Using async, await makes workbox without further transpilation break on Samsung Internet

[HenrikJoreteg]

See twitter discussion here: https://twitter.com/addyosmani/status/910631449753141253

@poshaughnessy noticed the starbucks PWA's SW isn't installing properly on Samsung Internet.

Turns out this is because of usage of async and await.

Library Affected:
all

Browser & Platform:
Samsung Internet

Issue or Feature Request Description:
Probably best to not use it in distributed versions if you expect people to be able to use it as is in Samsung Internet.

To repro, open https://preview.starbucks.com in inspect devices on samsung internet. It fails on line 80 of our SW which is the included Workbox code: https://preview.starbucks.com/serviceworker.js

WHich is the first usage of async/await.

[NekR]

I guess UCBrowser 5 latest UCBrowser which supports SW doesn't support async/await yet too.

[gauntface]

I'm in favor of dropping async and await usage in favor of promise chains. Seems like the sanest approach for developers using Workbox.

Tangental: we really should document our browser support.

[addyosmani]

I'm strongly in favor of us switching to just using promises. I would like to see if this is something we could do for the next release (2.0.2/2.1.0). @gauntface @jeffposnick wdyt?

It would unblock a few folks that are trying to use Workbox for production and as a forcing function would also help us figure out the browser support matrix for older versions of Chrome on mobile platforms.

Tentatively, latest version of mobile browsers - 2 sounds reasonable and if this included Samsung browser would catch some of their use of slightly older V8.

[jeffposnick]

While it's still open for discussion, I wanted to take a look at the impact of changing our current Babel usage to include babel-preset-env with the following configuration:

const babelPlugin = babel({
  presets: [['env', {
    targets: {
      browsers: ['chrome >= 51'],
    },
    modules: false,
  }], ['babili', {
    comments: false,
  }]],
  plugins: ['external-helpers'],
});

It brings the final size of workbox-sw.prod.v2.0.1.js up by 1.8kb, to a total of 48879 bytes.

[jeffposnick]

workbox-sw@2.0.2-rc1 is out (along with versions for our other modules), and it includes the transpilation.

It looks okay in my testing, but our naming convention for the built modules doesn't play nicely with the -rc1, so the one issue is that the output name is workbox-sw.prod.v2.0.2-rc1-2.0.2-rc1.0.js.

@HenrikJoreteg, if you could confirm that this works in your testing, we can tag it the official 2.0.2 release.

[jeffposnick]

Just a heads-up: we're going to tag this code as the official 2.0.2 release tomorrow. If there are any last-minute incompatibilities, let us know.

[jeffposnick]

This ended up published as https://github.com/GoogleChrome/workbox/releases/tag/v2.0.3