Add RESPECT NULLS / IGNORE NULLS window function syntax support

- Add IgnoreRespectNulls field to FunctionCall AST type
- Parse RESPECT NULLS and IGNORE NULLS clauses after function
  parameters and before OVER clause
- Update JSON marshaling to output IgnoreRespectNulls

Tests enabled:
- Baselines160_IgnoreRespectNullsSyntaxTests160
- IgnoreRespectNullsSyntaxTests160

Author: claude

ast/function_call.go

@@ -41,13 +41,14 @@ func (*WithinGroupClause) node() {}
 
 // FunctionCall represents a function call.
 type FunctionCall struct {
-	CallTarget        CallTarget         `json:"CallTarget,omitempty"`
-	FunctionName      *Identifier        `json:"FunctionName,omitempty"`
-	Parameters        []ScalarExpression `json:"Parameters,omitempty"`
-	UniqueRowFilter   string             `json:"UniqueRowFilter,omitempty"`
-	WithinGroupClause *WithinGroupClause `json:"WithinGroupClause,omitempty"`
-	OverClause        *OverClause        `json:"OverClause,omitempty"`
-	WithArrayWrapper  bool               `json:"WithArrayWrapper,omitempty"`
+	CallTarget         CallTarget         `json:"CallTarget,omitempty"`
+	FunctionName       *Identifier        `json:"FunctionName,omitempty"`
+	Parameters         []ScalarExpression `json:"Parameters,omitempty"`
+	UniqueRowFilter    string             `json:"UniqueRowFilter,omitempty"`
+	WithinGroupClause  *WithinGroupClause `json:"WithinGroupClause,omitempty"`
+	OverClause         *OverClause        `json:"OverClause,omitempty"`
+	IgnoreRespectNulls []*Identifier      `json:"IgnoreRespectNulls,omitempty"`
+	WithArrayWrapper   bool               `json:"WithArrayWrapper,omitempty"`
 }
 
 func (*FunctionCall) node()             {}

parser/marshal.go

@@ -1375,6 +1375,13 @@ func scalarExpressionToJSON(expr ast.ScalarExpression) jsonNode {
 				"$type": "OverClause",
 			}
 		}
+		if len(e.IgnoreRespectNulls) > 0 {
+			idents := make([]jsonNode, len(e.IgnoreRespectNulls))
+			for i, ident := range e.IgnoreRespectNulls {
+				idents[i] = identifierToJSON(ident)
+			}
+			node["IgnoreRespectNulls"] = idents
+		}
 		node["WithArrayWrapper"] = e.WithArrayWrapper
 		return node
 	case *ast.UserDefinedTypePropertyAccess:

parser/parse_select.go

@@ -1323,6 +1323,29 @@ func (p *Parser) parsePostExpressionAccess(expr ast.ScalarExpression) (ast.Scala
 			continue // continue to check for more clauses like OVER
 		}
 
+		// Check for RESPECT NULLS or IGNORE NULLS for window functions
+		if fc, ok := expr.(*ast.FunctionCall); ok {
+			upperLit := strings.ToUpper(p.curTok.Literal)
+			if upperLit == "RESPECT" || upperLit == "IGNORE" {
+				// Parse RESPECT NULLS or IGNORE NULLS
+				firstIdent := &ast.Identifier{
+					Value:     strings.ToUpper(p.curTok.Literal),
+					QuoteType: "NotQuoted",
+				}
+				p.nextToken() // consume RESPECT/IGNORE
+
+				if strings.ToUpper(p.curTok.Literal) == "NULLS" {
+					secondIdent := &ast.Identifier{
+						Value:     strings.ToUpper(p.curTok.Literal),
+						QuoteType: "NotQuoted",
+					}
+					p.nextToken() // consume NULLS
+					fc.IgnoreRespectNulls = []*ast.Identifier{firstIdent, secondIdent}
+				}
+				continue // continue to check for OVER clause
+			}
+		}
+
 		// Check for OVER clause for function calls
 		if fc, ok := expr.(*ast.FunctionCall); ok && strings.ToUpper(p.curTok.Literal) == "OVER" {
 			p.nextToken() // consume OVER

parser/testdata/Baselines160_IgnoreRespectNullsSyntaxTests160/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}

parser/testdata/IgnoreRespectNullsSyntaxTests160/metadata.json

@@ -1 +1 @@
-{"todo": true}
+{}