Pagination crashes when using Greek query arguments

[kouratoras]

I have an issue in both WordPress stable (4.6.1) and nightly build (4.7-alpha-38801).
It happens only when I have pretty permalinks structure (i.e. the default Day and name).

The steps to reproduce are:

1. Set pretty permalinks structure (let's say Day and name)
2. Create some posts in order to have pagination on the front-end
3. I visit the front-end
4. I go to page 2 (let's say /page/2/)
5. I manually add some Greek query arguments in the URL (let's say /page/2/?φοο=βαρ) and click enter

What I see: the page crashes with a browser message The page isn't redirecting properly. No errors in debug log.

[johnbillion]

Confirmed. This occurs in WordPress versions back to 4.1, but not in 4.0 or earlier.

[dgwatkins]

I did some debugging to see where this is coming from, here is what I found.

• In redirect_canonical() we use remove_query_arg() when there is pagination.

• This involves using parse_str() a couple of times, which has the side effect of urldecoding both the keys and the values in the query_string array.

• Immediately after we re-encode the values to compensate the said side effect, but we leave the keys behind.

This difference causes the redirect,

Im attaching a patch that works, Im not sure if there is a better way of doing it.

[dgwatkins]

re-encode keys and values

[bradleyt]

I'm currently unable to reproduce this issue. It looks like this may have been fixed in #43745.

[JeffPaul]

Closing as no longer reproducible, thanks all for the research & testing on this.