GH-232 Allow reference to a model from OpenApiContentProperty

examples/javalin-gradle-kotlin/src/main/java/io/javalin/openapi/plugin/test/JavalinTest.java

@@ -203,6 +203,7 @@ public static void main(String[] args) {
                 @OpenApiContent(mimeType = "image/png", type = "string", format = "base64"), // single file upload,
                 @OpenApiContent(mimeType = "multipart/form-data", properties = {
                     @OpenApiContentProperty(name = "form-element", type = "integer"), // random element in form-data
+                    @OpenApiContentProperty(name = "reference", from = KotlinEntity.class), // reference to another object
                     @OpenApiContentProperty(name = "file-name", isArray = true, type = "string", format = "base64") // multi-file upload
                 })
             }

examples/javalin-maven-java/src/main/java/io/javalin/openapi/plugin/test/JavalinTest.java

@@ -175,6 +175,7 @@ public static void main(String[] args) {
                 @OpenApiContent(mimeType = "image/png", type = "string", format = "base64"), // single file upload,
                 @OpenApiContent(mimeType = "multipart/form-data", properties = {
                         @OpenApiContentProperty(name = "form-element", type = "integer"), // random element in form-data
+                        @OpenApiContentProperty(name = "reference", from = KotlinEntity.class) // reference to another object
                         @OpenApiContentProperty(name = "file-name", isArray = true, type = "string", format = "base64") // multi-file upload
                 })
             }

openapi-annotation-processor/src/main/kotlin/io/javalin/openapi/processor/generators/OpenApiGenerator.kt

@@ -444,22 +444,29 @@ internal class OpenApiGenerator {
                     schema.addProperty("type", "object")
 
                     for (contentProperty in properties) {
-                        val propertyScheme = JsonObject()
                         val propertyFormat = contentProperty.format.takeIf { it != NULL_STRING }
 
-                        if (contentProperty.isArray) {
-                            propertyScheme.addProperty("type", "array")
-
-                            val items = JsonObject()
-                            items.addProperty("type", contentProperty.type)
-                            propertyFormat?.let { items.addProperty("format", it) }
-                            propertyScheme.add("items", items)
+                        val contentPropertyFrom = contentAnnotation.getTypeMirror { contentProperty.from }
+                        val propertyScheme = if (contentPropertyFrom.getFullName() != NULL_CLASS::class.java.name) {
+                            createTypeDescriptionWithReferences(contentPropertyFrom)
                         } else {
-                            propertyScheme.addProperty("type", contentProperty.type)
-                            propertyFormat?.let { propertyScheme.addProperty("format", it) }
+                            JsonObject().apply {
+                                addProperty("type", contentProperty.type)
+                                propertyFormat?.let { addProperty("format", it) }
+                            }
                         }
 
-                        propertiesSchema.add(contentProperty.name, propertyScheme)
+                        propertiesSchema.add(contentProperty.name,
+                            if (contentProperty.isArray) {
+                                // wrap into OpenAPI array object
+                                JsonObject().apply {
+                                    addProperty("type", "array")
+                                    add("items", propertyScheme)
+                                }
+                            } else {
+                                propertyScheme
+                            }
+                        )
                     }
 
                     schema.add("properties", propertiesSchema)

openapi-annotation-processor/src/test/kotlin/io/javalin/openapi/processor/TypeMappersTest.kt

@@ -197,4 +197,21 @@ internal class TypeMappersTest : OpenApiAnnotationProcessorSpecification() {
             ))
     }
 
-}
+    private class Loop(
+        val self: Loop?,
+    )
+
+
+    @OpenApi(
+        path = "recursive",
+        versions = ["should_map_recursive_type"],
+        responses = [OpenApiResponse(status = "200", content = [OpenApiContent(from = Loop::class)])]
+    )
+    @Test
+    fun should_map_recursive_type() = withOpenApi("should_map_recursive_type") {
+        assertThatJson(it)
+            .inPath("$.components.schemas.Loop.properties.self")
+            .isObject
+            .containsEntry("\$ref", "#/components/schemas/Loop")
+    }
+}

openapi-specification/src/main/kotlin/io/javalin/openapi/OpenApiAnnotations.kt

@@ -147,9 +147,10 @@ annotation class OpenApiContent(
 @Target()
 @Retention(RUNTIME)
 annotation class OpenApiContentProperty(
+    val from: KClass<*> = NULL_CLASS::class,
     val name: String,
     val isArray: Boolean = false,
-    val type: String,
+    val type: String = NULL_STRING,
     val format: String = NULL_STRING
 )