Fix possible panic in document symbols handler for files without an A…

…ST available yet

pkg/lsp/refactor.go

@@ -434,6 +434,8 @@ func newFieldVisitor(tracker *paths.AncestorTracker, paths *[]protopath.Values)
 		switch node.(type) {
 		case *ast.MessageNode, *ast.GroupNode, *ast.FieldNode, *ast.MapFieldNode:
 			return visitEnclosingRange(tracker, paths)
+		case *ast.FileNode:
+			return true
 		}
 		return false
 	}
@@ -480,7 +482,7 @@ func extractFields(ctx context.Context, request *protocol.CodeActionParams, link
 				continue
 			}
 			if parentNodePath.Len() == 0 {
-				parentNodePath = paths.Slice(path, 0, parentNodePath.Len()-1)
+				parentNodePath = paths.Slice(path, 0, path.Len()-1)
 			} else if !parentNodePath.Index(-1).Value.Equal(path.Index(-1).Value) {
 				return // fields in the range must share the same parent
 			}

pkg/lsp/search.go

@@ -799,6 +799,8 @@ func visitEnclosingRange(tracker *paths.AncestorTracker, paths *[]protopath.Valu
 func DefaultEnclosingRangeVisitor(tracker *paths.AncestorTracker, paths *[]protopath.Values) func(ast.Node) bool {
 	return func(node ast.Node) bool {
 		switch node.(type) {
+		case *ast.FileNode:
+			return true
 		case *ast.ImportNode,
 			*ast.SyntaxNode,
 			*ast.MessageNode,

pkg/lsp/symbols.go

@@ -28,6 +28,10 @@ func (c *Cache) documentSymbolsForFileLocked(uri protocol.DocumentURI) ([]protoc
 	var symbols []protocol.DocumentSymbol
 
 	fn := f.AST()
+	if fn == nil {
+		return nil, nil
+	}
+
 	for _, decl := range fn.Decls {
 		switch node := decl.Unwrap().(type) {
 		case *ast.MessageNode: