fix: assets precompile by using terser

importmaps broke precompiliation with uglifier
see: rails/importmap-rails#5

Gemfile

@@ -5,7 +5,6 @@ gem "rails", '~> 5.2'
 
 gem 'sass-rails'
 gem 'less-rails'
-gem 'uglifier', '>= 1.0.3'
 # See https://github.com/sstephenson/execjs#readme for more supported runtimes
 gem 'therubyracer', platforms: :ruby
 
@@ -121,3 +120,5 @@ group :test do
 end
 
 gem "importmap-rails", "~> 1.1"
+
+gem "terser", "~> 1.1"

Gemfile.lock

@@ -506,7 +506,9 @@ GEM
     sqlite3-ruby (1.3.3)
       sqlite3 (>= 1.3.3)
     table_print (1.5.7)
-    temple (0.8.2)
+    temple (0.9.1)
+    terser (1.1.13)
+      execjs (>= 0.3.0, < 3)
     therubyracer (0.12.3)
       libv8 (~> 3.16.14.15)
       ref
@@ -525,10 +527,8 @@ GEM
       railties (>= 3.1)
     twitter-text (1.14.7)
       unf (~> 0.1.0)
-    tzinfo (1.2.10)
-      thread_safe (~> 0.1)
-    uglifier (4.2.0)
-      execjs (>= 0.3.0, < 3)
+    tzinfo (2.0.5)
+      concurrent-ruby (~> 1.0)
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.8.2)
@@ -639,9 +639,9 @@ DEPENDENCIES
   sprockets (< 4)
   sqlite3 (~> 1.3.6)
   table_print
+  terser (~> 1.1)
   therubyracer
   twitter-bootstrap-rails (~> 2.2.8)
-  uglifier (>= 1.0.3)
   web-console
   whenever
 

config/environments/production.rb

@@ -27,7 +27,7 @@
   config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
 
   # Compress JavaScripts and CSS.
-  config.assets.js_compressor = :uglifier
+  config.assets.js_compressor = :terser
   config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.