Navigating to AMP-enabled sites on IE/Edge adds "undefined" to the url

[petetnt]

Steps to reproduce:

1. Navigate to https://ampproject.org/
2. After loading the page the url / document.location.href is now https://ampproject.org/undefined

Tested on Edge, IE11, Windows Phone 8.1 IE11.

This creates some unwanted effects, such as reloading leading to a 404 page.

[erwinmombay]

thanks for reporting! will take a look

[erwinmombay]

@petetnt confirmed. ANY amp page right now seems to trigger a url change to /undefined on Edge and IE11.

/cc @cramforce @dvoytenko

[erwinmombay]

looks like this is caused by https://github.com/ampproject/amphtml/blob/master/src/history.js#L285 (call to the browsers native replace state). unsure yet why it's happening

[erwinmombay]

looks like passing in undefined as the url (3rd argument), even though its marked as optional, really screws it up. not passing in undefined fixes the issue. (looks like its weirdly coerced into a string)

[petetnt]

@erwinmombay cool, I though it could be something that affected all the AMP sites but didn't have the time to check yesterday 👍

I noticed something else too: it coerces Booleans to strings too so replaceState({foo: "bar"}, foo, true}) results in foo.org/true 👻

It's not AMP's job to work around browser bugs, but I guess all of those kinds of weird behaviors (like someone accidentally passing true/false as an opt_url could be avoided by extending https://github.com/ampproject/amphtml/pull/746/files#diff-6d1071e9a4a9346d2d306a79be2de0d1R287 with:

if (opt_url && typeof opt_url === "string") {

(Actually it turns out that you can pass pretty much anything as the URL and browsers will comply)

[erwinmombay]

@petetnt thanks. that scenario should be caught once we get the closure compiler running so the only things that should come through as opt_url is of type {string|undefined} (i'll probably change my code to only check for undefined)

[petetnt]

Sounds good to me 👍

[erwinmombay]

landed in f268934

thanks again @petetnt!