[Kotlin][Client] Add option to make all api method return a nullable model (#4422)

* Added new additional parameter to allow nullable api return types

* Tweaking samples and .bat files

I've added new .bat files for the kotlin-client to alllow windows-devs to re-generate required samples via windows-shell (for CI).

Author: Mordag

bin/kotlin-client-all.sh

@@ -7,3 +7,4 @@
 ./bin/kotlin-client-petstore.sh
 ./bin/kotlin-client-string.sh
 ./bin/kotlin-client-threetenbp.sh
+./bin/kotlin-client-nullable.sh

bin/kotlin-client-nullable.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+SCRIPT="$0"
+echo "# START SCRIPT: $SCRIPT"
+
+while [ -h "$SCRIPT" ] ; do
+  ls=$(ls -ld "$SCRIPT")
+  link=$(expr "$ls" : '.*-> \(.*\)$')
+  if expr "$link" : '/.*' > /dev/null; then
+    SCRIPT="$link"
+  else
+    SCRIPT=$(dirname "$SCRIPT")/"$link"
+  fi
+done
+
+if [ ! -d "${APP_DIR}" ]; then
+  APP_DIR=$(dirname "$SCRIPT")/..
+  APP_DIR=$(cd "${APP_DIR}"; pwd)
+fi
+
+executable="./modules/openapi-generator-cli/target/openapi-generator-cli.jar"
+
+if [ ! -f "$executable" ]
+then
+  mvn -B clean package
+fi
+
+# if you've executed sbt assembly previously it will use that instead.
+export JAVA_OPTS="${JAVA_OPTS} -Xmx1024M -DloggerPath=conf/log4j.properties"
+ags="generate -t modules/openapi-generator/src/main/resources/kotlin-client -i modules/openapi-generator/src/test/resources/2_0/petstore.yaml -g kotlin --artifact-id kotlin-petstore-nullable --additional-properties nullableReturnType=true,serializableModel=true -o samples/client/petstore/kotlin-nullable $@"
+
+java ${JAVA_OPTS} -jar ${executable} ${ags}

bin/windows/kotlin-client-all.bat

@@ -0,0 +1,8 @@
+call powershell -command "& '%~dp0\kotlin-client-gson.bat'"
+call powershell -command "& '%~dp0\kotlin-client-nonpublic.bat'"
+call powershell -command "& '%~dp0\kotlin-client-okhttp3.bat'"
+call powershell -command "& '%~dp0\kotlin-client-petstore-multiplatform.bat'"
+call powershell -command "& '%~dp0\kotlin-client-petstore.bat'"
+call powershell -command "& '%~dp0\kotlin-client-string.bat'"
+call powershell -command "& '%~dp0\kotlin-client-threetenbp.bat'"
+call powershell -command "& '%~dp0\kotlin-client-nullable.bat'"

bin/windows/kotlin-client-nullable.bat

@@ -0,0 +1,10 @@
+set executable=.\modules\openapi-generator-cli\target\openapi-generator-cli.jar
+
+If Not Exist %executable% (
+  mvn clean package
+)
+
+REM set JAVA_OPTS=%JAVA_OPTS% -Xmx1024M -DloggerPath=conf/log4j.properties
+set ags=generate -i modules\openapi-generator\src\test\resources\2_0\petstore.yaml -g kotlin --artifact-id "kotlin-petstore-nullable" --additional-properties nullableReturnType=true,serializableModel=true -o samples\client\petstore\kotlin-nullable
+
+java %JAVA_OPTS% -jar %executable% %ags%

bin/windows/kotlin-client-petstore.bat

@@ -5,6 +5,6 @@ If Not Exist %executable% (
 )
 
 REM set JAVA_OPTS=%JAVA_OPTS% -Xmx1024M -DloggerPath=conf/log4j.properties
-set ags=generate  --artifact-id "kotlin-petstore-client" -i modules\openapi-generator\src\test\resources\2_0\petstore.yaml -g kotlin -o samples\client\petstore\kotlin
+set ags=generate  --artifact-id "kotlin-petstore-client" -i modules\openapi-generator\src\test\resources\2_0\petstore.yaml -g kotlin -o samples\client\petstore\kotlin --additional-properties dateLibrary=java8,serializableModel=true
 
 java %JAVA_OPTS% -jar %executable% %ags%

bin/windows/kotlin-client-string.bat

@@ -0,0 +1,10 @@
+set executable=.\modules\openapi-generator-cli\target\openapi-generator-cli.jar
+
+If Not Exist %executable% (
+  mvn clean package
+)
+
+REM set JAVA_OPTS=%JAVA_OPTS% -Xmx1024M -DloggerPath=conf/log4j.properties
+set ags=generate -i modules\openapi-generator\src\test\resources\2_0\petstore.yaml -g kotlin --artifact-id "kotlin-petstore-string" --additional-properties dateLibrary=string,serializableModel=true -o samples\client\petstore\kotlin-string
+
+java %JAVA_OPTS% -jar %executable% %ags%

bin/windows/kotlin-client-threetenbp.bat

@@ -0,0 +1,10 @@
+set executable=.\modules\openapi-generator-cli\target\openapi-generator-cli.jar
+
+If Not Exist %executable% (
+  mvn clean package
+)
+
+REM set JAVA_OPTS=%JAVA_OPTS% -Xmx1024M -DloggerPath=conf/log4j.properties
+set ags=generate -i modules\openapi-generator\src\test\resources\2_0\petstore.yaml -g kotlin --artifact-id "kotlin-petstore-threetenbp" --additional-properties dateLibrary=threetenbp -o samples\client\petstore\kotlin-threetenbp
+
+java %JAVA_OPTS% -jar %executable% %ags%

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

@@ -24,14 +24,14 @@ import {{packageName}}.infrastructure.toMultiValue
     * {{summary}}
     * {{notes}}
     {{#allParams}}* @param {{paramName}} {{description}} {{^required}}(optional{{#defaultValue}}, default to {{{.}}}{{/defaultValue}}){{/required}}
-    {{/allParams}}* @return {{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}void{{/returnType}}
+    {{/allParams}}* @return {{#returnType}}{{{returnType}}}{{#nullableReturnType}} or null{{/nullableReturnType}}{{/returnType}}{{^returnType}}void{{/returnType}}
     * @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
     */{{#returnType}}
     @Suppress("UNCHECKED_CAST"){{/returnType}}
     @Throws(UnsupportedOperationException::class, ClientException::class, ServerException::class)
-    fun {{operationId}}({{#allParams}}{{paramName}}: {{{dataType}}}{{^required}}?{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}) : {{#returnType}}{{{returnType}}}{{/returnType}}{{^returnType}}Unit{{/returnType}} {
+    fun {{operationId}}({{#allParams}}{{paramName}}: {{{dataType}}}{{^required}}?{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}) : {{#returnType}}{{{returnType}}}{{#nullableReturnType}}?{{/nullableReturnType}}{{/returnType}}{{^returnType}}Unit{{/returnType}} {
         val localVariableBody: kotlin.Any? = {{#hasBodyParam}}{{#bodyParams}}{{paramName}}{{/bodyParams}}{{/hasBodyParam}}{{^hasBodyParam}}{{^hasFormParams}}null{{/hasFormParams}}{{#hasFormParams}}mapOf({{#formParams}}"{{{baseName}}}" to "${{paramName}}"{{#hasMore}}, {{/hasMore}}{{/formParams}}){{/hasFormParams}}{{/hasBodyParam}}
         val localVariableQuery: MultiValueMap = {{^hasQueryParams}}mutableMapOf()
 {{/hasQueryParams}}{{#hasQueryParams}}mutableMapOf<kotlin.String, List<kotlin.String>>()
@@ -68,7 +68,7 @@ import {{packageName}}.infrastructure.toMultiValue
         )
 
         return when (localVarResponse.responseType) {
-            ResponseType.Success -> {{#returnType}}(localVarResponse as Success<*>).data as {{{returnType}}}{{/returnType}}{{^returnType}}Unit{{/returnType}}
+            ResponseType.Success -> {{#returnType}}(localVarResponse as Success<*>).data as {{{returnType}}}{{#nullableReturnType}}?{{/nullableReturnType}}{{/returnType}}{{^returnType}}Unit{{/returnType}}
             ResponseType.Informational -> throw UnsupportedOperationException("Client does not support Informational responses.")
             ResponseType.Redirection -> throw UnsupportedOperationException("Client does not support Redirection responses.")
             ResponseType.ClientError -> throw ClientException((localVarResponse as ClientError<*>).body as? String ?: "Client error")

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

@@ -30,7 +30,7 @@ val apiInstance = {{{classname}}}()
 val {{{paramName}}} : {{{dataType}}} = {{{example}}} // {{{dataType}}} | {{{description}}}
 {{/allParams}}
 try {
-    {{#returnType}}val result : {{{returnType}}} = {{/returnType}}apiInstance.{{{operationId}}}({{#allParams}}{{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}
+    {{#returnType}}val result : {{{returnType}}}{{#nullableReturnType}}?{{/nullableReturnType}} = {{/returnType}}apiInstance.{{{operationId}}}({{#allParams}}{{{paramName}}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}
     println(result){{/returnType}}
 } catch (e: ClientException) {
     println("4xx response calling {{{classname}}}#{{{operationId}}}")

modules/openapi-generator/src/main/resources/kotlin-client/libraries/jvm/infrastructure/ApiInfrastructureResponse.kt.mustache

