Presence of language prefix in URL incorrectly assigns admin session

[CherryDT]

I discovered the following strange behavior on a multi-language page with admin plugin:

• After logging into the admin, my username would appear in the navbar on the page, but only sometimes. Further investigation showed that it would be hidden on the homepage with language prefix without trailing slash (e.g. /en) but visible with the trailing slash (e.g. /en/) or on sub-pages (e.g. /en/blog). This particular symptom is actually because of Utils::pathPrefixedByLangCode doesn't detect homepage with prefix without trailing slash #2510 in combination with this bug.
• The "save language in session" feature would not work for me (after I "fixed" the previous issue using a htaccess redirect from /en to /en/ - I hadn't fully understood the problem yet). Further investigation showed that on / a different session would be used than on /en///de/, and hence the new language would be written to session A but / would read from session B and redirect to the wrong language.

Turns out that this is due to a bug in SessionServiceProvider.php: It sets $is_admin = true if the route starts with /admin or with a language prefix. It should instead check if it starts with /<prefix>/admin in that case!

[CherryDT]

I fixed the issue in #2512

[CherryDT]

Thanks for the commit, however I'm not sure I understand how this works. Won't Utils::pathPrefixedByLangCode simply return true, which - if you stuff it into string concatenation - will become 1, and hence you are now checking for /1/admin (or //admin if it was false)?

[rhukster]

There's a second commit with a change in the Utils function. 8a7f624

sorry, forgot i commited this first.

[CherryDT]

Ooh, right, I'm sorry, I didn't realize. Never mind then, thanks for the fix!!