Should Enumerator#initialize check frozen status?

[kachick]

ruby -v #=> ruby 2.0.0p247 (2013-06-27 revision 41674) [i686-linux]

Frozen Enumerator can modify positions.

enum = [1, 2].to_enum.freeze
enum.next #=> 1
enum.rewind
enum.next #=> 1

But it can't replace receiver-object/block on following methods.

• Enumerator#initialize_copy
• Enumerator::Lazy#initialize_copy
• Enumerator::Lazy#initialize

enum = [1, 2].to_enum.freeze
enum.send :initialize_copy, [1, 2]   #=> RuntimeError: can't modify frozen Enumerator

lazy = [1, 2].to_enum.lazy.freeze
lazy.send :initialize_copy, [1, 2]   #=> RuntimeError: can't modify frozen Enumerator::Lazy
lazy.send :initialize, [1, 2], &->{} #=> RuntimeError: can't modify frozen Enumerator::Lazy

Except Enumerator#initialize.

enum = [1, 2].to_enum.freeze
enum.send :initialize, [3, 4] #=> warning: Enumerator.new without a block is deprecated; use Object#to_enum
                              #   <Enumerator: [3, 4]:each>
enum.send :initialize, &->{}  #=> #<Enumerator: #<Enumerator::Generator:0xb7fa7258>:each>

Is this a spec?

[knu]

The reason #initialize_copy raises an error on a frozen object is just because of its common behavior (see rb_obj_init_copy()) and it is not because Enumerator explicitly checks the frozenness. Plus, using a private method #initialize to modify an enumerator object is an unsupported operation and kind of abuse.

To wrap up, my take is that Enumerator doesn't have the sense of frozenness, so there is no spec at the moment.

Given that, I'm not sure we would want to decently implement the frozenness in Enumerator because a frozen enumerator, if at all, would have no use. Even #peek could change the state of the object, so all you could do with it is call #size or #inspect. There should be something better to do than pass an unusable object around.

[kachick]

Thank you for sharing that with me!
I quite agree "#initialize to modify an enumerator object is an unsupported operation and kind of abuse".

I felt strange Enumerator#initialize. This is because Regexp#initialize explicitly checking frozen and I don't know when using frozen Regexp.
I guessed every #initialize required checking frozen.

But I'm sure frozen Enumerator has no meanings and the implementation is needless.
Thank you :)

[knu]

Actually, I didn't mean to reject this. What I wrote above was just an excuse for not eagerly supporting frozenness in Enumerator.
I think it makes much sense to prevent a frozen enumerator from being modified with #initialize, so I'm going to merge this.
Thanks for your report!

[kachick]

I'm happy with the results :)
Thank you!