TINKERPOP-3083 Change split to parse a string into individual characters if the separator is an empty string

CHANGELOG.asciidoc

@@ -44,6 +44,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 * Made `new` keyword optional in the Gremlin grammar.
 * Added TypeScript & ECMAScript module support.
 * Improved graph structures type definitions in TypeScript.
+* Modified the `split()` step to split a string into a list of its characters if the given separator is an empty string.
 
 == TinkerPop 3.7.0 (Gremfir Master of the Pan Flute)
 

docs/src/dev/provider/gremlin-semantics.asciidoc

@@ -1517,7 +1517,7 @@ link:https://tinkerpop.apache.org/docs/x.y.z/reference/#rTrim-step[reference]
 *Arguments:*
 
 * `separator` - The string character(s) used as delimiter to split the input string. Nullable, a null separator will split on
-whitespaces.
+whitespaces. An empty string separator will split on each character.
 * `scope` - Determines the type of traverser it operates on. Both scopes will operate on the level of individual traversers.
 The `global` scope will operate on individual string traverser. The `local` scope will operate on list traverser with string elements inside.
 

docs/src/reference/the-traversal.asciidoc

@@ -4455,21 +4455,23 @@ link:++https://tinkerpop.apache.org/javadocs/x.y.z/core/org/apache/tinkerpop/gre
 [[split-step]]
 === Split Step
 The `split()`-step (*map*) returns a list of strings created by splitting the incoming string traverser around the
-matches of the given separator. A null separator will split the string by whitespaces. Null values from the incoming
-traversers are not processed and remain as null when returned. If the incoming traverser is a non-String value then an
+matches of the given separator. A null separator will split the string by whitespaces. An empty string separator will split on each character.
+Null values from the incoming traversers are not processed and remain as null when returned. If the incoming traverser is a non-String value then an
 IllegalArgumentException will be thrown.
 
 [gremlin-groovy,modern]
 ----
 g.inject("that", "this", "test", null).split("h") <1>
 g.V().hasLabel("person").values("name").split("a") <2>
 g.inject("helloworld", "hello world", "hello   world").split(null) <3>
-g.V().hasLabel("person").values("name").fold().split(local, "a") <4>
+g.inject("hello", "world", null).split("") <4>
+g.V().hasLabel("person").values("name").fold().split(local, "a") <5>
 ----
 <1> Split the strings by "h".
 <2> Split person names by "a".
 <3> Splitting by null will split by whitespaces.
-<4> Use `Scope.local` to operate on individual string elements inside incoming list, which will return a list of results.
+<4> Splitting by "" will split by each character.
+<5> Use `Scope.local` to operate on individual string elements inside incoming list, which will return a list of results.
 
 *Additional References*
 link:++https://tinkerpop.apache.org/javadocs/x.y.z/core/org/apache/tinkerpop/gremlin/process/traversal/dsl/graph/GraphTraversal.html#split(java.lang.String)++[`split(String)`]

docs/src/upgrade/release-4.x.x.asciidoc

@@ -77,7 +77,7 @@ these were deserialized into arrays.
 
 ==== Gremlin Grammar Changes
 
-A number of changes have been introduce to the Gremlin grammar to help make it be more consistent and easier to use.
+A number of changes have been introduced to the Gremlin grammar to help make it be more consistent and easier to use.
 
 *`new` keyword is now optional*
 
@@ -113,6 +113,20 @@ The `none()` step, which was primarily used by `iterate()` to discard traversal
 renamed to `discard()`. In its place is a new list filtering step `none()`, which takes a predicate as an argument and
 passes lists with no elements matching the predicate.
 
+==== Splitting a string into characters using split()
+The `split()` step will now split a string into a list of its characters if the given separator is an empty string.
+[source,groovy]
+----
+// previous implementation
+g.inject("Hello").split("")
+==>[Hello]
+
+// new implementation
+g.inject("Hello").split("")
+==>[H,e,l,l,o]
+----
+See: link:https://issues.apache.org/jira/browse/TINKERPOP-3083[TINKERPOP-3083]
+
 ==== Improved handling of integer overflows
 
 Integer overflows caused by addition and multiplication operations will throw an exception instead of being silently

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

@@ -18,15 +18,13 @@
  */
 package org.apache.tinkerpop.gremlin.process.traversal.step.map;
 
-import org.apache.commons.lang3.StringUtils;
 import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
 import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
 import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
 import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
+import org.apache.tinkerpop.gremlin.util.StringUtil;
 
-import java.util.Arrays;
 import java.util.Collections;
-import java.util.List;
 import java.util.Set;
 
 /**
@@ -57,7 +55,7 @@ protected E map(final Traverser.Admin<S> traverser) {
         }
 
         // we will pass null values to next step
-        return null == item? null : (E) Arrays.asList(StringUtils.splitByWholeSeparator((String) item, this.separator));
+        return null == item? null : (E) StringUtil.split((String)item, this.separator);
     }
 
     public String getSeparator() {
@@ -75,4 +73,5 @@ public int hashCode() {
         result = 31 * result + (null != this.separator ? this.separator.hashCode() : 0);
         return result;
     }
+
 }

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

@@ -18,17 +18,10 @@
  */
 package org.apache.tinkerpop.gremlin.process.traversal.step.map;
 
-import org.apache.commons.lang3.StringUtils;
 import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
-import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
 import org.apache.tinkerpop.gremlin.process.traversal.step.TraversalParent;
 import org.apache.tinkerpop.gremlin.process.traversal.step.util.StringLocalStep;
-import org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
-
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.Set;
+import org.apache.tinkerpop.gremlin.util.StringUtil;
 
 /**
  * Reference implementation for substring step, a mid-traversal step which returns a list of strings created by
@@ -50,7 +43,7 @@ public SplitLocalStep(final Traversal.Admin traversal, final String separator) {
 
     @Override
     protected E applyStringOperation(String item) {
-        return (E) Arrays.asList((StringUtils.splitByWholeSeparator(item, this.separator)));
+        return (E) StringUtil.split(item, this.separator);
     }
 
     @Override

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/util/StringUtil.java

@@ -0,0 +1,53 @@
+/*
+ * 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.util;
+
+import java.util.Arrays;
+import java.util.List;
+import org.apache.commons.lang3.StringUtils;
+
+/**
+ * Utility class for Strings.
+ *
+ * @author Andrea Child
+ */
+public final class StringUtil {
+
+    private StringUtil() {
+    }
+
+    /**
+     * Splits the provided string into a List of string by the given separator, which will not be included in the returned List.
+     *
+     * @param toSplit the string to split
+     * @param separator the separator string to split by - empty will split into a List of characters
+     * @return a List of parsed strings, not including the given separator
+     */
+    public static List<String> split(final String toSplit, final String separator) {
+        if (toSplit == null) {
+            throw new IllegalArgumentException("toSplit cannot be null");
+        }
+        if (StringUtils.EMPTY.equals(separator)) {
+            // split into a list of character strings
+            // ie. "ab cd" -> ["a","b"," ","c","d"]
+            return Arrays.asList(toSplit.split(StringUtils.EMPTY));
+        }
+        return Arrays.asList(StringUtils.splitByWholeSeparator(toSplit, separator));
+    }
+}

gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/SplitGlobalStepTest.java

@@ -48,7 +48,7 @@ public void testReturnTypes() {
         assertArrayEquals(new String[]{"helloworld"}, __.__("helloworld").split(null).next().toArray());
         assertArrayEquals(new String[]{"hello", "world"}, __.__("hello world").split(null).next().toArray());
         assertArrayEquals(new String[]{"hello", "world"}, __.__("hello   world").split(null).next().toArray());
-        assertArrayEquals(new String[]{"hello", "world"}, __.__("hello world").split("").next().toArray());
+        assertArrayEquals(new String[]{"h","e","l","l","o"," ", "w","o","r","l","d"}, __.__("hello world").split("").next().toArray());
         assertArrayEquals(new String[]{"hello", "world"}, __.__("hello world").split(" ").next().toArray());
         assertArrayEquals(new String[]{"hello world"}, __.__("hello world").split("  ").next().toArray());
 

gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/SplitLocalStepTest.java

@@ -42,6 +42,7 @@ protected List<Traversal> getTraversals() {
     public void testReturnTypes() {
         assertArrayEquals(new String[]{"h", "llo"}, __.__("hello").split(Scope.local, "e").next().toArray());
         assertArrayEquals(new String[]{"ab", "bc"}, __.__("abc|abc").split(Scope.local, "c|a").next().toArray());
+        assertArrayEquals(new String[]{"t","e","s","t"}, __.__("test").split(Scope.local, "").next().toArray());
 
         List<List<String>> resList = new ArrayList<>();
         resList.add(Arrays.asList("helloworld"));

gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/util/StringUtilTest.java

@@ -0,0 +1,62 @@
+/*
+ * 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.util;
+
+import java.util.Arrays;
+import org.apache.tinkerpop.gremlin.AssertHelper;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Andrea Child
+ */
+public class StringUtilTest {
+
+    @Test
+    public void shouldBeUtilityClass() throws Exception {
+        AssertHelper.assertIsUtilityClass(StringUtil.class);
+    }
+
+    @Test
+    public void shouldSplitBySeparatorAndNotContainSeparator() {
+        assertEquals(Arrays.asList("h","llo"), StringUtil.split("hello", "e"));
+    }
+
+    @Test
+    public void shouldNotBeSplitIfSeparatorNotPresentInString() {
+        final String toSplit = "test";
+        assertEquals(Arrays.asList(toSplit), StringUtil.split(toSplit, "x"));
+    }
+
+    @Test
+    public void shouldSplitByCharacterIfSeparatorIsEmpty() {
+        assertEquals(Arrays.asList("t","e","s","t"," ","1","2","3"), StringUtil.split("test 123", ""));
+    }
+
+    @Test
+    public void shouldSplitByWhitespaceIfSeparatorIsNull() {
+        assertEquals(Arrays.asList("test","123"), StringUtil.split("test 123", null));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void shouldThrowIfStringToSplitIsNull() {
+        StringUtil.split(null, "test");
+    }
+}

gremlin-dotnet/test/Gremlin.Net.IntegrationTest/Gherkin/Gremlin.cs

@@ -1204,9 +1204,11 @@ private static IDictionary<string, List<Func<GraphTraversalSource, IDictionary<s
                {"g_V_hasXname_vadasX_shortestPath_distanceXweightX_maxDistanceX1_3X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().Has("name", "vadas").ShortestPath().With("~tinkerpop.shortestPath.distance", "weight").With("~tinkerpop.shortestPath.maxDistance", 1.3)}}, 
                {"g_injectXthat_this_testX_spiltXhX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject<object>("that", "this", "test", null).Split("h")}}, 
                {"g_injectXhello_worldX_spiltXnullX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject<object>("hello world").Split(null)}}, 
+               {"g_injectXthat_this_test_nullX_splitXemptyX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject<object>("that", "this", "test", null).Split("")}}, 
                {"g_injectXListXa_bXcX_splitXa_bX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject<object>(p["xx1"]).Split("a")}}, 
                {"g_V_hasLabelXpersonX_valueXnameX_splitXnullX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().HasLabel("person").Values<object>("name").Split(null)}}, 
                {"g_V_hasLabelXpersonX_valueXnameX_order_fold_splitXlocal_aX_unfold", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().HasLabel("person").Values<object>("name").Order().Fold().Split<object>(Scope.Local, "a").Unfold<object>()}}, 
+               {"g_V_hasLabelXpersonX_valueXnameX_order_fold_splitXlocal_emptyX_unfold", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().HasLabel("person").Values<object>("name").Order().Fold().Split<object>(Scope.Local, "").Unfold<object>()}}, 
                {"g_injectXthat_this_testX_substringX1_8X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject<object>("test", "hello world", null).Substring(1, 8)}}, 
                {"g_injectXListXa_bXcX_substringX1_2X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject<object>(p["xx1"]).Substring(1, 2)}}, 
                {"g_V_hasLabelXpersonX_valueXnameX_substringX2X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().HasLabel("software").Values<object>("name").Substring(2)}}, 

