[BUG][Kotlin-client] Handling default values of parameters (#12255)

* Bugfix Kotlin-client: Handling default values of parameters

* Adding object

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/apis/DefaultApi.kt

@@ -0,0 +1,232 @@
+/**
+ * Demo
+ *
+ * No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * Please note:
+ * This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * Do not edit this file manually.
+ */
+
+@file:Suppress(
+    "ArrayInDataClass",
+    "EnumEntryName",
+    "RemoveRedundantQualifierName",
+    "UnusedImport"
+)
+
+package org.openapitools.client.apis
+
+import java.io.IOException
+
+
+import com.squareup.moshi.Json
+
+import org.openapitools.client.infrastructure.ApiClient
+import org.openapitools.client.infrastructure.ApiResponse
+import org.openapitools.client.infrastructure.ClientException
+import org.openapitools.client.infrastructure.ClientError
+import org.openapitools.client.infrastructure.ServerException
+import org.openapitools.client.infrastructure.ServerError
+import org.openapitools.client.infrastructure.MultiValueMap
+import org.openapitools.client.infrastructure.PartConfig
+import org.openapitools.client.infrastructure.RequestConfig
+import org.openapitools.client.infrastructure.RequestMethod
+import org.openapitools.client.infrastructure.ResponseType
+import org.openapitools.client.infrastructure.Success
+import org.openapitools.client.infrastructure.toMultiValue
+
+class DefaultApi(basePath: kotlin.String = defaultBasePath) : ApiClient(basePath) {
+    companion object {
+        @JvmStatic
+        val defaultBasePath: String by lazy {
+            System.getProperties().getProperty(ApiClient.baseUrlKey, "http://localhost")
+        }
+    }
+
+    /**
+     * Tests default values
+     * Tests default values of different parameters
+     * @param pi0  (default to 10)
+     * @param pi1 
+     * @param pn0  (default to 10.0)
+     * @param pn1 
+     * @param qi0  (optional, default to 10)
+     * @param qi1  (default to 71)
+     * @param qi2  (optional)
+     * @param qi3 
+     * @param qn0  (optional, default to 10.0)
+     * @param qn1  (default to 71.0)
+     * @param qn2  (optional)
+     * @param qn3 
+     * @param hi0  (optional, default to 10)
+     * @param hi1  (default to 71)
+     * @param hi2  (optional)
+     * @param hi3 
+     * @param hn0  (optional, default to 10.0)
+     * @param hn1  (default to 71.0)
+     * @param hn2  (optional)
+     * @param hn3 
+     * @param fi0  (optional, default to 10)
+     * @param fi1  (default to 71)
+     * @param fi2  (optional)
+     * @param fi3 
+     * @param fn0  (optional, default to 10.0)
+     * @param fn1  (default to 71.0)
+     * @param fn2  (optional)
+     * @param fn3 
+     * @return void
+     * @throws IllegalStateException If the request is not correctly configured
+     * @throws IOException Rethrows the OkHttp execute method exception
+     * @throws UnsupportedOperationException If the API returns an informational or redirection response
+     * @throws ClientException If the API returns a client error response
+     * @throws ServerException If the API returns a server error response
+     */
+    @Throws(IllegalStateException::class, IOException::class, UnsupportedOperationException::class, ClientException::class, ServerException::class)
+    fun test(pi0: kotlin.Int = 10, pi1: kotlin.Int, pn0: java.math.BigDecimal = java.math.BigDecimal("10.0"), pn1: java.math.BigDecimal, qi0: kotlin.Int? = 10, qi1: kotlin.Int = 71, qi2: kotlin.Int? = null, qi3: kotlin.Int, qn0: java.math.BigDecimal? = java.math.BigDecimal("10.0"), qn1: java.math.BigDecimal = java.math.BigDecimal("71.0"), qn2: java.math.BigDecimal? = null, qn3: java.math.BigDecimal, hi0: kotlin.Int? = 10, hi1: kotlin.Int = 71, hi2: kotlin.Int? = null, hi3: kotlin.Int, hn0: java.math.BigDecimal? = java.math.BigDecimal("10.0"), hn1: java.math.BigDecimal = java.math.BigDecimal("71.0"), hn2: java.math.BigDecimal? = null, hn3: java.math.BigDecimal, fi0: kotlin.Int? = 10, fi1: kotlin.Int = 71, fi2: kotlin.Int? = null, fi3: kotlin.Int, fn0: java.math.BigDecimal? = java.math.BigDecimal("10.0"), fn1: java.math.BigDecimal = java.math.BigDecimal("71.0"), fn2: java.math.BigDecimal? = null, fn3: java.math.BigDecimal) : Unit {
