Preserve tuple SpacedCommas flag in EXPLAIN AST output

Track whether tuples have spaces after commas in the source code and
preserve this formatting when outputting EXPLAIN AST. This is needed
for Ring/Polygon/MultiPolygon type literals to match ClickHouse output.

Changes:
- Add formatTupleAsStringFromLiteral to respect SpacedCommas flag
- Track spacedCommas when parsing tuples in parseGroupedOrTuple
- Fixes 00727_concat/stmt44 and 02935_format_with_arbitrary_types/stmt44

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: kyleconroy

internal/explain/format.go

@@ -576,7 +576,7 @@ func formatExprAsString(expr ast.Expression) string {
 		case ast.LiteralArray:
 			return formatArrayAsStringFromLiteral(e)
 		case ast.LiteralTuple:
-			return formatTupleAsString(e.Value)
+			return formatTupleAsStringFromLiteral(e)
 		default:
 			return fmt.Sprintf("%v", e.Value)
 		}
@@ -659,6 +659,24 @@ func formatArrayAsString(val interface{}) string {
 	return "[" + strings.Join(parts, ", ") + "]"
 }
 
+// formatTupleAsStringFromLiteral formats a tuple literal as a string for :: cast syntax
+// respecting the SpacedCommas flag to preserve original formatting
+func formatTupleAsStringFromLiteral(lit *ast.Literal) string {
+	exprs, ok := lit.Value.([]ast.Expression)
+	if !ok {
+		return "()"
+	}
+	var parts []string
+	for _, e := range exprs {
+		parts = append(parts, formatElementAsString(e))
+	}
+	separator := ","
+	if lit.SpacedCommas {
+		separator = ", "
+	}
+	return "(" + strings.Join(parts, separator) + ")"
+}
+
 // formatTupleAsString formats a tuple literal as a string for :: cast syntax
 func formatTupleAsString(val interface{}) string {
 	exprs, ok := val.([]ast.Expression)
@@ -707,7 +725,7 @@ func formatElementAsString(expr ast.Expression) string {
 		case ast.LiteralArray:
 			return formatArrayAsStringFromLiteral(e)
 		case ast.LiteralTuple:
-			return formatTupleAsString(e.Value)
+			return formatTupleAsStringFromLiteral(e)
 		default:
 			return fmt.Sprintf("%v", e.Value)
 		}

parser/expression.go

@@ -1238,8 +1238,15 @@ func (p *Parser) parseGroupedOrTuple() ast.Expression {
 	// Check if it's a tuple
 	if p.currentIs(token.COMMA) {
 		elements := []ast.Expression{first}
+		spacedCommas := false
 		for p.currentIs(token.COMMA) {
+			commaPos := p.current.Pos.Offset
 			p.nextToken()
+			// Check if there's whitespace between comma and next token
+			// A comma is 1 byte, so if offset difference > 1, there's whitespace
+			if p.current.Pos.Offset > commaPos+1 {
+				spacedCommas = true
+			}
 			// Handle trailing comma: (1,) should create tuple with single element
 			if p.currentIs(token.RPAREN) {
 				break
@@ -1248,9 +1255,10 @@ func (p *Parser) parseGroupedOrTuple() ast.Expression {
 		}
 		p.expect(token.RPAREN)
 		return &ast.Literal{
-			Position: pos,
-			Type:     ast.LiteralTuple,
-			Value:    elements,
+			Position:     pos,
+			Type:         ast.LiteralTuple,
+			Value:        elements,
+			SpacedCommas: spacedCommas,
 		}
 	}
 

parser/testdata/00727_concat/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt44": true
-  }
-}
+{}

parser/testdata/02935_format_with_arbitrary_types/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt44": true
-  }
-}
+{}