[TINKERPOP-2927] Relax steps extensibility strictness

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/BranchStep.java

@@ -52,8 +52,8 @@ public class BranchStep<S, E, M> extends ComputerAwareStep<S, E> implements Trav
     protected Map<Pick, List<Traversal.Admin<S, E>>> traversalPickOptions = new HashMap<>();
     protected List<Pair<Traversal.Admin<M, ?>, Traversal.Admin<S, E>>> traversalOptions = new ArrayList<>();
 
-    private boolean first = true;
-    private boolean hasBarrier;
+    protected boolean first = true;
+    protected boolean hasBarrier;
 
     public BranchStep(final Traversal.Admin traversal) {
         super(traversal);
@@ -142,7 +142,7 @@ protected Iterator<Traverser.Admin<E>> standardAlgorithm() {
     /**
      * Choose the right traversal option to apply and seed those options with this traverser.
      */
-    private void applyCurrentTraverser(final Traverser.Admin<S> start) {
+    protected void applyCurrentTraverser(final Traverser.Admin<S> start) {
         // first get the value of the choice based on the current traverser and use that to select the right traversal
         // option to which that traverser should be routed
         final M choice = TraversalUtil.apply(start, this.branchTraversal);
@@ -188,7 +188,7 @@ protected Iterator<Traverser.Admin<E>> computerAlgorithm() {
         return ends.iterator();
     }
 
-    private List<Traversal.Admin<S, E>> pickBranches(final M choice) {
+    protected List<Traversal.Admin<S, E>> pickBranches(final M choice) {
         final List<Traversal.Admin<S, E>> branches = new ArrayList<>();
         if (choice instanceof Pick) {
             if (this.traversalPickOptions.containsKey(choice)) {
@@ -259,4 +259,24 @@ public void reset() {
         this.getGlobalChildren().forEach(Traversal.Admin::reset);
         this.first = true;
     }
+
+    public Traversal.Admin<S, M> getBranchTraversal() {
+        return branchTraversal;
+    }
+
+    public Map<Pick, List<Traversal.Admin<S, E>>> getTraversalPickOptions() {
+        return traversalPickOptions;
+    }
+
+    public List<Pair<Traversal.Admin<M, ?>, Traversal.Admin<S, E>>> getTraversalOptions() {
+        return traversalOptions;
+    }
+
+    public boolean isFirst() {
+        return first;
+    }
+
+    public boolean isHasBarrier() {
+        return hasBarrier;
+    }
 }

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/ChooseStep.java

@@ -28,7 +28,7 @@
  * @author Joshua Shinavier (http://fortytwo.net)
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class ChooseStep<S, E, M> extends BranchStep<S, E, M> {
+public class ChooseStep<S, E, M> extends BranchStep<S, E, M> {
 
     public ChooseStep(final Traversal.Admin traversal, final Traversal.Admin<S, M> choiceTraversal) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/LocalStep.java

@@ -34,10 +34,10 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class LocalStep<S, E> extends AbstractStep<S, E> implements TraversalParent {
+public class LocalStep<S, E> extends AbstractStep<S, E> implements TraversalParent {
 
-    private Traversal.Admin<S, E> localTraversal;
-    private boolean first = true;
+    protected Traversal.Admin<S, E> localTraversal;
+    protected boolean first = true;
 
     public LocalStep(final Traversal.Admin traversal, final Traversal.Admin<S, E> localTraversal) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/OptionalStep.java

@@ -34,9 +34,9 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class OptionalStep<S> extends AbstractStep<S, S> implements TraversalParent {
+public class OptionalStep<S> extends AbstractStep<S, S> implements TraversalParent {
 
-    private Traversal.Admin<S, S> optionalTraversal;
+    protected Traversal.Admin<S, S> optionalTraversal;
 
     public OptionalStep(final Traversal.Admin traversal, final Traversal.Admin<S, S> optionalTraversal) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/RepeatStep.java

@@ -38,12 +38,12 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class RepeatStep<S> extends ComputerAwareStep<S, S> implements TraversalParent {
+public class RepeatStep<S> extends ComputerAwareStep<S, S> implements TraversalParent {
 
-    private Traversal.Admin<S, S> repeatTraversal = null;
-    private Traversal.Admin<S, ?> untilTraversal = null;
-    private Traversal.Admin<S, ?> emitTraversal = null;
-    private String loopName = null;
+    protected Traversal.Admin<S, S> repeatTraversal = null;
+    protected Traversal.Admin<S, ?> untilTraversal = null;
+    protected Traversal.Admin<S, ?> emitTraversal = null;
+    protected String loopName = null;
     public boolean untilFirst = false;
     public boolean emitFirst = false;
 
@@ -113,11 +113,11 @@ public List<Traversal.Admin<S, S>> getGlobalChildren() {
         return list;
     }
 
-    public final boolean doUntil(final Traverser.Admin<S> traverser, boolean utilFirst) {
+    public boolean doUntil(final Traverser.Admin<S> traverser, boolean utilFirst) {
         return utilFirst == this.untilFirst && null != this.untilTraversal && TraversalUtil.test(traverser, this.untilTraversal);
     }
 