@@ -10,7 +10,7 @@ package {{packageName}}.infrastructure
 }
 
 {{#nonPublicApi}}internal {{/nonPublicApi}}class Success<T>(
-    val data: T,
+    val data: T{{#nullableReturnType}}?{{/nullableReturnType}},
     override val statusCode: Int = -1,
     override val headers: Map<String, List<String>> = mapOf()
 ): ApiInfrastructureResponse<T>(ResponseType.Success)

samples/client/petstore/kotlin-nullable/.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-nullable/.openapi-generator/VERSION

@@ -0,0 +1 @@
+4.2.1-SNAPSHOT

samples/client/petstore/kotlin-nullable/README.md

@@ -0,0 +1,90 @@
+# org.openapitools.client - Kotlin client library for OpenAPI Petstore
+
+## Requires
+
+* Kotlin 1.3.41
+* Gradle 4.9
+
+## Build
+
+First, create the gradle wrapper script:
+
+```
+gradle wrapper
+```
+
+Then, run:
+
+```
+./gradlew check assemble
+```
+
+This runs all tests and packages the library.
+
+## Features/Implementation Notes
+
+* Supports JSON inputs/outputs, File inputs, and Form inputs.
+* Supports collection formats for query parameters: csv, tsv, ssv, pipes.
+* Some Kotlin and Java types are fully qualified to avoid conflicts with types defined in OpenAPI definitions.
+* Implementation of ApiClient is intended to reduce method counts, specifically to benefit Android targets.
+
+<a name="documentation-for-api-endpoints"></a>
+## Documentation for API Endpoints
+
+All URIs are relative to *http://petstore.swagger.io/v2*
+
+Class | Method | HTTP request | Description
+------------ | ------------- | ------------- | -------------
+*PetApi* | [**addPet**](docs/PetApi.md#addpet) | **POST** /pet | Add a new pet to the store
+*PetApi* | [**deletePet**](docs/PetApi.md#deletepet) | **DELETE** /pet/{petId} | Deletes a pet
+*PetApi* | [**findPetsByStatus**](docs/PetApi.md#findpetsbystatus) | **GET** /pet/findByStatus | Finds Pets by status
+*PetApi* | [**findPetsByTags**](docs/PetApi.md#findpetsbytags) | **GET** /pet/findByTags | Finds Pets by tags
+*PetApi* | [**getPetById**](docs/PetApi.md#getpetbyid) | **GET** /pet/{petId} | Find pet by ID
+*PetApi* | [**updatePet**](docs/PetApi.md#updatepet) | **PUT** /pet | Update an existing pet
+*PetApi* | [**updatePetWithForm**](docs/PetApi.md#updatepetwithform) | **POST** /pet/{petId} | Updates a pet in the store with form data
+*PetApi* | [**uploadFile**](docs/PetApi.md#uploadfile) | **POST** /pet/{petId}/uploadImage | uploads an image
+*StoreApi* | [**deleteOrder**](docs/StoreApi.md#deleteorder) | **DELETE** /store/order/{orderId} | Delete purchase order by ID
+*StoreApi* | [**getInventory**](docs/StoreApi.md#getinventory) | **GET** /store/inventory | Returns pet inventories by status
+*StoreApi* | [**getOrderById**](docs/StoreApi.md#getorderbyid) | **GET** /store/order/{orderId} | Find purchase order by ID
+*StoreApi* | [**placeOrder**](docs/StoreApi.md#placeorder) | **POST** /store/order | Place an order for a pet
+*UserApi* | [**createUser**](docs/UserApi.md#createuser) | **POST** /user | Create user
+*UserApi* | [**createUsersWithArrayInput**](docs/UserApi.md#createuserswitharrayinput) | **POST** /user/createWithArray | Creates list of users with given input array
+*UserApi* | [**createUsersWithListInput**](docs/UserApi.md#createuserswithlistinput) | **POST** /user/createWithList | Creates list of users with given input array
+*UserApi* | [**deleteUser**](docs/UserApi.md#deleteuser) | **DELETE** /user/{username} | Delete user
+*UserApi* | [**getUserByName**](docs/UserApi.md#getuserbyname) | **GET** /user/{username} | Get user by user name
+*UserApi* | [**loginUser**](docs/UserApi.md#loginuser) | **GET** /user/login | Logs user into the system
+*UserApi* | [**logoutUser**](docs/UserApi.md#logoutuser) | **GET** /user/logout | Logs out current logged in user session
+*UserApi* | [**updateUser**](docs/UserApi.md#updateuser) | **PUT** /user/{username} | Updated user
+
+
+<a name="documentation-for-models"></a>
+## Documentation for Models
+
+ - [org.openapitools.client.models.ApiResponse](docs/ApiResponse.md)
+ - [org.openapitools.client.models.Category](docs/Category.md)
+ - [org.openapitools.client.models.Order](docs/Order.md)
+ - [org.openapitools.client.models.Pet](docs/Pet.md)
+ - [org.openapitools.client.models.Tag](docs/Tag.md)
+ - [org.openapitools.client.models.User](docs/User.md)
+
+
+<a name="documentation-for-authorization"></a>
+## Documentation for Authorization
+
+<a name="api_key"></a>
+### api_key
+
+- **Type**: API key
+- **API key parameter name**: api_key
+- **Location**: HTTP header
+
+<a name="petstore_auth"></a>
+### petstore_auth
+
+- **Type**: OAuth
+- **Flow**: implicit
+- **Authorization URL**: http://petstore.swagger.io/api/oauth/dialog
+- **Scopes**: 
+  - write:pets: modify pets in your account
+  - read:pets: read your pets
+

