`values` validator and `allow_blank`

[maciejpankanin]

Consider this params definition:

params do
  requires :id, type: String
  optional :some_param, type: String, values: ["value1", "value2"]
end

Recently I spent couple of hours figuring out why null is valid value for some_param.

I think there should be a few words in documentation about values validator saying that allow_blank defaults to true and it is stronger than supplied values options.

[dblock]

Make sense, please contribute! Also double check that we have specs for this exact behavior.

[dblock]

Closed via #2186

[flosacca]

I was confused by the fact that the empty string is not a special case that is allowed by default. I've tested the following example mentioned in README and an empty string cannot pass.

params do
  requires :state, type: Symbol, values: [:active, :inactive]
end

There may be a misunderstanding in the original problem. When optional is used, null would be allowed unless allow_blank is explicitly specified to false.

I found that allow_blank: false enables AllowBlankValidator while allow_blank: true actually does nothing. So, whether an empty string is allowed by default depends totally on other factors.

[maciejpankanin]

Ops, you are right, I think it should be:

params do
  optional :state, type: Symbol, values: [:active, :inactive]
end

But still, isn't it misbehavior? If I understand it well, when it is optional and I send null or '' validation will pas but if it was requires I would get a validation error.

It behaves like null or empty strings weren't values.

[dblock]

Current behavior looks suspicious to me: I certainly don't expect an optional value to allow an empty string. Try writing a spec for this, fixing it and seeing if any other specs fail? Either way I think opening an issue for this specific case is a good idea.