Allow to make ERB marshalable

lib/erb.rb

@@ -268,6 +268,28 @@ def self.version
     VERSION
   end
 
+  module Unmarshalable # :nodoc:
+    def initialize_for_marshal
+      @_init = self.class.singleton_class
+    end
+    private :initialize_for_marshal
+
+    def pre_eval_check
+      unless @_init.equal?(self.class.singleton_class)
+        raise ArgumentError, "not initialized"
+      end
+    end
+    private :pre_eval_check
+  end
+  include Unmarshalable
+
+  # Module to make ERB marshalable.
+  module Marshalable # :nodoc:
+    Unmarshalable.private_instance_methods.each do |m|
+      define_method(m) {}
+    end
+  end
+
   #
   # Constructs a new ERB object with the template specified in _str_.
   #
@@ -351,7 +373,7 @@ def initialize(str, safe_level=NOT_GIVEN, legacy_trim_mode=NOT_GIVEN, legacy_eou
     @src, @encoding, @frozen_string = *compiler.compile(str)
     @filename = nil
     @lineno = 0
-    @_init = self.class.singleton_class
+    initialize_for_marshal
   end
   NOT_GIVEN = Object.new
   private_constant :NOT_GIVEN
@@ -423,9 +445,7 @@ def run(b=new_toplevel)
   # code evaluation.
   #
   def result(b=new_toplevel)
-    unless @_init.equal?(self.class.singleton_class)
-      raise ArgumentError, "not initialized"
-    end
+    pre_eval_check
     eval(@src, b, (@filename || '(erb)'), @lineno)
   end
 

test/erb/test_erb.rb

@@ -714,6 +714,19 @@ def test_prohibited_marshal_load
     assert_raise(ArgumentError) {erb.result}
   end
 
+  class MarshalableERB < ERB
+    include Marshalable
+  end
+
+  def test_marshalable_subclass_marshal
+    erb = MarshalableERB.new("<%=x%>")
+    dump = assert_nothing_raised(TypeError) {Marshal.dump(erb)}
+    loaded = Marshal.load(dump)
+    bind = binding
+    bind.local_variable_set(:x, 42)
+    assert_equal("42", loaded.result(bind))
+  end
+
   def test_multi_line_comment_lineno
     erb = ERB.new(<<~EOS)
       <%= __LINE__ %>