fix(openapi): handle responses for status codes not in specification.

mock/openapi/src/main/java/io/gatehill/imposter/plugin/openapi/OpenApiPluginImpl.kt

@@ -298,52 +298,47 @@ class OpenApiPluginImpl @Inject constructor(
                 return@build completedUnitFuture()
             }
 
-            val context = mutableMapOf<String, Any>()
-            context["operation"] = operation
-
             val resourceConfig = httpExchange.get<BasicResourceConfig>(ResourceUtil.RESOURCE_CONFIG_KEY)
 
             val defaultBehaviourHandler: DefaultBehaviourHandler = { responseBehaviour: ResponseBehaviour ->
                 // set status code regardless of response strategy
-                val response = httpExchange.response.setStatusCode(responseBehaviour.statusCode)
-
-                findApiResponse(operation, responseBehaviour.statusCode)?.let { specResponse ->
-                    if (!responseBehaviour.responseHeaders.containsKey(HttpUtil.CONTENT_TYPE)) {
-                        setContentTypeFromSpec(httpExchange, responseBehaviour, specResponse)
-                    }
-
-                    // build a response from the specification
-                    val exampleSender =
-                        ResponseSender { httpExchange: HttpExchange, responseBehaviour: ResponseBehaviour ->
-                            exampleService.serveExample(
-                                imposterConfig,
-                                pluginConfig,
-                                httpExchange,
-                                responseBehaviour,
-                                specResponse,
-                                spec
-                            )
+                httpExchange.response.setStatusCode(responseBehaviour.statusCode)
+
+                // build a response from the specification
+                val exampleSender = ResponseSender { httpExchange: HttpExchange, _: ResponseBehaviour ->
+                    findApiResponse(operation, responseBehaviour.statusCode)?.let { specResponse ->
+                        LOGGER.trace("Using output response: {}", specResponse)
+
+                        if (!responseBehaviour.responseHeaders.containsKey(HttpUtil.CONTENT_TYPE)) {
+                            setContentTypeFromSpec(httpExchange, responseBehaviour, specResponse)
                         }
 
-                    // attempt to serve an example from the specification, falling back if not present
-                    return@let responseService.sendResponse(
-                        pluginConfig,
-                        resourceConfig,
-                        httpExchange,
-                        responseBehaviour,
-                        exampleSender,
-                        this::fallback
-                    )
-                } ?: run {
-                    LOGGER.warn(
-                        "No response found in specification for {} and status code {}",
-                        describeRequestShort(httpExchange),
-                        responseBehaviour.statusCode
-                    )
-                    makeFuture { response.end() }
+                        exampleService.serveExample(
+                            imposterConfig,
+                            pluginConfig,
+                            httpExchange,
+                            responseBehaviour,
+                            specResponse,
+                            spec
+                        )
+                    } ?: return@ResponseSender false
                 }
+
+                // attempt to serve an example from the specification, falling back if not present
+                responseService.sendResponse(
+                    pluginConfig,
+                    resourceConfig,
+                    httpExchange,
+                    responseBehaviour,
+                    exampleSender,
+                    this::fallback
+                )
             }
 
+            val context = mutableMapOf(
+                "operation" to operation,
+            )
+
             responseRoutingService.route(
                 pluginConfig,
                 resourceConfig,
@@ -421,10 +416,12 @@ class OpenApiPluginImpl @Inject constructor(
      */
     private fun fallback(httpExchange: HttpExchange, responseBehaviour: ResponseBehaviour): Boolean {
         LOGGER.warn(
-            "No example match found and no response file set for mock response for {} with status code {}" +
-                    " - sending empty response", describeRequestShort(httpExchange), responseBehaviour.statusCode
+            "No example match found in OpenAPI specification for {} with status code {} and no response file or content set - sending empty response",
+            describeRequestShort(httpExchange),
+            responseBehaviour.statusCode,
         )
+        // should this be a 400, as it's not in the spec?
         httpExchange.response.end()
         return true
     }
-}
+}

mock/openapi/src/test/java/io/gatehill/imposter/plugin/openapi/UndefinedResourceTest.kt

