FEATURE: Overwrite server side I18n keys with API

app/models/translation_override.rb

@@ -0,0 +1,11 @@
+class TranslationOverride < ActiveRecord::Base
+  validates_uniqueness_of :translation_key, scope: :locale
+  validates_presence_of :locale, :translation_key, :value
+
+  def self.upsert!(locale, key, value)
+    params = { locale: locale, translation_key: key }
+    row_count = where(params).update_all(value: value)
+    create!(params.merge(value: value)) if row_count == 0
+  end
+
+end

db/migrate/20151113205046_create_translation_overrides.rb

@@ -0,0 +1,12 @@
+class CreateTranslationOverrides < ActiveRecord::Migration
+  def change
+    create_table :translation_overrides, force: true do |t|
+      t.string :locale, length: 30, null: false
+      t.string :translation_key, null: false
+      t.string :value, null: false
+      t.timestamps null: false
+    end
+
+    add_index :translation_overrides, [:locale, :translation_key], unique: true
+  end
+end

lib/i18n/backend/discourse_i18n.rb

@@ -12,6 +12,24 @@ module I18n
         LocaleSiteSetting.supported_locales.map(&:to_sym)
       end
 
+      def reload!
+        @overrides = {}
+        super
+      end
+
+      def overrides_for(locale)
+        @overrides ||= {}
+        return @overrides[locale] if @overrides[locale]
+
+        @overrides[locale] = {}
+
+        TranslationOverride.where(locale: locale).pluck(:translation_key, :value).each do |tuple|
+          @overrides[locale][tuple[0]] = tuple[1]
+        end
+
+        @overrides[locale]
+      end
+
       # force explicit loading
       def load_translations(*filenames)
         unless filenames.empty?
@@ -23,6 +41,10 @@ module I18n
         [locale, SiteSetting.default_locale.to_sym, :en].uniq.compact
       end
 
+      def translate(locale, key, options = {})
+        overrides_for(locale)[key] || super(locale, key, options)
+      end
+
       def exists?(locale, key)
         fallbacks(locale).each do |fallback|
           begin

spec/components/discourse_i18n_spec.rb

@@ -1,11 +1,13 @@
 require 'spec_helper'
 require 'i18n/backend/discourse_i18n'
+require 'translation_override'
 
 describe I18n::Backend::DiscourseI18n do
 
   let(:backend) { I18n::Backend::DiscourseI18n.new }
 
   before do
+    backend.reload!
     backend.store_translations(:en, :foo => 'Foo in :en', :bar => 'Bar in :en')
     backend.store_translations(:en, :items => {:one => 'one item', :other => "%{count} items" })
     backend.store_translations(:de, :bar => 'Bar in :de')
@@ -50,4 +52,18 @@ describe I18n::Backend::DiscourseI18n do
     end
   end
 
+  describe 'with overrides' do
+    before do
+      TranslationOverride.upsert!('en', 'foo', 'Overwritten foo')
+    end
+
+    it 'returns the overrided key' do
+      expect(backend.translate(:en, 'foo')).to eq('Overwritten foo')
+
+      TranslationOverride.upsert!('en', 'foo', 'new value')
+      backend.reload!
+      expect(backend.translate(:en, 'foo')).to eq('new value')
+    end
+  end
+
 end