spmallette commented on code in PR #3458: URL: https://github.com/apache/tinkerpop/pull/3458#discussion_r3439677402
########## gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/util/ChildTraversalValidator.java: ########## @@ -0,0 +1,45 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +package org.apache.tinkerpop.gremlin.process.traversal.util; + +import org.apache.tinkerpop.gremlin.process.traversal.Traversal; +import org.apache.tinkerpop.gremlin.process.traversal.step.Mutating; + +/** + * Validates that child traversals do not contain mutating steps. Child traversals used as + * arguments to filter predicates ({@code has()}, {@code is()}, etc.), lookup steps + * ({@code V(traversal)}, {@code E(traversal)}), and mutation steps ({@code property(traversal)}) + * must be read-only - their purpose is to compute values, not produce side effects. + */ +public final class ChildTraversalValidator { + + private ChildTraversalValidator() { + } + + /** + * Validates that a child traversal contains no {@link Mutating} steps at any nesting depth. + * Throws {@link IllegalArgumentException} if one is found. + */ + public static void validate(final Traversal.Admin<?, ?> child) { + if (TraversalHelper.hasStepOfAssignableClassRecursively(Mutating.class, child)) { + throw new IllegalArgumentException("Child traversal contains a mutating step. " + Review Comment: would we help folks by telling them the `Mutating` step we found and in what parent? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
