Use param foo in default for bar

[jamesarosen]

What I'd like to do:

params do
  requires :foo
  optional :bar, default: -> (other_params) { "bar from foo #{other_params[:foo]} }
end

or perhaps

params do
  requires :foo
  optional :bar, coerce: -> (bar_value, other_params) { "bar from foo #{other_params[:foo]} }
end

Unfortunately, neither default nor coerce seems to accept the other params as an argument. It may be possible to get them from self (which is a ParamsScope) within that block, but it's not obvious how.

[dblock]

Does params[:foo] work? If not this is a great feature request. Note that circular dependencies might become possible 🤔

[dblock]

Closed via #2371.