Brought back some changes from gvalue branch bound to master

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Operator.java

@@ -186,7 +186,7 @@ public Object apply(final Object a, final Object b) {
 
             if (a instanceof Map && b instanceof Map)
                 ((Map<?,?>) a).putAll((Map) b);
-            else if (a instanceof Collection && a instanceof Collection)
+            else if (a instanceof Collection && b instanceof Collection)
                 ((Collection<?>) a).addAll((Collection) b);
             else
                 throw new IllegalArgumentException(String.format("Objects must be both of Map or Collection: a=%s b=%s",

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/P.java

@@ -25,7 +25,9 @@
 import java.io.Serializable;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.List;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 /**
  * Predefined {@code Predicate} values that can be used to define filters to {@code has()} and {@code where()}.
@@ -75,10 +77,22 @@ public void setValue(final V value) {
 
     @Override
     public boolean test(final V testValue) {
-        if (this.value instanceof GValue)
+        if (this.value instanceof GValue) {
             return this.biPredicate.test(testValue, ((GValue<V>) this.value).get());
-        else
-            return this.biPredicate.test(testValue, this.value);
+        } else {
+            // this might be a bunch of GValue that need to be resolved. zomg
+            if (this.value instanceof List) {
+                return this.biPredicate.test(testValue, (V) ((List) this.value).stream().map(o -> {
+                    if (o instanceof GValue) {
+                        return ((GValue) o).get();
+                    } else {
+                        return o;
+                    }
+                }).collect(Collectors.toList()));
+            } else {
+                return this.biPredicate.test(testValue, this.value);
+            }
+        }
     }
 
     @Override

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/dsl/graph/GraphTraversal.java

@@ -458,6 +458,30 @@ public default GraphTraversal<S, E> hasLabel(final Object label, final Object...
             return TraversalHelper.addHasContainer(this.asAdmin(), new HasContainer(T.label.getAccessor(), labels.length == 1 ? P.eq(labels[0]) : P.within(labels)));
         }
 
+        /**
+         * This is a step modulator to a {@link TraversalOptionParent} like {@code choose()} or {@code mergeV()} where the
+         * provided argument associated to the {@code token} is applied according to the semantics of the step. Please see
+         * the documentation of such steps to understand the usage context.
+         *
+         * @param token       the token that would trigger this option which may be a {@link Pick}, {@link Merge},
+         *                    a {@link Traversal}, {@link Predicate}, or object depending on the step being modulated.
+         * @param traversalOption the option as a traversal
+         * @return the traversal with the modulated step
+         * @see <a href="http://tinkerpop.apache.org/docs/${project.version}/reference/#choose-step" target="_blank">Reference Documentation - Choose Step</a>
+         * @see <a href="http://tinkerpop.apache.org/docs/${project.version}/reference/#mergev-step" target="_blank">Reference Documentation - MergeV Step</a>
+         * @see <a href="http://tinkerpop.apache.org/docs/${project.version}/reference/#mergee-step" target="_blank">Reference Documentation - MergeE Step</a>
+         * @since 3.0.0-incubating
+         */
+        public default <M, E2> GraphTraversal<S, E> option(final GValue<M> token, final Traversal<?, E2> traversalOption) {
+            this.asAdmin().getBytecode().addStep(GraphTraversal.Symbols.option, token, traversalOption);
+
+            // handle null similar to how option() with Map handles it, otherwise we get a NPE if this one gets used
+            final Traversal.Admin<E,E2> t = null == traversalOption ?
+                    new ConstantTraversal<>(null) : (Traversal.Admin<E, E2>) traversalOption.asAdmin();
+            ((TraversalOptionParent<M, E, E2>) this.asAdmin().getEndStep()).addChildOption(token.get(), t);
+            return this;
+        }
+
         /**
          * This is a step modulator to a {@link TraversalOptionParent} like {@code choose()} or {@code mergeV()} where the
          * provided argument associated to the {@code token} is applied according to the semantics of the step. Please see
@@ -501,6 +525,46 @@ public default <M, E2> GraphTraversal<S, E> option(final Merge merge, final GVal
             return this;
         }
 
+        /**
+         * When used as a modifier to {@link #addE(String)} this method specifies the traversal to use for selecting the
+         * incoming vertex of the newly added {@link Edge}.
+         *
+         * @param toVertex the vertex for selecting the incoming vertex
+         * @return the traversal with the modified {@link AddEdgeStep}
+         * @see <a href="http://tinkerpop.apache.org/docs/${project.version}/reference/#addedge-step" target="_blank">Reference Documentation - From Step</a>
+         * @since 4.0.0
+         */
+        public default GraphTraversal<S, E> to(final GValue<Vertex> toVertex) {
+            final Step<?,?> prev = this.asAdmin().getEndStep();
+            if (!(prev instanceof FromToModulating))
+                throw new IllegalArgumentException(String.format(
+                        "The to() step cannot follow %s", prev.getClass().getSimpleName()));
+
+            this.asAdmin().getBytecode().addStep(GraphTraversal.Symbols.to, toVertex);
+            ((FromToModulating) prev).addTo(__.constant(toVertex).asAdmin());
+            return this;
+        }
+
+        /**
+         * When used as a modifier to {@link #addE(String)} this method specifies the traversal to use for selecting the
+         * outgoing vertex of the newly added {@link Edge}.
+         *
+         * @param fromVertex the vertex for selecting the outgoing vertex
+         * @return the traversal with the modified {@link AddEdgeStep}
+         * @see <a href="http://tinkerpop.apache.org/docs/${project.version}/reference/#addedge-step" target="_blank">Reference Documentation - From Step</a>
+         * @since 4.0.0
+         */
+        public default GraphTraversal<S, E> from(final GValue<Vertex> fromVertex) {
+            final Step<?,?> prev = this.asAdmin().getEndStep();
+            if (!(prev instanceof FromToModulating))
+                throw new IllegalArgumentException(String.format(
+                        "The from() step cannot follow %s", prev.getClass().getSimpleName()));
+
+            this.asAdmin().getBytecode().addStep(GraphTraversal.Symbols.from, fromVertex);
+            ((FromToModulating) prev).addFrom(__.constant(fromVertex).asAdmin());
+            return this;
+        }
+
         @Override
         public default <E2> GraphTraversal.Admin<S, E2> addStep(final Step<?, E2> step) {
             return (GraphTraversal.Admin<S, E2>) Traversal.Admin.super.addStep((Step) step);

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/dsl/graph/GraphTraversalSource.java

@@ -27,6 +27,7 @@
 import org.apache.tinkerpop.gremlin.process.traversal.TraversalSource;
 import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategies;
 import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategy;
+import org.apache.tinkerpop.gremlin.process.traversal.step.GValue;
 import org.apache.tinkerpop.gremlin.process.traversal.step.branch.UnionStep;
 import org.apache.tinkerpop.gremlin.process.traversal.step.map.AddEdgeStartStep;
 import org.apache.tinkerpop.gremlin.process.traversal.step.map.AddVertexStartStep;
@@ -68,6 +69,7 @@ public class GraphTraversalSource implements TraversalSource {
     protected final Graph graph;
     protected TraversalStrategies strategies;
     protected Bytecode bytecode = new Bytecode();
+    protected Admin admin;
 
     ////////////////
 
@@ -100,6 +102,12 @@ public GraphTraversalSource(final RemoteConnection connection) {
         this.strategies.addStrategies(new RemoteStrategy(connection));
     }
 
+    public GraphTraversalSource.Admin asAdmin() {
+        if (null == this.admin)
+            this.admin = new Admin();
+        return this.admin;
+    }
+
     @Override
     public Optional<Class<?>> getAnonymousTraversalClass() {
         return Optional.of(__.class);
@@ -624,4 +632,39 @@ public String toString() {
         return StringFactory.traversalSourceString(this);
     }
 
+    /**
+     * This class masks spawn steps that are more reserved for advanced usage.
+     */
+    public class Admin {
+
+        /**
+         * Spawns a {@link GraphTraversal} by doing a merge (i.e. upsert) style operation for an {@link Vertex} using a
+         * {@code Map} as an argument. The {@code Map} represents search criteria and will match each of the supplied
+         * key/value pairs where the keys may be {@code String} property values or a value of {@link T}. If a match is not
+         * made it will use that search criteria to create the new {@link Vertex}.
+         *
+         * @param searchCreate This {@code Map} can have a key of {@link T} or a {@code String}.
+         * @since 4.0.0
+         */
+        public GraphTraversal<Vertex, Vertex> mergeV(final GValue<Map<Object, Object>> searchCreate) {
+            final GraphTraversalSource clone = GraphTraversalSource.this.clone();
+            clone.bytecode.addStep(GraphTraversal.Symbols.mergeV, searchCreate);
+            final GraphTraversal.Admin<Vertex, Vertex> traversal = new DefaultGraphTraversal<>(clone);
+            return traversal.addStep(new MergeVertexStep(traversal, true, searchCreate));
+        }
+
+        /**
+         * Spawns a {@link GraphTraversal} by doing a merge (i.e. upsert) style operation for an {@link Edge} using a
+         * {@code Map} as an argument.
+         *
+         * @param searchCreate This {@code Map} can have a key of {@link T} {@link Direction} or a {@code String}.
+         * @since 4.0.0
+         */
+        public GraphTraversal<Edge, Edge> mergeE(final GValue<Map<?, Object>> searchCreate) {
+            final GraphTraversalSource clone = GraphTraversalSource.this.clone();
+            clone.bytecode.addStep(GraphTraversal.Symbols.mergeE, searchCreate);
+            final GraphTraversal.Admin<Edge, Edge> traversal = new DefaultGraphTraversal<>(clone);
+            return traversal.addStep(new MergeEdgeStep(traversal, true, searchCreate));
+        }
+    }
 }

