Possible way to express conditionals in dual purpose (rails + mustache) templates.

mustache_if.rb

# The following is a possible way we can express conditionals in templates that
# are written to be rendered *both* by Rails and for the front-end in Mustache.
#
# ```haml
#    - task.if 'assignee' do
#      %label.subtle 'assigned to'
#      = task.assignee_name
#
#    - task.unless 'assignee' do
#      %label.subtle 'not assigned'
# ```
#
def if(property, &block)
  internal_markup = capture block
  if js?
    "{{##{property}}}" + \
      internal_markup
    "{{/#{property}}}"
  else
    if model.send(property).present?
      internal_markup
    end
  end
end