{uid} cannot be used as hostname

[Netspider]

Steps to reproduce

1. set the hostname of the external site to "https://{uid}/"
2. press [Enter]

Expected behaviour

hostname field should get a green border and save

Actual behaviour

hostname field has a red border and is not saved

Server configuration

PHP version:
7.4
Nextcloud version: (see Nextcloud admin page)
18.0.1
List of activated apps:
external 3.5.0

"https://example.org/{uid}" is working, but not if the variable is used in the hostname part like above.

[yrammos]

Confirming the problem also whenever {uid} is passed as a GET URL parameter, as in example.org/?user={uid}.

[yrammos]

UPDATE: In fact it does work. Might it be that you're referring to the external site with a localhost URL? This was the cause of the error in my case. Replacing with a truly external URL resolved it.

[Netspider]

I wanted https://webmail.{uid}/ so there is no localhost involved.

[nickvergessen]

But we replace it in the full URL
https://github.com/nextcloud/external/blob/master/lib/SitesManager.php#L110

Do that should really work

[Netspider]

but the javascript does not allow this syntax, it draws a red border around the url field and does not save.

[nickvergessen]

I guess this is blocking it:

external/lib/SitesManager.php

Lines 222 to 227 in e4e5f93

	if (filter_var($url, FILTER_VALIDATE_URL) === false ||
	(strpos($url, 'http://') !== 0
	&& strpos($url, 'https://') !== 0
	&& strpos($url, 'mailto:') !== 0)) {
	throw new InvalidURLException();
	}

We need to do the replacements with the values of the current admin before checking if the URL is valid.