Rails i18n for ERB views, automated

How it works

Text in ERB views becomes <%= t('key', name: @user.name) %>, with %{name} placeholders in config/locales/<locale>.yml, under the language key. Logic tags split sentences; <script> and <code> are left alone.

A ternary on a count becomes a plural with one: and other: forms (and whatever else each language needs), called with count:.

Before and after

The engine’s real output for this file. In a real run, the hosted model names the keys from context.

<h1>Welcome back, <%= @user.name %>!</h1>
<% if @items.any? %>
  <p><%= @items.count %> <%= @items.count == 1 ? 'item' : 'items' %> in your cart</p>
<% end %>
<input placeholder="Search products" type="text">

<h1><%= t('show.welcome_back', name: @user.name) %></h1>
<% if @items.any? %>
  <p><%= t('show.items_in_your_cart', count: @items.count) %></p>
<% end %>
<input placeholder="<%= t('show.search_products') %>" type="text">

en:
  show:
    welcome_back: Welcome back, %{name}!
    items_in_your_cart:
      one: "%{count} item in your cart"
      other: "%{count} items in your cart"
    search_products: Search products

What the setup adds

The first run sets up Rails I18n if the project doesn’t have it yet:

• config.i18n.available_locales in config/application.rb
• A switch_locale around-action in ApplicationController: ?locale=, then a lang cookie, then Accept-Language

Run it

The CLI needs Node.js 22 or later, nothing else: npx runs it without adding a package.json to the project. No Node on your machine? The GitHub Action below runs it for you.

npx localize-dev login

# Preview, then write the changes
npx localize-dev run --dry-run -l es,fr,de
npx localize-dev run -l es,fr,de

# Or open a pull request instead
npx localize-dev pr -l es,fr,de

Or add the GitHub Action and get a pull request on every push. Try it on your own code first in the playground.