[ruby-core:24579] Re: [Bug #1711] Marshal Failing to Round-Trip Certain Recurisve Data Structures

On Jul 27, 2009, at 06:14, Yukihiro Matsumoto wrote:
> In message "Re: [ruby-core:24105] [Bug #1711] Marshal Failing to  
> Round-Trip Certain Recurisve Data Structures"
>    on Thu, 2 Jul 2009 02:30:15 +0900, Run Paint Run Run <[e-mail] 
> > writes:
>
>> I have attached a script that fails to round-trip a recursive data  
>> structure on 1.9, but succeeds on 1.8. IOW, it prints true on 1.8;  
>> false on 1.9. I haven't been able to reduce it further because I'm  
>> unfamiliar with Marshal.
>>
>
> 1.9 Marshal.load with proc is incompatible with 1.8, as following:
>
>  * 1.8 load ignores the value returned from proc, whereas 1.9 load
>    replaces the object by the value from proc.
>
>  * 1.9 load calls proc for recursively visited data.  1.8 dump only
>    calls proc once.
>
> That is to allow rebuilding loading data using proc.  For
> the example in [ruby-core:24361], replacing
>
> myproc = Proc.new { |o| arr << o }
>
> by
>
> myproc = Proc.new { |o| arr << o; o }
>
> should work as expected.  The future action would be either:
>
> (a) the new 1.9 behavior has meaning.  since virtually no one uses
>     Marshal.load with proc, it's OK to change it for a good reason.
>
> (b) incompatibility is bad.  should be reverted to the original 1.8
>     behavior.
>
> (c) or probably add another optional (or keyword) argument to enable
>     the new behavior, keeping the old behavior by default.
>
> Any opinion?

I haven't seen Marshal.load with proc in the wild, so I prefer (a).

In the future, I could imagine using the new 1.9 behavior in RubyGems  
for backwards compatibility.