Add t Liquid filter, allow I18n fallbacks

bridgetown-core/lib/bridgetown-core.rb

@@ -51,10 +51,14 @@ def require_all(path)
 require "kramdown"
 require "colorator"
 require "i18n"
+require "i18n/backend/fallbacks"
 require "faraday"
 require "thor"
 require "zeitwerk"
 
+# Ensure we can set up fallbacks so the default locale gets used
+I18n::Backend::Simple.include I18n::Backend::Fallbacks
+
 module HashWithDotAccess
   class Hash # :nodoc:
     def to_liquid

bridgetown-core/lib/bridgetown-core/concerns/site/localizable.rb

@@ -12,6 +12,10 @@ def locale
         end
         I18n.available_locales = config[:available_locales]
         I18n.default_locale = locale
+        I18n.fallbacks.each do |k, v|
+          v.push(locale) if k != locale && !v.include?(locale)
+        end
+        locale
       end
     end
 

bridgetown-core/lib/bridgetown-core/filters.rb

@@ -435,3 +435,6 @@ def as_liquid(item)
 Liquid::Template.register_filter(
   Bridgetown::Filters
 )
+Liquid::Template.register_filter(
+  Bridgetown::Filters::TranslationFilters
+)

bridgetown-core/lib/bridgetown-core/filters/translation_filters.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Bridgetown
+  module Filters
+    module TranslationFilters
+      def t(input)
+        I18n.t(input.to_s)
+      end
+    end
+  end
+end

bridgetown-core/test/resources/src/_locales/en.yml

@@ -0,0 +1,4 @@
+en:
+  en: English
+  test:
+    name: Test Name

bridgetown-core/test/resources/src/_locales/fr.yml

@@ -0,0 +1,2 @@
+en:
+  fr: Français

bridgetown-core/test/resources/src/_pages/multi-page.multi.md

@@ -7,3 +7,5 @@ locale_overrides:
 ---
 
 {% if site.locale == "en" %}English:{% elsif site.locale == "fr" %}French:{% endif %} {{ resource.data.title }}
+
+{{ site.locale | t }}: {{ "test.name" | t }}

bridgetown-core/test/test_locales.rb

@@ -126,5 +126,26 @@ class TestLocales < BridgetownUnitTest
     <li>Sur mesure: /basefolder/fr/multi-page/</li>
       HTML
     end
+
+    context "translation filters" do
+      setup do
+        @site = resources_site
+        @site.process
+        # @type [Bridgetown::Resource::Base]
+        @resources = @site.collections.pages.resources.select do |page|
+          page.relative_path.to_s == "_pages/multi-page.multi.md"
+        end
+        @english_resource = @resources.find { |page| page.data.locale == :en }
+        @french_resource = @resources.find { |page| page.data.locale == :fr }
+      end
+
+      should "pull in the right English translation" do
+        assert_includes @english_resource.output, "<p>English: Test Name</p>"
+      end
+
+      should "fall back to English on missing translation" do
+        assert_includes @french_resource.output, "<p>Français: Test Name</p>"
+      end
+    end
   end
 end