Suppress one of the validation errors from `allow_blank` on a required parameter

[andrykonchin]

Using allow_blank validator for the required parameter may lead to two validation errors, but I expected to have only one.

Example:

requires :customer_key, type: String, allow_blank: false

If there is no customer_key parameter in request then we receive the following Grape::Exceptions::ValidationErrors exception:

error
=> #<Grape::Exceptions::ValidationErrors: Grape::Exceptions::ValidationErrors>

error.errors
=> {["customer_key"]=>[#<Grape::Exceptions::Validation: is missing>, #<Grape::Exceptions::Validation: is empty>]}

So we receive

• one error because the required parameter "is missing" and
• another one caused by allow_blank validator because the parameter "is empty"

The second error (produced by the allow_blank) doesn't make sense and looks a bit annoying. The expected behavior is to receive only "is missing" error.

[dblock]

Agreed, but be careful about breaking backwards compatibility if you try to fix. It might make sense to keep things "dumb" like this where validators don't know much about each-other to avoid too clever of a behavior.

From the machine POV a client can easily suppress one of the two when these come back from a REST API.