Module:Namespace detect

This Lua module is used in system messages, and on approximately 15,500,000 pages, or roughly 69141% of all pages.
Changes to it can cause immediate changes to the Wikipedia user interface.
To avoid major disruption and server load, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Please discuss changes on the talk page before implementing them.

This module is subject to page protection. It is a highly visible module in use by a very large number of pages, or is substituted very frequently. Because vandalism or mistakes would affect many pages, and even trivial editing might cause substantial load on the servers, it is protected from editing.

This module allows you to output different text depending on the namespace that a given page is in. It is a Lua implementation of the {{namespace detect}} template, with a few improvements: all namespaces and all namespace aliases are supported, and namespace names are detected automatically for the local wiki.

Usage

{{#invoke: Namespace detect | main
| page              = <!-- page to detect namespace for, if not the current page -->
| main              = <!-- text to return for the main namespace -->
| talk              = <!-- text to return for talk namespaces -->

<!-- text to return for specific subject namespaces -->
| portal            = 
| category          = 
| user 	            = 
| wikipedia         = 
| mediawiki         = 
| book              = 
| timedtext         = 
| template          = 
| special           = 
| media             = 
| file              = 
| image             = 
| help 	            = 
| module            = 

| other             = <!-- text to return for unspecified namespaces -->
| demospace         = <!-- namespace to display text for -->

| subjectns         = <!-- set to "yes" to treat talk pages as the corresponding subject page -->
}}

Parameters

main - text to return if the page is in the main namespace.
talk - text to return if the page is in a talk namespace. This can be any talk namespace - it will match any of "Talk:", "Wikipedia talk:", "User talk:", etc.
Subject namespace parameters, e.g. wikipedia, user, file... - the text to return if the page is in the corresponding namespace. This module accepts all subject namespaces as parameters, including namespace aliases and virtual namespaces. See below for a list of supported values.
other - text to return if no parameters for the page's namespace were specified. This text is also returned if |demospace= is set to an invalid namespace value.
subjectns - if on a talk page, use the corresponding subject page. Can be set with values of "yes", "y", "true" or "1".
demopage - specifies a page to detect the namespace of. If not specified, and if the |demospace= parameter is not set, then the module uses the current page.
demospace - force the module to behave as if the page was in the specified namespace. Often used for demonstrations.

Namespace parameters

Possible values for subject namespace parameters are as follows:

Namespace	Aliases
`main`
`user`	`u`
`semina verbi`	`project`, `p`, `wp`
`file`	`f`, `image`
`mediawiki`
`template`	`t`
`help`	`h`
`category`	`c`
`item`
`property`
`lexeme`
`schema`
`timedtext`
`module`
`translations`

Table function

Use the following to display a table with the different possible namespace parameters:

{{#invoke:Namespace detect|table|talk=yes}}

To include the parameter for talk namespaces, use |talk=yes.

Porting to different wikis

This module is designed to be portable. To use it on a different wiki, all you need to do is to change the values in Module:Namespace detect/config. Instructions are available on that page.

Technical details

The module uses a data page at Module:Namespace detect/data. This page is loaded with mw.loadData, which means it is processed once per page rather than once per #invoke. This was done for performance reasons.

--[[
--------------------------------------------------------------------------------
--                                                                            --
--                            NAMESPACE DETECT                                --
--                                                                            --
-- This module implements the {{namespace detect}} template in Lua, with a    --
-- few improvements: all namespaces and all namespace aliases are supported,  --
-- and namespace names are detected automatically for the local wiki. The     --
-- module can also use the corresponding subject namespace value if it is     --
-- used on a talk page. Parameter names can be configured for different wikis --
-- by altering the values in the "cfg" table in                               --
-- Module:Namespace detect/config.                                            --
--                                                                            --
--------------------------------------------------------------------------------
--]]

local data = mw.loadData('Module:Namespace detect/data')
local argKeys = data.argKeys
local cfg = data.cfg
local mappings = data.mappings

local yesno = require('Module:Yesno')
local mArguments -- Lazily initialise Module:Arguments
local mTableTools -- Lazily initilalise Module:TableTools
local ustringLower = mw.ustring.lower

local p = {}

local function fetchValue(t1, t2)
	-- Fetches a value from the table t1 for the first key in array t2 where
	-- a non-nil value of t1 exists.
	for i, key in ipairs(t2) do
		local value = t1[key]
		if value ~= nil then
			return value
		end
	end
	return nil
end

local function equalsArrayValue(t, value)
	-- Returns true if value equals a value in the array t. Otherwise
	-- returns false.
	for i, arrayValue in ipairs(t) do
		if value == arrayValue then
			return true
		end
	end
	return false
end

function p.getPageObject(page)
	-- Get the page object, passing the function through pcall in case of
	-- errors, e.g. being over the expensive function count limit.
	if page then
		local success, pageObject = pcall(mw.title.new, page)
		if success then
			return pageObject
		else
			return nil
		end
	else
		return mw.title.getCurrentTitle()
	end
end

-- Provided for backward compatibility with other modules
function p.getParamMappings()
	return mappings
end

local function getNamespace(args)
	-- This function gets the namespace name from the page object.
	local page = fetchValue(args, argKeys.demopage)
	if page == '' then
		page = nil
	end
	local demospace = fetchValue(args, argKeys.demospace)
	if demospace == '' then
		demospace = nil
	end
	local subjectns = fetchValue(args, argKeys.subjectns)
	local ret
	if demospace then
		-- Handle "demospace = main" properly.
		if equalsArrayValue(argKeys.main, ustringLower(demospace)) then
			ret = mw.site.namespaces[0].name
		else
			ret = demospace
		end
	else
		local pageObject = p.getPageObject(page)
		if pageObject then
			if pageObject.isTalkPage then
				-- Get the subject namespace if the option is set,
				-- otherwise use "talk".
				if yesno(subjectns) then
					ret = mw.site.namespaces[pageObject.namespace].subject.name
				else
					ret = 'talk'
				end
			else
				ret = pageObject.nsText
			end
		else
			return nil -- return nil if the page object doesn't exist.
		end
	end
	ret = ret:gsub('_', ' ')
	return ustringLower(ret)
end

function p._main(args)
	-- Check the parameters stored in the mappings table for any matches.
	local namespace = getNamespace(args) or 'other' -- "other" avoids nil table keys
	local params = mappings[namespace] or {}
	local ret = fetchValue(args, params)
	--[[
	-- If there were no matches, return parameters for other namespaces.
	-- This happens if there was no text specified for the namespace that
	-- was detected or if the demospace parameter is not a valid
	-- namespace. Note that the parameter for the detected namespace must be
	-- completely absent for this to happen, not merely blank.
	--]]
	if ret == nil then
		ret = fetchValue(args, argKeys.other)
	end
	return ret
end

function p.main(frame)
	mArguments = require('Module:Arguments')
	local args = mArguments.getArgs(frame, {removeBlanks = false})
	local ret = p._main(args)
	return ret or ''
end

function p.table(frame)
	--[[
	-- Create a wikitable of all subject namespace parameters, for
	-- documentation purposes. The talk parameter is optional, in case it
	-- needs to be excluded in the documentation.
	--]]
	
	-- Load modules and initialise variables.
	mTableTools = require('Module:TableTools')
	local namespaces = mw.site.namespaces
	local cfg = data.cfg
	local useTalk = type(frame) == 'table' 
		and type(frame.args) == 'table' 
		and yesno(frame.args.talk) -- Whether to use the talk parameter.
	
	-- Get the header names.
	local function checkValue(value, default)
		if type(value) == 'string' then
			return value
		else
			return default
		end
	end
	local nsHeader = checkValue(cfg.wikitableNamespaceHeader, 'Namespace')
	local aliasesHeader = checkValue(cfg.wikitableAliasesHeader, 'Aliases')

	-- Put the namespaces in order.
	local mappingsOrdered = {}
	for nsname, params in pairs(mappings) do
		if useTalk or nsname ~= 'talk' then
			local nsid = namespaces[nsname].id
			-- Add 1, as the array must start with 1; nsid 0 would be lost otherwise.
			nsid = nsid + 1 
			mappingsOrdered[nsid] = params
		end
	end
	mappingsOrdered = mTableTools.compressSparseArray(mappingsOrdered)

	-- Build the table.
	local ret = '{| class="wikitable"'
		.. '\n|-'
		.. '\n! ' .. nsHeader
		.. '\n! ' .. aliasesHeader
	for i, params in ipairs(mappingsOrdered) do
		for j, param in ipairs(params) do
			if j == 1 then
				ret = ret .. '\n|-'
					.. '\n| <code>' .. param .. '</code>'
					.. '\n| '
			elseif j == 2 then
				ret = ret .. '<code>' .. param .. '</code>'
			else
				ret = ret .. ', <code>' .. param .. '</code>'
			end
		end
	end
	ret = ret .. '\n|-'
		.. '\n|}'
	return ret
end

return p