Multiple response content types (#90)

* Add extra route with multiple responses

* Change response type when there are multiple different response schemas

* Use JsonNode in case the response is an array

* Update test

* Exclude default response

README.md

@@ -11,7 +11,7 @@ This library was built to take advantage of the complex modeling features availa
 
 More than just bootstrapping, this library can be permanently integrated into a gradle or maven build and will ensure contract and code always match, even as APIs evolve in complexity. 
 
-The team that built this tool initially contributed to the Kotlin code generation ability in [OpenApiTools](https://github.com/OpenAPITools/openapi-generator), but reached the limits of what could be achieved with template-based generation. This library levarages the rich OpenApi3 model provided by [KaiZen-OpenApi-Parser](https://github.com/RepreZen/KaiZen-OpenApi-Parser) and uses [Kotlin Poet](https://square.github.io/kotlinpoet/) to programatically construct Kotlin classes for maximum flexibility. 
+The team that built this tool initially contributed to the Kotlin code generation ability in [OpenApiTools](https://github.com/OpenAPITools/openapi-generator), but reached the limits of what could be achieved with template-based generation. This library leverages the rich OpenApi3 model provided by [KaiZen-OpenApi-Parser](https://github.com/RepreZen/KaiZen-OpenApi-Parser) and uses [Kotlin Poet](https://square.github.io/kotlinpoet/) to programmatically construct Kotlin classes for maximum flexibility. 
 
 It was built at [Zalando Tech](https://opensource.zalando.com/) and is battle-tested in production there. It is particulary well suited to API's built according to Zalando's [REST API guidelines](https://opensource.zalando.com/restful-api-guidelines/). It is [available on Maven Central](https://search.maven.org/artifact/com.cjbooms/fabrikt) at the following coordinates:
 

src/main/kotlin/com/cjbooms/fabrikt/generators/GeneratorUtils.kt

@@ -120,6 +120,9 @@ object GeneratorUtils {
 
     fun Operation.hasMultipleContentMediaTypes(): Boolean? = this.firstResponse()?.hasMultipleContentMediaTypes()
 
+    fun Operation.hasMultipleResponseSchemas(): Boolean =
+            getBodyResponses().flatMap { it.contentMediaTypes.values }.map { it.schema.name }.distinct().size > 1
+
     fun Operation.getPathParams(): List<Parameter> = this.filterParams("path")
 
     fun Operation.getQueryParams(): List<Parameter> = this.filterParams("query")

src/main/kotlin/com/cjbooms/fabrikt/generators/client/ClientGeneratorUtils.kt

@@ -2,10 +2,12 @@ package com.cjbooms.fabrikt.generators.client
 
 import com.cjbooms.fabrikt.configurations.Packages
 import com.cjbooms.fabrikt.generators.GeneratorUtils.getPrimaryContentMediaType
+import com.cjbooms.fabrikt.generators.GeneratorUtils.hasMultipleResponseSchemas
 import com.cjbooms.fabrikt.generators.GeneratorUtils.toClassName
 import com.cjbooms.fabrikt.generators.model.JacksonModelGenerator.Companion.toModelType
 import com.cjbooms.fabrikt.model.ClientType
 import com.cjbooms.fabrikt.model.KotlinTypeInfo
+import com.fasterxml.jackson.databind.JsonNode
 import com.reprezen.kaizen.oasparser.model3.Operation
 import com.squareup.kotlinpoet.ParameterizedTypeName.Companion.parameterizedBy
 import com.squareup.kotlinpoet.TypeName
@@ -16,18 +18,24 @@ object ClientGeneratorUtils {
     const val ADDITIONAL_HEADERS_PARAMETER_NAME = "additionalHeaders"
 
