Add support for dotted paths in JSON type parameters and unwrap SKIP

Two changes for JSON/OBJECT type parsing and explain output:

1. Parser: Parse dotted paths (like a.b.c) for JSON type parameter names
   Previously only single identifiers were captured as parameter names.

2. Explain: Unwrap SKIP function calls in ObjectTypeArgument
   ClickHouse shows just the path/pattern, not the SKIP wrapper.

Fixes 18 statements across 8 test files:
- 03205_json_syntax (12 statements)
- 03227_json_invalid_regexp (2 statements)
- 03620_json_advanced_shared_data_seek_bug (1 statement)
- Plus metadata updates for other JSON-related tests

Author: claude

internal/explain/statements.go

@@ -1014,6 +1014,15 @@ func explainDataType(sb *strings.Builder, n *ast.DataType, indent string, depth
 
 func explainObjectTypeArgument(sb *strings.Builder, n *ast.ObjectTypeArgument, indent string, depth int) {
 	fmt.Fprintf(sb, "%sASTObjectTypeArgument (children %d)\n", indent, 1)
+	// SKIP function calls are unwrapped - only the path/pattern is shown
+	if fn, ok := n.Expr.(*ast.FunctionCall); ok {
+		if strings.ToUpper(fn.Name) == "SKIP" || strings.ToUpper(fn.Name) == "SKIP REGEXP" {
+			if len(fn.Arguments) > 0 {
+				Node(sb, fn.Arguments[0], depth+1)
+				return
+			}
+		}
+	}
 	Node(sb, n.Expr, depth+1)
 }
 

parser/parser.go

@@ -3689,11 +3689,27 @@ func (p *Parser) parseDataType() *ast.DataType {
 				}
 			}
 
+
 			if isNamedParam {
 				// Parse as name + type pair
+				// For JSON/OBJECT types, the name can be a dotted path like a.b.c
 				pos := p.current.Pos
-				paramName := p.current.Value
+				var nameParts []string
+				nameParts = append(nameParts, p.current.Value)
 				p.nextToken()
+				// Parse additional dotted parts if this is a JSON/OBJECT type
+				if isObjectType {
+					for p.currentIs(token.DOT) {
+						p.nextToken() // consume dot
+						if p.currentIs(token.IDENT) || p.current.Token.IsKeyword() {
+							nameParts = append(nameParts, p.current.Value)
+							p.nextToken()
+						} else {
+							break
+						}
+					}
+				}
+				paramName := strings.Join(nameParts, ".")
 				// Parse the type for this parameter
 				paramType := p.parseDataType()
 				if paramType != nil {

parser/testdata/03205_json_syntax/metadata.json

@@ -1,16 +1 @@
-{
-  "explain_todo": {
-    "stmt15": true,
-    "stmt17": true,
-    "stmt19": true,
-    "stmt21": true,
-    "stmt23": true,
-    "stmt25": true,
-    "stmt27": true,
-    "stmt29": true,
-    "stmt31": true,
-    "stmt33": true,
-    "stmt35": true,
-    "stmt37": true
-  }
-}
+{}

parser/testdata/03207_json_read_subcolumns_1_memory/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt14": true,
-    "stmt6": true
+    "stmt14": true
   }
 }

parser/testdata/03207_json_read_subcolumns_2_memory/metadata.json

@@ -1,6 +1,5 @@
 {
   "explain_todo": {
-    "stmt14": true,
-    "stmt6": true
+    "stmt14": true
   }
 }

parser/testdata/03208_array_of_json_read_subcolumns_2_memory/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt5": true
-  }
-}
+{}

parser/testdata/03227_json_invalid_regexp/metadata.json

@@ -1,6 +1 @@
-{
-  "explain_todo": {
-    "stmt2": true,
-    "stmt3": true
-  }
-}
+{}

parser/testdata/03272_json_to_json_cast_1/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt5": true
-  }
-}
+{}

parser/testdata/03301_subcolumns_in_mv/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt5": true
-  }
-}
+{}

parser/testdata/03620_json_advanced_shared_data_seek_bug/metadata.json

@@ -1,5 +1 @@
-{
-  "explain_todo": {
-    "stmt3": true
-  }
-}
+{}