Support signed numeric literals in BSL filter translation

Python parses -5 as ast.UnaryOp(USub, Constant(5)), not as a negative
Constant. _expr_to_sql only handled Constant, so filters like
_.delta > -5 produced None on the RHS and failed at parse time.
Handle UnaryOp with USub to emit the negated value.

Author: nicosuave

sidemantic/adapters/bsl_expr.py

@@ -127,6 +127,12 @@ def _expr_to_sql(node: ast.AST) -> str | None:
         if isinstance(node.value, (int, float)):
             return str(node.value)
 
+    # Python parses -5 as UnaryOp(USub, Constant(5))
+    if isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
+        operand = _expr_to_sql(node.operand)
+        if operand is not None:
+            return f"-{operand}"
+
     if isinstance(node, ast.Name) and node.id == "_":
         return None
 

tests/adapters/bsl/test_parsing.py

@@ -1148,6 +1148,12 @@ def test_notnull(self):
         result = bsl_filter_to_sql("_.origin.notnull()")
         assert result == "origin IS NOT NULL"
 
+    def test_negative_number(self):
+        assert bsl_filter_to_sql("_.delta > -5") == "delta > -5"
+
+    def test_negative_float(self):
+        assert bsl_filter_to_sql("_.score < -0.5") == "score < -0.5"
+
 
 class TestBSLFilterAutoApply:
     """Tests that model-level filters are auto-applied in queries via model.sql."""