Use Terser instead of Uglifier

govuk_publishing_components has govuk-frontend as a dependency.

govuk-frontend v5 now targets browsers that support ES6. This means that the UMD modules used in govuk_publsihing_components from govuk-frontend use features of ES6 and so it means that Uglifier can't be used anymore because it only supports ES5.

Gemfile

@@ -22,7 +22,7 @@ gem "rinku", require: "rails_rinku"
 gem "rss"
 gem "slimmer"
 gem "sprockets-rails"
-gem "uglifier"
+gem "terser"
 
 group :development, :test do
   gem "govuk_schemas"

Gemfile.lock

@@ -128,7 +128,7 @@ GEM
     domain_name (0.6.20240107)
     drb (2.2.1)
     erubi (1.12.0)
-    execjs (2.8.1)
+    execjs (2.9.1)
     faker (3.3.1)
       i18n (>= 1.8.11, < 2)
     gds-api-adapters (95.1.0)
@@ -634,13 +634,13 @@ GEM
     stringio (3.1.0)
     terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
+    terser (1.2.2)
+      execjs (>= 0.3.0, < 3)
     thor (1.3.1)
     timecop (0.9.8)
     timeout (0.4.1)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    uglifier (4.2.0)
-      execjs (>= 0.3.0, < 3)
     unicode-display_width (2.5.0)
     webmock (3.23.0)
       addressable (>= 2.8.0)
@@ -692,8 +692,8 @@ DEPENDENCIES
   simplecov
   slimmer
   sprockets-rails
+  terser
   timecop
-  uglifier
   webmock
 
 RUBY VERSION

config/environments/production.rb

@@ -25,7 +25,7 @@
   config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
 
   # Compress JS using a preprocessor.
-  config.assets.js_compressor = :uglifier
+  config.assets.js_compressor = :terser
 
   # Compress CSS using a preprocessor.
   # config.assets.css_compressor = :sass