lib/parser/source/tree_rewriter.rb in parser-2.7.1.0 vs lib/parser/source/tree_rewriter.rb in parser-2.7.1.1

@@ -116,10 +116,47 @@
         all_encompassing_range = @source_buffer.source_range.adjust(begin_pos: -1, end_pos: +1)
         @action_root = TreeRewriter::Action.new(all_encompassing_range, @enforcer)
       end
 
       ##
+      # Returns true iff no (non trivial) update has been recorded
+      #
+      # @return [Boolean]
+      #
+      def empty?
+        @action_root.empty?
+      end
+
+      ##
+      # Merges the updates of argument with the receiver.
+      # Policies of the receiver are used.
+      #
+      # @param [Rewriter] with
+      # @return [Rewriter] self
+      # @raise [ClobberingError] when clobbering is detected
+      #
+      def merge!(with)
+        raise 'TreeRewriter are not for the same source_buffer' unless
+          source_buffer == with.source_buffer
+
+        @action_root = @action_root.combine(with.action_root)
+        self
+      end
+
+      ##
+      # Returns a new rewriter that consists of the updates of the received
+      # and the given argument. Policies of the receiver are used.
+      #
+      # @param [Rewriter] with
+      # @return [Rewriter] merge of receiver and argument
+      # @raise [ClobberingError] when clobbering is detected
+      #
+      def merge(with)
+        dup.merge!(with)
+      end
+
+      ##
       # Replaces the code of the source range `range` with `content`.
       #
       # @param [Range] range
       # @param [String] content
       # @return [Rewriter] self
@@ -201,14 +238,13 @@
       end
 
       ##
       # Provides a protected block where a sequence of multiple rewrite actions
       # are handled atomically. If any of the actions failed by clobbering,
-      # all the actions are rolled back.
+      # all the actions are rolled back. Transactions can be nested.
       #
       # @raise [RuntimeError] when no block is passed
-      # @raise [RuntimeError] when already in a transaction
       #
       def transaction
         unless block_given?
           raise "#{self.class}##{__method__} requires block"
         end
@@ -253,9 +289,13 @@
         'TreeRewriter#insert_before_multi and insert_before_multi exist only for legacy compatibility.',
         'Please update your code to use `wrap`, `insert_before` or `insert_after` instead.'
       ].join("\n").freeze
 
       extend Deprecation
+
+      protected
+
+      attr_reader :action_root
 
       private
 
       ACTIONS = %i[accept warn raise].freeze
       def check_policy_validity