1 files changed, 125 insertions, 0 deletions
diff --git a/lib/prism/translation/ripper/sexp.rb b/lib/prism/translation/ripper/sexp.rb
new file mode 100644
index 0000000000..dc26a639a3
--- /dev/null
+++ b/lib/prism/translation/ripper/sexp.rb
@@ -0,0 +1,125 @@
+# frozen_string_literal: true
+
+require_relative "../ripper"
+
+module Prism
+  module Translation
+    class Ripper
+      # This class mirrors the ::Ripper::SexpBuilder subclass of ::Ripper that
+      # returns the arrays of [type, *children].
+      class SexpBuilder < Ripper
+        # :stopdoc:
+
+        attr_reader :error
+
+        private
+
+        def dedent_element(e, width)
+          if (n = dedent_string(e[1], width)) > 0
+            e[2][1] += n
+          end
+          e
+        end
+
+        def on_heredoc_dedent(val, width)
+          sub = proc do |cont|
+            cont.map! do |e|
+              if Array === e
+                case e[0]
+                when :@tstring_content
+                  e = dedent_element(e, width)
+                when /_add\z/
+                  e[1] = sub[e[1]]
+                end
+              elsif String === e
+                dedent_string(e, width)
+              end
+              e
+            end
+          end
+          sub[val]
+          val
+        end
+
+        events = private_instance_methods(false).grep(/\Aon_/) {$'.to_sym}
+        (PARSER_EVENTS - events).each do |event|
+          module_eval(<<-End, __FILE__, __LINE__ + 1)
+            def on_#{event}(*args)
+              args.unshift :#{event}
+            end
+          End
+        end
+
+        SCANNER_EVENTS.each do |event|
+          module_eval(<<-End, __FILE__, __LINE__ + 1)
+            def on_#{event}(tok)
+              [:@#{event}, tok, [lineno(), column()]]
+            end
+          End
+        end
+
+        def on_error(mesg)
+          @error = mesg
+        end
+        remove_method :on_parse_error
+        alias on_parse_error on_error
+        alias compile_error on_error
+
+        # :startdoc:
+      end
+
+      # This class mirrors the ::Ripper::SexpBuilderPP subclass of ::Ripper that
+      # returns the same values as ::Ripper::SexpBuilder except with a couple of
+      # niceties that flatten linked lists into arrays.
+      class SexpBuilderPP < SexpBuilder
+        # :stopdoc:
+
+        private
+
+        def on_heredoc_dedent(val, width)
+          val.map! do |e|
+            next e if Symbol === e and /_content\z/ =~ e
+            if Array === e and e[0] == :@tstring_content
+              e = dedent_element(e, width)
+            elsif String === e
+              dedent_string(e, width)
+            end
+            e
+          end
+          val
+        end
+
+        def _dispatch_event_new
+          []
+        end
+
+        def _dispatch_event_push(list, item)
+          list.push item
+          list
+        end
+
+        def on_mlhs_paren(list)
+          [:mlhs, *list]
+        end
+
+        def on_mlhs_add_star(list, star)
+          list.push([:rest_param, star])
+        end
+
+        def on_mlhs_add_post(list, post)
+          list.concat(post)
+        end
+
+        PARSER_EVENT_TABLE.each do |event, arity|
+          if /_new\z/ =~ event and arity == 0
+            alias_method "on_#{event}", :_dispatch_event_new
+          elsif /_add\z/ =~ event
+            alias_method "on_#{event}", :_dispatch_event_push
+          end
+        end
+
+        # :startdoc:
+      end
+    end
+  end
+end