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

@@ -52,12 +52,26 @@ public enum GType {
     GType() {}
 
     /**
-     * Returns true if the type is a number.
+     * Returns {@code true} if the type is a number.
      */
     public boolean isNumeric() {
         return this == INTEGER || this == DOUBLE || this == LONG || this == BIG_INTEGER || this == BIG_DECIMAL;
     }
 
+    /**
+     * Returns {@code true} if the type is a collection.v
+     */
+    public boolean isCollection() {
+        return this == LIST || this == SET;
+    }
+
+    /**
+     * Returns {@code true} if the type is an element.
+     */
+    public boolean isElement() {
+        return this == VERTEX || this == EDGE;
+    }
+
     /**
      * Convert an object to a matching {@link GType} and if not matched return {@link GType#UNKNOWN}.
      */
@@ -78,4 +92,4 @@ public static GType getType(final Object object) {
         else if (object instanceof BigDecimal) return BIG_DECIMAL;
         else return UNKNOWN;
     }
-}
+}

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

@@ -66,8 +66,8 @@ public boolean isVariable() {
     /**
      * Gets the name of the variable if it was defined as such and returns empty if the value was a literal.
      */
-    public Optional<String> getName() {
-        return Optional.ofNullable(this.name);
+    public String getName() {
+        return this.name;
     }
 
     /**
@@ -79,6 +79,13 @@ public GType getType() {
         return this.type;
     }
 
+    /**
+     * Determines if the value held is of a {@code null} value.
+     */
+    public boolean isNull() {
+        return this.value == null;
+    }
+
     /**
      * Gets the value.
      */
@@ -96,7 +103,7 @@ public String toString() {
     public boolean equals(final Object o) {
         if (this == o) return true;
         if (o == null || getClass() != o.getClass()) return false;
-        GValue<?> gValue = (GValue<?>) o;
+        final GValue<?> gValue = (GValue<?>) o;
         return Objects.equals(name, gValue.name) && type == gValue.type && Objects.equals(value, gValue.value);
     }
 
@@ -123,6 +130,7 @@ public static <V> GValue<V> of(final V value) {
     public static <V> GValue<V> of(final String name, final V value) {
         return new GValue<>(name, GType.getType(value), value);
     }
+
     /**
      * Create a new {@code GValue} for a string value.
      */
@@ -238,14 +246,14 @@ public static GValue<Map> ofMap(final String name, final Map value) {
     /**
      * Create a new {@code GValue} for a list value.
      */
-    public static GValue<List> ofList(final List value) {
+    public static <T> GValue<List<T>> ofList(final List<T> value) {
         return new GValue<>(GType.LIST, value);
     }
 
     /**
      * Create a new {@code GValue} for a list value with a specified name.
      */
-    public static GValue<List> ofList(final String name, final List value) {
+    public static <T> GValue<List<T>> ofList(final String name, final List<T> value) {
         return new GValue<>(name, GType.LIST, value);
     }
 
@@ -318,4 +326,4 @@ public static GValue<Property> ofProperty(final Property value) {
     public static GValue<Property> ofProperty(final String name, final Property value) {
         return new GValue<>(name, GType.PROPERTY, value);
     }
-}
+}

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/sideEffect/InjectStep.java

@@ -19,36 +19,40 @@
 package org.apache.tinkerpop.gremlin.process.traversal.step.sideEffect;
 
 import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
+import org.apache.tinkerpop.gremlin.process.traversal.step.GValue;
 import org.apache.tinkerpop.gremlin.util.iterator.ArrayIterator;
 
 /**
  * @author Marko A. Rodriguez (http://markorodriguez.com)
  */
 public final class InjectStep<S> extends StartStep<S> {
 
-    private final S[] injections;
+    private final GValue<S>[] injections;
 
     @SafeVarargs
     public InjectStep(final Traversal.Admin traversal, final S... injections) {
         super(traversal);
-        this.injections = injections;
-        this.start = new ArrayIterator<>(this.injections);
+        this.injections = convertToGValues(injections);
+        this.start = new ArrayIterator<>(resolveToValues(this.injections));
     }
 
     @Override
     public InjectStep<S> clone() {
         final InjectStep<S> clone = (InjectStep<S>) super.clone();
-        clone.start = new ArrayIterator<>(clone.injections);
+        clone.start = new ArrayIterator<>(resolveToValues(clone.injections));
         return clone;
     }
 
     @Override
     public void reset() {
         super.reset();
-        this.start = new ArrayIterator<>(this.injections);
+        this.start = new ArrayIterator<>(resolveToValues(this.injections));
     }
 
-    public S[] getInjections() {
+    /**
+     * Get the injections of the step.
+     */
+    public GValue<S>[] getInjections() {
         return this.injections;
     }
-}
+}