Kotlinx polymorphism with custom discriminator support (#21531)

* kotlinx serialization fixes

- added new config with kotlinx, discriminator (/w custom name) and
  kotlinx_serialization
- remove discriminator properties from the generator in both base and
  derived classes
- set discriminatorValue in additionalProperties of derived classes
- add JsonClassDiscriminator the derived classes in the template
- set SerialName to discriminatorValue in the template
- change base classes to sealed class instead of interface
- make variables in base classes abstract

* Generated kotlin-allOff-discriminator-kotlinx-serialization sample

* Added test for kotlinx_serialization with discriminator

* renamed yaml

* Added new sample to github workflow

* Added comments to KotlinClientCodegen::postProcessAllModels

Author: some00

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

@@ -66,6 +66,7 @@ jobs:
           - samples/client/petstore/kotlin-name-parameter-mappings
           - samples/client/others/kotlin-jvm-okhttp-parameter-tests
           - samples/client/others/kotlin-jvm-okhttp-path-comments
+          - samples/client/petstore/kotlin-allOff-discriminator-kotlinx-serialization
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-java@v4

bin/configs/kotlin-allOff-discriminator-kotlinx-serialization.yaml

@@ -0,0 +1,10 @@
+generatorName: kotlin
+outputDir: samples/client/petstore/kotlin-allOff-discriminator-kotlinx-serialization
+inputSpec: modules/openapi-generator/src/test/resources/3_0/kotlin/polymorphism.yaml
+templateDir: modules/openapi-generator/src/main/resources/kotlin-client
+additionalProperties:
+  artifactId: kotlin-allOff-discriminator
+  serializableModel: "false"
+  dateLibrary: java8
+  enumUnknownDefaultCase: true
+  serializationLibrary: kotlinx_serialization

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

@@ -963,6 +963,44 @@ public ModelsMap postProcessModels(ModelsMap objs) {
         return objects;
     }
 
+    @Override
+    public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs) {
+        objs = super.postProcessAllModels(objs);
+        if (getSerializationLibrary() == SERIALIZATION_LIBRARY_TYPE.kotlinx_serialization) {
+            // The loop removes unneeded variables so commas are handled correctly in the related templates
+            for (Map.Entry<String, ModelsMap> modelsMap : objs.entrySet()) {
+                for (ModelMap mo : modelsMap.getValue().getModels()) {
+                    CodegenModel cm = mo.getModel();
+                    CodegenDiscriminator discriminator = cm.getDiscriminator();
+                    if (discriminator == null) {
+                        continue;
+                    }
+                    // Remove discriminator property from the base class, it is not needed in the generated code
+                    getAllVarProperties(cm).forEach(list -> list.removeIf(var -> var.name == discriminator.getPropertyName()));
+
+                    for (CodegenDiscriminator.MappedModel mappedModel : discriminator.getMappedModels()) {
+                        // Add the mapping name to additionalProperties.disciminatorValue
+                        // The mapping name is used to define SerializedName, which in result makes derived classes
+                        // found by kotlinx-serialization during deserialization
+                        CodegenProperty additionalProperties = mappedModel.getModel().getAdditionalProperties();
+                        if (additionalProperties == null) {
+                            additionalProperties = new CodegenProperty();
+                            mappedModel.getModel().setAdditionalProperties(additionalProperties);
+                        }
+                        additionalProperties.discriminatorValue = mappedModel.getMappingName();
+                        // Remove the discriminator property from the derived class, it is not needed in the generated code
+                        getAllVarProperties(mappedModel.getModel()).forEach(list -> list.removeIf(prop -> prop.name == discriminator.getPropertyName()));
+                    }
+
+                }
+            }
+        }
+        return objs;
+    }
+    private Stream<List<CodegenProperty>> getAllVarProperties(CodegenModel model) {
+        return Stream.of(model.vars, model.allVars, model.optionalVars, model.requiredVars, model.readOnlyVars, model.readWriteVars);
+    }
+
     private boolean usesRetrofit2Library() {
         return getLibrary() != null && getLibrary().contains(JVM_RETROFIT2);
     }

