Module:category tree

පහත දැක්වෙන උපදෙස්, Module:category tree/documentation හි පිහිටා ඇත. Module:category tree/documentation]]. ^{[සංස්කරණය]}

ප්‍රයෝජනවත් සබැඳි: උප පිටු ලැයිස්තුව • සබැඳි • transclusions • testcases • sandbox (වෙනස)

This module is used for generating category boilerplate templates. It is not meant to be used directly. Rather, each template will have its own submodule, which handles the specifics of that template.

This documentation only covers the generics of the category tree system. If you are looking for documentation on a specific template, or on how to add or modify category information, see the documentation of that template.

Consider using poscatboiler handlers instead.

If you are considering creating a new category tree submodule, you may find it easier to instead add a poscatboiler handler. Generally, much less code is required, and there is no need to modify Module:auto cat to recognize the categories in question. See Module:category tree/poscatboiler/data/documentation for more info. For examples, see e.g. the handlers in Module:category tree/poscatboiler/data/terms by etymology that handle categories of the form LANG terms coined by COINER and LANG terms with POS1 and POS2 etymologies.

Parameters

The category tree module is invoked as:

{{#invoke:category tree|show|template=name of the template|...other parameters...}}

Every template that uses this module should have a submodule of this module with the name given in the |template= parameter. At present, only three such templates exist:

{{poscatboiler}} uses Module:category tree/poscatboiler
{{topic cat}} uses Module:category tree/topic cat
{{ws topic cat}} uses Module:category tree/ws topic cat

The submodule should export a function named new which takes a single parameter: a table named info that contains the various parameters that were passed to the template initially. This function should return a new Category object representing those parameters, or nil if the combination of parameters was not valid (i.e. no such category exists).

General workings

The module is based on the principle of two main kinds of category:

Basic categories belong to a specific language (or similar) and are the "regular" categories. Examples are: Category:English nouns, Category:French templates, Category:nl:Linguistics, Category:English terms derived from Japanese, Category:Latin script characters.

Umbrella categories do not have a code, but contain all basic categories of their label, one for each code. These are the "by language" type categories. Examples are: Category:Nouns by language, Category:Templates by language, Category:Linguistics, Category:Terms derived from Japanese, Category:Characters by script.

Some templates also distinguish a third type of category, the fundamental category. This category is used as the parent category for umbrella categories.

Category objects

	This documentation is out of date.
	The documentation on this page or section no longer reflects its current state, and some information may be missing or incorrect. Please help by editing the documentation page, and adding information about undocumented features, while removing information that is no longer applicable.

Category objects are returned by each submodule's new function. They represent a single category in the tree. A category object has a variety of methods which may be called on it to ask for information about the category.

getBreadcrumbName

getBreadcrumbName()

Returns the name that is used for the category in the "breadcrumbs" at the top of the category page.

getDataModule

getDataModule()

Returns the name of the module which contains the data for this category. This is used to create an "edit" link on the category, which allows users to find and edit the information more easily.

canBeEmpty

canBeEmpty()

Returns true either if the category contains pages but might be empty or if the category only contains categories, otherwise returns false.

getCategoryName

getCategoryName()

Returns the name of the category that this category object represents.

getDescription

getDescription()

Returns the description text that is shown at the top of the category page. If the category has no description, this returns nil.

getParents

getParents()

Returns a table of the parent categories of this category. Each element in the table is a table itself, with two elements:

.name: One of two possibilities: An category object representing the parent category, or a string that directly specifies the name of the parent category.
.sort: The sorting key that should be used when categorizing the current category in the parent.

If the category has no parents, this returns nil.

If there are two or more parent categories, the first will be used to generate the breadcrumbs that are displayed at the top of the category page. For example, Category:English language is in numerous categories (All languages, West Germanic languages, Latin script languages, Braille script languages, and so on), but the first category, All languages, is the one displayed in the breadcrumbs: Fundamental » All languages » English language.

getChildren

getChildren()

Returns a table of the child categories of this category. Each element in the table is a category object representing the child category. If the category has no children, this returns nil.

getUmbrella

getUmbrella()

Returns a category object for the current category's corresponding umbrella category. If the current category is already an umbrella category, this returns nil. It also returns nil if the category has no umbrella category.

getAppendix

getAppendix()

Returns an appendix link (such as Appendix:French verbs) if the page exists, else returns nil.

getTOCTemplateName

getTOCTemplateName()

Returns the title for a template used as table of contents with the namespace prefix.

