Remove support for taint_mode on ruby versions that don't support it

lib/liquid/template.rb

@@ -69,7 +69,14 @@ module Liquid
       # :lax is the default, and ignores the taint flag completely
       # :warn adds a warning, but does not interrupt the rendering
       # :error raises an error when tainted output is used
-      attr_writer :taint_mode
+      # @deprecated Since it is being deprecated in ruby itself.
+      def taint_mode=(mode)
+        taint_supported = Object.new.taint.tainted?
+        if mode != :lax && !taint_supported
+          raise NotImplementedError, "#{RUBY_ENGINE} #{RUBY_VERSION} doesn't support taint checking"
+        end
+        @taint_mode = mode
+      end
 
       attr_accessor :default_exception_renderer
       Template.default_exception_renderer = lambda do |exception|

lib/liquid/variable.rb

@@ -143,8 +143,8 @@ module Liquid
     end
 
     def taint_check(context, obj)
-      return unless obj.tainted?
       return if Template.taint_mode == :lax
+      return unless obj.tainted?
 
       @markup =~ QuotedFragment
       name = Regexp.last_match(0)

test/integration/drop_test.rb

@@ -114,6 +114,7 @@ class DropsTest < Minitest::Test
     assert_equal('  ', tpl.render!('product' => ProductDrop.new))
   end
 
+  if taint_supported?
     def test_rendering_raises_on_tainted_attr
       with_taint_mode(:error) do
         tpl = Liquid::Template.parse('{{ product.user_input }}')
@@ -139,6 +140,7 @@ class DropsTest < Minitest::Test
         tpl.render!('product' => ProductDrop.new)
       end
     end
+  end
 
   def test_drop_does_only_respond_to_whitelisted_methods
     assert_equal("", Liquid::Template.parse("{{ product.inspect }}").render!('product' => ProductDrop.new))

test/integration/tags/render_tag_test.rb

@@ -42,6 +42,7 @@ class RenderTagTest < Minitest::Test
     assert_template_result('', "{% assign snippet = 'should not be visible' %}{% render 'snippet' %}")
   end
 
+  if taint_supported?
     def test_render_sets_the_correct_template_name_for_errors
       Liquid::Template.file_system = StubFileSystem.new('snippet' => '{{ unsafe }}')
 
@@ -67,6 +68,7 @@ class RenderTagTest < Minitest::Test
         assert_equal 'snippet', context.warnings.first.template_name
       end
     end
+  end
 
   def test_render_does_not_mutate_parent_scope
     Liquid::Template.file_system = StubFileSystem.new('snippet' => '{% assign inner = 1 %}')

test/integration/template_test.rb

@@ -361,4 +361,12 @@ class TemplateTest < Minitest::Test
     result = t.render('x' => 1, 'y' => 5)
     assert_equal('12345', result)
   end
+
+  unless taint_supported?
+    def test_taint_mode
+      assert_raises(NotImplementedError) do
+        Template.taint_mode = :warn
+      end
+    end
+  end
 end

test/test_helper.rb

@@ -32,6 +32,10 @@ module Minitest
     def fixture(name)
       File.join(File.expand_path(__dir__), "fixtures", name)
     end
+
+    def self.taint_supported?
+      Object.new.taint.tainted?
+    end
   end
 
   module Assertions