Precaching modules throws error to console

[bennypowers]

Thank you for this excellent and highly useful software.

Library Affected:
workbox-sw

Browser & Platform:
Chrome 68

Issue or Feature Request Description:
When precaching modules (by which I mean standard or es modules) with workbox, I see errors in browser console such as

Uncaught (in promise) SyntaxError: Unexpected token {
    at Object.<anonymous> (workbox-core.dev.js:941)
    at Generator.next (<anonymous>)
    at step (workbox-core.dev.js:14)
    at workbox-core.dev.js:25
(anonymous) @ workbox-core.dev.js:941
step @ workbox-core.dev.js:14
(anonymous) @ workbox-core.dev.js:25

The error in question was throw from https://github.com/bennypowers/mws-restaurant-stage-1/blob/a46986f1b896847e7374c02839a5abc6a73278c5/js/lib.js#L1

Repro by installing that repo and running.

For reference, the workbox-config.js at that commit is

module.exports = {
  "globDirectory": ".",
  "globIgnores": [
    "js/idb-keyval.js",
    "**/service-worker.js",
    "node_modules/**/node_modules/**/*",
    "node_modules/**/bower_components/**/*"
  ],
  "globPatterns": [
    "js/*",
    "css/*",
    "index.html",
    "manifest.json"
  ],
  swSrc: 'service-worker.src.js',
  swDest: 'service-worker.js',
};

and the service-worker.src.js is

importScripts('https://storage.googleapis.com/workbox-cdn/releases/3.0.0/workbox-sw.js');

/* global workbox */

workbox.skipWaiting();
workbox.clientsClaim();

workbox.routing.registerNavigationRoute('/index.html');

workbox.routing.registerRoute(
  /.*(?:googleapis|gstatic)\.com.*$/,
  workbox.strategies.staleWhileRevalidate({cacheName: 'googleapi-cache'}),
);

workbox.routing.registerRoute(
  /.*\.(?:js|html|css)/,
  workbox.strategies.cacheFirst({cacheName: workbox.core.cacheNames.precache})
);

workbox.routing.registerRoute(
  /.*\.(?:png|jpe?g|svg|gif)/,
  workbox.strategies.cacheFirst({cacheName: 'img-cache'})
);

workbox.routing.registerRoute(
  /\/api\/.*/,
  workbox.strategies.cacheFirst({cacheName: 'data-cache'})
);

workbox.precaching.precacheAndRoute([]);

[jamrelian]

I'm getting the same type of errors when using ES6 Modules with Workbox precaching:

This is "for real", as the service worker doesn't get registered:

and the built-in Lighthouse audit tool reports that "user will not be prompted to install the Web App":

This is on Google Chrome 65.0.3325.181 (Official Build) (64-bit), running on Windows 10 Home 10.0.16299 Build 16299.

This is the workbox-config.js:

module.exports = {
    "globDirectory": "./docs",
    "globPatterns": [
        "*.html",
        "scripts/*.js",
        "styles/*.css"
    ],
    "swDest": "./docs/sw.js"
};

The hello.js file that throws the error is native JavaScript module with a single export default function. On refresh, I get the error in app.js, which is a script module that imports the function from hello.js.

What's even stranger is that, on Chrome on Android 7.0, on a cached PWA that uses Workbox, the Add to Home screen which used to install the PWA, after refresh now it only offers to add it as a simple shortcut.

[jeffposnick]

I've opened up a fresh issue, https://bugs.chromium.org/p/chromium/issues/detail?id=833501, to track this from a Chrome perspective. I'm assuming that, like the last time this cropped up, it's something outside of Workbox's control, so I'm going to close this issue.

Please star, and follow-up on that new Chromium Tracker issue.

[jamrelian]

@jeffposnick Issue 833501 has been merged into issue 832202, so the new URL is
https://bugs.chromium.org/p/chromium/issues/detail?id=832202

Indeed, it's a Chrome issue, can be reproduced using standard Cache API instead of Workbox:
https://github.com/hwalab-developer/swesmit