CODEWITHSUNDEEP
ruby-on-railscoffeescriptruby-on-rails-5asset-pipeline
Nijeesh Joshy
Nijeesh Joshy

Reputation: 1481

Coffeescript is not being compiled correctly in rails with async and await syntax

i have a similar coffee-script like this in my assets/javascript directory 

#COFFEE SCRIPT CODE
class TestClass
  speak: ()->
    response = await fetch(location.url)
    console.log(response)

its being compiled correctly with proper async/await syntax in coffee-script's official playground 

# COMPILED JS FROM COFFEESCRIPT OFFICIAL PLAYGROUND
var TestClass;

TestClass = class TestClass {
  async speak() {
    var response;
    response = (await fetch(location.url));
    return console.log(response);
  }

};

but when i write this in a file and make it compile through assets pipeline it get compiled incorrectly 

# COMPILED JS FROM COFFEESCRIPT ASSESTS PIPELINE
TestClass = (function() {
    function TestClass() {}

    TestClass.prototype.speak = function() {
      var response;
      response = await(fetch(location.url));
      return console.log(response);
    };

    return TestClass;

  })();

i am on rails v5.2 and ruby v2.6.4 on macOS v10.14

$ bundle info coffee-script
      * coffee-script (2.4.1)
            Summary: Ruby CoffeeScript Compiler
            Homepage: http://github.com/josh/ruby-coffee-script
            Path: /Users/<username>/.rvm/gems/ruby-2.6.4/gems/coffee-script-2.4.1

my gemlock file

why is this happening and how to fix it.

i need the proper async/await syntax via my assests pipeline

Upvotes: 0

Views: 1163

Answers (2)

caffeinated.tech
caffeinated.tech

Reputation: 6548

The coffee-script-source gem is out of date. It is suggested to use webpacker instead of the asset pipeline for newer js setups. But that could be a large restructure.

Workaround

There was a pull request suggesting a workaround to use coffeescript 2 :

you can use this library with other versions of CoffeeScript by setting the COFFEESCRIPT_SOURCE_PATH environment variable, but we recommend using WebPacker for CoffeeScript 2 and up.

export COFFEESCRIPT_SOURCE_PATH=/path/to/coffee-script/extras/coffee-script.js

You will need to install & locate your coffee-script 2 executable (if globally it would be found with which coffee, and if locally with npm, it would be ./node_modules/.bin/coffee). I'm not sure if your gem will include the correct coffee-script version, so I would suggest using npm or another node package manager instead.

On Heroku

How to run on heroku based on this Github comment

  1. Download and save the standalone coffeescript compiler in your rails project (eg. make a new directory in the project root called tools

  2. Set the env var for heroku so the coffee-script-source gem uses the correct compiler:

    heroku config:set COFFEESCRIPT_SOURCE_PATH=/app/tools/coffeescript.js

(usually /app is the project directory on heroku, but you may have to change this)

Upvotes: 1

calebkm
calebkm

Reputation: 1033

Unfortunately the coffee-rails gem doesn't use the most up-to-date version of CoffeeScript and is thus missing some of the ES2017 features like await that you're looking for.

coffee-rails itself depends on the coffee-script-source gem which you can see is still using CoffeeScript v1.12.6:

# https://github.com/jessedoyle/coffee-script-source/blob/master/src/js/coffee-script.js

/**
 * CoffeeScript Compiler v1.12.6
 * http://coffeescript.org
 *
 * Copyright 2011, Jeremy Ashkenas
 * Released under the MIT License
 */

Upvotes: 2

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