+        val localVarResponse = testWithHttpInfo(pi0 = pi0, pi1 = pi1, pn0 = pn0, pn1 = pn1, qi0 = qi0, qi1 = qi1, qi2 = qi2, qi3 = qi3, qn0 = qn0, qn1 = qn1, qn2 = qn2, qn3 = qn3, hi0 = hi0, hi1 = hi1, hi2 = hi2, hi3 = hi3, hn0 = hn0, hn1 = hn1, hn2 = hn2, hn3 = hn3, fi0 = fi0, fi1 = fi1, fi2 = fi2, fi3 = fi3, fn0 = fn0, fn1 = fn1, fn2 = fn2, fn3 = fn3)
+
+        return when (localVarResponse.responseType) {
+            ResponseType.Success -> Unit
+            ResponseType.Informational -> throw UnsupportedOperationException("Client does not support Informational responses.")
+            ResponseType.Redirection -> throw UnsupportedOperationException("Client does not support Redirection responses.")
+            ResponseType.ClientError -> {
+                val localVarError = localVarResponse as ClientError<*>
+                throw ClientException("Client error : ${localVarError.statusCode} ${localVarError.message.orEmpty()}", localVarError.statusCode, localVarResponse)
+            }
+            ResponseType.ServerError -> {
+                val localVarError = localVarResponse as ServerError<*>
+                throw ServerException("Server error : ${localVarError.statusCode} ${localVarError.message.orEmpty()}", localVarError.statusCode, localVarResponse)
+            }
+        }
+    }
+
+    /**
+     * Tests default values
+     * Tests default values of different parameters
+     * @param pi0  (default to 10)
+     * @param pi1 
+     * @param pn0  (default to 10.0)
+     * @param pn1 
+     * @param qi0  (optional, default to 10)
+     * @param qi1  (default to 71)
+     * @param qi2  (optional)
+     * @param qi3 
+     * @param qn0  (optional, default to 10.0)
+     * @param qn1  (default to 71.0)
+     * @param qn2  (optional)
+     * @param qn3 
+     * @param hi0  (optional, default to 10)
+     * @param hi1  (default to 71)
+     * @param hi2  (optional)
+     * @param hi3 
+     * @param hn0  (optional, default to 10.0)
+     * @param hn1  (default to 71.0)
+     * @param hn2  (optional)
+     * @param hn3 
+     * @param fi0  (optional, default to 10)
+     * @param fi1  (default to 71)
+     * @param fi2  (optional)
+     * @param fi3 
+     * @param fn0  (optional, default to 10.0)
+     * @param fn1  (default to 71.0)
+     * @param fn2  (optional)
+     * @param fn3 
+     * @return ApiResponse<Unit?>
+     * @throws IllegalStateException If the request is not correctly configured
+     * @throws IOException Rethrows the OkHttp execute method exception
+     */
+    @Throws(IllegalStateException::class, IOException::class)
+    fun testWithHttpInfo(pi0: kotlin.Int, pi1: kotlin.Int, pn0: java.math.BigDecimal, pn1: java.math.BigDecimal, qi0: kotlin.Int?, qi1: kotlin.Int, qi2: kotlin.Int?, qi3: kotlin.Int, qn0: java.math.BigDecimal?, qn1: java.math.BigDecimal, qn2: java.math.BigDecimal?, qn3: java.math.BigDecimal, hi0: kotlin.Int?, hi1: kotlin.Int, hi2: kotlin.Int?, hi3: kotlin.Int, hn0: java.math.BigDecimal?, hn1: java.math.BigDecimal, hn2: java.math.BigDecimal?, hn3: java.math.BigDecimal, fi0: kotlin.Int?, fi1: kotlin.Int, fi2: kotlin.Int?, fi3: kotlin.Int, fn0: java.math.BigDecimal?, fn1: java.math.BigDecimal, fn2: java.math.BigDecimal?, fn3: java.math.BigDecimal) : ApiResponse<Unit?> {
+        val localVariableConfig = testRequestConfig(pi0 = pi0, pi1 = pi1, pn0 = pn0, pn1 = pn1, qi0 = qi0, qi1 = qi1, qi2 = qi2, qi3 = qi3, qn0 = qn0, qn1 = qn1, qn2 = qn2, qn3 = qn3, hi0 = hi0, hi1 = hi1, hi2 = hi2, hi3 = hi3, hn0 = hn0, hn1 = hn1, hn2 = hn2, hn3 = hn3, fi0 = fi0, fi1 = fi1, fi2 = fi2, fi3 = fi3, fn0 = fn0, fn1 = fn1, fn2 = fn2, fn3 = fn3)
+
+        return request<Map<String, PartConfig<*>>, Unit>(
+            localVariableConfig
+        )
+    }
+
+    /**
+     * To obtain the request config of the operation test
+     *
+     * @param pi0  (default to 10)
+     * @param pi1 
+     * @param pn0  (default to 10.0)
+     * @param pn1 
