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Surprising behavior with Rails I18n Lazy Lookups and Partials

Zee on May 16, 2019

Rails i18n supports lazy lookup so that if you have a locales file shaped like this: en: newsletter_cta: title: "Stay Up To Date With The Lat...
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yourivdlans profile image
Youri van der Lans •

I've also been running into this issue. But because I use the i18n-tasks gem to keep my localisation file in check I've chosen to write out the absolute path for a translation when using them within render blocks.

Basically what happens is as soon as you put a relative translation in a render block the path gets changed. In your example it would be: "application.section.title".

One way to approach this could be to pass the i18n scope of the view to the partial and use that when translating a key.

Something like:

<%= render "section", i18n_scope: @virtual_path.gsub(%r{/_?}, ".") do %>
  <h2><%= t('title', scope: i18n_scope) %></h2>
<% end %>

Note the removed dot before "title" indicating this is not a relative lookup.

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zspencer profile image
Zee •

I think landing on "Use absolute paths at all times with I18n" is great advice, especially since the lookup inference pattern is pretty unique to Rails.

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joshantbrown profile image
Josh Brown •

When you call render "section" what it seems actually happens is it treats the partial as a template, this changes the scope of execution and therefore changes where those translations are executed.

Instead you can explicitly render it as a partial by passing it as render partial: "section". However, partials don't allow you to pass blocks to them, instead you'll need to capture the content into a variable and pass it as a local:

<% content = capture do %>
  <!-- Your complex HTML/ERB code here -->
<% end %>

<%= render partial: "shared/section", locals: { content: content } %>
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Putting these in a helper tidies things up in the views:

module ApplicationHelper
  def section(&block)
    content = capture(&block)
    render partial: "shared/section", locals: { content: content }
  end
end
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Then in your view you can do:

<%= section do %>
  <h2><%= t('.title') %></h2>
<% end %>
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krebbl profile image
Marcus Krejpowicz •

In case somebody is looking for a workaround, here it is:

module ApplicationHelper
...
def render(*args, &block)
  if block
    vpath = instance_variable_get(:@virtual_path)
    super(*args) do |*kwargs|
      original_path = instance_variable_get(:@virtual_path)
      instance_variable_set(:@virtual_path, vpath)
      ret = capture(*kwargs, &block)
      instance_variable_set(:@virtual_path, original_path)
      ret
    end
  else
    super(*args, &block)
  end
end
...
end
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