The table of contents is designed for categories with terms in a certain language, The TOC template should be a small, one-line template; a larger template will be used if available with the suffix /full. For example, if getTOCTemplateName() returns Template:en-categoryTOC, {{en-categoryTOC}} will be used as the small table of contents template (for categories with more than 200 but less than 2500 entries) and {{en-categoryTOC/full}} as the full table of contents template (for categories with more than 2500 entries).

If the function returns nil, no such template will be used.

-- Prevent substitution.
if mw.isSubsting() then
	return require("Module:unsubst")
end

local export = {}

local m_str_utils = require("Module:string utilities")
local m_template_parser = require("Module:template parser")
local m_utilities = require("Module:utilities")

local class_else_type = m_template_parser.class_else_type
local concat = table.concat
local deep_copy = require("Module:table").deepCopy
local full_url = mw.uri.fullUrl
local insert = table.insert
local new_title = mw.title.new
local pages_in_category = mw.site.stats.pagesInCategory
local parse = m_template_parser.parse
local remove_comments = m_str_utils.remove_comments
local sort = table.sort
local split = m_str_utils.split
local string_sort = require("Module:collation").string_sort
local trim = m_str_utils.trim
local uupper = m_str_utils.upper
local yesno = require("Module:yesno")

local current_frame = mw.getCurrentFrame()
local current_title = mw.title.getCurrentTitle()
local inFundamental = mw.loadData("Module:category tree/data")
local namespace = current_title.namespace

local poscatboiler = "poscatboiler"
local topic_cat = "topic cat"
local ws_topic_cat = "ws topic cat"

local extra_args_error = "Extra arguments to {{((}}auto cat{{))}} are not allowed for this category."

function export.split_lang_label(title_text)
	local getByCanonicalName = require("Module:languages").getByCanonicalName
	
	-- Progressively remove a word from the potential canonical name until it
	-- matches an actual canonical name.
	local words = split(title_text, " ", true)
	for i = #words - 1, 1, -1 do
		local lang = getByCanonicalName(concat(words, " ", 1, i))
		if lang then
			return lang, concat(words, " ", i + 1)
		end
	end
	
	return nil, title_text
end

local function show_error(text)
	return require("Module:message box").maintenance(
		"red",
		"[[File:Ambox warning pn.svg|50px]]",
		"මෙම ප්‍රවර්ගය වික්ෂණරියේ ප්‍රවර්ග පද්ධතිය තුළ අර්ථ දක්වා නොමැත.",
		text
	)
end

-- Show the text that goes at the very top right of the page.
local function show_topright(current)
	return current.getTopright and current:getTopright() or nil
end

local function link_box(content)
	return ("<div class=\"noprint plainlinks\" style=\"float: right; clear: both; margin: 0 0 .5em 1em; background: var(--wikt-palette-paleblue, #f9f9f9); border: 1px var(--border-color-base, #aaaaaa) solid; margin-top: -1px; padding: 5px; font-weight: bold;\">%s</div>"):format(content)
end

local function show_editlink(current)
	return link_box(("[%s ප්‍රවර්ග දත්ත සංස්කරණය]"):format(tostring(full_url(current:getDataModule(), "action=edit"))))
end

function show_related_changes()
	local title = current_title.fullText
	return link_box(("[%s <span title=\"Recent edits and other changes to pages in %s\">නව වෙනස්වීම්</span>]"):format(
		tostring(full_url("Special:RecentChangesLinked", {
			target = title,
			showlinkedto = 0,
		})),
		title
	))
end

local function show_pagelist(current)
	local namespace = "namespace="
	local info = current:getInfo()
	
