[rspec-users] Name collision - how would you handle this?

David Chelimsky dchelimsky at gmail.com
Sun Aug 8 21:29:48 EDT 2010


On Aug 8, 2010, at 11:58 AM, Myron Marston wrote:

> Good error messages are important to a library's usability.  Could we
> find away to give the user a good error message when they override a
> "reserved method"?
> 
> I'm thinking this could be accomplished with 2 simple pieces:
> 
> 1. A method_added hook in Rspec-core that gives a warning or error
> when a reserved method is overridden.
> 2. An API that allows libraries to add to the reserved methods list.
> 
> That way, rspec doesn't have to have knowledge of other libraries; it
> would be the responsibility of other libraries to add their reserved
> methods to the list.

Yehuda Katz made a similar suggestion to me, referencing some code from merb: http://github.com/merb/merb/blob/master/merb-core/lib/merb-core/controller/merb_controller.rb#L508

Merb also has an override! method that end users can use to override the registered reserved methods, which I agree would be a necessary part of this. The idea being that any user that does that does so explicitly and knowingly.

The blacklist comment probably wouldn't work for upstream libs like Rails, Test::Unit or MiniUnit. It would be up to RSpec to define those lists. But maybe that's an acceptable tradeoff. WDYT?


> Myron
> 
> On Aug 8, 9:13 am, Matt Wynne <m... at mattwynne.net> wrote:
>> On 8 Aug 2010, at 16:53, David Chelimsky wrote:
>> 
>> 
>> 
>> 
>> 
>>> On Aug 8, 2010, at 10:40 AM, Matt Wynne wrote:
>>>> On 8 Aug 2010, at 16:38, David Chelimsky wrote:
>>>>> On Aug 7, 2010, at 4:10 PM, David Chelimsky wrote:
>> 
>>>>>> Hey all,
>> 
>>>>>> It turns out that if you have
>> 
>>>>>> * Rails (2 or 3)
>>>>>> * Ruby-1.9
>>>>>> * a model named Message
>>>>>> * let(:message) or def message in an example group
>>>>>> * a Rails assertion in an example in that group
>>>>>> * note that rspec-rails' matchers delegate to Rails' assertions
>> 
>>>>>> You'll get an error saying "wrong number of arguments (1 for 0)"
>> 
>>>>>> This is because the rails assertion, which, when running with Ruby-1.9, delegates to Minitest::Assertions#assert_block, which delegates to a message() method that it defines. So the message() method defined by let() overrides the message() method in the Assertions module, and results in unexpected and undesirable outcomes.
>> 
>>>>>> So - what should we do? I don't think changing Minitest is really an option, as too many assertion libraries already wrap Minitest assertions. I don't think RSpec should be in the business of monitoring methods end-users define to make sure they're not overriding pre-existing methods (what if you override a method intentionally?). The only thing I'm left with is document this particular case and hope for the best, but that feels unsatisfactory as well.
>> 
>>>>>> Recommendations? Words of wisdom?
>> 
>>>>> FYI - here's the issue that spawned this thread:http://github.com/rspec/rspec-rails/issues/152
>> 
>>>> Can you use the Assertions module some other way than mixing it into the example (thereby polluting it with the Assertions module's methods?)
>> 
>>> I like the idea in the abstract, but most of the rails assertions rely on some state that is local to the example (@response, @controller, @request, etc, etc). RSpec _could_ gather up all those instance variables and pass them into an assertion-wrapper object, but then it would be highly coupled to that implementation and would lead us down a familiar and unfriendly path of forcing rspec-rails releases for every rails release. That's a world I hope to leave behind with Rails 3 :)
>> 
>> So leave the rails assertions mixed into the example, but forward all the calls to the MiniTest::Assertions methods to some other object that has them mixed in. Won't that work?
>> 
>> 
>> 
>>> It would also eliminate the option to use the Rails assertions directly in examples.
>> 
>>> Oh, well :)
>> 
>>>> cheers,
>>>> Matt
>> 
>>>> http://blog.mattwynne.net
>>>> +44(0)7974 430184
>> 
>>> _______________________________________________
>>> rspec-users mailing list
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>> 
>> cheers,
>> Matt
>> 
>> http://blog.mattwynne.net+44(0)7974 430184
>> 
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