Rework operation customizing to consider returned value. Fixes #1025

Author: romash1408

springdoc-openapi-common/src/main/java/org/springdoc/api/AbstractOpenApiResource.java

@@ -400,7 +400,9 @@ protected void calculatePath(HandlerMethod handlerMethod, RouterOperation router
 			buildCallbacks(openAPI, methodAttributes, operation, apiCallbacks);
 
 			// allow for customisation
-			customiseOperation(operation, handlerMethod);
+			operation = customiseOperation(operation, handlerMethod);
+			if (operation == null)
+				continue;
 
 			PathItem pathItemObject = buildPathItem(requestMethod, operation, operationPath, paths);
 			paths.addPathItem(operationPath, pathItemObject);
@@ -703,8 +705,13 @@ protected Set<RequestMethod> getDefaultAllowedHttpMethods() {
 	 * @return the operation
 	 */
 	protected Operation customiseOperation(Operation operation, HandlerMethod handlerMethod) {
-		operationCustomizers.ifPresent(customizers -> customizers.forEach(customizer -> customizer.customize(operation, handlerMethod)));
-		return operation;
+		if (!operationCustomizers.isPresent())
+			return operation;
+		Operation customizedOperation = operation;
+		for (OperationCustomizer customizer : operationCustomizers.get()) {
+			customizedOperation = customizer.customize(customizedOperation, handlerMethod);
+		}
+		return customizedOperation;
 	}
 
 	/**

springdoc-openapi-common/src/main/java/org/springdoc/core/customizers/OperationCustomizer.java

@@ -22,6 +22,7 @@
 
 import io.swagger.v3.oas.models.Operation;
 
+import org.springframework.lang.Nullable;
 import org.springframework.web.method.HandlerMethod;
 
 /**
@@ -37,8 +38,7 @@ public interface OperationCustomizer {
 	 *
 	 * @param operation input operation
 	 * @param handlerMethod original handler method
-	 * @return customized operation
+	 * @return customized operation or null to hide operation
 	 */
 	Operation customize(Operation operation, HandlerMethod handlerMethod);
 }
-