DEV: Compile theme migrations javascript files when running theme qunit (#25219)

Why this change?

Currently, is it hard to iteratively write a theme settings migrations
because our theme migrations system does not rollback. Therefore, we
want to allow theme developers to be able to write QUnit tests for their
theme migrations files enabling them to iteratively write their theme
migrations.

What does this change do?

1. Update `Theme#baked_js_tests_with_digest` to include all `ThemeField`
records of `ThemeField#target` equal to `migrations`. Note that we do
not include the `settings` and `themePrefix` variables for migration files.

2. Don't minify JavaScript test files becasue it makes debugging in
   development hard.

app/models/theme.rb

@@ -913,21 +913,27 @@ class Theme < ActiveRecord::Base
 
   def baked_js_tests_with_digest
     tests_tree =
-      theme_fields
-        .where(target_id: Theme.targets[:tests_js])
-        .order(name: :asc)
-        .pluck(:name, :value)
-        .to_h
+      theme_fields_to_tree(
+        theme_fields.where(target_id: Theme.targets[:tests_js]).order(name: :asc),
+      )
 
     return nil, nil if tests_tree.blank?
 
-    compiler = ThemeJavascriptCompiler.new(id, name)
-    compiler.append_tree(tests_tree, for_tests: true)
+    migrations_tree =
+      theme_fields_to_tree(
+        theme_fields.where(target_id: Theme.targets[:migrations]).order(name: :asc),
+      )
+
+    compiler = ThemeJavascriptCompiler.new(id, name, minify: false)
+    compiler.append_tree(migrations_tree, include_variables: false)
+    compiler.append_tree(tests_tree)
+
     compiler.append_raw_script "test_setup.js", <<~JS
       (function() {
         require("discourse/lib/theme-settings-store").registerSettings(#{self.id}, #{cached_default_settings.to_json}, { force: true });
       })();
     JS
+
     content = compiler.content
 
     if compiler.source_map
@@ -942,6 +948,13 @@ class Theme < ActiveRecord::Base
 
   attr_accessor :theme_setting_requests_refresh
 
+  def theme_fields_to_tree(theme_fields_scope)
+    theme_fields_scope.reduce({}) do |tree, theme_field|
+      tree[theme_field.file_path] = theme_field.value
+      tree
+    end
+  end
+
   def to_scss_variable(name, value)
     escaped = SassC::Script::Value::String.quote(value.to_s, sass: true)
     "$#{name}: unquote(#{escaped});"

lib/theme_javascript_compiler.rb

@@ -18,24 +18,27 @@ class ThemeJavascriptCompiler
     @@terser_disabled = false
   end
 
-  def initialize(theme_id, theme_name)
+  def initialize(theme_id, theme_name, minify: true)
     @theme_id = theme_id
     @output_tree = []
     @theme_name = theme_name
+    @minify = minify
   end
 
   def compile!
     if !@compiled
       @compiled = true
       @output_tree.freeze
+
       output =
         if !has_content?
           { "code" => "" }
-        elsif @@terser_disabled
+        elsif @@terser_disabled || !@minify
           { "code" => raw_content }
         else
           DiscourseJsProcessor::Transpiler.new.terser(@output_tree.to_h, terser_config)
         end
+
       @content = output["code"]
       @source_map = output["map"]
     end
@@ -92,7 +95,7 @@ class ThemeJavascriptCompiler
     JS
   end
 
-  def append_tree(tree, for_tests: false)
+  def append_tree(tree, include_variables: true)
     # Replace legacy extensions
     tree.transform_keys! do |filename|
       if filename.ends_with? ".js.es6"
@@ -168,9 +171,9 @@ class ThemeJavascriptCompiler
     # Transpile and write to output
     tree.each_pair do |filename, content|
       module_name, extension = filename.split(".", 2)
-      module_name = "test/#{module_name}" if for_tests
+
       if extension == "js" || extension == "gjs"
-        append_module(content, module_name, extension)
+        append_module(content, module_name, extension, include_variables:)
       elsif extension == "hbs"
         append_ember_template(module_name, content)
       elsif extension == "hbr"
@@ -238,6 +241,7 @@ class ThemeJavascriptCompiler
 
     script = "#{theme_settings}#{script}" if include_variables
     transpiler = DiscourseJsProcessor::Transpiler.new
+
     @output_tree << ["#{original_filename}.#{extension}", <<~JS]
       if ('define' in window) {
       #{transpiler.perform(script, "", name, theme_id: @theme_id, extension: extension).strip}

spec/models/theme_spec.rb

@@ -916,12 +916,14 @@ HTML
         name: "yaml",
         value: "some_number: 1",
       )
+
       theme.set_field(
         target: :tests_js,
         type: :js,
         name: "acceptance/some-test.js",
         value: "assert.ok(true);",
       )
+
       theme.save!
     end
 
@@ -930,6 +932,21 @@ HTML
       expect(theme.baked_js_tests_with_digest).to eq([nil, nil])
     end
 
+    it "includes theme's migrations theme fields" do
+      theme.set_field(
+        target: :migrations,
+        type: :js,
+        name: "0001-some-migration",
+        value: "export default function migrate(settings) { return settings; }",
+      )
+
+      theme.save!
+
+      content, _digest = theme.baked_js_tests_with_digest
+
+      expect(content).to include("function migrate(settings)")
+    end
+
     it "digest does not change when settings are changed" do
       content, digest = theme.baked_js_tests_with_digest
       expect(content).to be_present

spec/requests/theme_javascripts_controller_spec.rb

@@ -229,13 +229,5 @@ RSpec.describe ThemeJavascriptsController do
       expect(response.status).to eq(200)
       expect(response.body).to include("assert.ok(343434);")
     end
-
-    it "includes inline sourcemap" do
-      ThemeJavascriptCompiler.enable_terser!
-      content, digest = component.baked_js_tests_with_digest
-      get "/theme-javascripts/tests/#{component.id}-#{digest}.js"
-      expect(response.status).to eq(200)
-      expect(response.body).to include("//# sourceMappingURL=data:application/json;base64,")
-    end
   end
 end