibrary) support this option."));
+        cliOptions.add(CliOption.newBoolean(GENERATE_ONEOF_ANYOF_WRAPPERS, "Generate oneOf, anyOf schemas as wrappers. Only `jvm-retrofit2`(library) with `gson` or `kotlinx_serialization`(serializationLibrary) support this option."));
 
         CliOption serializationLibraryOpt = new CliOption(CodegenConstants.SERIALIZATION_LIBRARY, SERIALIZATION_LIBRARY_DESC);
         cliOptions.add(serializationLibraryOpt.defaultValue(serializationLibrary.name()));
@@ -567,6 +567,7 @@ public void processOpts() {
         // We replace paths like `/v1/foo/*` with `/v1/foo/<*>` to avoid this
         additionalProperties.put("sanitizePathComment", new ReplaceAllLambda("\\/\\*", "/<*>"));
         additionalProperties.put("fnToOneOfWrapperName", new ToOneOfWrapperName());
+        additionalProperties.put("fnToValueClassName", new ToValueClassName());
     }
 
     private void processDateLibrary() {
@@ -1155,6 +1156,28 @@ public String formatFragment(String fragment) {
         }
     }
 
+    private static class ToValueClassName extends CustomLambda {
+        @Override
+        public String formatFragment(String fragment) {
+            // Strip generic type parameters and extract simple class names
+            // e.g. "kotlin.collections.List<kotlin.String>" -> "ListStringValue"
+            // e.g. "kotlin.String" -> "StringValue"
+            // e.g. "User" -> "UserValue"
+            StringBuilder sb = new StringBuilder();
+            for (String part : fragment.split("[<>,]")) {
+                String trimmed = part.trim();
+                if (trimmed.isEmpty()) continue;
+                String simpleName = trimmed.contains(".")
+                    ? trimmed.substring(trimmed.lastIndexOf('.') + 1)
+                    : trimmed;
+                sb.append(Character.toUpperCase(simpleName.charAt(0)));
+                sb.append(simpleName.substring(1));
+            }
+            sb.append("Value");
+            return sb.toString();
+        }
+    }
+
     @Override
     public void postProcess() {
         System.out.println("################################################################################");

modules/openapi-generator/src/main/resources/kotlin-client/anyof_class.mustache

@@ -37,6 +37,25 @@ import kotlinx.serialization.builtins.serializer
 import kotlinx.serialization.encoding.Decoder
 import kotlinx.serialization.encoding.Encoder
 {{/enumUnknownDefaultCase}}
+{{^enumUnknownDefaultCase}}
+{{#generateOneOfAnyOfWrappers}}
+import kotlinx.serialization.KSerializer
+import kotlinx.serialization.encoding.Decoder
+import kotlinx.serialization.encoding.Encoder
+{{/generateOneOfAnyOfWrappers}}
+{{/enumUnknownDefaultCase}}
+{{#generateOneOfAnyOfWrappers}}
+import kotlinx.serialization.SerializationException
+import kotlinx.serialization.descriptors.SerialDescriptor
+import kotlinx.serialization.descriptors.buildClassSerialDescriptor
+import kotlinx.serialization.json.JsonDecoder
+import kotlinx.serialization.json.JsonEncoder
+import kotlinx.serialization.json.JsonArray
+import kotlinx.serialization.json.JsonElement
+import kotlinx.serialization.json.JsonPrimitive
+import kotlinx.serialization.json.decodeFromJsonElement
+import kotlinx.serialization.json.encodeToJsonElement
+{{/generateOneOfAnyOfWrappers}}
 {{#hasEnums}}
 {{/hasEnums}}
 {{/kotlinx_serialization}}
@@ -57,7 +76,9 @@ import java.io.Serializable
 import {{roomModelPackage}}.{{classname}}RoomModel
 import {{packageName}}.infrastructure.ITransformForStorage
 {{/generateRoomModels}}
+{{^kotlinx_serialization}}
 import java.io.IOException
+{{/kotlinx_serialization}}
 
 /**
  * {{{description}}}
@@ -66,12 +87,144 @@ import java.io.IOException
 {{#parcelizeModels}}
 @Parcelize
 {{/parcelizeModels}}
+{{^generateOneOfAnyOfWrappers}}
 {{#multiplatform}}{{^discriminator}}@Serializable{{/discriminator}}{{/multiplatform}}{{#kotlinx_serialization}}{{#serializableModel}}@KSerializable{{/serializableModel}}{{^serializableModel}}@Serializable{{/serializableModel}}{{/kotlinx_serialization}}{{#moshi}}{{#moshiCodeGen}}@JsonClass(generateAdapter = true){{/moshiCodeGen}}{{/moshi}}{{#jackson}}{{#discriminator}}{{>typeInfoAnnotation}}{{/discriminator}}{{/jackson}}
+{{/generateOneOfAnyOfWrappers}}
+{{#kotlinx_serialization}}
+{{#generateOneOfAnyOfWrappers}}
+{{#serializableModel}}@KSerializable(with = {{classname}}Serializer::class){{/serializableModel}}{{^serializableModel}}@Serializable(with = {{classname}}Serializer::class){{/serializableModel}}
+{{/generateOneOfAnyOfWrappers}}
+{{/kotlinx_serialization}}
 {{#isDeprecated}}
 @Deprecated(message = "This schema is deprecated.")
 {{/isDeprecated}}
 {{>additionalModelTypeAnnotations}}
 