     /**
-     * It resolves the API operation response to its body type. It iterates over all non-default responses
-     * by filtering those ones with content media. If multiple medias are found, then it will resolve to the schema
-     * reference of the first media type found, otherwise it'll resolve to Unit by assuming no response body
-     * for the given operation.
+     * Gives the Kotlin return type for an API call based on the Content-Types specified in the Operation.
+     * If multiple media types are found, but their response schema is the same, then the first media type is used and kotlin model for the schema is returned.
+     * If there are several possible response schemas, then the return type is JsonNode, so they are all covered.
+     * If no response body is found, Unit is returned.
      */
     fun Operation.toClientReturnType(packages: Packages): TypeName {
-        val returnType = this.getPrimaryContentMediaType()?.let {
-            toModelType(
-                packages.base,
-                KotlinTypeInfo.from(it.value.schema)
-            )
-        } ?: Unit::class.asTypeName()
+        val returnType =
+                if (hasMultipleResponseSchemas()) {
+                    JsonNode::class.asTypeName()
+                } else {
+                    this.getPrimaryContentMediaType()?.let {
+                        toModelType(
+                                packages.base,
+                                KotlinTypeInfo.from(it.value.schema)
+                        )
+                    } ?: Unit::class.asTypeName()
+                }
+
         return "ApiResponse".toClassName(packages.client)
             .parameterizedBy(returnType.copy(nullable = true))
     }

src/test/resources/examples/okHttpClientMultiMediaType/api.yaml

@@ -21,7 +21,15 @@ paths:
                 $ref: "#/components/schemas/QueryResult"
             application/vnd.custom.media+json:
               schema:
-                $ref: "#/components/schemas/QueryResult"  
+                $ref: "#/components/schemas/QueryResult"
+        default:
+          description: >-
+            error occurred - see status code and problem object for more information.
+          content:
+            application/problem+json:
+              schema:
+                $ref: 'https://opensource.zalando.com/problem/schema.yaml#/Problem'
+
   /example-path-2:
     get:
       summary: "GET example path 1"
@@ -43,6 +51,25 @@ paths:
               schema:
                 $ref: "#/components/schemas/QueryResult"
 
+  /multiple-response-schemas:
+    get:
+      summary: "GET with multiple response content schemas"
+      parameters:
+        - $ref: "#/components/parameters/Accept"
+      responses:
+        200:
+          description: "successful operation"
+          headers:
+            Cache-Control:
+              $ref: "#/components/headers/CacheControl"
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/QueryResult'
+            application/vnd.custom.media+json:
+              schema:
+                $ref: '#/components/schemas/OtherQueryResult'
+
 components:
   parameters:
     ListQueryParamExploded:
@@ -83,6 +110,7 @@ components:
       x-extensible-enum:
         - application/json
         - application/vnd.custom.media+json
+
     QueryResult:
       type: "object"
       required:
@@ -96,6 +124,16 @@ components:
               - $ref: "#/components/schemas/FirstModel"
               - $ref: "#/components/schemas/SecondModel"
               - $ref: "#/components/schemas/ThirdModel"
+    OtherQueryResult:
+      type: "object"
+      required:
+        - "items"
+      properties:
+        items:
+          type: "array"
+          minItems: 0
+          items:
+            $ref: "#/components/schemas/AlternateResponseModel"
     Content:
       type: "object"
       required:
@@ -188,3 +226,17 @@ components:
               description: "The attribute 2 for model 3"
               type: integer
               readOnly: true
+
+    AlternateResponseModel:
+      type: "object"
+      properties:
+        extra_first_attr:
+          description: "The attribute 1 for model 3"
+          type: "string"
+          format: "date-time"
+          example: "2016-01-27T10:52:46.406Z"
+          readOnly: true
+        extra_second_attr:
+          description: "The attribute 2 for model 3"
+          type: integer
+          readOnly: true