@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2024.
+ *
+ * This file is part of Imposter.
+ *
+ * "Commons Clause" License Condition v1.0
+ *
+ * The Software is provided to you by the Licensor under the License, as
+ * defined below, subject to the following condition.
+ *
+ * Without limiting other conditions in the License, the grant of rights
+ * under the License will not include, and the License does not grant to
+ * you, the right to Sell the Software.
+ *
+ * For purposes of the foregoing, "Sell" means practicing any or all of
+ * the rights granted to you under the License to provide to third parties,
+ * for a fee or other consideration (including without limitation fees for
+ * hosting or consulting/support services related to the Software), a
+ * product or service whose value derives, entirely or substantially, from
+ * the functionality of the Software. Any license notice or attribution
+ * required by the License must also include this Commons Clause License
+ * Condition notice.
+ *
+ * Software: Imposter
+ *
+ * License: GNU Lesser General Public License version 3
+ *
+ * Licensor: Peter Cornish
+ *
+ * Imposter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Imposter is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Imposter.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package io.gatehill.imposter.plugin.openapi
+
+import io.gatehill.imposter.server.BaseVerticleTest
+import io.gatehill.imposter.util.HttpUtil
+import io.restassured.RestAssured
+import io.restassured.http.ContentType
+import io.vertx.ext.unit.TestContext
+import org.hamcrest.Matchers.equalTo
+import org.junit.Before
+import org.junit.Test
+
+/**
+ * Tests for mock responses when the status code is not defined within the OpenAPI spec.
+ *
+ * @author Pete Cornish
+ */
+class UndefinedResourceTest : BaseVerticleTest() {
+    override val pluginClass = OpenApiPluginImpl::class.java
+
+    @Before
+    @Throws(Exception::class)
+    override fun setUp(testContext: TestContext) {
+        super.setUp(testContext)
+        RestAssured.baseURI = "http://$host:$listenPort"
+    }
+
+    override val testConfigDirs = listOf(
+        "/openapi3/undefined-resource"
+    )
+
+    /**
+     * Should trigger warning and fallback handler.
+     *
+     * @param testContext
+     */
+    @Test
+    fun `should return fallback response`(testContext: TestContext) {
+        RestAssured.given()
+            .log().ifValidationFails()
+            .accept(ContentType.JSON)
+            .`when`().get("/cats")
+            .then()
+            .log().ifValidationFails()
+            .statusCode(HttpUtil.HTTP_CREATED)
+    }
+
+    /**
+     * Should return custom response.
+     *
+     * @param testContext
+     */
+    @Test
+    fun `should return custom response`(testContext: TestContext) {
+        RestAssured.given()
+            .log().ifValidationFails()
+            .accept(ContentType.JSON)
+            .`when`().get("/dogs")
+            .then()
+            .log().ifValidationFails()
+            .statusCode(HttpUtil.HTTP_ACCEPTED)
+            .body(equalTo("Custom response"))
+    }
+}

mock/openapi/src/test/resources/openapi3/undefined-resource/mock-config.yaml

@@ -0,0 +1,15 @@
+---
+plugin: openapi
+specFile: spec.yaml
+
+resources:
+  - method: get
+    path: /cats
+    response:
+      statusCode: 201
+
+  - method: get
+    path: /dogs
+    response:
+      statusCode: 202
+      content: "Custom response"

mock/openapi/src/test/resources/openapi3/undefined-resource/spec.yaml

@@ -0,0 +1,49 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Swagger Petstore
+  license:
+    name: MIT
+paths:
+  /cats:
+    get:
+      summary: List all cats
+      operationId: listCats
+      responses:
+        "200":
+          description: cats response
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/PetResponse"
+
+  /dogs:
+    get:
+      summary: List all dogs
+      operationId: listDogs
+      responses:
+        "200":
+          description: dogs response
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/PetResponse"
+
+components:
+  schemas:
+    PetResponse:
+      type: object
+      required:
+        - code
+        - message
+      properties:
+        code:
+          type: integer
+          format: int32
+        message:
+          type: string
+      example:
+        {
+          "code": 1,
+          "message": "Pet response"
+        }