+     * @param qi0  (optional, default to 10)
+     * @param qi1  (default to 71)
+     * @param qi2  (optional)
+     * @param qi3 
+     * @param qn0  (optional, default to 10.0)
+     * @param qn1  (default to 71.0)
+     * @param qn2  (optional)
+     * @param qn3 
+     * @param hi0  (optional, default to 10)
+     * @param hi1  (default to 71)
+     * @param hi2  (optional)
+     * @param hi3 
+     * @param hn0  (optional, default to 10.0)
+     * @param hn1  (default to 71.0)
+     * @param hn2  (optional)
+     * @param hn3 
+     * @param fi0  (optional, default to 10)
+     * @param fi1  (default to 71)
+     * @param fi2  (optional)
+     * @param fi3 
+     * @param fn0  (optional, default to 10.0)
+     * @param fn1  (default to 71.0)
+     * @param fn2  (optional)
+     * @param fn3 
+     * @return RequestConfig
+     */
+    fun testRequestConfig(pi0: kotlin.Int, pi1: kotlin.Int, pn0: java.math.BigDecimal, pn1: java.math.BigDecimal, qi0: kotlin.Int?, qi1: kotlin.Int, qi2: kotlin.Int?, qi3: kotlin.Int, qn0: java.math.BigDecimal?, qn1: java.math.BigDecimal, qn2: java.math.BigDecimal?, qn3: java.math.BigDecimal, hi0: kotlin.Int?, hi1: kotlin.Int, hi2: kotlin.Int?, hi3: kotlin.Int, hn0: java.math.BigDecimal?, hn1: java.math.BigDecimal, hn2: java.math.BigDecimal?, hn3: java.math.BigDecimal, fi0: kotlin.Int?, fi1: kotlin.Int, fi2: kotlin.Int?, fi3: kotlin.Int, fn0: java.math.BigDecimal?, fn1: java.math.BigDecimal, fn2: java.math.BigDecimal?, fn3: java.math.BigDecimal) : RequestConfig<Map<String, PartConfig<*>>> {
+        val localVariableBody = mapOf(
+            "fi0" to PartConfig(body = fi0, headers = mutableMapOf()),
+            "fi1" to PartConfig(body = fi1, headers = mutableMapOf()),
+            "fi2" to PartConfig(body = fi2, headers = mutableMapOf()),
+            "fi3" to PartConfig(body = fi3, headers = mutableMapOf()),
+            "fn0" to PartConfig(body = fn0, headers = mutableMapOf()),
+            "fn1" to PartConfig(body = fn1, headers = mutableMapOf()),
+            "fn2" to PartConfig(body = fn2, headers = mutableMapOf()),
+            "fn3" to PartConfig(body = fn3, headers = mutableMapOf()),)
+        val localVariableQuery: MultiValueMap = mutableMapOf<kotlin.String, kotlin.collections.List<kotlin.String>>()
+            .apply {
+                if (qi0 != null) {
+                    put("qi0", listOf(qi0.toString()))
+                }
+                put("qi1", listOf(qi1.toString()))
+                if (qi2 != null) {
+                    put("qi2", listOf(qi2.toString()))
+                }
+                put("qi3", listOf(qi3.toString()))
+                if (qn0 != null) {
+                    put("qn0", listOf(qn0.toString()))
+                }
+                put("qn1", listOf(qn1.toString()))
+                if (qn2 != null) {
+                    put("qn2", listOf(qn2.toString()))
+                }
+                put("qn3", listOf(qn3.toString()))
+            }
+        val localVariableHeaders: MutableMap<String, String> = mutableMapOf("Content-Type" to "multipart/form-data")
+        hi0?.apply { localVariableHeaders["hi0"] = this.toString() }
+        hi1.apply { localVariableHeaders["hi1"] = this.toString() }
+        hi2?.apply { localVariableHeaders["hi2"] = this.toString() }
+        hi3.apply { localVariableHeaders["hi3"] = this.toString() }
+        hn0?.apply { localVariableHeaders["hn0"] = this.toString() }
+        hn1.apply { localVariableHeaders["hn1"] = this.toString() }
+        hn2?.apply { localVariableHeaders["hn2"] = this.toString() }
+        hn3.apply { localVariableHeaders["hn3"] = this.toString() }
+        
+        return RequestConfig(
+            method = RequestMethod.POST,
+            path = "/test".replace("{"+"pi0"+"}", "$pi0").replace("{"+"pi1"+"}", "$pi1").replace("{"+"pn0"+"}", "$pn0").replace("{"+"pn1"+"}", "$pn1"),
+            query = localVariableQuery,
+            headers = localVariableHeaders,
+            body = localVariableBody
+        )
+    }
+
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiAbstractions.kt

