Support kotlin.coroutines.Continuation default response type

core/src/main/java/io/smallrye/openapi/api/constants/KotlinConstants.java

@@ -0,0 +1,17 @@
+package io.smallrye.openapi.api.constants;
+
+import org.jboss.jandex.DotName;
+
+/**
+ * Constants related to the Kotlin language
+ * 
+ * @author Michael Edgar {@literal <michael@xlate.io>}
+ */
+public class KotlinConstants {
+
+    public static final DotName CONTINUATION = DotName
+            .createSimple("kotlin.coroutines.Continuation");
+
+    private KotlinConstants() {
+    }
+}

core/src/main/java/io/smallrye/openapi/runtime/scanner/spi/AnnotationScanner.java

@@ -36,8 +36,10 @@
 import org.jboss.jandex.MethodInfo;
 import org.jboss.jandex.ParameterizedType;
 import org.jboss.jandex.Type;
+import org.jboss.jandex.Type.Kind;
 
 import io.smallrye.openapi.api.OpenApiConfig.OperationIdStrategy;
+import io.smallrye.openapi.api.constants.KotlinConstants;
 import io.smallrye.openapi.api.constants.OpenApiConstants;
 import io.smallrye.openapi.api.constants.SecurityConstants;
 import io.smallrye.openapi.api.models.OperationImpl;
@@ -410,8 +412,9 @@ default void createResponseFromRestMethod(final AnnotationScannerContext context
                 Schema schema;
 
                 if (isMultipartOutput(returnType)) {
-                    schema = new SchemaImpl();
-                    schema.setType(Schema.SchemaType.OBJECT);
+                    schema = new SchemaImpl().type(Schema.SchemaType.OBJECT);
+                } else if (isKotlinContinuation(method)) {
+                    schema = kotlinContinuationToSchema(context, method);
                 } else {
                     schema = SchemaFactory.typeToSchema(context, returnType, context.getExtensions());
                 }
@@ -492,6 +495,35 @@ default boolean isVoidResponse(final MethodInfo method) {
         return false;
     }
 
+    default boolean isKotlinContinuation(MethodInfo method) {
+        if (method.parameters().size() != 1) {
+            return false;
+        }
+
+        return KotlinConstants.CONTINUATION.equals(method.parameters().get(0).name());
+    }
+
+    default Schema kotlinContinuationToSchema(AnnotationScannerContext context, MethodInfo method) {
+        Schema schema;
+        Type type = context.getResourceTypeResolver().resolve(method.parameters().get(0));
+
+        if (type.kind() == Kind.PARAMETERIZED_TYPE) {
+            type = type.asParameterizedType().arguments().get(0);
+
+            if (type.kind() == Kind.WILDCARD_TYPE) {
+                Type extendsBound = type.asWildcardType().extendsBound();
+                Type superBound = type.asWildcardType().superBound();
+                type = superBound != null ? superBound : extendsBound;
+            }
+
+            schema = SchemaFactory.typeToSchema(context, type, context.getExtensions());
+        } else {
+            schema = new SchemaImpl().type(Schema.SchemaType.OBJECT);
+        }
+
+        return schema;
+    }
+
     /**
      * Determine if the default response information should be generated.
      * It should be done when no responses have been declared or if the default

extension-jaxrs/pom.xml

@@ -88,7 +88,13 @@
             <scope>test</scope>
             <type>pom</type>
         </dependency>
-
+        <dependency>
+            <groupId>io.quarkus</groupId>
+            <artifactId>quarkus-kotlin</artifactId>
+            <version>${version.quarkus}</version>
+            <scope>test</scope>
+        </dependency>
+
         <!-- Depend on core tests -->
         <dependency>
             <groupId>${project.groupId}</groupId>

extension-jaxrs/src/test/java/io/smallrye/openapi/runtime/scanner/ApiResponseTests.java

@@ -237,4 +237,42 @@ public jakarta.ws.rs.core.MultivaluedMap<String, Map<String, CustomResponse>> ge
                 NavigableMap.class,
                 HashMap.class);
     }
+
+    @Test
+    void testKotlinContinuationStringResponse() throws IOException, JSONException {
+        @jakarta.ws.rs.Path("/hello")
+        class Resource {
+
+            /**
+             * Java equivalent of Kotlin function
+             * <code>
+             * suspend fun hello(): String {
+             *     return "Hello RESTEasy Reactive"
+             * }
+             * </code>
+             *
+             * @param completion maps to Kotlin string return type when using `suspend`
+             * @return nothing
+             */
+            @jakarta.ws.rs.GET
+            @jakarta.ws.rs.Path("/async")
+            @jakarta.ws.rs.Produces({ "text/plain" })
+            public Object hello1(kotlin.coroutines.Continuation<? super String> completion) {
+                return null;
+            }
+
+            @jakarta.ws.rs.GET
+            @jakarta.ws.rs.Path("/sync")
+            @jakarta.ws.rs.Produces({ "text/plain" })
+            public String hello2() {
+                return "Hello";
+            }
+        }
+
+        test("responses.kotlin-continuation.json",
+                Resource.class,
+                kotlin.coroutines.Continuation.class,
+                kotlin.coroutines.CoroutineContext.class);
+    }
+
 }

extension-jaxrs/src/test/resources/io/smallrye/openapi/runtime/scanner/responses.kotlin-continuation.json

@@ -0,0 +1,37 @@
+{
+  "openapi": "3.0.3",
+  "paths": {
+    "/hello/async": {
+      "get": {
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "text/plain": {
+                "schema": {
+                  "type": "string"
+                }
+              }
+            }
+          }
+        }
+      }
+    },
+    "/hello/sync": {
+      "get": {
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "text/plain": {
+                "schema": {
+                  "type": "string"
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}