src/test/resources/examples/okHttpClientMultiMediaType/client/ApiClient.kt

@@ -1,5 +1,6 @@
 package examples.okHttpClientMultiMediaType.client
 
+import com.fasterxml.jackson.databind.JsonNode
 import com.fasterxml.jackson.databind.ObjectMapper
 import com.fasterxml.jackson.module.kotlin.jacksonTypeRef
 import examples.okHttpClientMultiMediaType.models.ContentType
@@ -98,3 +99,40 @@ class ExamplePath2Client(
         return request.execute(client, objectMapper, jacksonTypeRef())
     }
 }
+
+@Suppress("unused")
+class MultipleResponseSchemasClient(
+    private val objectMapper: ObjectMapper,
+    private val baseUrl: String,
+    private val client: OkHttpClient
+) {
+    /**
+     * GET with multiple response content schemas
+     *
+     * @param accept the content type accepted by the client
+     */
+    @Throws(ApiException::class)
+    fun getMultipleResponseSchemas(
+        accept: ContentType?,
+        additionalHeaders: Map<String, String> =
+            emptyMap()
+    ): ApiResponse<JsonNode?> {
+        val httpUrl: HttpUrl = "$baseUrl/multiple-response-schemas"
+            .toHttpUrl()
+            .newBuilder()
+            .build()
+
+        val headerBuilder = Headers.Builder()
+            .header("Accept", accept?.value)
+        additionalHeaders.forEach { headerBuilder.header(it.key, it.value) }
+        val httpHeaders: Headers = headerBuilder.build()
+
+        val request: Request = Request.Builder()
+            .url(httpUrl)
+            .headers(httpHeaders)
+            .get()
+            .build()
+
+        return request.execute(client, objectMapper, jacksonTypeRef())
+    }
+}

src/test/resources/examples/okHttpClientMultiMediaType/client/ApiService.kt

@@ -1,5 +1,6 @@
 package examples.okHttpClientMultiMediaType.client
 
+import com.fasterxml.jackson.databind.JsonNode
 import com.fasterxml.jackson.databind.ObjectMapper
 import examples.okHttpClientMultiMediaType.models.ContentType
 import examples.okHttpClientMultiMediaType.models.QueryResult
@@ -73,3 +74,37 @@ class ExamplePath2Service(
             apiClient.getExamplePath2(explodeListQueryParam, queryParam2, accept, additionalHeaders)
         }
 }
+
+/**
+ * The circuit breaker registry should have the proper configuration to correctly action on circuit
+ * breaker transitions based on the client exceptions [ApiClientException], [ApiServerException] and
+ * [IOException].
+ *
+ * @see ApiClientException
+ * @see ApiServerException
+ */
+@Suppress("unused")
+class MultipleResponseSchemasService(
+    private val circuitBreakerRegistry: CircuitBreakerRegistry,
+    objectMapper: ObjectMapper,
+    baseUrl: String,
+    client: OkHttpClient
+) {
+    var circuitBreakerName: String = "multipleResponseSchemasClient"
+
+    private val apiClient: MultipleResponseSchemasClient = MultipleResponseSchemasClient(
+        objectMapper,
+        baseUrl,
+        client
+    )
+
+    @Throws(ApiException::class)
+    fun getMultipleResponseSchemas(
+        accept: ContentType?,
+        additionalHeaders: Map<String, String> =
+            emptyMap()
+    ): ApiResponse<JsonNode?> =
+        withCircuitBreaker(circuitBreakerRegistry, circuitBreakerName) {
+            apiClient.getMultipleResponseSchemas(accept, additionalHeaders)
+        }
+}

src/test/resources/examples/okHttpClientMultiMediaType/models/Models.kt

@@ -38,6 +38,24 @@ data class QueryResult(
     val items: List<Content>
 )
 
+data class OtherQueryResult(
+    @param:JsonProperty("items")
+    @get:JsonProperty("items")
+    @get:NotNull
+    @get:Size(min = 0)
+    @get:Valid
+    val items: List<AlternateResponseModel>
+)
+
+data class AlternateResponseModel(
+    @param:JsonProperty("extra_first_attr")
+    @get:JsonProperty("extra_first_attr")
+    val extraFirstAttr: OffsetDateTime? = null,
+    @param:JsonProperty("extra_second_attr")
+    @get:JsonProperty("extra_second_attr")
+    val extraSecondAttr: Int? = null
+)
+
 @JsonTypeInfo(
     use = JsonTypeInfo.Id.NAME,
     include = JsonTypeInfo.As.EXISTING_PROPERTY,