fix: OAS 3.1 schema generation for raw Object properties

modules/swagger-core/src/main/java/io/swagger/v3/core/jackson/ModelResolver.java

@@ -3215,8 +3215,8 @@ protected void resolveSchemaMembers(Schema schema, Annotated a, Annotation[] ann
         }
 
         if (openapi31 && schemaAnnotation != null) {
-            for (String type : schemaAnnotation.types()) {
-                schema.addType(type);
+            if (schemaAnnotation.types().length > 0) {
+                schema.setTypes(new LinkedHashSet<>(Arrays.asList(schemaAnnotation.types())));
             }
             BigDecimal exclusiveMaximumValue = resolveExclusiveMaximumValue(a, annotations, schemaAnnotation);
             if (exclusiveMaximumValue != null) {

modules/swagger-core/src/main/java/io/swagger/v3/core/util/AnnotationsUtils.java

@@ -678,12 +678,7 @@ public static Optional<Schema> getSchemaFromAnnotation(
         }
 
         if (schema.types().length > 0) {
-            if (schema.types().length == 1) {
-                schemaObject.setType(schema.types()[0]);
-            }
-            for (String type : schema.types()) {
-                schemaObject.addType(type);
-            }
+            schemaObject.setTypes(new LinkedHashSet<>(Arrays.asList(schema.types())));
         }
         if (StringUtils.isNotBlank(schema.$id())) {
             schemaObject.set$id(schema.$id());

modules/swagger-core/src/main/java/io/swagger/v3/core/util/PrimitiveType.java

@@ -239,7 +239,7 @@ public Schema createProperty() {
         }
         @Override
         public Schema createProperty31() {
-            return new JsonSchema();
+            return explicitObjectType == null || explicitObjectType ? new JsonSchema().typesItem("object") : new JsonSchema();
         }
     };
 

modules/swagger-core/src/test/java/io/swagger/v3/core/resolving/v31/ModelResolverOAS31Test.java

@@ -240,7 +240,8 @@ public void testOAS31Fields() {
                 "        creditCard:\n" +
                 "          $ref: \"#/components/schemas/CreditCard\"\n" +
                 "      properties:\n" +
-                "        extraObject: {}\n" +
+                "        extraObject:\n" +
+                "          type: object\n" +
                 "MultipleBaseBean:\n" +
                 "  type: object\n" +
                 "  description: MultipleBaseBean\n" +

modules/swagger-core/src/test/java/io/swagger/v3/core/serialization/Oas31ObjectFieldTest.java