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

@@ -40,6 +40,10 @@ import kotlinx.serialization.encoding.Encoder
 {{/enumUnknownDefaultCase}}
 {{#hasEnums}}
 {{/hasEnums}}
+{{#discriminator}}
+import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.json.JsonClassDiscriminator
+{{/discriminator}}
 {{/kotlinx_serialization}}
 {{#parcelizeModels}}
 import android.os.Parcelable
@@ -78,13 +82,21 @@ import {{packageName}}.infrastructure.ITransformForStorage
 {{#vendorExtensions.x-class-extra-annotation}}
 {{{vendorExtensions.x-class-extra-annotation}}}
 {{/vendorExtensions.x-class-extra-annotation}}
-{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}{{#discriminator}}interface{{/discriminator}}{{^discriminator}}{{#hasVars}}data {{/hasVars}}class{{/discriminator}} {{classname}}{{^discriminator}} (
+{{#kotlinx_serialization}}{{#discriminator}}
+@OptIn(ExperimentalSerializationApi::class)
+@JsonClassDiscriminator(discriminator = "{{{discriminator.propertyName}}}")
+{{/discriminator}}
+{{#additionalProperties.discriminatorValue}}
+@SerialName(value = {{#lambda.doublequote}}{{{additionalProperties.discriminatorValue}}}{{/lambda.doublequote}})
+{{/additionalProperties.discriminatorValue}}
+{{/kotlinx_serialization}}
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}{{#discriminator}}{{#kotlinx_serialization}}sealed class{{/kotlinx_serialization}}{{^kotlinx_serialization}}interface{{/kotlinx_serialization}}{{/discriminator}}{{^discriminator}}{{#hasVars}}data {{/hasVars}}class{{/discriminator}} {{classname}}{{^discriminator}} (
 
 {{#allVars}}
 {{#required}}{{>data_class_req_var}}{{/required}}{{^required}}{{>data_class_opt_var}}{{/required}}{{^-last}},{{/-last}}
 
 {{/allVars}}
-){{/discriminator}}{{#parent}}{{^serializableModel}}{{^parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#parent}}{{#serializableModel}}{{^parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}, Serializable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#parent}}{{^serializableModel}}{{#parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}, Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#parent}}{{#serializableModel}}{{#parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}, Serializable, Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{^parent}}{{#serializableModel}}{{^parcelizeModels}} : Serializable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{^parent}}{{^serializableModel}}{{#parcelizeModels}} : Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{^parent}}{{#serializableModel}}{{#parcelizeModels}} : Serializable, Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#generateRoomModels}}{{#parent}}, {{/parent}}{{^discriminator}}{{^parent}}:{{/parent}} ITransformForStorage<{{classname}}RoomModel>{{/discriminator}}{{/generateRoomModels}}{{#vendorExtensions.x-has-data-class-body}} {
+){{/discriminator}}{{#parent}}{{^serializableModel}}{{^parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#kotlinx_serialization}}(){{/kotlinx_serialization}}{{#isArray}}(){{/isArray}}{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#parent}}{{#serializableModel}}{{^parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}, Serializable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#parent}}{{^serializableModel}}{{#parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}, Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#parent}}{{#serializableModel}}{{#parcelizeModels}} : {{{parent}}}{{#isMap}}(){{/isMap}}{{#isArray}}(){{/isArray}}, Serializable, Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{^parent}}{{#serializableModel}}{{^parcelizeModels}} : Serializable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{^parent}}{{^serializableModel}}{{#parcelizeModels}} : Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{^parent}}{{#serializableModel}}{{#parcelizeModels}} : Serializable, Parcelable{{/parcelizeModels}}{{/serializableModel}}{{/parent}}{{#generateRoomModels}}{{#parent}}, {{/parent}}{{^discriminator}}{{^parent}}:{{/parent}} ITransformForStorage<{{classname}}RoomModel>{{/discriminator}}{{/generateRoomModels}}{{#vendorExtensions.x-has-data-class-body}} {
 {{/vendorExtensions.x-has-data-class-body}}
 {{#generateRoomModels}}
     companion object { }

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

@@ -15,4 +15,4 @@
     {{^isEnum}}{{^isArray}}{{^isPrimitiveType}}{{^isModel}}@Contextual {{/isModel}}{{/isPrimitiveType}}{{/isArray}}{{/isEnum}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}")
     {{/kotlinx_serialization}}
     {{/multiplatform}}
-    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") {{/multiplatform}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}?
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") {{/multiplatform}}{{#kotlinx_serialization}}abstract {{/kotlinx_serialization}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}?

