Last modified on 23 January 2013, at 14:36

Basepage subpage/doc

This template is used on 410,000+ pages.
To avoid large-scale disruption and unnecessary server load, any changes to this template should first be tested in the template's /sandbox or /testcases subpages, or in your own user space. The tested changes can then be added in one single edit to the template. Please consider discussing any changes on the talk page before implementing them.

This is the {{basepage subpage}} meta-template.

This template helps other templates detect if they are on a basepage, subpage or subsubpage. However, a subpage can be detected without using another template, by instead using a single #ifeq with parser function #titleparts (see below: Alternatives for simpler text).

Usage

This template takes one or more parameters, like this: 

{{basepage subpage
| Basepage text
| Subpage text
}}

If the template is on the page "User:Example", it shall return this:

Basepage text

If the template is on "User:Example/test" or "User:Example/test/test" or any page lower than that, it will return this:

Subpage text

This template can also detect "subsubpages", like this: 

{{basepage subpage
| Basepage text
| Subpage text
| Subsubpage text
}}

If the template is on "User:Example/test/test" or any page lower than that, it will return this:

Subsubpage text

By using an empty parameter you can make it so the template doesn't render anything for some specific page type. Like this: 

{{basepage subpage
| Basepage text
| Subpage text
| 
}}

The code above will render nothing when on "User:Example/test/test" or lower, but will return this when on "User:Example/test":

Subpage text

The "page" parameter

For testing and demonstration purposes this template can take a parameter named page. Like this: 

{{basepage subpage
| Basepage text
| Subpage text
| page = User:Example/test
}}

No matter on what kind of page the code above is used it will return this:

Subpage text

The page parameter makes this template behave exactly as if on that page. Thus, if a subsubpagename like "User:Example/test/test" is fed, then it returns the subsubpage text if there is one, otherwise it returns the subpage text.

The pagename doesn't have to be an existing page.

If the parameter is empty or undefined, the name of the current page determines the result.

You can make it so your template also understands the page parameter. That means you can demonstrate the different appearances of your template in the documentation for your template. Then do like this: 

{{basepage subpage
| Basepage text
| Subpage text
| page = {{{page|}}}
}}

Technical details

Templates have a problem to handle parameter data that contains equal signs "=". But that is easily solved by using numbered parameters. Like this: 

{{basepage subpage
| 1 = Basepage text
| 2 = Subpage text
| 3 = Subsubpage text
| page = {{{page|}}}
}}

This template detects subpages even when used in namespaces that doesn't have the MediaWiki subpage feature enabled. Thus this template works the same in all namespaces.

Alternatives for simpler text

A subpage can be detected without using another template, by instead using a single #ifeq along with the title-splitting parser function #titleparts, with expansion depth +1, as follows:

{{#ifeq: {{#titleparts:{{PAGENAME}}|1|1}} | {{PAGENAME}}
| ...then on base page...
| ...else on a subpage...
}}

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

{{#ifeq: {{#titleparts:{{PAGENAME}}|1|1}} | {{PAGENAME}}
| {{documentation}}
| {{template sandbox notice}}
}}

That simple logic works because 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 #ifeq, 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

Pagename-handling and detection templates:

  • {{basepage subpage}} – For detecting if on a basepage, subpage or subsubpage.
  • {{pgn}} – Can take apart and put together pagenames in several ways.
  • {{if pagename}} – For pattern matching on the pagename.
  • {{if pagename multi}} – For pattern matching on the pagename, has input reuse.
  • {{IP-user other}} – For detecting IP-user pages.
  • {{IP-talk}} - Return: 1) IP user talk page 2) registered user talk page 3) not user talk page.

Easy to use namespace-detection templates:

More complex namespace-detection templates:

Technical stuff: