Promise polyfill not working on IE11

[nanomad]

Version

3.0.0-beta.1

Reproduction link

https://github.com/nanomad/vue-cli-promise-test

Steps to reproduce

• Create a new project via vue-cli (accepts the defaults)
• Add the following to main.js

Promise.all([0]).then(function() {
  alert("ALL OK");
})

• Run yarn serve
• Open IE11

What is expected?

An alert with "ALL OK" appears

What is actually happening?

• No alert
• Error in console Unhandled promise rejection TypeError: 0 is not iterable!

---

Seems like the babel preset for vue is pulling in the wrong polyfill

[LinusBorg]

No, the template works fine - Your Javascript is invalid. Promise.all() expects an array of Promise objects - you passed it an array containing a Number.

The error message tells you that Promise itself has been polyfilled - it's a promise rejection error after all, and it tells you that you passed it the wrong kind of content.

[nanomad]

@LinusBorg Please re-open because the following fails as well:

var p = Promise.resolve(0);
Promise.all([p]).then(function() {
  alert("ALL OK");
});

with error:

Unhandled promise rejection TypeError: [object Object] is not iterable!

Also, it's totally legal to use an object in place of a promise. See:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all

[nanomad]

Ok, so i've done some digging by playing around with the built-in babel preset (@vue/babel-preset-app).
Seems like the culprit is the following piece of code:

vue-cli/packages/@vue/babel-preset-app/index.js

Lines 43 to 44 in 399e759

	polyfill: false,
	regenerator: false,

If I switch polyfill to true babel will insert the non-global polluting version of the Promise polyfill that works properly on IE10

[LinusBorg]

Then the question is why the normal polyfill doesn't work on IE10?

And the side-question is why do you have to support IE10? Poor guy, you have my sympthy :(

I don't think we want to add the ponyfills from babel-transform, as some libs (like vuex) need them available as globals anyway, so we would have to include a polyfill as well, which would blow up code size etc.

[nanomad]

@LinusBorg I think I can manage to leave IE10 out but I was a bit surprised it didn't work since it was theoretically included in the list of supported browsers.

Given that I can reproduce it successfully without vue, do you think it may be worth opening a ticket in the babel repo? Maybe that combination is not supposed to work on IE10

[nanomad]

Filed a babel issue, seems like a feature detection error on IE10

babel/babel#7395