Template:When on basepage/doc

This is the When on basepage meta-template. It helps other templates detect if they are on a basepage (i.e. a page whose name matches the pattern "x:x") subpage ("x:x/x") or subsubpage ("x:x/x/x").

An alternative way to detect whether a page is a subpage is to combine the parser functions and. See Alternatives for simpler text below.

Usage


For example, on the page "User:Example" would return:  whilst on "User:Example/page" (or "User:Example/page/page", "User:Example/page/page/page", etc) it would return:

On a subsubpage such as "User:Example/page/page" (or "User:Example/page/page/page", etc), would return:

Use an empty parameter to specify no action for a particular type of page. on "User:Example/page", for example, would return nothing, but would return "Subsubpage" if on "User:Example/page/page", "User:Example/page/page/page", etc (and "Basepage" if on "User:Example").

Handling equals-signs ("=")
Use numbered parameters if their values include equals-signs ("="), i.e.

page parameter
The page parameter is included for testing/demonstration. For example:

Regardless of where the above is placed, it will return: (because "User:Example/test" is a subpage). The page doesn't have to exist.

If page is left empty (page) or undefined, the page where the template is transcluded (i.e. ) is used.

page also accepts variables, e.g.

Technical note
This template detects subpages in all namespaces, including those without the MediaWiki subpage feature enabled.

Alternatives for simpler text
A subpage can be detected without using another template, by instead using the title-splitting parser function with :

For example, many templates can check if the page is a /sandbox version, by the similar markup with  and  :

That simple logic works because Template:Template_sandbox_notice also checks the page name for "/sandbox" before displaying the sandbox notice; otherwise, any other subpage would show no extra text. By avoiding a template, and using a single, then the processing uses only +2 expansion depth levels, rather than +7 levels, and avoids "wp:exceeded template limits" inside a complex /doc page.