@@ -0,0 +1,23 @@
+package org.openapitools.client.infrastructure
+
+typealias MultiValueMap = MutableMap<String,List<String>>
+
+fun collectionDelimiter(collectionFormat: String) = when(collectionFormat) {
+    "csv" -> ","
+    "tsv" -> "\t"
+    "pipe" -> "|"
+    "space" -> " "
+    else -> ""
+}
+
+val defaultMultiValueConverter: (item: Any?) -> String = { item -> "$item" }
+
+fun <T : Any?> toMultiValue(items: Array<T>, collectionFormat: String, map: (item: T) -> String = defaultMultiValueConverter)
+        = toMultiValue(items.asIterable(), collectionFormat, map)
+
+fun <T : Any?> toMultiValue(items: Iterable<T>, collectionFormat: String, map: (item: T) -> String = defaultMultiValueConverter): List<String> {
+    return when(collectionFormat) {
+        "multi" -> items.map(map)
+        else -> listOf(items.joinToString(separator = collectionDelimiter(collectionFormat), transform = map))
+    }
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiClient.kt

@@ -0,0 +1,238 @@
+package org.openapitools.client.infrastructure
+
+import okhttp3.OkHttpClient
+import okhttp3.RequestBody
+import okhttp3.RequestBody.Companion.asRequestBody
+import okhttp3.RequestBody.Companion.toRequestBody
+import okhttp3.FormBody
+import okhttp3.HttpUrl.Companion.toHttpUrlOrNull
+import okhttp3.ResponseBody
+import okhttp3.MediaType.Companion.toMediaTypeOrNull
+import okhttp3.Request
+import okhttp3.Headers
+import okhttp3.Headers.Companion.toHeaders
+import okhttp3.MultipartBody
+import okhttp3.Call
+import okhttp3.Callback
+import okhttp3.Response
+import okhttp3.internal.EMPTY_REQUEST
+import java.io.BufferedWriter
+import java.io.File
+import java.io.FileWriter
+import java.io.IOException
+import java.net.URLConnection
+import java.time.LocalDate
+import java.time.LocalDateTime
+import java.time.LocalTime
+import java.time.OffsetDateTime
+import java.time.OffsetTime
+import java.util.Locale
+import com.squareup.moshi.adapter
+
+open class ApiClient(val baseUrl: String) {
+    companion object {
+        protected const val ContentType = "Content-Type"
+        protected const val Accept = "Accept"
+        protected const val Authorization = "Authorization"
+        protected const val JsonMediaType = "application/json"
+        protected const val FormDataMediaType = "multipart/form-data"
+        protected const val FormUrlEncMediaType = "application/x-www-form-urlencoded"
+        protected const val XmlMediaType = "application/xml"
+
+        val apiKey: MutableMap<String, String> = mutableMapOf()
+        val apiKeyPrefix: MutableMap<String, String> = mutableMapOf()
+        var username: String? = null
+        var password: String? = null
+        var accessToken: String? = null
+        const val baseUrlKey = "org.openapitools.client.baseUrl"
+
+        @JvmStatic
+        val client: OkHttpClient by lazy {
+            builder.build()
+        }
+
+        @JvmStatic
+        val builder: OkHttpClient.Builder = OkHttpClient.Builder()
+    }
+
+    /**
+     * Guess Content-Type header from the given file (defaults to "application/octet-stream").
+     *
+     * @param file The given file
+     * @return The guessed Content-Type
+     */
+    protected fun guessContentTypeFromFile(file: File): String {
+        val contentType = URLConnection.guessContentTypeFromName(file.name)
+        return contentType ?: "application/octet-stream"
+    }
+
+    protected inline fun <reified T> requestBody(content: T, mediaType: String?): RequestBody =
+        when {
+            mediaType == FormDataMediaType ->
+                MultipartBody.Builder()
+                    .setType(MultipartBody.FORM)
+                    .apply {
+                        // content's type *must* be Map<String, PartConfig<*>>
+                        @Suppress("UNCHECKED_CAST")
+                        (content as Map<String, PartConfig<*>>).forEach { (name, part) ->
+                            val contentType = part.headers.remove("Content-Type")