gremlin-go/driver/cucumber/gremlin.go

@@ -1175,9 +1175,11 @@ var translationMap = map[string][]func(g *gremlingo.GraphTraversalSource, p map[
     "g_V_hasXname_vadasX_shortestPath_distanceXweightX_maxDistanceX1_3X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().Has("name", "vadas").ShortestPath().With("~tinkerpop.shortestPath.distance", "weight").With("~tinkerpop.shortestPath.maxDistance", 1.3)}}, 
     "g_injectXthat_this_testX_spiltXhX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject("that", "this", "test", nil).Split("h")}}, 
     "g_injectXhello_worldX_spiltXnullX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject("hello world").Split(nil)}}, 
+    "g_injectXthat_this_test_nullX_splitXemptyX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject("that", "this", "test", nil).Split("")}}, 
     "g_injectXListXa_bXcX_splitXa_bX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Split("a")}}, 
     "g_V_hasLabelXpersonX_valueXnameX_splitXnullX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().HasLabel("person").Values("name").Split(nil)}}, 
     "g_V_hasLabelXpersonX_valueXnameX_order_fold_splitXlocal_aX_unfold": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().HasLabel("person").Values("name").Order().Fold().Split(gremlingo.Scope.Local, "a").Unfold()}}, 
+    "g_V_hasLabelXpersonX_valueXnameX_order_fold_splitXlocal_emptyX_unfold": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().HasLabel("person").Values("name").Order().Fold().Split(gremlingo.Scope.Local, "").Unfold()}}, 
     "g_injectXthat_this_testX_substringX1_8X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject("test", "hello world", nil).Substring(1, 8)}}, 
     "g_injectXListXa_bXcX_substringX1_2X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Substring(1, 2)}}, 
     "g_V_hasLabelXpersonX_valueXnameX_substringX2X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().HasLabel("software").Values("name").Substring(2)}}, 

gremlin-python/src/main/python/radish/gremlin.py

@@ -1178,9 +1178,11 @@
     'g_V_hasXname_vadasX_shortestPath_distanceXweightX_maxDistanceX1_3X': [(lambda g:g.V().has('name', 'vadas').shortest_path().with_('~tinkerpop.shortestPath.distance', 'weight').with_('~tinkerpop.shortestPath.maxDistance', 1.3))], 
     'g_injectXthat_this_testX_spiltXhX': [(lambda g:g.inject('that', 'this', 'test', None).split('h'))], 
     'g_injectXhello_worldX_spiltXnullX': [(lambda g:g.inject('hello world').split(None))], 
+    'g_injectXthat_this_test_nullX_splitXemptyX': [(lambda g:g.inject('that', 'this', 'test', None).split(''))], 
     'g_injectXListXa_bXcX_splitXa_bX': [(lambda g, xx1=None:g.inject(xx1).split('a'))], 
     'g_V_hasLabelXpersonX_valueXnameX_splitXnullX': [(lambda g:g.V().has_label('person').values('name').split(None))], 
     'g_V_hasLabelXpersonX_valueXnameX_order_fold_splitXlocal_aX_unfold': [(lambda g:g.V().has_label('person').values('name').order().fold().split(Scope.local, 'a').unfold())], 
+    'g_V_hasLabelXpersonX_valueXnameX_order_fold_splitXlocal_emptyX_unfold': [(lambda g:g.V().has_label('person').values('name').order().fold().split(Scope.local, '').unfold())], 
     'g_injectXthat_this_testX_substringX1_8X': [(lambda g:g.inject('test', 'hello world', None).substring(1, 8))], 
     'g_injectXListXa_bXcX_substringX1_2X': [(lambda g, xx1=None:g.inject(xx1).substring(1, 2))], 
     'g_V_hasLabelXpersonX_valueXnameX_substringX2X': [(lambda g:g.V().has_label('software').values('name').substring(2))],