	local lang_code = info.code
	if info.label == "citations" or info.label == "citations of undefined terms" then
		namespace = namespace .. "Citations"
	elseif lang_code then
		local lang = require("Module:languages").getByCode(lang_code, true)
		if lang then
			-- Proto-Norse (gmq-pro) is the probably language with a code ending in -pro
			-- that's intended to have mostly non-reconstructed entries.
			if (lang_code:find("%-pro$") and lang_code ~= "gmq-pro") or lang:hasType("reconstructed") then
				namespace = namespace .. "Reconstruction"
			elseif lang:hasType("appendix-constructed") then
				namespace = namespace .. "Appendix"
			end
		end
	elseif info.label:match("templates") then
		namespace = namespace .. "Template"
	elseif info.label:match("modules") then
		namespace = namespace .. "Module"
	elseif info.label:match("^Wiktionary") or info.label:match("^Pages") then
		namespace = ""
	end
	
	return ([=[
{| id="newest-and-oldest-pages" class="wikitable mw-collapsible mw-collapsed" style="float: right; clear: both; margin: 0 0 .5em 1em;"
! නවතම සහ පැරණිතම පිටු&nbsp;
|-
| id="recent-additions" style="font-size:0.9em;" | '''Newest pages ordered by last [[mw:Manual:Categorylinks table#cl_timestamp|category link update]]:'''
%s
|-
| id="oldest-pages" style="font-size:0.9em;" | '''Oldest pages ordered by last edit:'''
%s
|}]=]):format(
	current_frame:extensionTag(
		"DynamicPageList",
		([=[
category=%s
%s
count=10
mode=ordered
ordermethod=categoryadd
order=descending]=]
		):format(current_title.text, namespace)
	),
	current_frame:extensionTag(
		"DynamicPageList",
		([=[
category=%s
%s
count=10
mode=ordered
ordermethod=lastedit
order=ascending]=]
		):format(current_title.text, namespace)
	)
)
end

-- Show navigational "breadcrumbs" at the top of the page.
local function show_breadcrumbs(current)
	local steps = {}
	
	-- Start at the current label and move our way up the "chain" from child to parent, until we can't go further.
	while current do
		local category, display_name, nocap
		
		if type(current) == "string" then
			category = current
			display_name = current:gsub("^ප්‍රවර්ගය:", "")
		else
			if not current.getCategoryName then
				error("Internal error: Bad format in breadcrumb chain structure, probably a misformatted value for `parents`: " ..
					mw.dumpObject(current))
			end
			category = "ප්‍රවර්ගය:" .. current:getCategoryName()
			display_name, nocap = current:getBreadcrumbName()
		end

		if not nocap then
			display_name = mw.getContentLanguage():ucfirst(display_name)
		end
		insert(steps, 1, ("[[:%s|%s]]"):format(category, display_name))
		
		-- Move up the "chain" by one level.
		if type(current) == "string" then
			current = nil
		else
			current = current:getParents()
		end
		
		if current then
			current = current[1].name
		elseif inFundamental[category] then
			current = "ප්‍රවර්ගය:මූලධර්ම"
		end	
	end
	
	local templateStyles = require("Module:TemplateStyles")("Module:category tree/styles.css")
	
	local ol = mw.html.create("ol")
	for i, step in ipairs(steps) do
		local li = mw.html.create("li")
		if i ~= 1 then
			local span = mw.html.create("span")
				:attr("aria-hidden", "true")
				:addClass("ts-categoryBreadcrumbs-separator")
				:wikitext(" » ")
			li:node(span)
		end
		li:wikitext(step)
		ol:node(li)
	end
	
	return templateStyles .. tostring(mw.html.create("div")
		:attr("role", "navigation")
		:attr("aria-label", "Breadcrumb")
		:addClass("ts-categoryBreadcrumbs")
		:node(ol))
end

local function show_also(current)
	local also = current._info.also
	if also and #also > 0 then
		return ('<div style="margin-top:-1em;margin-bottom:1.5em">%s</div>'):format(require("Module:also").main(also))
	end
	return nil
end

