Rails core - Sep 2012 - Proposal for a new ActiveModel::Errors structure

There are few issues with the current ActiveModel::Errors class.

Firstly, when an error is added to ActiveModel::Errors class via #add 
method 
(https://github.com/rails/rails/blob/master/activemodel/lib/active_model/errors.rb#L294)
its translation is added. It should not be translated when being added, but 
only when being read.

The second issue is a bit bigger. We''d like to create error responses
in
our API similar to GitHub: 

{
   "message": "Validation Failed",
   "errors": [
     {
       "resource": "Issue",
       "field": "title",
       "code": "missing_field"
     }
   ]
 }


Currently it''s impossible to figure out which validations actually
failed
for a given field, as AM::Errors provides only field name and translated 
error message. We''ve got a simple workaround for this issue:

module ActiveModel
  class Errors
    def error_types
      @_error_types ||= Hash.new{|hash,k| hash[k] = []}
    end

    def add_with_save_names(attribute, message = nil, options = {})
      message ||= :invalid
      message = message.call if message.is_a?(Proc)
      error_types[attribute] << message
      add_without_save_names(attribute, message, options)
    end

    alias_method_chain :add, :save_names
  end
end 


This solution is far from perfect, but it''s relatively simple and so
far
works for us.

The best solution would be to actually build a structure similar to GitHub 
response - from that structure it would be trivial to build #full_messages 
and similar methods and it would provide a lot of additional info which 
would be extremely useful for creating APIs.

Cheers,
Szymon

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I would really love to see such changes in AM::Errors. +1 from me.

On Tue, Sep 25, 2012 at 3:39 PM, Szymon Nowak <szimek@gmail.com> wrote:
> There are few issues with the current ActiveModel::Errors class.
>
> Firstly, when an error is added to ActiveModel::Errors class via #add
> method (
>
https://github.com/rails/rails/blob/master/activemodel/lib/active_model/errors.rb#L294)
> its translation is added. It should not be translated when being added, but
> only when being read.
>
> The second issue is a bit bigger. We''d like to create error
responses in
> our API similar to GitHub:
>
> {
>    "message": "Validation Failed",
>    "errors": [
>      {
>        "resource": "Issue",
>        "field": "title",
>        "code": "missing_field"
>      }
>    ]
>  }
>
>
> Currently it''s impossible to figure out which validations actually
failed
> for a given field, as AM::Errors provides only field name and translated
> error message. We''ve got a simple workaround for this issue:
>
> module ActiveModel
>   class Errors
>     def error_types
>       @_error_types ||= Hash.new{|hash,k| hash[k] = []}
>     end
>
>     def add_with_save_names(attribute, message = nil, options = {})
>       message ||= :invalid
>       message = message.call if message.is_a?(Proc)
>       error_types[attribute] << message
>       add_without_save_names(attribute, message, options)
>     end
>
>     alias_method_chain :add, :save_names
>   end
> end
>
>
> This solution is far from perfect, but it''s relatively simple and
so far
> works for us.
>
> The best solution would be to actually build a structure similar to GitHub
> response - from that structure it would be trivial to build #full_messages
> and similar methods and it would provide a lot of additional info which
> would be extremely useful for creating APIs.
>
> Cheers,
> Szymon
>
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-- 
Piotr Sarnacki
http://piotrsarnacki.com

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On Tue, Sep 25, 2012 at 06:39:58AM -0700, Szymon Nowak
wrote:
> There are few issues with the current ActiveModel::Errors class.
> 
> Firstly, when an error is added to ActiveModel::Errors class via #add 
> method 
>
(https://github.com/rails/rails/blob/master/activemodel/lib/active_model/errors.rb#L294)
> its translation is added. It should not be translated when being added, but
> only when being read.
> 
> The second issue is a bit bigger. We''d like to create error
responses in
> our API similar to GitHub: 
> 
> {
>    "message": "Validation Failed",
>    "errors": [
>      {
>        "resource": "Issue",
>        "field": "title",
>        "code": "missing_field"
>      }
>    ]
>  }
> 
> 
> Currently it''s impossible to figure out which validations actually
failed
> for a given field, as AM::Errors provides only field name and translated 
> error message. We''ve got a simple workaround for this issue:
> 
> module ActiveModel
>   class Errors
>     def error_types
>       @_error_types ||= Hash.new{|hash,k| hash[k] = []}
>     end
> 
>     def add_with_save_names(attribute, message = nil, options = {})
>       message ||= :invalid
>       message = message.call if message.is_a?(Proc)
>       error_types[attribute] << message
>       add_without_save_names(attribute, message, options)
>     end
> 
>     alias_method_chain :add, :save_names
>   end
> end 
> 
> 
> This solution is far from perfect, but it''s relatively simple and
so far
> works for us.
> 
> The best solution would be to actually build a structure similar to GitHub 
> response - from that structure it would be trivial to build #full_messages 
> and similar methods and it would provide a lot of additional info which 
> would be extremely useful for creating APIs.
Seems good.  Can you work on a patch and send a PR?  If we can maintain
backwards compat, I am happy.

-- 
Aaron Patterson
http://tenderlovemaking.com/

On Tuesday, 25 September 2012 19:26:40 UTC+2, Aaron Patterson wrote:
> On Tue, Sep 25, 2012 at 06:39:58AM -0700, Szymon Nowak wrote: 
> > There are few issues with the current ActiveModel::Errors class. 
> > 
> > Firstly, when an error is added to ActiveModel::Errors class via #add 
> > method 
> > (
>
https://github.com/rails/rails/blob/master/activemodel/lib/active_model/errors.rb#L294)
>
> > its translation is added. It should not be translated when being
added,
> but 
> > only when being read. 
> > 
> > The second issue is a bit bigger. We''d like to create error
responses in
> > our API similar to GitHub: 
> > 
> > { 
> >    "message": "Validation Failed", 
> >    "errors": [ 
> >      { 
> >        "resource": "Issue", 
> >        "field": "title", 
> >        "code": "missing_field" 
> >      } 
> >    ] 
> >  } 
> > 
> > 
> > Currently it''s impossible to figure out which validations
actually
> failed 
> > for a given field, as AM::Errors provides only field name and
translated
> > error message. We''ve got a simple workaround for this issue: 
> > 
> > module ActiveModel 
> >   class Errors 
> >     def error_types 
> >       @_error_types ||= Hash.new{|hash,k| hash[k] = []} 
> >     end 
> > 
> >     def add_with_save_names(attribute, message = nil, options = {}) 
> >       message ||= :invalid 
> >       message = message.call if message.is_a?(Proc) 
> >       error_types[attribute] << message 
> >       add_without_save_names(attribute, message, options) 
> >     end 
> > 
> >     alias_method_chain :add, :save_names 
> >   end 
> > end 
> > 
> > 
> > This solution is far from perfect, but it''s relatively simple
and so far
> > works for us. 
> > 
> > The best solution would be to actually build a structure similar to 
> GitHub 
> > response - from that structure it would be trivial to build 
> #full_messages 
> > and similar methods and it would provide a lot of additional info
which
> > would be extremely useful for creating APIs. 
>
> Seems good.  Can you work on a patch and send a PR?  If we can maintain 
> backwards compat, I am happy. 
>
I''ll make all current methods to return the same result as they do now 
(even #to_json and similar methods) and use new structure only internally. 
The only question is how this new structure should be accessed via 
ActiveModel object - object.errors.errors? :)

BTW. Aaron, if you have a while could you check PR about 
ActionDispatch::ParamsParser (https://github.com/rails/rails/pull/7444)?

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