ExecJS::ProgramError: Unexpected token punc «(», expected punc «:» when running rake assets:precompile on production

Question

When deploying my Rails app I get the following error:

rake aborted!
   ExecJS::ProgramError: Unexpected token punc «(», expected punc «:» (line: 15, col: 14         


        

Answer 1

Here I found help for the same problem you had.

Run rails console and:

JS_PATH = "app/assets/javascripts/**/*.js"; 
Dir[JS_PATH].each do |file_name|
  puts "\n#{file_name}"
  puts Uglifier.compile(File.read(file_name), harmony: true)
end

It will show you the file and the line where the Uglifier is making the problem.

Answer 2

If Radovan's answer isn't working for you due to a problem in a library instead of your code, you can try upgrading Uglifier and enabling ES6 compilation.

Gemfile.lock

gem 'uglifier', '~> 4.1'

config/environments/production.rb

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

Answer 3

I'm not sure of your build chain, but I got here by pasting the same error message into Google.

That is called 'shorthand properties' in ES2015. I'm using Babel 6 with Gulp and needed to do an npm install babel-plugin-transform-es2015-shorthand-properties --save-dev and add that transform to my babel plugins.

.pipe(babel({
    plugins: [
        'transform-es2015-shorthand-properties'
    ]
}))

https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-es2015-shorthand-properties

Answer 4

December/2019 answer: starting on version 4.2.0 (released in Sept/2019), Uglifier now shows a beautiful (colored!) debug output showing you the offending line of code.

I was having a Uglifier::Error: Unexpected character ''` error and I couldn't find it even following all the other solutions in this page.

So go to your Gemfile, and set your Uglifier to be at least 4.2:

# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 4.2'

Run bundle update uglifier to update it.

And then just look at the output, it will show you something like this: