Example how mdc form builder could be implemented

_form.html.erb

<%= mdc_form_with model: @my_model do |f| %>
  <%= f.mdc_text_field :last_name %>
<% end %>

_mdc_text_field.html.erb

<label class="mdc-text-field mdc-text-field--outlined mdc-text-field--fullwidth <%= 'mdc-text-field--invalid' if errors.any? %>">
  <%= f.text_field method, options %>
  <span class="mdc-notched-outline">
    <span class="mdc-notched-outline__leading"></span>
    <span class="mdc-notched-outline__notch">
      <span class="mdc-floating-label" id="<%= options["aria-labelledby"] %>"><%= label %></span>
    </span>
    <span class="mdc-notched-outline__trailing"></span>
  </span>
</label>
<% if errors.any? %>
  <div class="mdc-text-field-helper-line">
    <div id="<%= object_name %>-#{method}-helper-text" class="mdc-text-field-helper-text mdc-text-field-helper-text--persistent mdc-text-field-helper-text--validation-msg">
      <%= errors.to_sentence %>
    </div>
  </div>
<% end %>

application_helper.rb

module ApplicationHelper < ActionView::Base
  def mdc_form_with(model: nil, scope: nil, url: nil, format: nil, **options, &block)
    options[:builder] = MdcFormBuilder
    form_with(model: model, scope: scope, url: url, format: format, options, &block)
  end
end

mdc_form_builder.rb

class MdcFormBuilder < ActionView::Helpers::FormBuilder
  def mdc_text_field(method, options = {})
    options[:class] = "mdc-text-field__input" # this does not handle case if custom class is already added
    options["aria-labelledby"] = "#{object_name}_#{method}_label"
    label = options.delete(:label) || label_for(method)
    errors = errors_for(method)
    
    render("mdc_text_field", method: method, options: options, label: label, errors: errors)
  end
  
  private
  
  def label_for(method)
    # Use `object_name` and `method` to build logic to get label from i18n files
    # (optimal solution would be to use same logic as rails label helper)
  end
  
  def errors_for(method)
    # Something similar to https://github.com/betterdoc-org/case-cs-medicalinformation/blob/master/app/helpers/mdc_form_helper.rb#L78-L84
  end
end