-- Show a short description text for the category.
local function show_description(current)
	return current.getDescription and current:getDescription() or nil
end

local function show_appendix(current)
	local appendix = current.getAppendix and current:getAppendix()
	return appendix and ("For more information, see [[%s]]."):format(appendix) or nil
end

local function sort_children(child1, child2)
	return string_sort(uupper(child1.sort), uupper(child2.sort))
end

-- Show a list of child categories.
local function show_children(current)
	local children = current.getChildren and current:getChildren() or nil
	if not children then
		return nil
	end
	
	sort(children, sort_children)
	
	local children_list = {}
	
	for _, child in ipairs(children) do
		local child_name, child_pagetitle = child.name
		if type(child_name) == "string" then
			child_pagetitle = child_name
		else
			child_pagetitle = "ප්‍රවර්ගය:" .. child_name:getCategoryName()
		end
		
		if new_title(child_pagetitle).exists then
			insert(children_list, ("* [[:%s]]: %s"):format(
				child_pagetitle,
				child.description or
					type(child_name) == "string" and child_name:gsub("^ප්‍රවර්ගය:", "") .. "." or
					child_name:getDescription("child")
			))
		end
	end
	
	return concat(children_list, "\n")
end

-- Show a table of contents with links to each letter in the language's script.
local function show_TOC(current)
	local titleText = current_title.text
	
	local inCategoryPages = pages_in_category(titleText, "pages")
	local inCategorySubcats = pages_in_category(titleText, "subcats")

	local TOC_type

	-- Compute type of table of contents required.
	if inCategoryPages > 2500 or inCategorySubcats > 2500 then
		TOC_type = "full"
	elseif inCategoryPages > 200 or inCategorySubcats > 200 then
		TOC_type = "normal"
	else
		-- No (usual) need for a TOC if all pages or subcategories can fit on one page;
		-- but allow this to be overridden by a custom TOC handler.
		TOC_type = "none"
	end

	if current.getTOC then
		local TOC_text = current:getTOC(TOC_type)
		if TOC_text ~= true then
			return TOC_text or nil
		end
	end

	if TOC_type ~= "none" then
		local templatename = current:getTOCTemplateName()

		local TOC_template
		if TOC_type == "full" then
			-- This category is very large, see if there is a "full" version of the TOC.
			local TOC_template_full = new_title(templatename .. "/full")
			
			if TOC_template_full.exists then
				TOC_template = TOC_template_full
			end
		end

		if not TOC_template then
			local TOC_template_normal = new_title(templatename)
			if TOC_template_normal.exists then
				TOC_template = TOC_template_normal
			end
		end

		if TOC_template then
			return current_frame:expandTemplate{title = TOC_template.text, args = {}}
		end
	end

	return nil
end

-- Show the "catfix" that adds language attributes and script classes to the page.
local function show_catfix(current)
	local lang, sc = current:getCatfixInfo()
	return lang and m_utilities.catfix(lang, sc) or nil
end

-- Show the parent categories that the current category should be placed in.
local function show_categories(current, categories)
	local parents = current.getParents and current:getParents() or nil
	if not parents then
		return nil
	end
	
	for _, parent in ipairs(parents) do
		local parent_name = parent.name
		local sortkey = type(parent.sort) == "table" and parent.sort:makeSortKey() or parent.sort
		if type(parent_name) == "string" then
			insert(categories, ("[[%s|%s]]"):format(parent_name, sortkey))
		else
			insert(categories, ("[[ප්‍රවර්ගය:%s|%s]]"):format(parent_name:getCategoryName(), sortkey))
		end
	end
	
	-- Also put the category in its corresponding "umbrella" or "by language" category.
	local umbrella = current:getUmbrella()
	
	if umbrella then
		-- FIXME: use a language-neutral sorting function like the Unicode Collation Algorithm.
		local sortkey = current._lang and current._lang:getCanonicalName() or current:getCategoryName()
		sortkey = require("Module:languages").getByCode("en", true):makeSortKey(sortkey)
		if type(umbrella) == "string" then
			insert(categories, ("[[%s|%s]]"):format(umbrella, sortkey))
		else
			insert(categories, ("[[ප්‍රවර්ගය:%s|%s]]"):format(umbrella:getCategoryName(), sortkey))
		end
	end
	
