Module:Category pair

This module is rated as ready for general use. It has reached a mature form and is thought to be relatively bug-free and ready for use wherever appropriate. It is ready to mention on help pages and other Wikipedia resources as an option for new users to learn. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

This Lua module is used on approximately 6,700 pages and changes may be widely noticed. Test changes in the module's /sandbox or /testcases subpages. Consider discussing changes on the talk page before implementing them.

Transclusion count updated automatically (see documentation).

This module depends on the following other modules:

Implements {{Category pair}}, {{Preceding category}}, and {{Succeeding category}}

Usage

{{#invoke:Category pair|_pair|title object for first page|title object for second page}}

require('strict')
local getArgs = require('Module:Arguments').getArgs
local hatnote = require('Module:Hatnote')._hatnote
local formatLink = require('Module:Format link')._formatLink

local p = {}

local catNS = mw.site.namespaces.Category.id -- category namespace number

-- Lua implementation of [[Template:CategoryPair]]
-- Arguments:
--   prevTitle -- mw.title.Title object for preceding category
--   nextTitle -- mw.title.Title object for succeeding category
-- Returns:
--   hatnote that says "see also" for one or both of prev/next (depending on whether they exist)
function p._pair(prevTitle, nextTitle)
	prevTitle = prevTitle and prevTitle.exists and formatLink{link = prevTitle.fullText}
	nextTitle = nextTitle and nextTitle.exists and formatLink{link = nextTitle.fullText}
	local note = ''
	if prevTitle and nextTitle then -- if both
		note = mw.ustring.format('See also the preceding %s and the succeeding %s',prevTitle, nextTitle)
	elseif prevTitle then -- if only prevTitle
		note = mw.ustring.format('See also the preceding %s', prevTitle)
	elseif nextTitle then -- if only nextTitle
		note = mw.ustring.format('See also the succeeding %s', nextTitle)
	else                  -- otherwise neither
		return mw.title.getCurrentTitle().namespace == catNS and '[[Category:Pages using category pair with no output]]' or ''
	end
	return hatnote(note, {extraclasses = 'seealso'})
end

function p.catPair(frame)
	local args = getArgs(frame, {wrappers={'Template:Category pair'}})
	local prevTitle = args[1] and mw.title.new(args[1],catNS)
	local nextTitle = args[2] and mw.title.new(args[2],catNS)
	return p._pair(prevTitle, nextTitle)
end

function p.prevCat(frame)
	local args = getArgs(frame, {wrappers={'Template:Preceding category'}})
	local prevTitle = args[1] and mw.title.new(args[1], catNS)
	return p._pair(prevTitle, nil)
end

function p.nextCat(frame)
	local args = getArgs(frame, {wrappers={'Template:Succeeding category'}})
	local nextTitle = args[1] and mw.title.new(args[1], catNS)
	return p._pair(nil, nextTitle)
end

return p