@@ -0,0 +1,91 @@
+package io.swagger.v3.core.serialization;
+
+import io.swagger.v3.core.converter.ModelConverters;
+import io.swagger.v3.oas.models.media.Schema;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.util.List;
+import java.util.Map;
+
+public class Oas31ObjectFieldTest {
+    @Test(description = "Repro #4682: In OAS 3.1, raw Object property should not be rendered as an empty schema")
+    public void rawObjectPropertyShouldBeObjectSchema() {
+        Map<String, Schema> schemas = ModelConverters.getInstance(true).readAll(PojoUsingObjectField.class);
+        Schema pojo = schemas.get("PojoUsingObjectField");
+        Assert.assertNotNull(pojo, "PojoUsingObjectField schema should exist");
+
+        Schema myField = (Schema) pojo.getProperties().get("myField");
+        Assert.assertNotNull(myField, "myField schema should exist");
+        Assert.assertTrue(isObjectSchema(myField), "Expected raw Object property to be an object schema in OAS 3.1, but was: type=" + myField.getType() + ", types=" + myField.getTypes() + ", class=" + myField.getClass());
+    }
+
+    @Test(description = "OAS 3.1: List<Object> items schema should be object")
+    public void listOfObjectItemsShouldBeObjectSchema() {
+        Map<String, Schema> schemas = ModelConverters.getInstance(true).readAll(PojoUsingListOfObject.class);
+        Schema pojo = schemas.get("PojoUsingListOfObject");
+        Assert.assertNotNull(pojo, "PojoUsingListOfObject schema should exist");
+        Schema itemsProp = (Schema) pojo.getProperties().get("items");
+        Assert.assertNotNull(itemsProp, "items property schema should exist");
+        Schema itemSchema = itemsProp.getItems();
+        Assert.assertNotNull(itemSchema, "List<Object> items schema should exist");
+        Assert.assertTrue(isObjectSchema(itemSchema), "Expected List<Object> items to be an object schema in OAS 3.1, but was: type=" + itemSchema.getType() + ", types=" + itemSchema.getTypes() + ", class=" + itemSchema.getClass());
+    }
+
+    @Test(description = "OAS 3.1: Map<String,Object> additionalProperties schema should be object")
+    public void mapOfObjectAdditionalPropertiesShouldBeObjectSchema() {
+        Map<String, Schema> schemas = ModelConverters.getInstance(true).readAll(PojoUsingMapStringToObject.class);
+        Schema pojo = schemas.get("PojoUsingMapStringToObject");
+        Assert.assertNotNull(pojo, "PojoUsingMapStringToObject schema should exist");
+        Schema additionalProp = (Schema) pojo.getProperties().get("additional");
+        Assert.assertNotNull(additionalProp, "additional property schema should exist");
+        Schema valueSchema = (Schema) additionalProp.getAdditionalProperties();
+        Assert.assertNotNull(valueSchema, "Map<String,Object> additionalProperties (value schema) should exist");
+        Assert.assertTrue(isObjectSchema(valueSchema), "Expected Map<String,Object> additionalProperties to be an object schema in OAS 3.1, but was: type=" + valueSchema.getType() + ", types=" + valueSchema.getTypes() + ", class=" + valueSchema.getClass());
+    }
+
+    /**
+     * OAS 3.1 may represent types via Schema#getTypes() (JSON Schema style) rather than Schema#getType().
+     */
+    private static boolean isObjectSchema(Schema s) {
+        if (s == null) return false;
+        if ("object".equals(s.getType())) return true;
+        return s.getTypes() != null && s.getTypes().contains("object");
+    }
+
+    private static class PojoUsingObjectField {
+        private Object myField;
+
+        public Object getMyField() {
+            return myField;
+        }
+
+        public void setMyField(Object myField) {
+            this.myField = myField;
+        }
+    }
+
+    private static class PojoUsingListOfObject {
+        private List<Object> items;
+
+        public List<Object> getItems() {
+            return items;
+        }
+
+        public void setItems(List<Object> items) {
+            this.items = items;
+        }
+    }
+
+    private static class PojoUsingMapStringToObject {
+        private Map<String, Object> additional;
+
+        public Map<String, Object> getAdditional() {
+            return additional;
+        }
+
+        public void setAdditional(Map<String, Object> additional) {
+            this.additional = additional;
+        }
+    }
+}

