FEATURE: Introduce theme/component QUnit tests (take 2) (#12661)

This commit allows themes and theme components to have QUnit tests. To add tests to your theme/component, create a top-level directory in your theme and name it `test`, and Discourse will save all the files in that directory (and its sub-directories) as "tests files" in the database. While tests files/directories are not required to be organized in a specific way, we recommend that you follow Discourse core's tests [structure](https://github.com/discourse/discourse/tree/master/app/assets/javascripts/discourse/tests).

Writing theme tests should be identical to writing plugins or core tests; all the `import` statements and APIs that you see in core (or plugins) to define/setup tests should just work in themes.

You do need a working Discourse install to run theme tests, and you have 2 ways to run theme tests:

* In the browser at the `/qunit` route. `/qunit` will run tests of all active themes/components as well as core and plugins. The `/qunit` now accepts a `theme_name` or `theme_url` params that you can use to run tests of a specific theme/component like so: `/qunit?theme_name=<your_theme_name>`.

* In the command line using the `themes:qunit` rake task. This take is meant to run tests of a single theme/component so you need to provide it with a theme name or URL like so: `bundle exec rake themes:qunit[name=<theme_name>]` or `bundle exec rake themes:qunit[url=<theme_url>]`.

There are some refactors to how Discourse processes JavaScript that comes with themes/components, and these refactors may break your JS customizations; see https://meta.discourse.org/t/upcoming-core-changes-that-may-break-some-themes-components-april-12/186252?u=osama for details on how you can check if your themes/components are affected and what you need to do to fix them.

This commit also improves theme error handling in Discourse. We will now be able to catch errors that occur when theme initializers are run and prevent them from breaking the site and other themes/components.

lib/theme_javascript_compiler.rb

@@ -151,6 +151,18 @@ class ThemeJavascriptCompiler
   class CompileError < StandardError
   end
 
+  def self.force_default_settings(content, theme)
+    settings_hash = {}
+    theme.settings.each do |setting|
+      settings_hash[setting.name] = setting.default
+    end
+    content.prepend <<~JS
+      (function() {
+        require("discourse/lib/theme-settings-store").registerSettings(#{theme.id}, #{settings_hash.to_json}, { force: true });
+      })();
+    JS
+  end
+
   attr_accessor :content
 
   def initialize(theme_id, theme_name)
@@ -162,10 +174,8 @@ class ThemeJavascriptCompiler
   def prepend_settings(settings_hash)
     @content.prepend <<~JS
       (function() {
-        if ('Discourse' in window && Discourse.__container__) {
-          Discourse.__container__
-            .lookup("service:theme-settings")
-            .registerSettings(#{@theme_id}, #{settings_hash.to_json});
+        if ('require' in window) {
+          require("discourse/lib/theme-settings-store").registerSettings(#{@theme_id}, #{settings_hash.to_json});
         }
       })();
     JS
@@ -173,8 +183,14 @@ class ThemeJavascriptCompiler
 
   # TODO Error handling for handlebars templates
   def append_ember_template(name, hbs_template)
+    if !name.start_with?("javascripts/")
+      prefix = "javascripts"
+      prefix += "/" if !name.start_with?("/")
+      name = prefix + name
+    end
     name = name.inspect
     compiled = EmberTemplatePrecompiler.new(@theme_id).compile(hbs_template)
+    # the `'Ember' in window` check is needed for no_ember pages
     content << <<~JS
       (function() {
         if ('Ember' in window) {
@@ -204,18 +220,19 @@ class ThemeJavascriptCompiler
     raise CompileError.new e.instance_variable_get(:@error) # e.message contains the entire template, which could be very long
   end
 
-  def append_plugin_script(script, api_version)
-    @content << transpile(script, api_version)
-  end
-
   def append_raw_script(script)
     @content << script + "\n"
   end
 
   def append_module(script, name, include_variables: true)
-    script = "#{theme_variables}#{script}" if include_variables
+    name = "discourse/theme-#{@theme_id}/#{name.gsub(/^discourse\//, '')}"
+    script = "#{theme_settings}#{script}" if include_variables
     transpiler = DiscourseJsProcessor::Transpiler.new
-    @content << transpiler.perform(script, "", name)
+    @content << <<~JS
+      if ('define' in window) {
+      #{transpiler.perform(script, "", name).strip}
+      }
+    JS
   rescue MiniRacer::RuntimeError => ex
     raise CompileError.new ex.message
   end
@@ -226,36 +243,11 @@ class ThemeJavascriptCompiler
 
   private
 
-  def theme_variables
+  def theme_settings
     <<~JS
-      const __theme_name__ = "#{@theme_name.gsub('"', "\\\"")}";
-      const settings = Discourse.__container__
-        .lookup("service:theme-settings")
+      const settings = require("discourse/lib/theme-settings-store")
         .getObjectForTheme(#{@theme_id});
       const themePrefix = (key) => `theme_translations.#{@theme_id}.${key}`;
     JS
   end
-
-  def transpile(es6_source, version)
-    transpiler = DiscourseJsProcessor::Transpiler.new(skip_module: true)
-    wrapped = <<~PLUGIN_API_JS
-      (function() {
-        if ('Discourse' in window && typeof Discourse._registerPluginCode === 'function') {
-          #{theme_variables}
-          Discourse._registerPluginCode('#{version}', api => {
-            try {
-            #{es6_source}
-            } catch(err) {
-              const rescue = require("discourse/lib/utilities").rescueThemeError;
-              rescue(__theme_name__, err, api);
-            }
-          });
-        }
-      })();
-    PLUGIN_API_JS
-
-    transpiler.perform(wrapped)
-  rescue MiniRacer::RuntimeError => ex
-    raise CompileError.new ex.message
-  end
 end