[ruby/prism] Make the ripper shim work with rdoc

The filter class is a 1:1 copy of ruby.

rdoc has 32 test failures. It seems to expect `on_sp` in some cases to render code as written.

https://github.com/ruby/prism/commit/74bb12c825

4 files changed, 61 insertions, 10 deletions

diff --git a/lib/prism/prism.gemspec b/lib/prism/prism.gemspec
index 463387e55c..283c7b04aa 100644
--- a/lib/prism/prism.gemspec
+++ b/lib/prism/prism.gemspec
@@ -104,6 +104,7 @@ Gem::Specification.new do |spec|
     "lib/prism/translation/parser/compiler.rb",
     "lib/prism/translation/parser/lexer.rb",
     "lib/prism/translation/ripper.rb",
+    "lib/prism/translation/ripper/filter.rb",
     "lib/prism/translation/ripper/lexer.rb",
     "lib/prism/translation/ripper/sexp.rb",
     "lib/prism/translation/ripper/shim.rb",
diff --git a/lib/prism/translation/ripper.rb b/lib/prism/translation/ripper.rb
index 6552d2dbb8..c8f9fa7731 100644
--- a/lib/prism/translation/ripper.rb
+++ b/lib/prism/translation/ripper.rb
@@ -437,6 +437,7 @@ module Prism
         end
       end
 
+      autoload :Filter, "prism/translation/ripper/filter"
       autoload :Lexer, "prism/translation/ripper/lexer"
       autoload :SexpBuilder, "prism/translation/ripper/sexp"
       autoload :SexpBuilderPP, "prism/translation/ripper/sexp"
diff --git a/lib/prism/translation/ripper/filter.rb b/lib/prism/translation/ripper/filter.rb
new file mode 100644
index 0000000000..19deef2d37
--- /dev/null
+++ b/lib/prism/translation/ripper/filter.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+module Prism
+  module Translation
+    class Ripper
+      class Filter # :nodoc:
+        # :stopdoc:
+        def initialize(src, filename = '-', lineno = 1)
+          @__lexer = Lexer.new(src, filename, lineno)
+          @__line = nil
+          @__col = nil
+          @__state = nil
+        end
+
+        def filename
+          @__lexer.filename
+        end
+
+        def lineno
+          @__line
+        end
+
+        def column
+          @__col
+        end
+
+        def state
+          @__state
+        end
+
+        def parse(init = nil)
+          data = init
+          @__lexer.lex.each do |pos, event, tok, state|
+            @__line, @__col = *pos
+            @__state = state
+            data = if respond_to?(event, true)
+                  then __send__(event, tok, data)
+                  else on_default(event, tok, data)
+                  end
+          end
+          data
+        end
+
+        private
+
+        def on_default(event, token, data)
+          data
+        end
+        # :startdoc:
+      end
+    end
+  end
+end
diff --git a/lib/prism/translation/ripper/lexer.rb b/lib/prism/translation/ripper/lexer.rb
index 787181b5a7..bd40fb4c5a 100644
--- a/lib/prism/translation/ripper/lexer.rb
+++ b/lib/prism/translation/ripper/lexer.rb
@@ -100,21 +100,17 @@ module Prism
           end
         end
 
-        def initialize(...)
-          super
-          @lex_compat = Prism.lex_compat(@source, filepath: filename, line: lineno)
+        # Pretty much just the same as Prism.lex_compat.
+        def lex(raise_errors: false)
+          Ripper.lex(@source, filename, lineno, raise_errors: raise_errors)
         end
 
         # Returns the lex_compat result wrapped in `Elem`. Errors are omitted.
         # Since ripper is a streaming parser, tokens are expected to be emitted in the order
         # that the parser encounters them. This is not implemented.
-        def parse(raise_errors: false)
-          if @lex_compat.failure? && raise_errors
-            raise SyntaxError, @lex_compat.errors.first.message
-          else
-            @lex_compat.value.map do |position, event, token, state|
-              Elem.new(position, event, token, state.to_int)
-            end
+        def parse(...)
+          lex(...).map do |position, event, token, state|
+            Elem.new(position, event, token, state.to_int)
           end
         end