checks added for :update_attribute for dynamic attributes refs #3875

[Shwetakale]

When we call process_attribute, it does all the checks for ensuring that
dynamic attributes are allowed.

Note This impacts the :counter_cache option as it requires dynamic fields.
When using the counter_cache, the model must include
Mongoid::Attributes::Dynamic

refs #3875

[arthurnn]

changing the behaviour of the counter_cache to make it add a include Mongoid::Attributes::Dynamic is probably not a good idea.

[gautamrege]

@arthurnn Considering that :counter_cache does imply adding Dynamic fields, I believe we should either include this module or explicitly added field <model>_count, type: Integer in the model.

[arthurnn]

@gautamrege thats right +1 , I will double check the documentation for counter_cache and see if we state this in there, before merging this.
thanks

[Shwetakale]

@durran Any feedback on this PR? This bug can still reproduced against master.

[estolfo]

@Shwetakale we still need to figure out how to allow counter_cache to continue to work with this change. Including Mongoid::Attributes::Dynamic is not a good idea as it'll have unexpected behavior.

[Shwetakale]

@estolfo As per this, In case of counter cache field needs to be manually added in parent document and here as field is not added in parent_document I have added Mongoid::Attributes::Dynamic so should we add field in parent document instead of Mongoid::Attributes::Dynamic ?

[estolfo]

Yes, we should add the attribute on the parent document and not rely on Mongoid::Attributes::Dynamic

[Shwetakale]

@estolfo Ok I will update PR.

[estolfo]

thanks!

[Shwetakale]

@estolfo Closing this PR as created new one with updated code from mongoid master branch.