	-- Check for various unwanted parser functions, which should be integrated into the category tree data instead.
	-- Note: HTML comments shouldn't be removed from `content` until after this step, as they can affect the result.
	local content = current_title:getContent()
	if not content then
		-- This happens when using [[Special:ExpandTemplates]] to call {{auto cat}} on a nonexistent category page,
		-- which is needed by Benwing's create_wanted_categories.py script.
		return
	end
	local defaultsort, displaytitle, page_has_param
	for node in parse(content):iterate_nodes() do
		local node_class = class_else_type(node)
		if node_class == "template" then
			local name = node:get_name()
			if name == "DEFAULTSORT:" and not defaultsort then
				insert(categories, "[[Category:Pages with DEFAULTSORT conflicts]]")
				defaultsort = true
			elseif name == "DISPLAYTITLE:" and not displaytitle then
				insert(categories,"[[Category:Pages with DISPLAYTITLE conflicts]]")
				displaytitle = true
			end
		elseif node_class == "parameter" and not page_has_param then
			insert(categories,"[[Category:Pages with raw triple-brace template parameters]]")
			page_has_param = true
		end
	end
	
	-- Check for raw category markup, which should also be integrated into the category tree data.
	content = remove_comments(content, "BOTH")
	local head = content:find("[[", 1, true)
	while head do
		local close = content:find("]]", head + 2, true)
		if not close then
			break
		end
		-- Make sure there are no intervening "[[" between head and close.
		local open = content:find("[[", head + 2, true)
		while open and open < close do
			head = open
			open = content:find("[[", head + 2, true)
		end
		local cat = content:sub(head + 2, close - 1)
		local colon = cat:match("^[ _\128-\244]*[Cc][Aa][Tt][EeGgOoRrYy _\128-\244]*():")
		if colon then
			local pipe = cat:find("|", colon + 1, true)
			if pipe ~= #cat then
				local title = new_title(pipe and cat:sub(1, pipe - 1) or cat)
				if title and title.namespace == 14 then
					insert(categories,"[[Category:Categories with categories using raw markup]]")
					break
				end
			end
		end
		head = open
	end
end

local function generate_output(current)
	if current then
		for _, functionName in pairs{
			"getBreadcrumbName",
			"getDataModule",
			"canBeEmpty",
			"getDescription",
			"getParents",
			"getChildren",
			"getUmbrella",
			"getAppendix",
			"getTOCTemplateName",
		} do
			if type(current[functionName]) ~= "function" then
				require("Module:debug").track{"category tree/missing function", "category tree/missing function/" .. functionName}
			end
		end
	end

	local boxes, display, categories = {}, {}, {}
	
	-- Categories should never show files as a gallery.
	insert(categories, "__NOGALLERY__")
	
	if current_frame:getParent():getTitle() == "Template:auto cat" then
		insert(categories, "[[Category:Categories calling Template:auto cat]]")
	end
	
	-- Check if the category is empty
	local totalPages = pages_in_category(current_title.text, "all")
	local hugeCategory = totalPages > 1000000 -- 1 million
	
	-- Categorize huge categories, as they cause DynamicPageList to time out and make the category inaccessible.
	if hugeCategory then
		insert(categories, "[[Category:Huge categories]]")
	end
	
