FIX: Allow theme translations to be accessed in initializers (#8285)

Previously theme translations were loaded along with other plugin API scripts. These run after pre-initializers and initializers when the app boots. This commit moves theme translation loading into pre-initializers, so their behaviour matches core translations more closely.

app/models/theme_field.rb

@@ -60,7 +60,7 @@ class ThemeField < ActiveRecord::Base
   validates :name, format: { with: /\A[a-z_][a-z0-9_-]*\z/i },
                    if: Proc.new { |field| ThemeField.theme_var_type_ids.include?(field.type_id) }
 
-  BASE_COMPILER_VERSION = 13
+  BASE_COMPILER_VERSION = 14
   DEPENDENT_CONSTANTS = [BASE_COMPILER_VERSION,
                         GlobalSetting.cdn_url]
   COMPILER_VERSION = Digest::SHA1.hexdigest(DEPENDENT_CONSTANTS.join)
@@ -181,6 +181,9 @@ class ThemeField < ActiveRecord::Base
       data = translation_data
 
       js = <<~JS
+        export default {
+          name: "theme-#{theme_id}-translations",
+          initialize() {
             /* Translation data for theme #{self.theme_id} (#{self.name})*/
             const data = #{data.to_json};
 
@@ -191,9 +194,11 @@ class ThemeField < ActiveRecord::Base
               }
               cursor[#{self.theme_id}] = data[lang];
             }
+          }
+        };
       JS
 
-      js_compiler.append_plugin_script(js, 0)
+      js_compiler.append_module(js, "discourse/pre-initializers/theme-#{theme_id}-translations", include_variables: false)
     rescue ThemeTranslationParser::InvalidYaml => e
       errors << e.message
     end

lib/theme_javascript_compiler.rb

@@ -208,8 +208,8 @@ class ThemeJavascriptCompiler
     @content << script + "\n"
   end
 
-  def append_module(script, name)
-    script.prepend theme_variables
+  def append_module(script, name, include_variables: true)
+    script = "#{theme_variables}#{script}" if include_variables
     template = Tilt::ES6ModuleTranspilerTemplate.new {}
     @content << template.module_transpile(script, "", name)
   rescue MiniRacer::RuntimeError => ex