fix: MediaType implementation of OpenApi 3.1 (#94)

OpenAPI 3.1 allows defining MediaTypes without a schema. But the current logic wasn't able to
detect this, because vertx-json-schema is adding internal properties to each JsonSchema.

Author: cavallium

src/main/java/io/vertx/openapi/contract/impl/MediaTypeImpl.java

@@ -33,7 +33,12 @@ public MediaTypeImpl(String identifier, JsonObject mediaTypeModel) {
       throw createUnsupportedFeature("Media Type without a schema");
     }
 
-    if (mediaTypeModel.isEmpty()) {
+    boolean emptySchema = mediaTypeModel
+      .fieldNames().stream()
+      // Ignore all the internal json-schema annotations, they start and end with "__"
+      .allMatch(name -> name.startsWith("__") && name.endsWith("__"));
+
+    if (emptySchema) {
       // OpenAPI 3.1 allows defining MediaTypes without a schema.
       schema = null;
     } else {

src/test/java/io/vertx/tests/contract/impl/MediaTypeImplTest.java

@@ -17,6 +17,7 @@
 import io.vertx.openapi.contract.MediaType;
 import io.vertx.openapi.contract.OpenAPIContractException;
 import io.vertx.openapi.contract.impl.MediaTypeImpl;
+import java.util.Map;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.Arguments;
@@ -33,12 +34,40 @@
 
 class MediaTypeImplTest {
   private static final String DUMMY_IDENTIFIER = APPLICATION_JSON.toString();
+  private static final String DUMMY_REF = "__dummy_unknown_ref__";
+  private static final String ABS_URI = "__absolute_uri__";
+  private static final String ABS_RECURSIVE_REF = "__absolute_recursive_ref__";
+  private static final String ABS_REF = "__absolute_ref__";
+  private static final String DUMMY_REF_VALUE = "dummy-ref-value";
 
   private static Stream<Arguments> testGetters() {
+    var partialSchemaJson = JsonObject.of("schema", stringSchema().toJson());
+
+    var partialUnknownAnnotation = JsonObject.of(DUMMY_REF, DUMMY_REF_VALUE);
+    var partialAbsoluteUri = JsonObject.of(ABS_URI, DUMMY_REF_VALUE);
+    var partialAbsoluteRecursiveRef = JsonObject.of(ABS_RECURSIVE_REF, DUMMY_REF_VALUE);
+    var partialAbsoluteRef = JsonObject.of(ABS_REF, DUMMY_REF_VALUE);
+    var partialMultipleAnnotations = partialAbsoluteUri.copy().mergeIn(partialUnknownAnnotation);
+
     return Stream.of(
-      Arguments.of("MediaType model defined", new JsonObject().put("schema", stringSchema().toJson()), List.of("type"
-        , "$id")),
-      Arguments.of("No MediaType model defined", EMPTY_JSON_OBJECT, List.of())
+      Arguments.of("MediaType model defined, with no internal annotations", partialSchemaJson,
+        List.of("type", "$id")),
+      Arguments.of("MediaType model defined, with an unknown internal annotation", partialSchemaJson
+        .copy().mergeIn(partialUnknownAnnotation), List.of("type", "$id")),
+      Arguments.of("MediaType model defined, with multiple internal annotations", partialSchemaJson
+        .copy().mergeIn(partialMultipleAnnotations), List.of("type", "$id")),
+      Arguments.of("No MediaType model defined, with an unknown internal annotation",
+        partialUnknownAnnotation, List.of()),
+      Arguments.of("No MediaType model defined, with absolute_uri internal annotation",
+        partialAbsoluteUri, List.of()),
+      Arguments.of("No MediaType model defined, with absolute_recursive_ref internal annotation",
+        partialAbsoluteRecursiveRef, List.of()),
+      Arguments.of("No MediaType model defined, with absolute_ref internal annotation",
+        partialAbsoluteRef, List.of()),
+      Arguments.of("No MediaType model defined, with multiple internal annotations",
+        partialMultipleAnnotations, List.of()),
+      Arguments.of("No MediaType model defined, with no internal annotations",
+        EMPTY_JSON_OBJECT, List.of())
     );
   }