spmallette commented on code in PR #1929: URL: https://github.com/apache/tinkerpop/pull/1929#discussion_r1063374730
########## gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MergeStep.java: ########## @@ -0,0 +1,299 @@ +/* + * 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.step.map; + +import java.util.ArrayList; +import java.util.Iterator; +import java.util.LinkedHashMap; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.Set; + +import org.apache.tinkerpop.gremlin.process.traversal.Merge; +import org.apache.tinkerpop.gremlin.process.traversal.Step; +import org.apache.tinkerpop.gremlin.process.traversal.Traversal; +import org.apache.tinkerpop.gremlin.process.traversal.Traverser; +import org.apache.tinkerpop.gremlin.process.traversal.TraverserGenerator; +import org.apache.tinkerpop.gremlin.process.traversal.lambda.ConstantTraversal; +import org.apache.tinkerpop.gremlin.process.traversal.lambda.IdentityTraversal; +import org.apache.tinkerpop.gremlin.process.traversal.step.Mutating; +import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalOptionParent; +import org.apache.tinkerpop.gremlin.process.traversal.step.util.Parameters; +import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.CallbackRegistry; +import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.Event; +import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.ListCallbackRegistry; +import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement; +import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil; +import org.apache.tinkerpop.gremlin.structure.Direction; +import org.apache.tinkerpop.gremlin.structure.Graph; +import org.apache.tinkerpop.gremlin.structure.T; +import org.apache.tinkerpop.gremlin.structure.util.StringFactory; + +/** + * Abstract base class for the {@code mergeV/E()} implementations. + */ +public abstract class MergeStep<S, E, C> extends FlatMapStep<S, E> implements Mutating<Event>, + TraversalOptionParent<Merge, S, C> { + + protected final boolean isStart; + protected boolean first = true; + protected Traversal.Admin<S, Map> mergeTraversal; + protected Traversal.Admin<S, Map> onCreateTraversal = null; + protected Traversal.Admin<S, Map<String, ?>> onMatchTraversal = null; + + protected CallbackRegistry<Event> callbackRegistry; + + public MergeStep(final Traversal.Admin traversal, final boolean isStart) { + this(traversal, isStart, new IdentityTraversal<>()); + } + + public MergeStep(final Traversal.Admin traversal, final boolean isStart, final Map mergeMap) { + this(traversal, isStart, new ConstantTraversal<>(mergeMap)); + validate(mergeMap, false); + } + + public MergeStep(final Traversal.Admin traversal, final boolean isStart, + final Traversal.Admin mergeTraversal) { + super(traversal); + this.isStart = isStart; + this.mergeTraversal = integrateChild(mergeTraversal); + } + + /** + * Gets the traversal that will be used to provide the {@code Map} that will be used to search for elements. + * This {@code Map} also will be used as the default data set to be used to create the element if the search is not + * successful. + */ + public Traversal.Admin<S, Map> getMergeTraversal() { + return mergeTraversal; + } + + /** + * Gets the traversal that will be used to provide the {@code Map} that will be used to create elements that + * do not match the search criteria of {@link #getMergeTraversal()}. + */ + public Traversal.Admin<S, Map> getOnCreateTraversal() { + return onCreateTraversal; + } + + /** + * Gets the traversal that will be used to provide the {@code Map} that will be used to modify elements that + * match the search criteria of {@link #getMergeTraversal()}. + */ + public Traversal.Admin<S, Map<String, ?>> getOnMatchTraversal() { + return onMatchTraversal; + } + + /** + * Determines if this is a start step. + */ + public boolean isStart() { + return isStart; + } + + /** + * Determine if this is the first pass through {@link #processNextStart()}. + */ + public boolean isFirst() { + return first; + } + + public CallbackRegistry<Event> getCallbackRegistry() { + return callbackRegistry; + } + + @Override + public void addChildOption(final Merge token, final Traversal.Admin<S, C> traversalOption) { + if (token == Merge.onCreate) { + this.onCreateTraversal = this.integrateChild(traversalOption); + } else if (token == Merge.onMatch) { + this.onMatchTraversal = this.integrateChild(traversalOption); + } else { + throw new UnsupportedOperationException(String.format("Option %s for Merge is not supported", token.name())); + } + } + + @Override + public <S, C> List<Traversal.Admin<S, C>> getLocalChildren() { + final List<Traversal.Admin<S, C>> children = new ArrayList<>(); + if (mergeTraversal != null) children.add((Traversal.Admin<S, C>) mergeTraversal); + if (onMatchTraversal != null) children.add((Traversal.Admin<S, C>) onMatchTraversal); + if (onCreateTraversal != null) children.add((Traversal.Admin<S, C>) onCreateTraversal); + return children; + } + + @Override + public void configure(final Object... keyValues) { + // this is a Mutating step but property() should not be folded into this step. The main issue here is that + // this method won't know what step called it - property() or with() or something else so it can't make the + // choice easily to throw an exception, write the keys/values to parameters, etc. It really is up to the + // caller to make sure it is handled properly at this point. this may best be left as a do-nothing method for + // now. + } + + @Override + public Parameters getParameters() { + // merge doesn't take fold ups of property() calls. those need to get treated as regular old PropertyStep + // instances. not sure if this should support with() though.....none of the other Mutating steps do. + return null; + } + + @Override + protected Traverser.Admin<E> processNextStart() { + // when it's a start step a traverser needs to be created to kick off the traversal. + if (isStart && first) { + first = false; + generateTraverser(false); + } + return super.processNextStart(); + } + + private void generateTraverser(final Object o) { + final TraverserGenerator generator = this.getTraversal().getTraverserGenerator(); + this.addStart(generator.generate(o, (Step) this, 1L)); + } + + protected Graph getGraph() { + return this.getTraversal().getGraph().get(); + } + + @Override + public CallbackRegistry<Event> getMutatingCallbackRegistry() { + if (null == callbackRegistry) callbackRegistry = new ListCallbackRegistry<>(); + return callbackRegistry; + } + + @Override + public int hashCode() { + int result = super.hashCode(); + if (mergeTraversal != null) + result ^= mergeTraversal.hashCode(); + if (onCreateTraversal != null) + result ^= onCreateTraversal.hashCode(); + if (onMatchTraversal != null) + result ^= onMatchTraversal.hashCode(); + return result; + } + + @Override + public void reset() { + super.reset(); + first = true; + mergeTraversal.reset(); + if (onCreateTraversal != null) onCreateTraversal.reset(); + if (onMatchTraversal != null) onMatchTraversal.reset(); + } + + @Override + public Set<TraverserRequirement> getRequirements() { + return this.getSelfAndChildRequirements(); + } + + @Override + public String toString() { + return StringFactory.stepString(this, mergeTraversal, onCreateTraversal, onMatchTraversal); + } + + @Override + public void setTraversal(final Traversal.Admin<?, ?> parentTraversal) { + super.setTraversal(parentTraversal); + this.integrateChild(mergeTraversal); + this.integrateChild(onCreateTraversal); + this.integrateChild(onMatchTraversal); + } + + @Override + public MergeStep<S, E, C> clone() { + final MergeStep<S, E, C> clone = (MergeStep<S, E, C>) super.clone(); + clone.mergeTraversal = mergeTraversal.clone(); + clone.onCreateTraversal = onCreateTraversal != null ? onCreateTraversal.clone() : null; + clone.onMatchTraversal = onMatchTraversal != null ? onMatchTraversal.clone() : null; + return clone; + } + + protected void validate(final Map map, final boolean ignoreTokens) { + final Set allowedTokens = getAllowedTokens(); + validate(map, ignoreTokens, allowedTokens); + } + + protected static void validate(final Map map, final boolean ignoreTokens, final Set allowedTokens) { + if (null == map) return; + + ((Map<?,?>) map).entrySet().forEach(e -> { + final Object k = e.getKey(); + final Object v = e.getValue(); + + if (v == null) { + throw new IllegalArgumentException(String.format("merge() does not allow null Map values - check: %s", k)); Review Comment: This message seems like it might be confusing because there technically is not `merge()` step - it is either `mergeV()` or `mergeE()`. could this be made to be more specific somehow? -- This is an automated message from the Apache Git Service. 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