-    public final boolean doEmit(final Traverser.Admin<S> traverser, boolean emitFirst) {
+    public boolean doEmit(final Traverser.Admin<S> traverser, boolean emitFirst) {
         return emitFirst == this.emitFirst && null != this.emitTraversal && TraversalUtil.test(traverser, this.emitTraversal);
     }
 
@@ -144,11 +144,11 @@ public void reset() {
             this.repeatTraversal.reset();
     }
 
-    private final String untilString() {
+    protected String untilString() {
         return null == this.untilTraversal ? "until(false)" : "until(" + this.untilTraversal + ')';
     }
 
-    private final String emitString() {
+    protected String emitString() {
         return null == this.emitTraversal ? "emit(false)" : "emit(" + this.emitTraversal + ')';
     }
 

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/branch/UnionStep.java

@@ -28,7 +28,7 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class UnionStep<S, E> extends BranchStep<S, E, Pick> {
+public class UnionStep<S, E> extends BranchStep<S, E, Pick> {
 
     public UnionStep(final Traversal.Admin traversal, final Traversal.Admin<?, E>... unionTraversals) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/AndStep.java

@@ -26,7 +26,7 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class AndStep<S> extends ConnectiveStep<S> {
+public class AndStep<S> extends ConnectiveStep<S> {
 
     public AndStep(final Traversal.Admin traversal, final Traversal<S, ?>... traversals) {
         super(traversal, traversals);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/ClassFilterStep.java

@@ -26,10 +26,10 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class ClassFilterStep<S, T> extends FilterStep<S> {
+public class ClassFilterStep<S, T> extends FilterStep<S> {
 
-    private final Class<T> classFilter;
-    private final boolean allowClasses;
+    protected final Class<T> classFilter;
+    protected final boolean allowClasses;
 
     public ClassFilterStep(final Traversal.Admin traversal, final Class<T> classFilter, final boolean allowClasses) {
         super(traversal);
@@ -48,4 +48,12 @@ public int hashCode() {
     public String toString() {
         return StringFactory.stepString(this, this.classFilter.getSimpleName());
     }
+
+    public Class<T> getClassFilter() {
+        return classFilter;
+    }
+
+    public boolean isAllowClasses() {
+        return allowClasses;
+    }
 }

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/CoinStep.java

@@ -31,10 +31,10 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class CoinStep<S> extends FilterStep<S> implements Seedable {
+public class CoinStep<S> extends FilterStep<S> implements Seedable {
 
-    private final Random random = new Random();
-    private final double probability;
+    protected final Random random = new Random();
+    protected final double probability;
 
     public CoinStep(final Traversal.Admin traversal, final double probability) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/DedupGlobalStep.java

@@ -53,16 +53,16 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class DedupGlobalStep<S> extends FilterStep<S> implements TraversalParent, Scoping, GraphComputing, Barrier<Map<Object, Traverser.Admin<S>>>, ByModulating, PathProcessor {
-
-    private Traversal.Admin<S, Object> dedupTraversal = null;
-    private Set<Object> duplicateSet = new HashSet<>();
-    private boolean onGraphComputer = false;
-    private final Set<String> dedupLabels;
-    private Set<String> keepLabels;
-    private boolean executingAtMaster = false;
-    private Map<Object, Traverser.Admin<S>> barrier;
-    private Iterator<Map.Entry<Object, Traverser.Admin<S>>> barrierIterator;
+public class DedupGlobalStep<S> extends FilterStep<S> implements TraversalParent, Scoping, GraphComputing, Barrier<Map<Object, Traverser.Admin<S>>>, ByModulating, PathProcessor {
+
+    protected Traversal.Admin<S, Object> dedupTraversal = null;
+    protected Set<Object> duplicateSet = new HashSet<>();
+    protected boolean onGraphComputer = false;
+    protected final Set<String> dedupLabels;
+    protected Set<String> keepLabels;
+    protected boolean executingAtMaster = false;
+    protected Map<Object, Traverser.Admin<S>> barrier;
+    protected Iterator<Map.Entry<Object, Traverser.Admin<S>>> barrierIterator;
 
     public DedupGlobalStep(final Traversal.Admin traversal, final String... dedupLabels) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/DropStep.java

@@ -39,7 +39,7 @@
  */
 public class DropStep<S> extends FilterStep<S> implements Mutating<Event> {
 
-    private CallbackRegistry<Event> callbackRegistry;
+    protected CallbackRegistry<Event> callbackRegistry;
 
     public DropStep(final Traversal.Admin traversal) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/HasStep.java

@@ -40,8 +40,8 @@
  */
 public class HasStep<S extends Element> extends FilterStep<S> implements HasContainerHolder, Configuring {
 
-    private final Parameters parameters = new Parameters();
-    private List<HasContainer> hasContainers;
+    protected Parameters parameters = new Parameters();
+    protected List<HasContainer> hasContainers;
 
     public HasStep(final Traversal.Admin traversal, final HasContainer... hasContainers) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/IsStep.java

