Fix Marshal serialization of Template, Environment, and ParseContext

lib/liquid/environment.rb

@@ -155,5 +155,18 @@ def freeze
       # @strainer_template.freeze
       super
     end
+
+    def marshal_dump
+      filter_modules = @strainer_template.ancestors[1...@strainer_template.ancestors.index(StrainerTemplate)]
+      [@tags, @error_mode, @file_system, @default_resource_limits, filter_modules]
+    end
+
+    def marshal_load(data)
+      @tags, @error_mode, @file_system, @default_resource_limits, filter_modules = data
+      @exception_renderer = ->(exception) { exception }
+      @strainer_template = Class.new(StrainerTemplate)
+      filter_modules.reverse_each { |m| @strainer_template.add_filter(m) }
+      @strainer_template_class_cache = {}
+    end
   end
 end

lib/liquid/parse_context.rb

@@ -88,5 +88,14 @@ def partial_options
         end
       end
     end
+
+    def marshal_dump
+      instance_variables.reject { |v| v == :@string_scanner }.map { |v| [v, instance_variable_get(v)] }.to_h
+    end
+
+    def marshal_load(data)
+      data.each { |k, v| instance_variable_set(k, v) }
+      @string_scanner = StringScanner.new("")
+    end
   end
 end

test/unit/template_unit_test.rb

@@ -46,4 +46,26 @@ def test_invalid_utf8
       error.message,
     )
   end
+
+  module UpFilter
+    def up(input) = input.upcase
+  end
+
+  def test_marshal_roundtrip
+    env = Liquid::Environment.build { |e| e.register_filter(UpFilter) }
+    t = Template.parse("Hello {{ name | up }}", environment: env)
+    t2 = Marshal.load(Marshal.dump(t))
+    assert_equal("Hello WORLD", t2.render("name" => "world"))
+  end
+
+  module ShoutFilter
+    def shout(input) = input.upcase + "!"
+  end
+
+  def test_marshal_roundtrip_with_custom_filter
+    env = Liquid::Environment.build { |e| e.register_filter(ShoutFilter) }
+    t = Template.parse("{{ name | shout }}", environment: env)
+    t2 = Marshal.load(Marshal.dump(t))
+    assert_equal("WORLD!", t2.render("name" => "world"))
+  end
 end