"NoMethodError" error raised when validating nil value with maybe(:array)

[hieuk09]

Describe the bug

When using maybe(:array), if the value is nil, error is raised instead of returning success object.

To Reproduce

schema = Dry::Schema.JSON do
  required(:list).maybe(:array).each(:string)
end

schema.call(list: nil) # raise NoMethodError

Expected behavior

It should be consistent with maybe behavior for other types and return a result object, something like:

#<Dry::Schema::Result{:list=>nil} errors={} path=[]>

My environment

• Affects my production application: NO
• Ruby version: 3.0.2
• OS: MacOS

[flash-gordon]

I think it's just maybe doesn't compose with each, use the lesser-known DSL instead required(:list).maybe(array[:string]).

[flash-gordon]

Alternatively:

schema = Dry::Schema.JSON do
  required(:list).maybe(:array) do
    nil? | each(:string)
  end
end

[hieuk09]

Thanks for the fast response! These options work for me. Do you mind if I update the doc to include them so that people are less confused when using maybe?

[flash-gordon]

@hieuk09 sure, feel free!

[bautrey37]

There is inconsistent behaviour now, because on dry-validation it is possible to use a rule.each on a maybe value. dry-rb/dry-validation#709

Maybe this should be fixed instead of documenting a caveat.

[flash-gordon]

I don't think it's a bug in the first place. OTOH, it's safe to be changed, it seems.