@@ -31,9 +31,9 @@
  * @author Daniel Kuppitz (http://gremlin.guru)
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class IsStep<S> extends FilterStep<S> {
+public class IsStep<S> extends FilterStep<S> {
 
-    private P<S> predicate;
+    protected P<S> predicate;
 
     public IsStep(final Traversal.Admin traversal, final P<S> predicate) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/LambdaFilterStep.java

@@ -28,9 +28,9 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class LambdaFilterStep<S> extends FilterStep<S> implements LambdaHolder {
+public class LambdaFilterStep<S> extends FilterStep<S> implements LambdaHolder {
 
-    private final Predicate<Traverser<S>> predicate;
+    protected final Predicate<Traverser<S>> predicate;
 
     public LambdaFilterStep(final Traversal.Admin traversal, final Predicate<Traverser<S>> predicate) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/NoneStep.java

@@ -26,7 +26,7 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class NoneStep<S> extends FilterStep<S> {
+public class NoneStep<S> extends FilterStep<S> {
 
     public NoneStep(final Traversal.Admin traversal) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/NotStep.java

@@ -32,9 +32,9 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class NotStep<S> extends FilterStep<S> implements TraversalParent{
+public class NotStep<S> extends FilterStep<S> implements TraversalParent{
 
-    private Traversal.Admin<S, ?> notTraversal;
+    protected Traversal.Admin<S, ?> notTraversal;
 
     public NotStep(final Traversal.Admin traversal, final Traversal<S, ?> notTraversal) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/OrStep.java

@@ -26,7 +26,7 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class OrStep<S> extends ConnectiveStep<S> {
+public class OrStep<S> extends ConnectiveStep<S> {
 
     public OrStep(final Traversal.Admin traversal, final Traversal<S, ?>... traversals) {
         super(traversal, traversals);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/PathFilterStep.java

@@ -41,13 +41,13 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class PathFilterStep<S> extends FilterStep<S> implements FromToModulating, ByModulating, TraversalParent, PathProcessor {
+public class PathFilterStep<S> extends FilterStep<S> implements FromToModulating, ByModulating, TraversalParent, PathProcessor {
 
     protected String fromLabel;
     protected String toLabel;
-    private boolean isSimple;
-    private TraversalRing<Object, Object> traversalRing;
-    private Set<String> keepLabels;
+    protected boolean isSimple;
+    protected TraversalRing<Object, Object> traversalRing;
+    protected Set<String> keepLabels;
 
     public PathFilterStep(final Traversal.Admin traversal, final boolean isSimple) {
         super(traversal);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/RangeGlobalStep.java

@@ -42,12 +42,12 @@
  * @author Bob Briody (http://bobbriody.com)
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class RangeGlobalStep<S> extends FilterStep<S> implements Ranging, Bypassing, Barrier<TraverserSet<S>> {
+public class RangeGlobalStep<S> extends FilterStep<S> implements Ranging, Bypassing, Barrier<TraverserSet<S>> {
 
-    private long low;
-    private final long high;
-    private AtomicLong counter = new AtomicLong(0l);
-    private boolean bypass;
+    protected long low;
+    protected final long high;
+    protected AtomicLong counter = new AtomicLong(0l);
+    protected boolean bypass;
 
     public RangeGlobalStep(final Traversal.Admin traversal, final long low, final long high) {
         super(traversal);
@@ -200,4 +200,20 @@ public TraverserSet<S> apply(final TraverserSet<S> mutatingSeed, final Traverser
             return mutatingSeed;
         }
     }
+
+    public long getLow() {
+        return low;
+    }
+
+    public long getHigh() {
+        return high;
+    }
+
+    public AtomicLong getCounter() {
+        return counter;
+    }
+
+    public boolean isBypass() {
+        return bypass;
+    }
 }

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/filter/SampleGlobalStep.java

@@ -41,11 +41,11 @@
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
-public final class SampleGlobalStep<S> extends CollectingBarrierStep<S> implements TraversalParent, ByModulating, Seedable {
+public class SampleGlobalStep<S> extends CollectingBarrierStep<S> implements TraversalParent, ByModulating, Seedable {
 
-    private Traversal.Admin<S, Number> probabilityTraversal = new ConstantTraversal<>(1.0d);
-    private final int amountToSample;
-    private final Random random = new Random();
+    protected Traversal.Admin<S, Number> probabilityTraversal = new ConstantTraversal<>(1.0d);
+    protected final int amountToSample;
+    protected final Random random = new Random();
 
     public SampleGlobalStep(final Traversal.Admin traversal, final int amountToSample) {
         super(traversal);
@@ -126,7 +126,7 @@ public void barrierConsumer(final TraverserSet<S> traverserSet) {
     }
 
 
-    private Optional<ProjectedTraverser<S, Number>> createProjectedTraverser(final Traverser.Admin<S> traverser) {
+    protected Optional<ProjectedTraverser<S, Number>> createProjectedTraverser(final Traverser.Admin<S> traverser) {
         final TraversalProduct product = TraversalUtil.produce(traverser, this.probabilityTraversal);
         if (product.isProductive()) {
             final Object o = product.get();