Webpack - compile JS even from imported npm dependencies

[himdel]

Right now, any JS code in our code base gets compiled to es5, except for apparenly anything from npm.

Quick way to test:

--- a/app/javascript/packs/application-common.js
+++ b/app/javascript/packs/application-common.js
@@ -1,3 +1,6 @@
+console.log('XXXXXXXXXXXXXXXXXXXXXXXXXXXXX');
+require('proxy-polyfill');
+
 // This file is automatically compiled by Webpack, along with any other files
 // present in this directory. You're encouraged to place your actual application logic in
 // a relevant structure within app/javascript and only use these pack files to reference

and run (in ui-classic)

$ yarn add proxy-polyfill
$ bin/webpack
$ grep -Hn "const unsafeHandler" ../manageiq/public/packs/manageiq-ui-classic/application-common.js
../manageiq/public/packs/manageiq-ui-classic/application-common.js:72501:    const unsafeHandler = handler;

As long as const doesn't get changed to var, we can't really use npm dependencies written is ES6.

This also affects travis because spec:javascript will silently ignore any files with const inside:

Enabling show_console_log: true in spec/javascripts/support/jasmine.yml and running be rake spec:javascript | grep XXXXX ... as long as the require is there (and this is not fixed), no XXXXX will get output anywhere, changing the require to proxy-polyfill/proxy.min.js (which is already es5) will cause XXXX to appear.

Cc @karelhala @vojtechszocs
(But I'd like to take this one to learn a bit more about webpack, maybe update to webpack 4 in the process.)

[karelhala]

I have solved this issue before, sadly don't remeber in which project and how 😞

But just by googling it looks like we have to add certain packages as non-exluded into build babel/babel-loader#171 (comment) (that's not how I solved it before, don't remeber really how, but definetely not like this 😄 ). I don't know if eslint will complain about this...

[himdel]

Interesting thread .. I wonder if I'm missing something but why do people even want to not compile something by default?

I ended up solving this by removing that exclude completely, I just can't imagine any case where compiling the dependencies would be the wrong thing to do.

(In fact, I was very surprised to find out that no other node modules in dependencies (as opposed to devDependencies) actually use const now, I would think that it is time for es2016+ js libraries now that webpack, etc. is being used ..even by us now :).)