Uglifier::Error during assets:precompile

[rzane]

It looks like this issue has come up before, but with a different version of Turbo. I'm using turbo-rails v2.0.3.

$ bundle exec rails assets:precompile                     
rails aborted!
Uglifier::Error: Unexpected token: keyword (const). To use ES6 syntax, harmony mode must be enabled with Uglifier.new(:harmony => true). (Uglifier::Error)
--
 22     submitter.type == "submit" || raise(TypeError, "The specified element is not a submit button");
 23     submitter.form == form || raise(DOMException, "The specified element is not owned by this form element", "NotFoundError");
 24   }
 25   function raise(errorConstructor, message, name) {
 26     throw new errorConstructor("Failed to execute 'requestSubmit' on 'HTMLFormElement': " + message + ".", name);
 27   }
 28 })(HTMLFormElement.prototype);
 29 
 => const submittersByForm = new WeakMap;
 31 
 32 function findSubmitterFromClickTarget(target) {
 33   const element = target instanceof Element ? target : target instanceof Node ? target.parentElement : null;
 34   const candidate = element ? element.closest("input, button") : null;
 35   return candidate?.type == "submit" ? candidate : null;
 36 }
 37 
 38 function clickCaptured(event) {
==

Tasks: TOP => assets:precompile
(See full trace by running task with --trace)

I followed the error message and added the following configuration.

config.assets.js_compressor = Uglifier.new(harmony: true)

But, unfortunately, I get the same error.

[rzane]

In my case, I don't actually want to precompile Turbo since I'm sourcing it from NPM. For me, this is the best solution: https://github.com/hotwired/turbo-rails/blob/v2.0.3/lib/turbo/engine.rb#L22-L27

[jeffcoh23]

@rzane Did you ever figure out the issue? I'm pretty stuck on this and not sure what to do. I need my app to work on older iOS versions.

[timhaak]

I think from the link the fix is to add

if config.assets.compile
config.after_initialize do
config.assets.precompile -= Turbo::Engine::PRECOMPILE_ASSETS
end
end

Which seems to have fixed the problem on my side

[kabasawakyohei]

In my case, my product used the uglifier gem to compress JavaScript, so I resolved the issue by switching to terser for compression. Note that uglifier mentions, “UglifyJS only works with ES5. If you need to compress ES6, ruby-terser is a better option.”