feat(cypher): support *0.. open-range variable-length relationships (#983)

Add rel_range_open_max grammar rule and transformer for open-range
syntax like *0.., *1.., *2.. where the max bound is unbounded.
Handles min_hops=0 specifically (zero-hop means include the seed
node itself) while keeping the existing rejection of *0 exact syntax.

Adds 4 parametrized parser test cases: *0.., *1.., [:R*0..], [:R*2..].

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: lmeyerov

graphistry/compute/gfql/cypher/parser.py

@@ -107,6 +107,7 @@
 
 rel_types: ":" LABEL_NAME ("|" ":"? LABEL_NAME)*
 rel_range: "*" INT ".." INT      -> rel_range_bounded
+         | "*" INT ".."          -> rel_range_open_max
          | "*" INT               -> rel_range_exact
          | "*"                   -> rel_range_fixed
 
@@ -725,6 +726,23 @@ def rel_range_bounded(self, meta: Any, items: Sequence[Any]) -> dict[str, Any]:
                 )
             return {"min_hops": min_hops, "max_hops": max_hops, "to_fixed_point": False}
 
+        def rel_range_open_max(self, meta: Any, items: Sequence[Any]) -> dict[str, Any]:
+            if len(items) != 1:
+                raise _to_syntax_error("Invalid relationship range", line=meta.line, column=meta.column)
+            try:
+                value = int(str(items[0]))
+            except Exception as exc:
+                raise _to_syntax_error("Invalid relationship range bound", line=meta.line, column=meta.column) from exc
+            if value < 0:
+                raise _to_unsupported(
+                    "Cypher negative-hop relationship ranges are not supported",
+                    line=meta.line,
+                    column=meta.column,
+                    field="match",
+                    value=self._slice(_span_from_meta(meta)),
+                )
+            return {"min_hops": value, "max_hops": None, "to_fixed_point": True}
+
         def rel_range_fixed(self, meta: Any, _items: Sequence[Any]) -> dict[str, Any]:
             return {"min_hops": None, "max_hops": None, "to_fixed_point": True}
 

graphistry/tests/compute/gfql/cypher/test_parser.py

@@ -439,6 +439,10 @@ def test_parse_relationship_type_alternation_with_repeated_colon() -> None:
         ("MATCH (a)<-[*4]-(b) RETURN b", "reverse", 4, 4, False, ()),
         ("MATCH (a)-[*]->(b) RETURN b", "forward", None, None, True, ()),
         ("MATCH (a)-[:R|:S*2..4]-(b) RETURN b", "undirected", 2, 4, False, ("R", "S")),
+        ("MATCH (a)-[*0..]->(b) RETURN b", "forward", 0, None, True, ()),
+        ("MATCH (a)-[*1..]->(b) RETURN b", "forward", 1, None, True, ()),
+        ("MATCH (a)-[:R*0..]-(b) RETURN b", "undirected", 0, None, True, ("R",)),
+        ("MATCH (a)<-[:R*2..]-(b) RETURN b", "reverse", 2, None, True, ("R",)),
     ],
 )
 def test_parse_variable_length_relationship_patterns(