	-- Are the parameters valid?
	if not current then
		insert(categories, "[[ප්‍රවර්ගය:ප්‍රවර්ග පද්ධතිය තුළ අර්ථ දක්වා නොමැති ප්‍රවර්ග]]")
		insert(categories, totalPages == 0 and "[[ප්‍රවර්ගය:හිස් ප්‍රවර්ග]]" or nil)
		insert(display, show_error(
			"ප්‍රවර්ග නාමය තුළ යතුරු ලියන දෝෂ පවතී දැයි නැවත පරීක්ෂා කර බලන්න. <br>" ..
			'මෙම ප්‍රවර්ගය වෙනත් නාමයක් යටතේ නිර්මාණය කළ යුතු දැයි (උදාහරණ, "Fruits" වෙනුවට "Fruit") පරීක්ෂා කිරීම සඳහා:<br>' ..
			"[[Special:Search/Category: " .. current_title.text:gsub("^.+:", ""):gsub(" ", "~2 ") .. '~2|දැනට පවතින ප්‍රවර්ග තුළ සෝදිසි කර බලන්න]]. <br>' ..
			"වික්ෂණරි ප්‍රවර්ග පද්ධතිය තුළට නව ප්‍රවර්ගයක් එක් කිරීම සඳහා, " .. current_frame:expandTemplate{title = "section link", args = {
				"Help:Category#How_to_create_a_category",
			}} .. " කියවා බලන්න."))
		
		-- Exit here, as all code beyond here relies on current not being nil
		return concat(categories, "") .. concat(display, "\n\n"), true
	end
	
	-- Does the category have the correct name?
	local currentName = current:getCategoryName()
	local correctName = current_title.text == currentName
	if not correctName then
		insert(categories, "[[ප්‍රවර්ගය:දෝෂ සහගත නාම සහිත ප්‍රවර්ග]]")
		insert(display, show_error(("ප්‍රවර්ග පද්ධතිය තුළ පවතින දත්ත වලට අනුව, මෙම ප්‍රවර්ගයේ නාමය විය යුත්තේ '''[[:ප්‍රවර්ගය:%s]]''' වෙයි."):format(currentName)))
	end
	
	-- Add cleanup category for empty categories.
	local canBeEmpty = current:canBeEmpty()
	if canBeEmpty and correctName then
		insert(categories, " __EXPECTUNUSEDCATEGORY__")
	elseif totalPages == 0 then
		insert(categories, "[[ප්‍රවර්ගය:හිස් ප්‍රවර්ග]]")
	end
	
	if current:isHidden() then
		insert(categories, "__HIDDENCAT__")
	end

	-- Put all the float-right stuff into a <div> that does not clear, so that float-left stuff like the breadcrumbs and
	-- description can go opposite the float-right stuff without vertical space.
	insert(boxes, "<div style=\"float: right;\">")
	insert(boxes, show_topright(current))
	insert(boxes, show_editlink(current))
	insert(boxes, show_related_changes())
	
	-- Show pagelist, unless it's a huge category (since they can't use DynamicPageList - see above).
	if not hugeCategory then
		insert(boxes, show_pagelist(current))
	end
	
	insert(boxes, "</div>")
	
	-- Generate the displayed information
	insert(display, show_breadcrumbs(current))
	insert(display, show_also(current))
	insert(display, show_description(current))
	insert(display, show_appendix(current))
	insert(display, show_children(current))
	insert(display, show_TOC(current))
	insert(display, show_catfix(current))
	insert(display, '<br class="clear-both-in-vector-2022-only">')
	
	show_categories(current, categories)
	
	return concat(boxes, "\n") .. "\n" .. concat(display, "\n\n") .. concat(categories, "")
end

--[==[
List of handler functions that try to match the page name. A handler should return the name of a submodule to
[[Module:category tree]] and an info table which is passed as an argument to the submodule. If a handler does not
recognize the page name, it should return nil. Note that the order of handlers matters!
]==]
local handlers = {}

-- ws topic cat
insert(handlers, function(title)
	local code, label = title:match("^Thesaurus:(%l[%a-]*%a):(.+)")
	if code then
		return ws_topic_cat, {label = label, code = code}
	end
end)

-- Topical categories
insert(handlers, function(title)
	local code, label = title:match("^(%l[%a-]*%a):(.+)")
	if code then
		return topic_cat, {label = label, code = code}
	end
end)

-- Lect categories e.g. for [[:Category:New Zealand English]] or [[:Category:Issime Walser]]
insert(handlers, function(title, args)
	local lect = args.lect or args.dialect
	if lect ~= "" and yesno(lect, true) then -- Same as boolean in [[Module:parameters]].
		return poscatboiler, {label = title, args = args, raw = true}
	end
end)