+{{#kotlinx_serialization}}
+{{#generateOneOfAnyOfWrappers}}
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}sealed interface {{classname}} {
+{{#composedSchemas}}
+{{#anyOf}}
+{{^vendorExtensions.x-duplicated-data-type}}
+    @JvmInline
+    {{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}value class {{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}}(val value: {{{dataType}}}) : {{classname}}
+
+{{/vendorExtensions.x-duplicated-data-type}}
+{{/anyOf}}
+{{/composedSchemas}}
+}
+
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}object {{classname}}Serializer : KSerializer<{{classname}}> {
+    override val descriptor: SerialDescriptor = buildClassSerialDescriptor("{{classname}}")
+
+    override fun serialize(encoder: Encoder, value: {{classname}}) {
+        val jsonEncoder = encoder as? JsonEncoder ?: throw SerializationException("{{classname}} can only be serialized with Json")
+
+        when (value) {
+            {{#composedSchemas}}
+            {{#anyOf}}
+            {{^vendorExtensions.x-duplicated-data-type}}
+            {{#isArray}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeJsonElement(jsonEncoder.json.encodeToJsonElement(value.value))
+            {{/isArray}}
+            {{^isArray}}
+            {{#isPrimitiveType}}
+            {{#isString}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeString(value.value)
+            {{/isString}}
+            {{#isBoolean}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeBoolean(value.value)
+            {{/isBoolean}}
+            {{#isInteger}}
+            {{^isLong}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeInt(value.value)
+            {{/isLong}}
+            {{/isInteger}}
+            {{#isLong}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeLong(value.value)
+            {{/isLong}}
+            {{#isNumber}}
+            {{#isDouble}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeDouble(value.value)
+            {{/isDouble}}
+            {{#isFloat}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeFloat(value.value)
+            {{/isFloat}}
+            {{/isNumber}}
+            {{/isPrimitiveType}}
+            {{^isPrimitiveType}}
+            is {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}} -> jsonEncoder.encodeSerializableValue({{{dataType}}}.serializer(), value.value)
+            {{/isPrimitiveType}}
+            {{/isArray}}
+            {{/vendorExtensions.x-duplicated-data-type}}
+            {{/anyOf}}
+            {{/composedSchemas}}
+        }
+    }
+
+    override fun deserialize(decoder: Decoder): {{classname}} {
+        val jsonDecoder = decoder as? JsonDecoder ?: throw SerializationException("{{classname}} can only be deserialized with Json")
+        val jsonElement = jsonDecoder.decodeJsonElement()
+
+        val errorMessages = mutableListOf<String>()
+
+        {{#composedSchemas}}
+        {{#anyOf}}
+        {{^vendorExtensions.x-duplicated-data-type}}
+        {{#isArray}}
+        if (jsonElement is JsonArray) {
+            try {
+                val instance = jsonDecoder.json.decodeFromJsonElement<{{{dataType}}}>(jsonElement)
+                return {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}}(instance)
+            } catch (e: Exception) {
+                errorMessages.add("Failed to deserialize as {{{dataType}}}: ${e.message}")
+            }
+        }
+        {{/isArray}}
+        {{^isArray}}
+        {{#isPrimitiveType}}
+        {{#isString}}
+        if (jsonElement is JsonPrimitive && jsonElement.isString) {
+            try {
+                val instance = jsonDecoder.json.decodeFromJsonElement<{{{dataType}}}>(jsonElement)
+                return {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}}(instance)
+            } catch (e: Exception) {
+                errorMessages.add("Failed to deserialize as {{{dataType}}}: ${e.message}")
+            }
+        }
+        {{/isString}}
+        {{^isString}}
+        if (jsonElement is JsonPrimitive && !jsonElement.isString) {
+            try {
+                val instance = jsonDecoder.json.decodeFromJsonElement<{{{dataType}}}>(jsonElement)
+                return {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}}(instance)
+            } catch (e: Exception) {
+                errorMessages.add("Failed to deserialize as {{{dataType}}}: ${e.message}")
+            }
+        }
+        {{/isString}}
+        {{/isPrimitiveType}}
+        {{^isPrimitiveType}}
+        if (jsonElement !is JsonPrimitive) {
+            try {
+                val instance = jsonDecoder.json.decodeFromJsonElement<{{{dataType}}}>(jsonElement)
+                return {{classname}}.{{#fnToValueClassName}}{{{dataType}}}{{/fnToValueClassName}}(instance)
+            } catch (e: Exception) {
+                errorMessages.add("Failed to deserialize as {{{dataType}}}: ${e.message}")
+            }
+        }
+        {{/isPrimitiveType}}
+        {{/isArray}}
+        {{/vendorExtensions.x-duplicated-data-type}}
+        {{/anyOf}}
+        {{/composedSchemas}}
+
+        throw SerializationException("Cannot deserialize {{classname}}. Tried: ${errorMessages.joinToString(", ")}")
+    }
+}
+{{/generateOneOfAnyOfWrappers}}
+{{/kotlinx_serialization}}
+{{^kotlinx_serialization}}
 {{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}data class {{classname}}(var actualInstance: Any? = null) {
 
     class CustomTypeAdapterFactory : TypeAdapterFactory {
@@ -334,4 +487,5 @@ import java.io.IOException
             }
         }
     }
-}
+}
+{{/kotlinx_serialization}}