samples/client/petstore/kotlin-nullable/build.gradle

@@ -0,0 +1,37 @@
+group 'org.openapitools'
+version '1.0.0'
+
+wrapper {
+    gradleVersion = '4.9'
+    distributionUrl = "https://services.gradle.org/distributions/gradle-$gradleVersion-all.zip"
+}
+
+buildscript {
+    ext.kotlin_version = '1.3.50'
+
+    repositories {
+        mavenCentral()
+    }
+    dependencies {
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+apply plugin: 'kotlin'
+
+repositories {
+    mavenCentral()
+}
+
+test {
+    useJUnitPlatform()
+}
+
+dependencies {
+    compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+    compile "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"
+    compile "com.squareup.moshi:moshi-kotlin:1.8.0"
+    compile "com.squareup.moshi:moshi-adapters:1.8.0"
+    compile "com.squareup.okhttp3:okhttp:4.2.2"
+    testCompile "io.kotlintest:kotlintest-runner-junit5:3.1.0"
+}

samples/client/petstore/kotlin-nullable/docs/ApiResponse.md

@@ -0,0 +1,12 @@
+
+# ApiResponse
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**code** | **kotlin.Int** |  |  [optional]
+**type** | **kotlin.String** |  |  [optional]
+**message** | **kotlin.String** |  |  [optional]
+
+
+

samples/client/petstore/kotlin-nullable/docs/Category.md

@@ -0,0 +1,11 @@
+
+# Category
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**id** | **kotlin.Long** |  |  [optional]
+**name** | **kotlin.String** |  |  [optional]
+
+
+

samples/client/petstore/kotlin-nullable/docs/Order.md

@@ -0,0 +1,22 @@
+
+# Order
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**id** | **kotlin.Long** |  |  [optional]
+**petId** | **kotlin.Long** |  |  [optional]
+**quantity** | **kotlin.Int** |  |  [optional]
+**shipDate** | [**java.time.LocalDateTime**](java.time.LocalDateTime.md) |  |  [optional]
+**status** | [**inline**](#StatusEnum) | Order Status |  [optional]
+**complete** | **kotlin.Boolean** |  |  [optional]
+
+
+<a name="StatusEnum"></a>
+## Enum: status
+Name | Value
+---- | -----
+status | placed, approved, delivered
+
+
+

samples/client/petstore/kotlin-nullable/docs/Pet.md

@@ -0,0 +1,22 @@
+
+# Pet
+
+## Properties
+Name | Type | Description | Notes
+------------ | ------------- | ------------- | -------------
+**id** | **kotlin.Long** |  |  [optional]
+**category** | [**Category**](Category.md) |  |  [optional]
+**name** | **kotlin.String** |  | 
+**photoUrls** | **kotlin.Array<kotlin.String>** |  | 
+**tags** | [**kotlin.Array<Tag>**](Tag.md) |  |  [optional]
+**status** | [**inline**](#StatusEnum) | pet status in the store |  [optional]
+
+
+<a name="StatusEnum"></a>
+## Enum: status
+Name | Value
+---- | -----
+status | available, pending, sold
+
+
+