-- poscatboiler lang-specific
insert(handlers, function(title, args)
	local lang, label = export.split_lang_label(title)
	if not lang then
		return
	end
	local baseLabel, script = label:match("(.+), (.-) අක්ෂරක්‍රමය භාවිතා කොට ලියන ලද$")
	if script and baseLabel ~= "යෙදුම්" then
		local scriptObj = require("Module:scripts").getByCanonicalName(script)
		if scriptObj then
			return poscatboiler, {label = baseLabel, code = lang:getCode(), sc = scriptObj:getCode(), args = args}
		end
	end
	return poscatboiler, {label = label, code = lang:getCode(), args = args}
end)

-- poscatboiler umbrella category
insert(handlers, function(title, args)
	local label = title:match("භාෂාව අනුව (.+)$")
	if label then
		-- The poscatboiler code will appropriately lowercase if needed.
		return poscatboiler, {label = label, args = args}
	end
end)

-- ws topic cat
insert(handlers, function(title)
	local label = title:match("^Thesaurus:(.+)")
	if label then
		return ws_topic_cat, {label = label}
	end
end)

-- topic cat
insert(handlers, function(title)
	return topic_cat, {label = title}
end)

-- poscatboiler raw handlers
insert(handlers, function(title, args)
	return poscatboiler, {label = title, args = args, raw = true}
end)

-- poscatboiler umbrella handlers without 'by language'
insert(handlers, function(title, args)
	return poscatboiler, {label = title, args = args}
end)

function export.show(frame)
	local args, other_args = require("Module:parameters").process(frame:getParent().args, {
		["also"] = {type = "title", sublist = "comma without whitespace", namespace = 14}
	}, true)
	
	if args.also then
		for k, arg in next, args.also do
			args.also[k] = arg.prefixedText
		end
	end
	
	for k, arg in next, other_args do
		other_args[k] = trim(arg)
	end
	
	if namespace == 10 then -- Template
		return "(This template should be used on pages in the [[Help:Namespaces#Category|ප්‍රවර්ගය:]] namespace.)"
	elseif namespace ~= 14 then -- Category
		error("This template/module can only be used on pages in the [[mw:Help:Namespaces#Category|ප්‍රවර්ගය:]] namespace.")
	end

	local first_fail_args_handled, first_fail_cattext

	-- Go through each handler in turn. If a handler doesn't recognize the format of the
	-- category, it will return nil, and we will consider the next handler. Otherwise,
	-- it returns a template name and arguments to call it with, but even then, that template
	-- might return an error, and we need to consider the next handler. This happens,
	-- for example, with the category "CAT:Mato Grosso, Brazil", where "Mato" is the name of
	-- a language, so the handler for {{poscatboiler}} fires and tries to find a label
	-- "Grosso, Brazil". This throws an error, and previously, this blocked fruther handler
	-- consideration, but now we check for the error and continue checking handlers;
	-- eventually, {{topic cat}} will fire and correctly handle the category.
	for _, handler in ipairs(handlers) do
		-- Use a new title object and args table for each handler, to keep them isolated.
		local submodule, info = handler(current_title.text, deep_copy(other_args))
		if submodule then
			info.also = deep_copy(args.also)
			require("Module:debug").track("auto cat/" .. submodule)
			-- `failed` is true if no match was found.
			submodule = require("Module:category tree/" .. submodule)
			local cattext, failed = generate_output(submodule.main(info))
			if failed then
				if not first_fail_cattext then
					first_fail_cattext = cattext
					first_fail_args_handled = info.args and true or false
				end
			elseif not info.args and next(other_args) then
				error(extra_args_error)
			else
				return cattext
			end
		end
	end
	
	-- If there were no matches, throw an error if any arguments were given, or otherwise return the cattext
	-- from the first fail encountered. The final handlers call the boilers unconditionally, so there should
	-- always be something to return.
	if not first_fail_args_handled and next(other_args) then
		error(extra_args_error)
	end
	return first_fail_cattext
end

-- TODO: new test entrypoint.

return export