Switch from babel to buble

[benmccann]

As suggested by @leeoniya in #6835. Thanks @leeoniya!

Builds much faster and results in a slightly smaller minifed file

$ gulp build
[15:16:38] Using gulpfile ~/src/Chart.js/gulpfile.js
[15:16:38] Starting 'build'...

src/index.js → dist/Chart.esm.js...
created dist/Chart.esm.js in 5s

src/index.js → dist/Chart.esm.min.js...
created dist/Chart.esm.min.js in 6.2s

src/index.js → dist/Chart.js...
created dist/Chart.js in 3.5s

src/index.js → dist/Chart.min.js...
created dist/Chart.min.js in 6.4s
[15:16:59] Finished 'build' after 22 s

$ ls -lh dist
total 1.3M
811 Dec 15 15:10 Chart.css
811 Dec 15 15:10 Chart.esm.css
462K Dec 15 15:10 Chart.esm.js
521 Dec 15 15:10 Chart.esm.min.css
176K Dec 15 15:10 Chart.esm.min.js
463K Dec 15 15:10 Chart.js
521 Dec 15 15:10 Chart.min.css
177K Dec 15 15:10 Chart.min.js

$ gulp build
[15:14:10] Using gulpfile ~/src/Chart.js/gulpfile.js
[15:14:10] Starting 'build'...

src/index.js → dist/Chart.esm.js...
created dist/Chart.esm.js in 2s

src/index.js → dist/Chart.esm.min.js...
created dist/Chart.esm.min.js in 4.3s

src/index.js → dist/Chart.js...
created dist/Chart.js in 1.5s

src/index.js → dist/Chart.min.js...
created dist/Chart.min.js in 4.3s
[15:14:22] Finished 'build' after 13 s

$ ls -lh dist
total 1.2M
811 Dec 15 15:11 Chart.css
811 Dec 15 15:11 Chart.esm.css
425K Dec 15 15:11 Chart.esm.js
521 Dec 15 15:11 Chart.esm.min.css
174K Dec 15 15:11 Chart.esm.min.js
426K Dec 15 15:11 Chart.js
521 Dec 15 15:11 Chart.min.css
174K Dec 15 15:11 Chart.min.js

[etimberg]

I'm ok with this if we also drop IE11 support and only target the latest browsers.

[benmccann]

I'm ok with this if we also drop IE11 support and only target the latest browsers.

Why would it be necessary to drop IE support to make this change? buble transpiles to ES5 which is supported on IE11, so IE11 should work just fine with this change

[benmccann]

Hmm. It seems that gulp test --coverage is broken. It works without the --coverage flag which is why I didn't notice any problems in my own testing

[benmccann]

I had tried getting it to work by replacing istanbul with c8, but I'm not quite sure it'll be an option in the short-term at least: bcoe/c8#175

[kurkle]

Did you test with IE if the build works ok?

[benmccann]

No, I don't have a windows machine, so don't have a way to test. I'd love it if you have IE available if you're able to check

[kurkle]

IE: Object doesn't support property or method 'assign'
(and on master: Object doesn't support property or method 'entries')

[kurkle]

So, dug into this a bit. Buble uses Object.assign instead of spread operator.
Can't use Chart.helpers.extend, because helpers is build using spread operator.
Could add a polyfill for Object.assign, or change the layout so that extend can be used. But IMO this would be waste of time for supporting a soon to be completely dead product.

Those Object.entries will need to be rewritten to use Object.keys instead, for IE support.

StatCounter / IE:
WorldWide: 1.66% (went down 1,15% between 11/18-11/19)
USA: 2.73% (went down 2,33% between 11/18-11/19)

[benmccann]

Thanks so much for testing this out! There's not really any information on how to use polyfills with buble that I can easily find. Perhaps it's better just to stick with babel since it's more widely used and better documented and things are working a bit better with it