Allow negative values for ra and dec

Fix an issue where ra and dec values in POINT() query expressions could not be negative.

python/lsst/daf/butler/queries/_expression_strings.py

@@ -365,5 +365,7 @@ def _get_float_literal_value(value: _VisitorResult, node: Node) -> float:
             return expr.value
         elif expr.expression_type == "int":
             return float(expr.value)
+        elif expr.expression_type == "unary" and expr.operator == "-":
+            return -1 * _get_float_literal_value(_ColExpr(expr.operand), node)
 
     raise InvalidQueryError(f"Expression '{node}' in POINT() is not a literal number.")

python/lsst/daf/butler/tests/butler_queries.py

@@ -800,6 +800,17 @@ def _check_visit_id(query: Query) -> None:
             # conversion of integer to float.
             _check_visit_id(query.where(f"visit_detector_region.region OVERLAPS POINT({ra}, 1)"))
 
+            # Negative values are allowed for dec, since it's defined as -90 to
+            # 90.  Tract 1, patch 4 slightly overlaps some negative dec values.
+            result = list(query.where("patch.region OVERLAPS POINT(0.335, -0.0000001)").data_ids(["patch"]))
+            self.assertEqual(len(result), 1)
+            id = result[0]
+            self.assertEqual(id["patch"], 4)
+            self.assertEqual(id["tract"], 1)
+
+            # Negative ra values are also allowed.
+            _check_visit_id(query.where(f"POINT({ra-360}, {dec}) OVERLAPS visit_detector_region.region"))
+
             # Substitute ra and dec values via bind instead of literals in the
             # string.
             _check_visit_id(