[GitHub] [tinkerpop] jorgebay commented on a change in pull request #1211: TINKERPOP-1568 Changed Strategy Application Methodology

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jorgebay commented on a change in pull request #1211: TINKERPOP-1568 Changed Strategy Application Methodology
URL: https://github.com/apache/tinkerpop/pull/1211#discussion_r341992514
 
 

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 File path: gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Traversal.java
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 @@ -476,21 +478,30 @@ public default void reset() {
         public TraversalStrategies getStrategies();
 
         /**
-         * Set the {@link org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent} {@link Step} that is the parent of this traversal.
-         * Traversals can be nested and this is the means by which the traversal tree is connected.
+         * Set the {@link org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent} {@link Step} that is
+         * the parent of this traversal. Traversals can be nested and this is the means by which the traversal tree is
+         * connected.
          *
          * @param step the traversal holder parent step
          */
         public void setParent(final TraversalParent step);
 
         /**
-         * Get the {@link org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent} {@link Step} that is the parent of this traversal.
-         * Traversals can be nested and this is the means by which the traversal tree is walked.
+         * Get the {@link org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent} {@link Step} that is
+         * the parent of this traversal. Traversals can be nested and this is the means by which the traversal tree is
+         * walked.
          *
          * @return the traversal holder parent step
          */
         public TraversalParent getParent();
 
+        /**
+         * Determines if the traversal is at the root level.
+         */
+        public default boolean isRoot() {
+            return null == getParent() || getParent() instanceof EmptyStep;
 
 Review comment:
   `Traversal` implementors should use `EmptyStep` to signal "no parent" in `getParent()` method. All the `getParent()` callers expect `EmptyStep`. Can we document that return value of `getParent()` must not be null and avoid adding a null check here?
   
   Maybe we could do that in a separate ticket.

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