[ruby/prism] Move LexRipper into its own file

It has a hard dependency on ripper that can't be removed.
This makes it so that ripper can be loaded only when the class is actually used.

https://github.com/ruby/prism/commit/3b5b4a8a6d

lib/prism.rb

@@ -20,7 +20,7 @@ module Prism
   autoload :DSL, "prism/dsl"
   autoload :InspectVisitor, "prism/inspect_visitor"
   autoload :LexCompat, "prism/lex_compat"
-  autoload :LexRipper, "prism/lex_compat"
+  autoload :LexRipper, "prism/lex_ripper"
   autoload :MutationCompiler, "prism/mutation_compiler"
   autoload :Pack, "prism/pack"
   autoload :Pattern, "prism/pattern"

lib/prism/lex_compat.rb

@@ -867,62 +867,4 @@ module Prism
   end
 
   private_constant :LexCompat
-
-  # This is a class that wraps the Ripper lexer to produce almost exactly the
-  # same tokens.
-  class LexRipper # :nodoc:
-    attr_reader :source
-
-    def initialize(source)
-      @source = source
-    end
-
-    def result
-      previous = [] #: [[Integer, Integer], Symbol, String, untyped] | []
-      results = [] #: Array[[[Integer, Integer], Symbol, String, untyped]]
-
-      lex(source).each do |token|
-        case token[1]
-        when :on_sp
-          # skip
-        when :on_tstring_content
-          if previous[1] == :on_tstring_content && (token[2].start_with?("\#$") || token[2].start_with?("\#@"))
-            previous[2] << token[2]
-          else
-            results << token
-            previous = token
-          end
-        when :on_words_sep
-          if previous[1] == :on_words_sep
-            previous[2] << token[2]
-          else
-            results << token
-            previous = token
-          end
-        else
-          results << token
-          previous = token
-        end
-      end
-
-      results
-    end
-
-    private
-
-    if Ripper.method(:lex).parameters.assoc(:keyrest)
-      def lex(source)
-        Ripper.lex(source, raise_errors: true)
-      end
-    else
-      def lex(source)
-        ripper = Ripper::Lexer.new(source)
-        ripper.lex.tap do |result|
-          raise SyntaxError, ripper.errors.map(&:message).join(' ;') if ripper.errors.any?
-        end
-      end
-    end
-  end
-
-  private_constant :LexRipper
 end

lib/prism/lex_ripper.rb

@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+# :markup: markdown
+
+require "ripper"
+
+module Prism
+  # This is a class that wraps the Ripper lexer to produce almost exactly the
+  # same tokens.
+  class LexRipper # :nodoc:
+    attr_reader :source
+
+    def initialize(source)
+      @source = source
+    end
+
+    def result
+      previous = [] #: [[Integer, Integer], Symbol, String, untyped] | []
+      results = [] #: Array[[[Integer, Integer], Symbol, String, untyped]]
+
+      lex(source).each do |token|
+        case token[1]
+        when :on_sp
+          # skip
+        when :on_tstring_content
+          if previous[1] == :on_tstring_content && (token[2].start_with?("\#$") || token[2].start_with?("\#@"))
+            previous[2] << token[2]
+          else
+            results << token
+            previous = token
+          end
+        when :on_words_sep
+          if previous[1] == :on_words_sep
+            previous[2] << token[2]
+          else
+            results << token
+            previous = token
+          end
+        else
+          results << token
+          previous = token
+        end
+      end
+
+      results
+    end
+
+    private
+
+    if Ripper.method(:lex).parameters.assoc(:keyrest)
+      def lex(source)
+        Ripper.lex(source, raise_errors: true)
+      end
+    else
+      def lex(source)
+        ripper = Ripper::Lexer.new(source)
+        ripper.lex.tap do |result|
+          raise SyntaxError, ripper.errors.map(&:message).join(' ;') if ripper.errors.any?
+        end
+      end
+    end
+  end
+
+  private_constant :LexRipper
+end

lib/prism/prism.gemspec

@@ -77,6 +77,7 @@ Gem::Specification.new do |spec|
     "lib/prism/ffi.rb",
     "lib/prism/inspect_visitor.rb",
     "lib/prism/lex_compat.rb",
+    "lib/prism/lex_ripper.rb",
     "lib/prism/mutation_compiler.rb",
     "lib/prism/node_ext.rb",
     "lib/prism/node.rb",