Rails - Apr 2008 - rescue_from issue with AWS - uninitialized constant

The new rescue_from in edge rails seems to conflict with
ActionWebService, which I need for various other purposes.  When I
define, for example (with AWS gem installed):

<b>rescue_from ActionController::RoutingError, :with
=> :page_not_found</b>

I get the exception:

<b>uninitialized constant
ActionWebService::Dispatcher::ActionController::Base</b>

OK, so AWS interfers with the inheritance chain I guess, but if I
define:

<b>rescue_from Object::ActionController::RoutingError, :with
=> :page_not_found</b>

I get no errors, but then the rescue_from method isn''t invoked either.

Anyone got any advice?  I can get around this with
rescue_action_in_public, but thats just not as nice.

Cheers, --Kip
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On Apr 30, 2008, at 8:19 , Kip wrote:
> The new rescue_from in edge rails
rescue_from comes with Rails 2.
> seems to conflict with
> ActionWebService, which I need for various other purposes.  When I
> define, for example (with AWS gem installed):
>
> <b>rescue_from ActionController::RoutingError, :with
> => :page_not_found</b>
>
> I get the exception:
>
> <b>uninitialized constant
> ActionWebService::Dispatcher::ActionController::Base</b>
>
> OK, so AWS interfers with the inheritance chain I guess, but if I
> define:
The problem seems to be that ActionController::RoutingError is an  
unknown constant at the time that file is being interpreted. If that''s
correct that''s unrelated to rescue_from, it just happens that Ruby  
sees a constant, tries to resolve it because it is an argument of a  
method it is calling (rescue_from), and fails.

The first thing I''d try is to pass the exception class name instead of
the exception class itself:

     rescue_from "ActionController::RoutingError", :with  
=> :page_not_found

If the exception gets raised it will be certainly already loaded and  
rescue_from will be able to find the match.

-- fxn


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> > <b>uninitialized constant
> > ActionWebService::Dispatcher::ActionController::Base</b>
>
> > OK, so AWS interfers with the inheritance chain I guess, but if I
> > define:
>
> The problem seems to be that ActionController::RoutingError is an  
> unknown constant at the time that file is being interpreted. If
that''s  
> correct that''s unrelated to rescue_from, it just happens that Ruby
 
> sees a constant, tries to resolve it because it is an argument of a  
> method it is calling (rescue_from), and fails.
>
> The first thing I''d try is to pass the exception class name
instead of  
> the exception class itself:
>
>      rescue_from "ActionController::RoutingError", :with  
> => :page_not_found
I''ve seen ::ActionController::RoutingError work too I think.

Fred
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On Apr 30, 2008, at 9:56 , Frederick Cheung wrote:
> I''ve seen ::ActionController::RoutingError work too I think.
Good.

For Kip: AWS defines a constant ActionController somewhere within its  
namespace. If putting a leading "::" works it would happen that  
rescue_from is invoked somehow within that namespace[*] and  
"ActionContoller" is found relative to something instead of as the
top-
level constant. The one in AWS does not have a child RoutingError  
constant, and since constant name resolution has no backtracking so to  
speak it fails at that point.

-- fxn

[*] Somehow means the way constant name resolution works.

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Very helpful guys, thank you.  The String argument to rescue_from
works fine.  Of course I made a stupid error for my example:
ActionController::RoutingError is never going to be rescued in this
way (since it relies on a normal controller execution).

Therefore there is still a reason to use rescue_action(_in_public) in
order to handle that error (unless I missed something entirely!)

Cheers, --Kip

On Apr 30, 6:35 pm, Xavier Noria
<f...-xlncskNFVEJBDgjK7y7TUQ@public.gmane.org>
wrote:
> On Apr 30, 2008, at 9:56 , Frederick Cheung wrote:
>
> > I''ve seen ::ActionController::RoutingError work too I think.
>
> Good.
>
> For Kip: AWS defines a constant ActionController somewhere within its  
> namespace. If putting a leading "::" works it would happen that  
> rescue_from is invoked somehow within that namespace[*] and  
> "ActionContoller" is found relative to something instead of as
the top-
> level constant. The one in AWS does not have a child RoutingError  
> constant, and since constant name resolution has no backtracking so to  
> speak it fails at that point.
>
> -- fxn
>
> [*] Somehow means the way constant name resolution works.
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On May 1, 2008, at 4:41 , Kip wrote:
> Very helpful guys, thank you.  The String argument to rescue_from
> works fine.  Of course I made a stupid error for my example:
> ActionController::RoutingError is never going to be rescued in this
> way (since it relies on a normal controller execution).
>
> Therefore there is still a reason to use rescue_action(_in_public) in
> order to handle that error (unless I missed something entirely!)
Why it follows?

rescue_from is written in a way that does not assume the exceptions  
you declare will ever exist. That''s why it understands a string with  
an exception class name as well as an excection class.

In its implementation if a string is unknown as constant by the time  
some exception is being processed it just ignores it and continues.  
That''s by design.

-- fxn


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On 1 May 2008, at 11:16, Xavier Noria wrote:
>
> On May 1, 2008, at 4:41 , Kip wrote:
>
>> Very helpful guys, thank you.  The String argument to rescue_from
>> works fine.  Of course I made a stupid error for my example:
>> ActionController::RoutingError is never going to be rescued in this
>> way (since it relies on a normal controller execution).
>>
>> Therefore there is still a reason to use rescue_action(_in_public) in
>> order to handle that error (unless I missed something entirely!)
>
> Why it follows?
>
> rescue_from is written in a way that does not assume the exceptions
> you declare will ever exist. That''s why it understands a string
with
> an exception class name as well as an excection class.
>
I think Kip''s point is that ActionController::RoutingError is thrown  
when a controller could not be found that matched the url, so having  
something in a controller to rescue_from it is futile.

Fred
> In its implementation if a string is unknown as constant by the time
> some exception is being processed it just ignores it and continues.
> That''s by design.
>
> -- fxn
>
>
> >

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On May 1, 2008, at 12:29 , Frederick Cheung wrote:
>
> On 1 May 2008, at 11:16, Xavier Noria wrote:
>
>>
>> On May 1, 2008, at 4:41 , Kip wrote:
>>
>>> Very helpful guys, thank you.  The String argument to rescue_from
>>> works fine.  Of course I made a stupid error for my example:
>>> ActionController::RoutingError is never going to be rescued in this
>>> way (since it relies on a normal controller execution).
>>>
>>> Therefore there is still a reason to use rescue_action(_in_public)
>>> in
>>> order to handle that error (unless I missed something entirely!)
>>
>> Why it follows?
>>
>> rescue_from is written in a way that does not assume the exceptions
>> you declare will ever exist. That''s why it understands a
string with
>> an exception class name as well as an excection class.
>>
> I think Kip''s point is that ActionController::RoutingError is
thrown
> when a controller could not be found that matched the url, so having
> something in a controller to rescue_from it is futile.
Oh yes.

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