User:Wlgrin/Sandbox/Generic/Main/Template001/doc

The At User template ({{@u}}) is a shortcut used to help transclude user pages (typically, user templates) within other user pages belonging to the same user. As a safeguard, the behaviour of {{@u}} depends on whether the transcluding page is itself within user space (as expected) or not, thereby avoiding the inadvertent transclusion of pages from user space into Wikipedia articles or project pages.

Usage

Basic usage

Template {{@u}} takes a single, unnamed parameter {{{1}}}: the name of a user page to transclude.

Using {{@u}}, one may replace calls such as

{{User:MeMyselfEtMoi/Template/My template|Parameter value}}

with the relatively simpler form

{{{{@u|My template}}|Parameter value}}

Since {{@u}} only expands the name of the transcluded page, the whole call (and any parameter list that may follow) must be nested within another pair of double braces.

If the transcluding page is in user space (i.e., in the User or User talk namespace), the template called through {{@u}} will be found in a sub-page of “User:user-name/Template/” (where user-name is derived from the name of the transcluding page). If the transcluding page is in any other namespace, the template is found normally (by default, in namespace Template).

Examples
For example, if the transcluding page is `“User:MeMyselfEtMoi/My current projects”`, using `{{{{@u\|My template}}\|Parameter value}}` will produce (during parsing) `{{User:MeMyselfEtMoi/Template/My template\|Parameter value}}` This expanded call will then be parsed to produce, on the page displayed, the result of transcluding `{{User:MeMyselfEtMoi/Template/My template}}`. If the same call was inadvertently copied into an article (outside user space), it would instead expand to `{{My template\|Parameter value}}` with the effect of transcluding `{{Template:My template}}`.

Prefixing with “/”

If the name of the transcluded page (passed as first parameter to {{@u}}) begins with a “/” and the transcluding page is in user space, the template is searched in a sub-page of “User:user-name” (instead of “User:user-name/Template/”). If the transcluding page is not in user space, only the terminal sub-page name is kept (i.e., the leading “/” and any parent sub-page names are dropped).

Examples
For example, `{{{{@u\|/Sandbox/My new template}}\|Parameter value}}` will produce `{{User:MeMyselfEtMoi/Sandbox/My new template\|Parameter value}}` If this same call was inadvertently copied into an article (outside user space), the leading “/” and parent sub-page name “Sandbox” would be stripped and the call would expand to `{{My new template\|Parameter value}}`

Using substitution

{{@u}} can be safely substituted, since it uses the “safesubst” modifier to call parser functions and magic words and it does not transclude any other page.

Rather than being just a typing aid, {{@u}} aims at reducing the visual clutter caused by a large number of transclusions of user templates in a user page. For that reason, it is generally best to transclude it and not substitute it. However, it is useful to substitute {{@u}} in two cases:

when substituting the page whose name is passed as parameter to {{@u}}, and
when eliminating {{@u}} from a page (for example, while moving the transcluding page from a user sandbox to main article space).

If you want to substitute the page whose name is passed as parameter to {{@u}}, you must also substitute template {{@u}} itself. This is because the MediaWiki parser performs all substitutions before performing any transclusion. The resulting notation is verbose and such use of {{@u}} has little appeal.

Examples
For example, this incorrect call: `{{safesubst:{{@u\|My template}}\|Parameter value}}` will produce the likely unintended reproduction, on the displayed page, of the code calling “My template” (instead of displaying the result of its actual transclusion or substitution): `{{safesubst:User:MeMyselfEtMoi/Template/My template\|Parameter value}}` By contrast, `{{safesubst:{{safesubst:@u\|My template}}\|Parameter value}}` will produce, as expected, the substituted output of `{{safesubst:User:MeMyselfEtMoi/Template/My template\|Parameter value}}`. On the other hand, you can safely substitute `{{@u}}` without substituting the transcluded page: `{{{{safesubst:@u\|My template}}\|Parameter value}}`

Caveats

If you do not need to pass any parameter, remember to separate the two closing sets of double braces; otherwise, the closing series of four braces will confuse the MediaWiki parser. For example, you can use as separator a space or a pipe. Using a pipe will cause an empty unnamed parameter to be passed to the transcluded page, which is generally without adverse consequences (but check the syntax of the transcluded page to confirm that assumption).

Examples
For example, this incorrect call: `{{{{@u\|My template}}}}` will produce the likely unintended output `{My template}` By contrast, `{{{{@u\|My template}} }}` will produce, as expected, `{{User:MeMyselfEtMoi/Template/My template}}` Similarly, using a pipe, `{{{{@u\|My template}}\|}}` will produce `{{User:MeMyselfEtMoi/Template/My template\|}}`

Automated processing

Since there are no valid reasons for this template to appear outside user space, an automatic script (bot) could be written to detect and strip it from non-user pages. Using substitution is the best option to do this. Otherwise, the call itself may be munged, leaving only the name of the transcluded page in its place ({{@u|Abc}} becoming Abc) and, if there is a leading “/”, taking care of stripping it as well as the names of any parent sub-pages ({{@u|/Xxx/Yyy/Abc}} also becoming Abc).