refactor Lexer to only take StringScanner

lib/liquid/lexer.rb

@@ -26,8 +26,7 @@ module Liquid
     WHITESPACE_OR_NOTHING = /\s*/
 
     class << self
-      def tokenize(input, ss = StringScanner.new(input))
-        ss.string = input
+      def tokenize(ss)
         output = []
 
         until ss.eos?
@@ -158,8 +157,7 @@ module Liquid
 
     # rubocop:disable Metrics/BlockNesting
     class << self
-      def tokenize(input, ss)
-        ss.string = input
+      def tokenize(ss)
         output = []
 
         until ss.eos?

lib/liquid/parse_context.rb

@@ -3,7 +3,7 @@
 module Liquid
   class ParseContext
     attr_accessor :locale, :line_number, :trim_whitespace, :depth
-    attr_reader :partial, :warnings, :error_mode, :environment, :string_scanner, :expression_cache
+    attr_reader :partial, :warnings, :error_mode, :environment
 
     def initialize(options = Const::EMPTY_HASH)
       @environment = options.fetch(:environment, Environment.default)
@@ -44,7 +44,7 @@ module Liquid
     end
 
     def parse_expression(markup)
-      Expression.parse(markup, string_scanner, expression_cache)
+      Expression.parse(markup, @string_scanner, @expression_cache)
     end
 
     def partial=(value)

lib/liquid/parser.rb

@@ -3,8 +3,8 @@
 module Liquid
   class Parser
     def initialize(input)
-      input = input.is_a?(StringScanner) ? input : StringScanner.new(input.to_s)
-      @tokens = Lexer.tokenize(input, string_scanner)
+      ss = input.is_a?(StringScanner) ? input : StringScanner.new(input)
+      @tokens = Lexer.tokenize(ss)
       @p      = 0 # pointer to current location
     end
 

test/unit/lexer_unit_test.rb

@@ -134,6 +134,6 @@ class LexerUnitTest < Minitest::Test
   private
 
   def tokenize(input)
-    Lexer.tokenize(input, StringScanner.new(""))
+    Lexer.tokenize(StringScanner.new(input))
   end
 end

test/unit/parser_unit_test.rb

@@ -85,6 +85,6 @@ class ParserUnitTest < Minitest::Test
   private
 
   def new_parser(str)
-    Parser.new(str, StringScanner.new(""))
+    Parser.new(StringScanner.new(str))
   end
 end