+                            val bodies = if (part.body is Iterable<*>) part.body else listOf(part.body)
+                            bodies.forEach { body ->
+                                val headers = part.headers.toMutableMap() +
+                                    ("Content-Disposition" to "form-data; name=\"$name\"" + if (body is File) "; filename=\"${body.name}\"" else "")
+                                addPart(headers.toHeaders(),
+                                    requestSingleBody(body, contentType))
+                            }
+                        }
+                    }.build()
+            else -> requestSingleBody(content, mediaType)
+        }
+
+    protected inline fun <reified T> requestSingleBody(content: T, mediaType: String?): RequestBody =
+        when {
+            content is File -> content.asRequestBody((mediaType ?: guessContentTypeFromFile(content)).toMediaTypeOrNull())
+            mediaType == FormUrlEncMediaType -> {
+                FormBody.Builder().apply {
+                    // content's type *must* be Map<String, PartConfig<*>>
+                    @Suppress("UNCHECKED_CAST")
+                    (content as Map<String, PartConfig<*>>).forEach { (name, part) ->
+                        add(name, parameterToString(part.body))
+                    }
+                }.build()
+            }
+            mediaType == null || mediaType.startsWith("application/") && mediaType.endsWith("json") ->
+                if (content == null) {
+                    EMPTY_REQUEST
+                } else {
+                    Serializer.moshi.adapter(T::class.java).toJson(content)
+                        .toRequestBody((mediaType ?: JsonMediaType).toMediaTypeOrNull())
+                }
+            mediaType == XmlMediaType -> throw UnsupportedOperationException("xml not currently supported.")
+            // TODO: this should be extended with other serializers
+            else -> throw UnsupportedOperationException("requestBody currently only supports JSON body and File body.")
+        }
+
+    @OptIn(ExperimentalStdlibApi::class)
+    protected inline fun <reified T: Any?> responseBody(body: ResponseBody?, mediaType: String? = JsonMediaType): T? {
+        if(body == null) {
+            return null
+        }
+        if (T::class.java == File::class.java) {
+            // return tempfile
+            // Attention: if you are developing an android app that supports API Level 25 and bellow, please check flag supportAndroidApiLevel25AndBelow in https://openapi-generator.tech/docs/generators/kotlin#config-options
+            val f = java.nio.file.Files.createTempFile("tmp.org.openapitools.client", null).toFile()
+            f.deleteOnExit()
+            body.byteStream().use { java.nio.file.Files.copy(it, f.toPath(), java.nio.file.StandardCopyOption.REPLACE_EXISTING) }
+            return f as T
+        }
+        val bodyContent = body.string()
+        if (bodyContent.isEmpty()) {
+            return null
+        }
+        return when {
+            mediaType==null || (mediaType.startsWith("application/") && mediaType.endsWith("json")) ->
+                Serializer.moshi.adapter<T>().fromJson(bodyContent)
+            else ->  throw UnsupportedOperationException("responseBody currently only supports JSON body.")
+        }
+    }
+
+
+    protected inline fun <reified I, reified T: Any?> request(requestConfig: RequestConfig<I>): ApiResponse<T?> {
+        val httpUrl = baseUrl.toHttpUrlOrNull() ?: throw IllegalStateException("baseUrl is invalid.")
+
+        val url = httpUrl.newBuilder()
+            .addPathSegments(requestConfig.path.trimStart('/'))
+            .apply {
+                requestConfig.query.forEach { query ->
+                    query.value.forEach { queryValue ->
+                        addQueryParameter(query.key, queryValue)
+                    }
+                }
+            }.build()
+
+        // take content-type/accept from spec or set to default (application/json) if not defined
+        if (requestConfig.headers[ContentType].isNullOrEmpty()) {
+            requestConfig.headers[ContentType] = JsonMediaType
+        }
+        if (requestConfig.headers[Accept].isNullOrEmpty()) {
+            requestConfig.headers[Accept] = JsonMediaType
+        }
+        val headers = requestConfig.headers
+
+        if(headers[ContentType].isNullOrEmpty()) {
+            throw kotlin.IllegalStateException("Missing Content-Type header. This is required.")
+        }
+
+        if(headers[Accept].isNullOrEmpty()) {
+            throw kotlin.IllegalStateException("Missing Accept header. This is required.")
+        }
+
+        // TODO: support multiple contentType options here.
+        val contentType = (headers[ContentType] as String).substringBefore(";").lowercase(Locale.getDefault())
+
+        val request = when (requestConfig.method) {
+            RequestMethod.DELETE -> Request.Builder().url(url).delete(requestBody(requestConfig.body, contentType))
+            RequestMethod.GET -> Request.Builder().url(url)
+            RequestMethod.HEAD -> Request.Builder().url(url).head()
+            RequestMethod.PATCH -> Request.Builder().url(url).patch(requestBody(requestConfig.body, contentType))
+            RequestMethod.PUT -> Request.Builder().url(url).put(requestBody(requestConfig.body, contentType))
+            RequestMethod.POST -> Request.Builder().url(url).post(requestBody(requestConfig.body, contentType))
+            RequestMethod.OPTIONS -> Request.Builder().url(url).method("OPTIONS", null)
+        }.apply {
+            headers.forEach { header -> addHeader(header.key, header.value) }
+        }.build()
+
+        val response = client.newCall(request).execute()
+
+        val accept = response.header(ContentType)?.substringBefore(";")?.lowercase(Locale.getDefault())
+
+        // TODO: handle specific mapping types. e.g. Map<int, Class<?>>
+        return when {
+            response.isRedirect -> Redirection(
+                response.code,
+                response.headers.toMultimap()
+            )
+            response.isInformational -> Informational(
+                response.message,
+                response.code,
+                response.headers.toMultimap()
+            )
+            response.isSuccessful -> Success(
+                responseBody(response.body, accept),
+                response.code,
+                response.headers.toMultimap()
+            )
+            response.isClientError -> ClientError(
+                response.message,
+                response.body?.string(),
+                response.code,
+                response.headers.toMultimap()
+            )
+            else -> ServerError(
+                response.message,
+                response.body?.string(),
+                response.code,
+                response.headers.toMultimap()
+            )
+        }
+    }
+
+    protected fun parameterToString(value: Any?): String = when (value) {
+        null -> ""
+        is Array<*> -> toMultiValue(value, "csv").toString()
+        is Iterable<*> -> toMultiValue(value, "csv").toString()
+        is OffsetDateTime, is OffsetTime, is LocalDateTime, is LocalDate, is LocalTime ->
+            parseDateToQueryString(value)
+        else -> value.toString()
+    }
+
+    protected inline fun <reified T: Any> parseDateToQueryString(value : T): String {
+        /*
+        .replace("\"", "") converts the json object string to an actual string for the query parameter.
+        The moshi or gson adapter allows a more generic solution instead of trying to use a native
+        formatter. It also easily allows to provide a simple way to define a custom date format pattern
+        inside a gson/moshi adapter.
+        */
+        return Serializer.moshi.adapter(T::class.java).toJson(value).replace("\"", "")
+    }
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ApiResponse.kt

