fix(kotlin): add JsonCreator/JsonValue for numeric enums

Author: ramononis

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

@@ -7,10 +7,13 @@ import com.squareup.moshi.Json
 import com.squareup.moshi.JsonClass
 {{/moshi}}
 {{#jackson}}
+import com.fasterxml.jackson.annotation.JsonCreator
 {{#enumUnknownDefaultCase}}
 import com.fasterxml.jackson.annotation.JsonEnumDefaultValue
 {{/enumUnknownDefaultCase}}
 import com.fasterxml.jackson.annotation.JsonProperty
+import com.fasterxml.jackson.annotation.JsonValue
+import kotlin.jvm.JvmStatic
 {{/jackson}}
 {{#kotlinx_serialization}}
 import kotlinx.serialization.SerialName
@@ -52,7 +55,7 @@ import kotlinx.serialization.*
 @JsonClass(generateAdapter = false)
 {{/moshi}}
 {{/multiplatform}}
-{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}enum class {{classname}}({{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}val value: {{{dataType}}}) {
+{{#nonPublicApi}}internal {{/nonPublicApi}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}enum class {{classname}}({{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}{{#jackson}}@get:JsonValue {{/jackson}}val value: {{{dataType}}}) {
 {{#allowableValues}}{{#enumVars}}
     {{^multiplatform}}
     {{#moshi}}
@@ -103,7 +106,9 @@ import kotlinx.serialization.*
         /**
          * Returns a valid [{{classname}}] for [data], null otherwise.
          */
-        {{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}fun decode(data: kotlin.Any?): {{classname}}? = data?.let {
+        {{#jackson}}@JvmStatic
+        @JsonCreator
+        {{/jackson}}{{^nonPublicApi}}{{#explicitApi}}public {{/explicitApi}}{{/nonPublicApi}}fun decode(data: kotlin.Any?): {{classname}}? = data?.let {
           val normalizedData = "$it".lowercase()
           values().firstOrNull { value ->
             it == value || normalizedData == "$value".lowercase()
@@ -146,4 +151,4 @@ internal object {{classname}}Serializer : KSerializer<{{classname}}> {
     }
 }
 {{/isString}}{{/enumUnknownDefaultCase}}
-{{/kotlinx_serialization}}
+{{/kotlinx_serialization}}

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

@@ -688,6 +688,32 @@ public void testIntArrayToEnum() throws IOException {
       TestUtils.assertFileContains(modelKt, "enum class DaysOfWeek(val value: kotlin.Int)");
   }
 
+  @Test
+  public void testJacksonNumericEnumsUseJsonCreator() 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, "jackson");
+                put(CodegenConstants.MODEL_PACKAGE, "model");
+              }})
+              .setInputSpec("src/test/resources/3_0/kotlin/issue22534-kotlin-numeric-enum.yaml")
+              .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+      final ClientOptInput clientOptInput = configurator.toClientOptInput();
+      DefaultGenerator generator = new DefaultGenerator();
+
+      generator.opts(clientOptInput).generate();
+
+      final Path enumKt = Paths.get(output + "/src/main/kotlin/model/ExampleNumericEnum.kt");
+
+      TestUtils.assertFileContains(enumKt, "@get:JsonValue");
+      TestUtils.assertFileContains(enumKt, "@JsonCreator");
+  }
+
     @Test(description = "convert an empty model to object")
     public void emptyModelKotlinxSerializationTest() throws IOException {
         final Schema<?> schema = new ObjectSchema()

modules/openapi-generator/src/test/resources/3_0/kotlin/issue22534-kotlin-numeric-enum.yaml

@@ -0,0 +1,31 @@
+openapi: 3.0.0
+info:
+  title: 'Issue 5077 Jackson numeric enum regression'
+  version: latest
+paths:
+  '/example':
+    get:
+      operationId: getExample
+      responses:
+        '200':
+          description: Success
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ExampleModel'
+components:
+  schemas:
+    ExampleModel:
+      required:
+        - source
+      type: object
+      properties:
+        source:
+          $ref: '#/components/schemas/ExampleNumericEnum'
+    ExampleNumericEnum:
+      type: integer
+      format: int32
+      enum:
+        - -1
+        - 0
+        - 1