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This is a meta-module that provides various functions for making hatnotes. It implements the {{hatnote}} template, for use in hatnotes at the top of pages, and the {{format hatnote link}} template, which is used to format a wikilink for use in hatnotes. It also contains a number of helper functions for use in other Lua hatnote modules.

Use from wikitext

The functions in this module cannot be used directly from #invoke, and must be used through templates instead. Please see Template:Hatnote and Template:Format link for documentation.

Use from other Lua modules

To load this module from another Lua module, use the following code.

<source lang="lua"> local mHatnote = require('Module:Hatnote') </source>

You can then use the functions as documented below.


<source lang="lua"> mHatnote._hatnote(s, options) </source>

Formats the string s as a hatnote. This encloses s in the tags <div class="hatnote">...</div>. Options are provided in the options table. Options include:

  • options.extraclasses - a string of extra classes to provide
  • options.selfref - if this is not nil or false, adds the class "selfref", used to denote self-references to Wikipedia (see Template:Selfref))

The CSS of the hatnote class is defined in MediaWiki:Common.css.

Example 1

<source lang="lua"> mHatnote._hatnote('This is a hatnote.') </source>

Produces: <div class="dablink">This is a hatnote.</div>

Displays as:

This is a hatnote.
Example 2

<source lang="lua"> mHatnote._hatnote('This is a hatnote.', {extraclasses = 'boilerplate seealso', selfref = true}) </source>

Produces: <div class="hatnote boilerplate seealso selfref">This is a hatnote.</div>

Displayed as:

This is a hatnote.

Format link

<source lang="lua"> mHatnote._formatLink(link, display) </source>

Formats link as a wikilink for display in hatnote templates, with optional display value display. Categories and files are automatically escaped with the colon trick, and links to sections are automatically formatted as page § section, rather than the MediaWiki default of page#section.

<syntaxhighlight lang="lua" enclose="none">mHatnote._formatLink('Lion')</syntaxhighlight> → [[Lion]] → Lion
<syntaxhighlight lang="lua" enclose="none">mHatnote._formatLink('Lion#Etymology')</syntaxhighlight> → [[Lion#Etymology|Lion § Etymology]] → Lion § Etymology
<syntaxhighlight lang="lua" enclose="none">mHatnote._formatLink('Category:Lions')</syntaxhighlight> → [[:Category:Lions]] → Category:Lions
<syntaxhighlight lang="lua" enclose="none">mHatnote._formatLink('Lion#Etymology', 'Etymology of lion')</syntaxhighlight> → [[Lion#Etymology|Etymology of lion]] → Etymology of lion

Format pages

<source lang="lua"> mHatnote.formatPages(...) </source>

Formats a list of pages using the _formatLink function, and returns the result as an array. For example, the code <syntaxhighlight lang="lua" enclose="none">mHatnote.formatPages('Lion', 'Category:Lions', 'Lion#Etymology')</syntaxhighlight> would produce an array like <syntaxhighlight lang="lua" enclose="none">{'Lion', 'Category:Lions', 'Lion § Etymology'}</syntaxhighlight>.

Format page tables

<source lang="lua"> mHatnote.formatPageTables(...) </source>

Takes a list of page/display tables, formats them with the _formatLink function, and returns the result as an array. Each item in the list must be a table. The first value in the table is the link, and is required. The second value in the table is the display value, and is optional. For example, the code <syntaxhighlight lang="lua" enclose="none">mHatnote.formatPages({'Lion', 'the Lion article'}, {'Category:Lions'}, {'Lion#Etymology', 'the etymology of lion'})</syntaxhighlight> would produce an array like <syntaxhighlight lang="lua" enclose="none">{'the Lion article', 'Category:Lions', 'the etymology of lion'}</syntaxhighlight>.

Find namespace id

<source lang="lua"> mHatnote.findNamespaceId(link, removeColon) </source>

Finds the namespace id of the string link, which should be a valid page name, with or without the section name. This function will not work if the page name is enclosed with square brackets. When trying to parse the namespace name, colons are removed from the start of the link by default. This is helpful if users have specified colons when they are not strictly necessary. If you do not need to check for initial colons, set removeColon to false.

<syntaxhighlight lang="lua" enclose="none">mHatnote.findNamespaceId('Lion')</syntaxhighlight> → 0
<syntaxhighlight lang="lua" enclose="none">mHatnote.findNamespaceId('Category:Lions')</syntaxhighlight> → 14
<syntaxhighlight lang="lua" enclose="none">mHatnote.findNamespaceId(':Category:Lions')</syntaxhighlight> → 14
<syntaxhighlight lang="lua" enclose="none">mHatnote.findNamespaceId(':Category:Lions', false)</syntaxhighlight> → 0 (the namespace is detected as ":Category", rather than "Category")

Make wikitext error

<source lang="lua"> mHatnote.makeWikitextError(msg, helpLink, addTrackingCategory) </source>

Formats the string msg as a red wikitext error message, with optional link to a help page helpLink. Normally this function also adds Category:Hatnote templates with errors; however, if addTrackingCategory is not false after being passed through Module:Yesno, then the category is suppressed. This means that the category can be suppressed with addTrackingCategory values including "no", "n", 0, "false", and <syntaxhighlight lang="lua" enclose="none">false</syntaxhighlight>.


<syntaxhighlight lang="lua" enclose="none">mHatnote.makeWikitextError('an error has occurred')</syntaxhighlight>Error: an error has occurred.
<syntaxhighlight lang="lua" enclose="none">mHatnote.makeWikitextError('an error has occurred', 'Template:Example#Errors')</syntaxhighlight>Error: an error has occurred (help).