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

@@ -15,4 +15,4 @@
     {{^isEnum}}{{^isArray}}{{^isPrimitiveType}}{{^isModel}}@Contextual {{/isModel}}{{/isPrimitiveType}}{{/isArray}}{{/isEnum}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}")
     {{/kotlinx_serialization}}
     {{/multiplatform}}
-    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required {{/multiplatform}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}{{#isNullable}}?{{/isNullable}}
+    {{#multiplatform}}@SerialName(value = "{{{vendorExtensions.x-base-name-literal}}}") @Required {{/multiplatform}}{{#kotlinx_serialization}}abstract {{/kotlinx_serialization}}{{>modelMutable}} {{{name}}}: {{#isArray}}{{#isList}}kotlin.collections.{{#modelMutable}}Mutable{{/modelMutable}}List{{/isList}}{{^isList}}kotlin.Array{{/isList}}<{{^items.isEnum}}{{^items.isPrimitiveType}}{{^items.isModel}}{{#kotlinx_serialization}}@Contextual {{/kotlinx_serialization}}{{/items.isModel}}{{/items.isPrimitiveType}}{{{items.dataType}}}{{/items.isEnum}}{{#items.isEnum}}{{classname}}.{{{nameInPascalCase}}}{{/items.isEnum}}>{{/isArray}}{{^isEnum}}{{^isArray}}{{{dataType}}}{{/isArray}}{{/isEnum}}{{#isEnum}}{{^isArray}}{{classname}}.{{{nameInPascalCase}}}{{/isArray}}{{/isEnum}}{{#isNullable}}?{{/isNullable}}

modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinClientCodegenModelTest.java

@@ -533,6 +533,46 @@ private void givenSchemaObjectPropertyNameContainsDollarSignWhenGenerateThenDoll
         Assert.assertEquals(customKotlinParseListener.getStringReferenceCount(), 0);
     }
 
+    @Test(description = "generate polymorphic kotlinx_serialization model")
+    public void polymorphicKotlinxSerialzation() throws IOException {
+        File output = Files.createTempDirectory("test").toFile();
+        output.deleteOnExit();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("kotlin")
+                .setLibrary("jvm-retrofit2")
+                .setAdditionalProperties(new HashMap<>() {{
+                    put(CodegenConstants.SERIALIZATION_LIBRARY, "kotlinx_serialization");
+                    put(CodegenConstants.MODEL_PACKAGE, "xyz.abcdef.model");
+                }})
+                .setInputSpec("src/test/resources/3_0/kotlin/polymorphism.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(clientOptInput).generate();
+
+        Assert.assertEquals(files.size(), 36);
+
+        final Path animalKt = Paths.get(output + "/src/main/kotlin/xyz/abcdef/model/Animal.kt");
+        // base doesn't contain discriminator
+        TestUtils.assertFileNotContains(animalKt, "val discriminator");
+        // base is sealed class
+        TestUtils.assertFileContains(animalKt, "sealed class Animal");
+        // base properties are abstract
+        TestUtils.assertFileContains(animalKt, "abstract val id");
+        TestUtils.assertFileContains(animalKt, "abstract val optionalProperty");
+        // base has extra imports
+        TestUtils.assertFileContains(animalKt, "import kotlinx.serialization.ExperimentalSerializationApi");
+        TestUtils.assertFileContains(animalKt, "import kotlinx.serialization.json.JsonClassDiscriminator");
+
+        final Path birdKt = Paths.get(output + "/src/main/kotlin/xyz/abcdef/model/Bird.kt");
+        // derived doesn't contain disciminator
+        TestUtils.assertFileNotContains(birdKt, "val discriminator");
+        // derived has serial name set to mapping key
+        TestUtils.assertFileContains(birdKt, "@SerialName(value = \"BIRD\")");
+    }
+
     private static class ModelNameTest {
         private final String expectedName;
         private final String expectedClassName;