@@ -0,0 +1,43 @@
+package org.openapitools.client.infrastructure
+
+enum class ResponseType {
+    Success, Informational, Redirection, ClientError, ServerError
+}
+
+interface Response
+
+abstract class ApiResponse<T>(val responseType: ResponseType): Response {
+    abstract val statusCode: Int
+    abstract val headers: Map<String,List<String>>
+}
+
+class Success<T>(
+    val data: T,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
+): ApiResponse<T>(ResponseType.Success)
+
+class Informational<T>(
+    val statusText: String,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
+) : ApiResponse<T>(ResponseType.Informational)
+
+class Redirection<T>(
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
+) : ApiResponse<T>(ResponseType.Redirection)
+
+class ClientError<T>(
+    val message: String? = null,
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>> = mapOf()
+) : ApiResponse<T>(ResponseType.ClientError)
+
+class ServerError<T>(
+    val message: String? = null,
+    val body: Any? = null,
+    override val statusCode: Int = -1,
+    override val headers: Map<String, List<String>>
+): ApiResponse<T>(ResponseType.ServerError)

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/BigDecimalAdapter.kt

@@ -0,0 +1,17 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.math.BigDecimal
+
+class BigDecimalAdapter {
+    @ToJson
+    fun toJson(value: BigDecimal): String {
+        return value.toPlainString()
+    }
+
+    @FromJson
+    fun fromJson(value: String): BigDecimal {
+        return BigDecimal(value)
+    }
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/BigIntegerAdapter.kt

@@ -0,0 +1,17 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.math.BigInteger
+
+class BigIntegerAdapter {
+    @ToJson
+    fun toJson(value: BigInteger): String {
+        return value.toString()
+    }
+
+    @FromJson
+    fun fromJson(value: String): BigInteger {
+        return BigInteger(value)
+    }
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ByteArrayAdapter.kt

@@ -0,0 +1,12 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+
+class ByteArrayAdapter {
+    @ToJson
+    fun toJson(data: ByteArray): String = String(data)
+
+    @FromJson
+    fun fromJson(data: String): ByteArray = data.toByteArray()
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/Errors.kt

@@ -0,0 +1,18 @@
+@file:Suppress("unused")
+package org.openapitools.client.infrastructure
+
+import java.lang.RuntimeException
+
+open class ClientException(message: kotlin.String? = null, val statusCode: Int = -1, val response: Response? = null) : RuntimeException(message) {
+
+    companion object {
+        private const val serialVersionUID: Long = 123L
+    }
+}
+
+open class ServerException(message: kotlin.String? = null, val statusCode: Int = -1, val response: Response? = null) : RuntimeException(message) {
+
+    companion object {
+        private const val serialVersionUID: Long = 456L
+    }
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/LocalDateAdapter.kt

@@ -0,0 +1,19 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.time.LocalDate
+import java.time.format.DateTimeFormatter
+
+class LocalDateAdapter {
+    @ToJson
+    fun toJson(value: LocalDate): String {
+        return DateTimeFormatter.ISO_LOCAL_DATE.format(value)
+    }
+
+    @FromJson
+    fun fromJson(value: String): LocalDate {
+        return LocalDate.parse(value, DateTimeFormatter.ISO_LOCAL_DATE)
+    }
+
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/LocalDateTimeAdapter.kt

@@ -0,0 +1,19 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.time.LocalDateTime
+import java.time.format.DateTimeFormatter
+
+class LocalDateTimeAdapter {
+    @ToJson
+    fun toJson(value: LocalDateTime): String {
+        return DateTimeFormatter.ISO_LOCAL_DATE_TIME.format(value)
+    }
+
+    @FromJson
+    fun fromJson(value: String): LocalDateTime {
+        return LocalDateTime.parse(value, DateTimeFormatter.ISO_LOCAL_DATE_TIME)
+    }
+
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/OffsetDateTimeAdapter.kt

@@ -0,0 +1,19 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.time.OffsetDateTime
+import java.time.format.DateTimeFormatter
+
+class OffsetDateTimeAdapter {
+    @ToJson
+    fun toJson(value: OffsetDateTime): String {
+        return DateTimeFormatter.ISO_OFFSET_DATE_TIME.format(value)
+    }
+
+    @FromJson
+    fun fromJson(value: String): OffsetDateTime {
+        return OffsetDateTime.parse(value, DateTimeFormatter.ISO_OFFSET_DATE_TIME)
+    }
+
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/PartConfig.kt

@@ -0,0 +1,11 @@
+package org.openapitools.client.infrastructure
+
+/**
+ * Defines a config object for a given part of a multi-part request.
+ * NOTE: Headers is a Map<String,String> because rfc2616 defines
+ *       multi-valued headers as csv-only.
+ */
+data class PartConfig<T>(
+    val headers: MutableMap<String, String> = mutableMapOf(),
+    val body: T? = null
+)