modules/swagger-jaxrs2/src/test/java/io/swagger/v3/jaxrs2/ReaderTest.java

@@ -3505,8 +3505,8 @@ public void testOas31Petstore() {
                 "          exclusiveMaximum: 4\n" +
                 "        foobar:\n" +
                 "          type:\n" +
-                "          - integer\n" +
                 "          - string\n" +
+                "          - integer\n" +
                 "          format: int32\n" +
                 "    Category:\n" +
                 "      type: object\n" +
@@ -3532,7 +3532,6 @@ public void testOas31Petstore() {
                 "          exclusiveMaximum: 2\n" +
                 "        foobar:\n" +
                 "          type:\n" +
-                "          - integer\n" +
                 "          - string\n" +
                 "          - object\n" +
                 "          format: int32\n" +
@@ -3550,7 +3549,6 @@ public void testOas31Petstore() {
                 "          exclusiveMaximum: 2\n" +
                 "        foobar:\n" +
                 "          type:\n" +
-                "          - integer\n" +
                 "          - string\n" +
                 "          - object\n" +
                 "          format: int32\n" +
@@ -3597,6 +3595,7 @@ public void testOas31Petstore() {
                 "        name:\n" +
                 "          type: string\n" +
                 "        annotated:\n" +
+                "          type: object\n" +
                 "          $ref: \"#/components/schemas/Category\"\n" +
                 "          description: child description\n" +
                 "          properties:\n" +
@@ -3643,14 +3642,14 @@ public void test31RefSiblings() {
                 "          exclusiveMaximum: 2\n" +
                 "        foobar:\n" +
                 "          type:\n" +
-                "          - integer\n" +
                 "          - string\n" +
                 "          - object\n" +
                 "          format: int32\n" +
                 "    SimpleTag:\n" +
                 "      type: object\n" +
                 "      properties:\n" +
                 "        annotated:\n" +
+                "          type: object\n" +
                 "          $ref: \"#/components/schemas/SimpleCategory\"\n" +
                 "          description: child description\n" +
                 "          properties:\n" +
@@ -4113,6 +4112,7 @@ public void testMisc31() {
                 "      type: object\n" +
                 "      properties:\n" +
                 "        country:\n" +
+                "          type: object\n" +
                 "          const: United States\n" +
                 "    CreditCard:\n" +
                 "      type: object\n" +
@@ -4123,11 +4123,13 @@ public void testMisc31() {
                 "      type: object\n" +
                 "      properties:\n" +
                 "        postalCode:\n" +
+                "          type: object\n" +
                 "          pattern: \"[0-9]{5}(-[0-9]{4})?\"\n" +
                 "    PostalCodePattern:\n" +
                 "      type: object\n" +
                 "      properties:\n" +
                 "        postalCode:\n" +
+                "          type: object\n" +
                 "          pattern: \"[A-Z][0-9][A-Z] [0-9][A-Z][0-9]\"\n" +
                 "    PropertyNamesPattern:\n" +
                 "      pattern: \"^[A-Za-z_][A-Za-z0-9_]*$\"\n";

modules/swagger-jaxrs2/src/test/resources/petstore/WebHookResource.yaml

@@ -24,9 +24,11 @@ webhooks:
                 $comment: random comment
                 $id: http://yourdomain.com/schemas/myschema.json
                 dependentSchemas:
-                  pet: {}
+                  pet:
+                    type: object
                 patternProperties:
-                  user: {}
+                  user:
+                    type: object
   webhook1:
     post:
       description: "subscribes a client to updates relevant to the requestor's account,\

modules/swagger-jaxrs2/src/test/resources/petstore/callbacks/ComplexCallback31Resource.yaml

@@ -32,9 +32,11 @@ paths:
                         $comment: random comment
                         $id: http://yourdomain.com/schemas/myschema.json
                         dependentSchemas:
-                          pet: { }
+                          pet:
+                            type: object
                         patternProperties:
-                          user: { }
+                          user:
+                            type: object
         testCallback2:
           http://www.url2.com:
             get:

modules/swagger-jaxrs2/src/test/resources/petstore/parameters/Parameters31Resource.yaml

@@ -96,7 +96,8 @@ paths:
                   user:
                     $ref: "#/components/schemas/User"
                 properties:
-                  extraObject: {}
+                  extraObject:
+                    type: object
 components:
   schemas:
     Category:

modules/swagger-jaxrs2/src/test/resources/petstore/requestbody/RequestBody31Resource.yaml

@@ -40,16 +40,20 @@ paths:
                 - string
                 - number
                 - object
-              if: {}
-              then: {}
-              else: {}
+              if:
+                type: object
+              then:
+                type: object
+              else:
+                type: object
               $anchor: parameter $anchor
               $schema: parameter $schema
               description: User description
               example: User Description
               exclusiveMaximum: 100
               exclusiveMinimum: 1
-              unevaluatedProperties: {}
+              unevaluatedProperties:
+                type: object
         required: true
       responses:
         default: