TINKERPOP-3130 Allowed none() as anonymous and chained

CHANGELOG.asciidoc

@@ -24,6 +24,7 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 === TinkerPop 4.0.0 (NOT OFFICIALLY RELEASED YET)
 
 * Bumped SLF4j to 2.0.16.
+* Modified grammar to make `discard()` usage more consistent as a filter step where it can now be used to chain additional traversal steps and be used anonymously.
 
 [[release-4-0-0-beta-1]]
 === TinkerPop 4.0.0-beta.1 (January 17, 2025)
@@ -106,6 +107,8 @@ image::https://raw.githubusercontent.com/apache/tinkerpop/master/docs/static/ima
 * Changed Gremlin grammar to make use of `g` to spawn child traversals a syntax error.
 * Added `unexpected-response` handler to `ws` for `gremlin-javascript`
 * Fixed bug in `TinkerTransactionGraph` where a read-only transaction may leave elements trapped in a "zombie transaction".
+* Modified grammar to make `none()` usage more consistent as a filter step where it can now be used to chain additional traversal steps and be used anonymously.
+* Added missing anonymous support for `disjunct()` in Python and Javascript.
 
 [[release-3-7-3]]
 === TinkerPop 3.7.3 (October 23, 2024)

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/language/grammar/DefaultGremlinBaseVisitor.java

@@ -143,10 +143,6 @@ protected void notImplemented(final ParseTree ctx) {
 	 * {@inheritDoc}
 	 */
 	@Override public T visitChainedTraversal(final GremlinParser.ChainedTraversalContext ctx) { notImplemented(ctx); return null; }
-	/**
-	 * {@inheritDoc}
-	 */
-	@Override public T visitChainedParentOfGraphTraversal(final GremlinParser.ChainedParentOfGraphTraversalContext ctx) { notImplemented(ctx); return null; }
 	/**
 	 * {@inheritDoc}
 	 */
@@ -355,7 +351,11 @@ protected void notImplemented(final ParseTree ctx) {
 	 * {@inheritDoc}
 	 */
 	@Override public T visitTraversalMethod_difference_Object(final GremlinParser.TraversalMethod_difference_ObjectContext ctx) { notImplemented(ctx); return null; }
-	/**
+    /**
+     * {@inheritDoc}
+     */
+    @Override public T visitTraversalMethod_discard(final GremlinParser.TraversalMethod_discardContext ctx) { notImplemented(ctx); return null; }
+    /**
 	 * {@inheritDoc}
 	 */
 	@Override public T visitTraversalMethod_disjunct_Object(final GremlinParser.TraversalMethod_disjunct_ObjectContext ctx) { notImplemented(ctx); return null; }
@@ -1127,10 +1127,6 @@ protected void notImplemented(final ParseTree ctx) {
 	 * {@inheritDoc}
 	 */
 	@Override public T visitTraversalSackMethod(final GremlinParser.TraversalSackMethodContext ctx) { notImplemented(ctx); return null; }
-	/**
-	 * {@inheritDoc}
-	 */
-	@Override public T visitTraversalSelfMethod(final GremlinParser.TraversalSelfMethodContext ctx) { notImplemented(ctx); return null; }
 	/**
 	 * {@inheritDoc}
 	 */
@@ -1255,10 +1251,6 @@ protected void notImplemented(final ParseTree ctx) {
 	 * {@inheritDoc}
 	 */
 	@Override public T visitTraversalTerminalMethod_toBulkSet(final GremlinParser.TraversalTerminalMethod_toBulkSetContext ctx) { notImplemented(ctx); return null; }
-	/**
-	 * {@inheritDoc}
-	 */
-	@Override public T visitTraversalSelfMethod_discard(final GremlinParser.TraversalSelfMethod_discardContext ctx) { notImplemented(ctx); return null; }
 	/**
 	 * {@inheritDoc}
 	 */

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/language/grammar/TraversalMethodVisitor.java

@@ -558,6 +558,14 @@ public GraphTraversal visitTraversalMethod_difference_Object(final GremlinParser
             return graphTraversal.difference(literalOrVar);
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    public Traversal visitTraversalMethod_discard(final GremlinParser.TraversalMethod_discardContext ctx) {
+        return graphTraversal.discard();
+    }
+
     /**
      * {@inheritDoc}
      */

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/language/grammar/TraversalRootVisitor.java

@@ -56,9 +56,6 @@ public TraversalRootVisitor(final GremlinAntlrToJava antlr, final Traversal trav
     public Traversal visitNestedTraversal(final GremlinParser.NestedTraversalContext ctx) {
         if (ctx.getChild(0) instanceof GremlinParser.RootTraversalContext) {
             return visitChildren(ctx);
-        } else if (ctx.getChild(2) instanceof GremlinParser.ChainedParentOfGraphTraversalContext) {
-            return new TraversalRootVisitor<Traversal>(antlr.createAnonymous.get()).
-                    visitChainedParentOfGraphTraversal(ctx.chainedTraversal().chainedParentOfGraphTraversal());
         } else {
             return new TraversalMethodVisitor(antlr, antlr.createAnonymous.get()).visitChainedTraversal(ctx.chainedTraversal());
         }
@@ -79,53 +76,14 @@ public Traversal visitRootTraversal(final GremlinParser.RootTraversalContext ctx
                 (GremlinParser.TraversalSourceSpawnMethodContext) ctx.getChild(childIndexOfTraversalSourceSpawnMethod));
 
         if (ctx.getChildCount() == 5) {
-            // handle chained traversal
-            final int childIndexOfChainedTraversal = 4;
-
-            if (ctx.getChild(childIndexOfChainedTraversal) instanceof GremlinParser.ChainedParentOfGraphTraversalContext) {
-                final TraversalRootVisitor traversalRootVisitor = new TraversalRootVisitor(traversal);
-                return traversalRootVisitor.visitChainedParentOfGraphTraversal(
-                        (GremlinParser.ChainedParentOfGraphTraversalContext) ctx.getChild(childIndexOfChainedTraversal));
-            } else {
-                final TraversalMethodVisitor traversalMethodVisitor = new TraversalMethodVisitor(antlr, traversal);
-                return traversalMethodVisitor.visitChainedTraversal(
-                        (GremlinParser.ChainedTraversalContext) ctx.getChild(childIndexOfChainedTraversal));
-            }
+            final TraversalMethodVisitor traversalMethodVisitor = new TraversalMethodVisitor(antlr, traversal);
+            return traversalMethodVisitor.visitChainedTraversal(
+                        (GremlinParser.ChainedTraversalContext) ctx.getChild(4));
         } else {
             return traversal;
         }
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    @Override
-    public Traversal visitTraversalSelfMethod(final GremlinParser.TraversalSelfMethodContext ctx) {
-        return visitChildren(ctx);
-    }
-
-    /**
-     * {@inheritDoc}
-     */
-    @Override
-    public Traversal visitTraversalSelfMethod_discard(final GremlinParser.TraversalSelfMethod_discardContext ctx) {
-        this.traversal = traversal.discard();
-        return this.traversal;
-    }
-
-    /**
-     * {@inheritDoc}
-     */
-    @Override
-    public Traversal visitChainedParentOfGraphTraversal(final GremlinParser.ChainedParentOfGraphTraversalContext ctx) {
-        if (ctx.getChildCount() == 1) {
-            return visitChildren(ctx);
-        } else {
-            visit(ctx.getChild(0));
-            return visit(ctx.getChild(2));
-        }
-    }
-
     /**
      * {@inheritDoc}
      */

gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/language/translator/TranslateVisitor.java

@@ -265,11 +265,6 @@ public Void visitChainedTraversal(final GremlinParser.ChainedTraversalContext ct
         return visitChildren(ctx);
     }
 
-    @Override
-    public Void visitChainedParentOfGraphTraversal(final GremlinParser.ChainedParentOfGraphTraversalContext ctx) {
-        return visitChildren(ctx);
-    }
-
     @Override
     public Void visitNestedTraversal(final GremlinParser.NestedTraversalContext ctx) {
         if (ctx.ANON_TRAVERSAL_ROOT() == null)
@@ -557,6 +552,11 @@ public Void visitTraversalMethod_difference_Object(final GremlinParser.Traversal
         return visitChildren(ctx);
     }
 
+    @Override
+    public Void visitTraversalMethod_discard(final GremlinParser.TraversalMethod_discardContext ctx) {
+        return visitChildren(ctx);
+    }
+
     @Override
     public Void visitTraversalMethod_disjunct_Object(final GremlinParser.TraversalMethod_disjunct_ObjectContext ctx) {
         return visitChildren(ctx);
@@ -1605,11 +1605,6 @@ public Void visitTraversalSackMethod(final GremlinParser.TraversalSackMethodCont
         return visitChildren(ctx);
     }
 
-    @Override
-    public Void visitTraversalSelfMethod(final GremlinParser.TraversalSelfMethodContext ctx) {
-        return visitChildren(ctx);
-    }
-
     @Override
     public Void visitTraversalComparator(final GremlinParser.TraversalComparatorContext ctx) {
         return visitChildren(ctx);
@@ -1809,11 +1804,6 @@ public Void visitTraversalTerminalMethod_toBulkSet(final GremlinParser.Traversal
         return visitChildren(ctx);
     }
 
-    @Override
-    public Void visitTraversalSelfMethod_discard(final GremlinParser.TraversalSelfMethod_discardContext ctx) {
-        return visitChildren(ctx);
-    }
-
     @Override
     public Void visitWithOptionKeys(final GremlinParser.WithOptionKeysContext ctx) {
         return visitChildren(ctx);

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

@@ -960,6 +960,13 @@ public static <A> GraphTraversal<A, Set<?>> difference(final GValue<Object> valu
         return __.<A>start().difference(values);
     }
 
+    /**
+     * @see GraphTraversal#discard()
+     */
+    public static <A> GraphTraversal<A, A> discard() {
+        return __.<A>start().discard();
+    }
+
     /**
      * @see GraphTraversal#disjunct(Object)
      */

gremlin-core/src/test/java/org/apache/tinkerpop/gremlin/language/grammar/TraversalMethodVisitorTest.java

@@ -1298,4 +1298,11 @@ public void shouldParseTraversalMethod_substring_long() throws Exception {
     public void shouldParseTraversalMethod_substring_long_long() throws Exception {
         compare(g.V().substring(1, 3), eval("g.V().substring(1, 3)"));
     }
+
+    @Test
+    public void shouldParseTraversalMethod_discard_somethingAfter() throws Exception {
+        compare(g.V().discard().path(), eval("g.V().discard().path()"));
+        compare(g.V().discard().E(), eval("g.V().discard().E()"));
+        compare(g.V().discard().discard(), eval("g.V().discard().discard()"));
+    }
 }

gremlin-dotnet/src/Gremlin.Net/Process/Traversal/__.cs

@@ -470,6 +470,14 @@ public static GraphTraversal<object, object> Difference(object differenceObject)
             return new GraphTraversal<object, object>().Difference(differenceObject);
         }
 
+        /// <summary>
+        ///     Spawns a <see cref="GraphTraversal{SType, EType}" /> and adds the none step to that traversal.
+        /// </summary>
+        public static GraphTraversal<object, object> Discard()
+        {
+            return new GraphTraversal<object, object>().Discard();
+        }
+
         /// <summary>
         ///     Spawns a <see cref="GraphTraversal{SType, EType}" /> and adds the disjunct step to that traversal.
         /// </summary>

gremlin-javascript/src/main/javascript/gremlin-javascript/lib/process/graph-traversal.ts

@@ -1780,6 +1780,8 @@ export const statics = {
   dateAdd: (...args: any[]) => callOnEmptyTraversal('dateAdd', args),
   dateDiff: (...args: any[]) => callOnEmptyTraversal('dateDiff', args),
   dedup: (...args: any[]) => callOnEmptyTraversal('dedup', args),
+  discard: (...args: any[]) => callOnEmptyTraversal('discard', args),
+  disjunct: (...args: any[]) => callOnEmptyTraversal('disjunct', args),
   drop: (...args: any[]) => callOnEmptyTraversal('drop', args),
   element: (...args: any[]) => callOnEmptyTraversal('element', args),
   elementMap: (...args: any[]) => callOnEmptyTraversal('elementMap', args),
@@ -1820,6 +1822,7 @@ export const statics = {
   mergeE: (...args: any[]) => callOnEmptyTraversal('mergeE', args),
   mergeV: (...args: any[]) => callOnEmptyTraversal('mergeV', args),
   min: (...args: any[]) => callOnEmptyTraversal('min', args),
+  none: (...args: any[]) => callOnEmptyTraversal('none', args),
   not: (...args: any[]) => callOnEmptyTraversal('not', args),
   optional: (...args: any[]) => callOnEmptyTraversal('optional', args),
   or: (...args: any[]) => callOnEmptyTraversal('or', args),

gremlin-language/src/main/antlr4/Gremlin.g4

@@ -54,7 +54,6 @@ transactionPart
 rootTraversal
     : traversalSource DOT traversalSourceSpawnMethod
     | traversalSource DOT traversalSourceSpawnMethod DOT chainedTraversal
-    | traversalSource DOT traversalSourceSpawnMethod DOT chainedParentOfGraphTraversal
     ;
 
 traversalSourceSelfMethod
@@ -163,12 +162,6 @@ traversalSourceSpawnMethod_union
 chainedTraversal
     : traversalMethod
     | chainedTraversal DOT traversalMethod
-    | chainedTraversal DOT chainedParentOfGraphTraversal
-    ;
-
-chainedParentOfGraphTraversal
-    : traversalSelfMethod
-    | chainedParentOfGraphTraversal DOT traversalSelfMethod
     ;
 
 nestedTraversal
@@ -209,6 +202,7 @@ traversalMethod
     | traversalMethod_cyclicPath
     | traversalMethod_dedup
     | traversalMethod_difference
+    | traversalMethod_discard
     | traversalMethod_disjunct
     | traversalMethod_drop
     | traversalMethod_elementMap
@@ -454,6 +448,10 @@ traversalMethod_difference
     : 'difference' LPAREN genericLiteralArgument RPAREN #traversalMethod_difference_Object
     ;
 
+traversalMethod_discard
+    : 'discard' LPAREN RPAREN
+    ;
+
 traversalMethod_disjunct
     : 'disjunct' LPAREN genericLiteralArgument RPAREN #traversalMethod_disjunct_Object
     ;
@@ -1102,10 +1100,6 @@ traversalSackMethod
     : traversalBarrier
     ;
 
-traversalSelfMethod
-    : traversalSelfMethod_discard
-    ;
-
 // Additional special rules that are derived from above
 // These are used to restrict broad method signatures that accept lambdas
 // to a smaller set.
@@ -1237,10 +1231,6 @@ traversalTerminalMethod_toBulkSet
     : 'toBulkSet' LPAREN RPAREN
     ;
 
-traversalSelfMethod_discard
-    : 'discard' LPAREN RPAREN
-    ;
-
 // Gremlin specific lexer rules
 
 withOptionKeys

gremlin-python/src/main/python/gremlin_python/process/graph_traversal.py

@@ -1205,6 +1205,10 @@ def dedup(cls, *args):
     def difference(cls, *args):
         return cls.graph_traversal(None, None, GremlinLang()).difference(*args)
 
+    @classmethod
+    def discard(cls, *args):
+        return cls.graph_traversal(None, None, GremlinLang()).discard(*args)
+
     @classmethod
     def disjunct(cls, *args):
         return cls.graph_traversal(None, None, GremlinLang()).disjunct(*args)
@@ -1469,6 +1473,10 @@ def min_(cls, *args):
     def none(cls, *args):
         return cls.graph_traversal(None, None, GremlinLang()).none(*args)
 
+    @classmethod
+    def none(cls, *args):
+        return cls.graph_traversal(None, None, Bytecode()).none(*args)
+
     @classmethod
     def not_(cls, *args):
         return cls.graph_traversal(None, None, GremlinLang()).not_(*args)
@@ -1945,6 +1953,14 @@ def dedup(*args):
     return __.dedup(*args)
 
 
+def discard(*args):
+    return __.discard(*args)
+
+
+def disjunct(*args):
+    return __.disjunct(*args)
+
+
 def drop(*args):
     return __.drop(*args)
 
@@ -2149,6 +2165,10 @@ def min_(*args):
     return __.min_(*args)
 
 
+def none(*args):
+    return __.none(*args)
+
+
 def not_(*args):
     return __.not_(*args)
 
@@ -2435,6 +2455,10 @@ def where(*args):
 
 statics.add_static('date_diff', date_diff)
 
+statics.add_static('discard', discard)
+
+statics.add_static('disjunct', disjunct)
+
 statics.add_static('dedup', dedup)
 
 statics.add_static('drop', drop)
@@ -2537,6 +2561,8 @@ def where(*args):
 
 statics.add_static('min_', min_)
 
+statics.add_static('none', none)
+
 statics.add_static('not_', not_)
 
 statics.add_static('optional', optional)