View source for Template:When on basepage/doc

{{Documentation subpage}}
<!--Categories where indicated at the bottom of this page, please; interwikis at Wikidata (see [[Wikipedia:Wikidata]])-->

This is the {{tl|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 <code>#ifeq:</code> and <code>#titleparts</code>. See [[#Alternatives for simpler text|Alternatives for simpler text]] below.

== Usage ==

: {{tlx|When on basepage&#32;|''result if on a basepage''&#32;(|''result if on a subpage'')&#32;(|''result if on a subsubpage'')&#32;(|page{{=}}''pagename'')}}

For example, {{tlf|When on basepage |Basepage |Subpage}} on the page "User:Example" would return: {{When on basepage|Basepage|Subpage|page=User:Example}}<br/>whilst on "User:Example/page" (or "User:Example/page/page", "User:Example/page/page/page", etc.) it would return: {{When on basepage|Basepage|Subpage|page=User:Example/page}}

On a subsubpage such as "User:Example/page/page" (or "User:Example/page/page/page", etc.), {{nowrap|{{tlf|When on basepage |Basepage |Subpage |Subsubpage}}}} would return: {{When on basepage |Basepage |Subpage |Subsubpage |page=User:Example/page/page}}

Use an empty parameter to specify no action for a particular type of page. {{nowrap|{{tlf|When on basepage |Basepage | |Subsubpage}}}} 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.
: {{tlf|When on basepage&#32;|1{{=}}''basepage result'' (|2{{=}}''subpage result'') (|3{{=}}''subsubpage result'')}}

===''page'' parameter===
The ''page'' parameter is included for testing/demonstration. For example:
: {{tlf|When on basepage&#32;|(basepage result) |(subpage result) |page{{=}}User:Example/test}}
Regardless of where the above is placed, it will return: {{When on basepage|(basepage result)|(subpage result)|page=User:Example/test}}<br/>(because "User:Example/test" is a subpage). The page doesn't have to exist.

If ''page'' is left empty ({{para|page}}) or undefined, the page where the template is transcluded (i.e. {{tld|PAGENAME}}) is used.

''page'' also accepts variables, e.g. {{nowrap|{{tlf|When on basepage |(basepage result) |(subpage result) |page<nowiki>={{{page|}}}</nowiki>&nbsp;}}}}

== Technical note ==

This template detects subpages in all namespaces, including those without the [[meta:Link#Subpage feature|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 <code>#titleparts</code> with <code>#ifeq</code>:
<pre>
{{#ifeq:{{#titleparts:{{PAGENAME}}|1|1}}|{{PAGENAME}}
 | [...code if on a basepage...]
 | [...code if on a subpage...]
}}
</pre>
For example, many templates can check if the page is a /sandbox version, by the similar markup with <code>#ifeq</code> and <code>#titleparts</code>:
: <nowiki>{{#ifeq: {{#titleparts:{{PAGENAME}}|1|1}} | {{PAGENAME}}</nowiki>
:: <nowiki> | {{documentation}}</nowiki>
:: <nowiki> | {{template sandbox notice}}</nowiki>
: <nowiki>}}</nowiki>
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 <code>#ifeq</code>, then the processing uses only +2 expansion depth levels, rather than +7 levels, and avoids "[[wp:exceeded template limits]]" inside a complex /doc page.

== See also ==
{{Namespace and pagename-detecting templates}}

<includeonly>{{Sandbox other||
<!--Categories below this line, please; interwikis at Wikidata-->
[[Category:Namespace manipulation templates]]
[[Category:Wikipedia metatemplates]]
}}</includeonly>