modules/openapi-generator/src/test/resources/3_0/kotlin/polymorphism.yaml

@@ -0,0 +1,59 @@
+openapi: 3.0.1
+info:
+  title: Example
+  description: An example
+  version: '0.1'
+  contact:
+    email: contact@example.org
+    url: 'https://example.org'
+servers:
+  - url: http://example.org
+tags:
+  - name: bird
+paths:
+  '/v1/bird/{id}':
+    get:
+      tags:
+        - bird
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/bird'
+      operationId: get-bird
+    parameters:
+      - schema:
+          type: string
+          format: uuid
+        name: id
+        in: path
+        required: true
+components:
+  schemas:
+    animal:
+      title: An animal
+      type: object
+      properties:
+        id:
+          type: string
+          format: uuid
+        optional_property:
+          type: number
+      required:
+        - id
+      discriminator:
+        propertyName: discriminator
+        mapping:
+          BIRD: '#/components/schemas/bird'
+    bird:
+      title: A bird
+      type: object
+      allOf:
+        - $ref: '#/components/schemas/animal'
+        - properties:
+            featherType:
+              type: string
+          required:
+            - featherType

samples/client/petstore/kotlin-allOff-discriminator-kotlinx-serialization/.openapi-generator-ignore

@@ -0,0 +1,23 @@
+# OpenAPI Generator Ignore
+# Generated by openapi-generator https://github.com/openapitools/openapi-generator
+
+# Use this file to prevent files from being overwritten by the generator.
+# The patterns follow closely to .gitignore or .dockerignore.
+
+# As an example, the C# client generator defines ApiClient.cs.
+# You can make changes and tell OpenAPI Generator to ignore just this file by uncommenting the following line:
+#ApiClient.cs
+
+# You can match any string of characters against a directory, file or extension with a single asterisk (*):
+#foo/*/qux
+# The above matches foo/bar/qux and foo/baz/qux, but not foo/bar/baz/qux
+
+# You can recursively match patterns against a directory, file or extension with a double asterisk (**):
+#foo/**/qux
+# This matches foo/bar/qux, foo/baz/qux, and foo/bar/baz/qux
+
+# You can also negate patterns with an exclamation (!).
+# For example, you can ignore all files in a docs folder with the file extension .md:
+#docs/*.md
+# Then explicitly reverse the ignore rule for a single file:
+#!docs/README.md

samples/client/petstore/kotlin-allOff-discriminator-kotlinx-serialization/.openapi-generator/FILES

@@ -0,0 +1,35 @@
+README.md
+build.gradle
+docs/Animal.md
+docs/Bird.md
+docs/BirdApi.md
+gradle/wrapper/gradle-wrapper.jar
+gradle/wrapper/gradle-wrapper.properties
+gradlew
+gradlew.bat
+proguard-rules.pro
+settings.gradle
+src/main/kotlin/org/openapitools/client/apis/BirdApi.kt
+src/main/kotlin/org/openapitools/client/infrastructure/ApiAbstractions.kt
+src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt
+src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt
+src/main/kotlin/org/openapitools/client/infrastructure/AtomicBooleanAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/AtomicIntegerAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/AtomicLongAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/BigDecimalAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/BigIntegerAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/Errors.kt
+src/main/kotlin/org/openapitools/client/infrastructure/LocalDateAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/LocalDateTimeAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/OffsetDateTimeAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/PartConfig.kt
+src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt
+src/main/kotlin/org/openapitools/client/infrastructure/RequestMethod.kt
+src/main/kotlin/org/openapitools/client/infrastructure/ResponseExtensions.kt
+src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt
+src/main/kotlin/org/openapitools/client/infrastructure/StringBuilderAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/URIAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/URLAdapter.kt
+src/main/kotlin/org/openapitools/client/infrastructure/UUIDAdapter.kt
+src/main/kotlin/org/openapitools/client/models/Animal.kt
+src/main/kotlin/org/openapitools/client/models/Bird.kt