Q:

How can I add classes to a simple_form input wrapper in Rails?

I need to add a data attribute to an f.association input in a simple form. To do this I found this article and subsequent reference to simpleform's documentation. It is easy enough to add classes with the standard syntax, I am wondering why it's proving difficult using a wrapper.
So rather than the standard:
<%= f.association :size, input_html:{class: 'sku-suffix-component'} %>

I am using:
<%= f.input :size, as: :select, input_html:{class: 'sku-suffix-component'} do %>
  <%= f.select :size, Size.all.map{ |s| [s.name, s.id, {'data-code-num' => s.code_num}] } %>
<% end %>

Much to my frustration, the added class is nowhere in the <select> tag (not to mention the missing other default classes and id naming convention [id="product_size_id"  becomes  id="product_size"]). I have tried various syntaxes and placements of the input_html hash.
Below you can see the difference in appearance etc. On the right is using the standard syntax.

And here is the resulting html:
<select name="product[size]" id="product_size"> (...)

Compared with:
<select class="form-control select required sku-suffix-component" name="product[color_id]" id="product_color_id"> (...)

A:

I found the solution combining strategies that I found on separate posts.
The long and the short of it was to utilize the map method but not within  a custom input wrapper.
<%= f.association :size, collection: Size.all.map{ |s| [s.name, s.id, {'data-code-num' => s.code_num}]}, input_html:{class: 'sku-suffix-component'} %>

This nets perfectly my desired <select> with an added class, and the <option>'s with a custom data- attribute.
<select class="form-control select required sku-suffix-component" name="product[size_id]" id="product_size_id">
  <option value=""></option>
  <option data-code-num="001" value="113">onesize</option>
(...)

