Added non_empty parameter validator to validate non-empty strings

[elado]

The PresenceValidator validates only that the param is sent, but not if it's empty. Using Regexp validator seems too cumbersome for such a common task.

An additional NonEmpty validator is very useful.

Also, I allowed myself to reorganize README validation section. I hope it's fine.

[dblock]

I am really not a fan of the non_empty name. What do you think of allow_nil: false for example?

[dblock]

The code looks good otherwise, could be squashed. Lets talk about how to call this option, I prefer "positive" names rather than negative names.

[elado]

I agree, non_empty sounds weird, I actually started it with empty but empty: false looks weirder. allow_nil: false sounds better. If I change the name, would this PR be merged? Or should I squash also?

Thanks

[dblock]

You should squash too, please, we like single nice looking commits. LMK if you need help with that.

[elado]

Actually, allow_nil is confusing. It's usually used when you want to treat nils specifically, but here, it depends on requires vs optional. Also, since it's an HTTP request, nils aren't real values. Either a key was sent with a string (that could be empty) as value, or it wasn't sent at all.

Thoughts? Is empty: false better?

[dm1try]

allow_blank?:grimacing:

Anyway, there is a little problem with optional group and non_empty validator:

    params do
      optional :user, type: Hash do
        requires :name, non_empty: true
      end
    end
    get '/allow_empty_in_optional_group'

    it '...' do
      get '/allow_empty_in_optional_group'
      expect(last_response.status).to eq(200) # fails
    end

See similar #635, #688, #723

I think, this behaviour should be documented before someone provides a common solution.

[elado]

OK. Renamed non_empty to allow_blank. Also took care of nested scopes. The condition that generates should_validate is quite complex, maybe should be extracted out of there, but it's ok for now.

Tried to use @scope.should_validate?(attr_name) but it failed with some cases.

Let me know if it's good now, I'll squash.

[dblock]

Perfect. Merged squashed via dfbeb22.

[dm1try]

@elado , thanks!

[elado]

Thank you guys!