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/RequestConfig.kt

@@ -0,0 +1,17 @@
+package org.openapitools.client.infrastructure
+
+/**
+ * Defines a config object for a given request.
+ * NOTE: This object doesn't include 'body' because it
+ *       allows for caching of the constructed object
+ *       for many request definitions.
+ * NOTE: Headers is a Map<String,String> because rfc2616 defines
+ *       multi-valued headers as csv-only.
+ */
+data class RequestConfig<T>(
+    val method: RequestMethod,
+    val path: String,
+    val headers: MutableMap<String, String> = mutableMapOf(),
+    val query: MutableMap<String, List<String>> = mutableMapOf(),
+    val body: T? = null
+)

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/RequestMethod.kt

@@ -0,0 +1,8 @@
+package org.openapitools.client.infrastructure
+
+/**
+ * Provides enumerated HTTP verbs
+ */
+enum class RequestMethod {
+    GET, DELETE, HEAD, OPTIONS, PATCH, POST, PUT
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/ResponseExtensions.kt

@@ -0,0 +1,24 @@
+package org.openapitools.client.infrastructure
+
+import okhttp3.Response
+
+/**
+ * Provides an extension to evaluation whether the response is a 1xx code
+ */
+val Response.isInformational : Boolean get() = this.code in 100..199
+
+/**
+ * Provides an extension to evaluation whether the response is a 3xx code
+ */
+@Suppress("EXTENSION_SHADOWED_BY_MEMBER")
+val Response.isRedirect : Boolean get() = this.code in 300..399
+
+/**
+ * Provides an extension to evaluation whether the response is a 4xx code
+ */
+val Response.isClientError : Boolean get() = this.code in 400..499
+
+/**
+ * Provides an extension to evaluation whether the response is a 5xx (Standard) through 999 (non-standard) code
+ */
+val Response.isServerError : Boolean get() = this.code in 500..999

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/Serializer.kt

@@ -0,0 +1,23 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.Moshi
+import com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterFactory
+
+object Serializer {
+    @JvmStatic
+    val moshiBuilder: Moshi.Builder = Moshi.Builder()
+        .add(OffsetDateTimeAdapter())
+        .add(LocalDateTimeAdapter())
+        .add(LocalDateAdapter())
+        .add(UUIDAdapter())
+        .add(ByteArrayAdapter())
+        .add(URIAdapter())
+        .add(KotlinJsonAdapterFactory())
+        .add(BigDecimalAdapter())
+        .add(BigIntegerAdapter())
+
+    @JvmStatic
+    val moshi: Moshi by lazy {
+        moshiBuilder.build()
+    }
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/URIAdapter.kt

@@ -0,0 +1,13 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.net.URI
+
+class URIAdapter {
+    @ToJson
+    fun toJson(uri: URI) = uri.toString()
+
+    @FromJson
+    fun fromJson(s: String): URI = URI.create(s)
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/infrastructure/UUIDAdapter.kt

@@ -0,0 +1,13 @@
+package org.openapitools.client.infrastructure
+
+import com.squareup.moshi.FromJson
+import com.squareup.moshi.ToJson
+import java.util.UUID
+
+class UUIDAdapter {
+    @ToJson
+    fun toJson(uuid: UUID) = uuid.toString()
+
+    @FromJson
+    fun fromJson(s: String): UUID = UUID.fromString(s)
+}

samples/client/petstore/kotlin-default-values-jvm-okhttp4/src/main/kotlin/org/openapitools/client/models/Apa.kt

@@ -0,0 +1,50 @@
+/**
+ * Demo
+ *
+ * No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * Please note:
+ * This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * Do not edit this file manually.
+ */
+
+@file:Suppress(
+    "ArrayInDataClass",
+    "EnumEntryName",
+    "RemoveRedundantQualifierName",
+    "UnusedImport"
+)
+
+package org.openapitools.client.models
+
+
+import com.squareup.moshi.Json
+
+/**
+ * 
+ *
+ * @param i0 
+ * @param n0 
+ * @param i1 
+ * @param n1 
+ */
+
+data class Apa (
+
+    @Json(name = "i0")
+    val i0: kotlin.Int,
+
+    @Json(name = "n0")
+    val n0: java.math.BigDecimal,
+
+    @Json(name = "i1")
+    val i1: kotlin.Int? = null,
+
+    @Json(name = "n1")
+    val n1: java.math.BigDecimal? = null
+
+)
+