Added feature test and docs

Author: GumpacG

CHANGELOG.asciidoc

@@ -36,6 +36,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 * Added `reuseConnectionsForSessions` to Java GLV settings to decide whether to use `SessionedChildClient` for remote transactions.
 * Added support for Node 22 and 24 alongside Node 20.
 * Fixed `cap()` step throwing an error when used mid-traversal in OLAP.
+* Fixed conjoin has incorrect null handling.
 
 [[release-3-7-5]]
 === TinkerPop 3.7.5 (Release Date: November 12, 2025)

docs/src/upgrade/release-3.7.x.asciidoc

@@ -59,6 +59,31 @@ See: link:https://issues.apache.org/jira/browse/TINKERPOP-3235[TINKERPOP-3235]
 
 Gremlin Javascript now supports Node 22 and 24 alongside Node 20.
 
+==== conjoin() Step Null Handling
+
+The `conjoin()` step previously returned `null` when elements in the incoming list are `null`. This behavior has
+been changed so that `conjoin()` now returns an empty string (`""`) in that case.
+
+[source,groovy]
+----
+// 3.7.5
+gremlin> g.inject([null]).conjoin("-")
+==>null
+gremlin> g.inject([null, null]).conjoin("-")
+==>null
+
+// 3.7.6
+gremlin> g.inject([null]).conjoin("+")
+==>
+gremlin> g.inject([null, null]).conjoin("+")
+==>
+----
+
+Code that checks the result of `conjoin()` for lists that include `null` elements should be updated to check for
+an empty string instead.
+
+See: link:https://issues.apache.org/jira/browse/TINKERPOP-3225[TINKERPOP-3225]
+
 === Upgrading for Providers
 
 ==== Graph System Providers

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

@@ -170,6 +170,7 @@ private static IDictionary<string, List<Func<GraphTraversalSource, IDictionary<s
                {"g_injectX7X_anyXeqX7XX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(7).Any(P.Eq(7))}}, 
                {"g_injectXnull_nullX_anyXeqXnullXX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(p["xx1"]).Any(P.Eq(null))}}, 
                {"g_injectX3_threeX_anyXeqX3XX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(p["xx1"]).Any(P.Eq(3))}}, 
+               {"g_V_coinX1_0X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().Coin(1.0)}}, 
                {"g_V_coinX1X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().Coin(1.0)}}, 
                {"g_V_coinX0X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().Coin(0.0)}}, 
                {"g_withStrategiesXSeedStrategyX_V_order_byXnameX_coinX50X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.WithStrategies(new SeedStrategy(seed: 999999)).V().Order().By("name").Coin(0.5)}}, 
@@ -632,6 +633,8 @@ private static IDictionary<string, List<Func<GraphTraversalSource, IDictionary<s
                {"g_V_out_out_path_byXnameX_conjoinXX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().Out().Out().Path().By("name").Conjoin("")}}, 
                {"g_injectXa_null_bX_conjoinXxyzX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(p["xx1"]).Conjoin("xyz")}}, 
                {"g_injectX3_threeX_conjoinX_X", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(p["xx1"]).Conjoin(";")}}, 
+               {"g_injectXnull_a_null_bX_fold_conjoinXplusX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(p["xx1"]).Conjoin("+")}}, 
+               {"g_injectXnull_nullX_conjoinXplusX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.Inject(p["xx1"]).Conjoin("+")}}, 
                {"g_V_connectedComponent_hasXcomponentX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().ConnectedComponent().Has("gremlin.connectedComponentVertexProgram.component")}}, 
                {"g_V_dedup_connectedComponent_hasXcomponentX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().Dedup().ConnectedComponent().Has("gremlin.connectedComponentVertexProgram.component")}}, 
                {"g_V_hasLabelXsoftwareX_connectedComponent_project_byXnameX_byXcomponentX", new List<Func<GraphTraversalSource, IDictionary<string, object>, ITraversal>> {(g,p) =>g.V().HasLabel("software").ConnectedComponent().Project<object>("name","component").By("name").By("gremlin.connectedComponentVertexProgram.component")}}, 

gremlin-go/driver/cucumber/gremlin.go

@@ -141,6 +141,7 @@ var translationMap = map[string][]func(g *gremlingo.GraphTraversalSource, p map[
     "g_injectX7X_anyXeqX7XX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(7).Any(gremlingo.P.Eq(7))}}, 
     "g_injectXnull_nullX_anyXeqXnullXX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Any(gremlingo.P.Eq(nil))}}, 
     "g_injectX3_threeX_anyXeqX3XX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Any(gremlingo.P.Eq(3))}}, 
+    "g_V_coinX1_0X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().Coin(1.0)}}, 
     "g_V_coinX1X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().Coin(1.0)}}, 
     "g_V_coinX0X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().Coin(0.0)}}, 
     "g_withStrategiesXSeedStrategyX_V_order_byXnameX_coinX50X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.WithStrategies(gremlingo.SeedStrategy(gremlingo.SeedStrategyConfig{Seed: 999999})).V().Order().By("name").Coin(0.5)}}, 
@@ -603,6 +604,8 @@ var translationMap = map[string][]func(g *gremlingo.GraphTraversalSource, p map[
     "g_V_out_out_path_byXnameX_conjoinXX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().Out().Out().Path().By("name").Conjoin("")}}, 
     "g_injectXa_null_bX_conjoinXxyzX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Conjoin("xyz")}}, 
     "g_injectX3_threeX_conjoinX_X": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Conjoin(";")}}, 
+    "g_injectXnull_a_null_bX_fold_conjoinXplusX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Conjoin("+")}}, 
+    "g_injectXnull_nullX_conjoinXplusX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.Inject(p["xx1"]).Conjoin("+")}}, 
     "g_V_connectedComponent_hasXcomponentX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().ConnectedComponent().Has("gremlin.connectedComponentVertexProgram.component")}}, 
     "g_V_dedup_connectedComponent_hasXcomponentX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().Dedup().ConnectedComponent().Has("gremlin.connectedComponentVertexProgram.component")}}, 
     "g_V_hasLabelXsoftwareX_connectedComponent_project_byXnameX_byXcomponentX": {func(g *gremlingo.GraphTraversalSource, p map[string]interface{}) *gremlingo.GraphTraversal {return g.V().HasLabel("software").ConnectedComponent().Project("name", "component").By("name").By("gremlin.connectedComponentVertexProgram.component")}}, 

gremlin-javascript/src/main/javascript/gremlin-javascript/test/cucumber/gremlin.js

@@ -143,6 +143,7 @@
     'g_injectX7X_anyXeqX7XX': [(lambda g:g.inject(7).any_(P.eq(7)))], 
     'g_injectXnull_nullX_anyXeqXnullXX': [(lambda g, xx1=None:g.inject(xx1).any_(P.eq(None)))], 
     'g_injectX3_threeX_anyXeqX3XX': [(lambda g, xx1=None:g.inject(xx1).any_(P.eq(3)))], 
+    'g_V_coinX1_0X': [(lambda g:g.V().coin(float(1.0)))], 
     'g_V_coinX1X': [(lambda g:g.V().coin(float(1.0)))], 
     'g_V_coinX0X': [(lambda g:g.V().coin(float(0.0)))], 
     'g_withStrategiesXSeedStrategyX_V_order_byXnameX_coinX50X': [(lambda g:g.with_strategies(*[TraversalStrategy('SeedStrategy',{'seed':999999,'strategy':'org.apache.tinkerpop.gremlin.process.traversal.strategy.decoration.SeedStrategy'}, 'org.apache.tinkerpop.gremlin.process.traversal.strategy.decoration.SeedStrategy')]).V().order().by('name').coin(float(0.5)))], 
@@ -605,6 +606,8 @@
     'g_V_out_out_path_byXnameX_conjoinXX': [(lambda g:g.V().out().out().path().by('name').conjoin(''))], 
     'g_injectXa_null_bX_conjoinXxyzX': [(lambda g, xx1=None:g.inject(xx1).conjoin('xyz'))], 
     'g_injectX3_threeX_conjoinX_X': [(lambda g, xx1=None:g.inject(xx1).conjoin(';'))], 
+    'g_injectXnull_a_null_bX_fold_conjoinXplusX': [(lambda g, xx1=None:g.inject(xx1).conjoin('+'))], 
+    'g_injectXnull_nullX_conjoinXplusX': [(lambda g, xx1=None:g.inject(xx1).conjoin('+'))], 
     'g_V_connectedComponent_hasXcomponentX': [(lambda g:g.V().connected_component().has('gremlin.connectedComponentVertexProgram.component'))], 
     'g_V_dedup_connectedComponent_hasXcomponentX': [(lambda g:g.V().dedup().connected_component().has('gremlin.connectedComponentVertexProgram.component'))], 
     'g_V_hasLabelXsoftwareX_connectedComponent_project_byXnameX_byXcomponentX': [(lambda g:g.V().has_label('software').connected_component().project('name','component').by('name').by('gremlin.connectedComponentVertexProgram.component'))], 
@@ -1456,6 +1459,7 @@
     'g_withSideEffectXa_xx1_addAllX_V_aggregateXlocal_aX_byXageX_capXaX': [(lambda g, xx1=None:g.with_side_effect('a',xx1,Operator.add_all).V().aggregate(Scope.local,'a').by('age').cap('a'))], 
     'g_withSideEffectXa_xx1_assignX_V_aggregateXaX_byXageX_capXaX': [(lambda g, xx1=None:g.with_side_effect('a',xx1,Operator.assign).V().aggregate('a').by('age').cap('a'))], 
     'g_withSideEffectXa_xx1_assignX_V_order_byXageX_aggregateXlocal_aX_byXageX_capXaX': [(lambda g, xx1=None:g.with_side_effect('a',xx1,Operator.assign).V().order().by('age').aggregate(Scope.local,'a').by('age').cap('a'))], 
+    'g_V_repeatXaggregateXaXX_timesX2X_capXaX_unfold': [(lambda g:g.V().repeat(__.aggregate('a')).times(2).cap('a').unfold())], 
     'g_V_aggregateXaX_capXaX_unfold_both': [(lambda g:g.V().aggregate('a').cap('a').unfold().both())], 
     'g_V_aggregateXaX_capXaX_unfold_barrier_both': [(lambda g:g.V().aggregate('a').cap('a').unfold().barrier().both())], 
     'g_V_fail': [(lambda g:g.V().fail())], 

gremlin-python/src/main/python/tests/feature/gremlin.py

@@ -153,3 +153,29 @@ Feature: Step - conjoin()
     Then the result should be unordered
       | result |
       | 3;three |
+
+  @GraphComputerVerificationInjectionNotSupported
+  Scenario: g_injectXnull_a_null_bX_fold_conjoinXplusX
+    Given the empty graph
+    And using the parameter xx1 defined as "l[null,a,null,b]"
+    And the traversal of
+      """
+      g.inject(xx1).conjoin("+")
+      """
+    When iterated to list
+    Then the result should be unordered
+      | result |
+      | str[a+b] |
+
+  @GraphComputerVerificationInjectionNotSupported
+  Scenario: g_injectXnull_nullX_conjoinXplusX
+    Given the empty graph
+    And using the parameter xx1 defined as "l[null,null]"
+    And the traversal of
+      """
+      g.inject(xx1).conjoin("+")
+      """
+    When iterated to list
+    Then the result should be unordered
+      | result |
+      | str[] |