For examples of how this module is used in other Lua modules, see the following (listed in order of complexity):

--                              Module:Hatnote                                --
--                                                                            --
-- This module produces hatnote links and links to related articles. It       --
-- implements the {{hatnote}} and {{format hatnote link}} meta-templates, and --
-- includes helper functions for other Lua hatnote modules.                   --

local libraryUtil = require('libraryUtil')
local checkType = libraryUtil.checkType
local mArguments -- lazily initialise [[Module:Arguments]]
local yesno -- lazily initialise [[Module:Yesno]]

local p = {}

-- Helper functions

local function getArgs(frame)
	-- Fetches the arguments from the parent frame. Whitespace is trimmed and
	-- blanks are removed.
	mArguments = require('Module:Arguments')
	return mArguments.getArgs(frame, {parentOnly = true})

local function removeInitialColon(s)
	-- Removes the initial colon from a string, if present.
	return s:match('^:?(.*)')

function p.findNamespaceId(link, removeColon)
	-- Finds the namespace id (namespace number) of a link or a pagename. This
	-- function will not work if the link is enclosed in double brackets. Colons
	-- are trimmed from the start of the link by default. To skip colon
	-- trimming, set the removeColon parameter to true.
	checkType('findNamespaceId', 1, link, 'string')
	checkType('findNamespaceId', 2, removeColon, 'boolean', true)
	if removeColon ~= false then
		link = removeInitialColon(link)
	local namespace = link:match('^(.-):')
	if namespace then
		local nsTable =[namespace]
		if nsTable then
	return 0

function p.formatPages(...)
	-- Formats a list of pages using formatLink and returns it as an array. Nil
	-- values are not allowed.
	local pages = {...}
	local ret = {}
	for i, page in ipairs(pages) do
		ret[i] = p._formatLink(page)
	return ret

function p.formatPageTables(...)
	-- Takes a list of page/display tables and returns it as a list of
	-- formatted links. Nil values are not allowed.
	local pages = {...}
	local links = {}
	for i, t in ipairs(pages) do
		checkType('formatPageTables', i, t, 'table')
		local link = t[1]
		local display = t[2]
		links[i] = p._formatLink(link, display)
	return links

function p.makeWikitextError(msg, helpLink, addTrackingCategory)
	-- Formats an error message to be returned to wikitext. If
	-- addTrackingCategory is not false after being returned from
	-- [[Module:Yesno]], and if we are not on a talk page, a tracking category
	-- is added.
	checkType('makeWikitextError', 1, msg, 'string')
	checkType('makeWikitextError', 2, helpLink, 'string', true)
	yesno = require('Module:Yesno')
	local title = mw.title.getCurrentTitle()
	-- Make the help link text.
	local helpText
	if helpLink then
		helpText = ' ([[' .. helpLink .. '|help]])'
		helpText = ''
	-- Make the category text.
	local category
	if not title.isTalkPage and yesno(addTrackingCategory) ~= false then
		category = 'Hatnote templates with errors'
		category = string.format(
		category = ''
	return string.format(
		'<strong class="error">Error: %s%s.</strong>%s',

-- Format link
-- Makes a wikilink from the given link and display values. Links are escaped
-- with colons if necessary, and links to sections are detected and displayed
-- with " § " as a separator rather than the standard MediaWiki "#". Used in
-- the {{format hatnote link}} template.

function p.formatLink(frame)
	local args = getArgs(frame)
	local link = args[1]
	local display = args[2]
	if not link then
		return p.makeWikitextError(
			'no link specified',
			'Template:Format hatnote link#Errors',
	return p._formatLink(link, display)

function p._formatLink(link, display)
	-- Find whether we need to use the colon trick or not. We need to use the
	-- colon trick for categories and files, as otherwise category links
	-- categorise the page and file links display the file.
	checkType('_formatLink', 1, link, 'string')
	checkType('_formatLink', 2, display, 'string', true)
	link = removeInitialColon(link)
	local namespace = p.findNamespaceId(link, false)
	local colon
	if namespace == 6 or namespace == 14 then
		colon = ':'
		colon = ''

	-- Find whether a faux display value has been added with the {{!}} magic
	-- word.
	if not display then
		local prePipe, postPipe = link:match('^(.-)|(.*)$')
		link = prePipe or link
		display = postPipe

	-- Find the display value.
	if not display then
		local page, section = link:match('^(.-)#(.*)$')
		if page then
			display = page .. ' § ' .. section

	-- Assemble the link.
	if display then
		return string.format('[[%s%s|%s]]', colon, link, display)
		return string.format('[[%s%s]]', colon, link)

-- Hatnote
-- Produces standard hatnote text. Implements the {{hatnote}} template.

function p.hatnote(frame)
	local args = getArgs(frame)
	local s = args[1]
	local options = {}
	if not s then
		return p.makeWikitextError(
			'no text specified',
	options.extraclasses = args.extraclasses
	options.selfref = args.selfref
	return p._hatnote(s, options)

function p._hatnote(s, options)
	checkType('_hatnote', 1, s, 'string')
	checkType('_hatnote', 2, options, 'table', true)
	local classes = {'hatnote'}
	local extraclasses = options.extraclasses
	local selfref = options.selfref
	if type(extraclasses) == 'string' then
		classes[#classes + 1] = extraclasses
	if selfref then
		classes[#classes + 1] = 'selfref'
	return string.format(
		'<div class="%s">%s</div>',
		table.concat(classes, ' '),

return p