Module:Redirect

-- This module provides functions for getting the target of a redirect page.

local p = {}

local char = mw.ustring.char

-- proxy to load the module lazily, replaced by the actual loaded function local getArgs = function(...) getArgs = require('Module:Arguments').getArgs return getArgs(...) end

-- Gets a mw.title object, using pcall to avoid generating script errors if we -- are over the expensive function count limit (among other possible causes). local function getTitle(...) local success, titleObj = pcall(mw.title.new, ...) if success then return titleObj else return nil end end

-- Detect hard redirect in wiki page content (not used inside this module) function p.getTargetFromText(text) text = text or '' return text:match('#[Rr][Ee][Dd]...[Cc][Tt][%s:]*%[%[([^]|]-)%s*%]%]') end

-- Detect soft redirect in wiki page content of 'Category:' pages, using template or one of its known aliases on Commons (there are too many!!!): The `target` value may be prefixed by 'Category:' or not (implied). For the full list of aliases, see	https://commons.wikimedia.org/w/index.php?title=Special:WhatLinksHere/Template:Category_redirect&hidetrans=1&hidelinks=1 function p.getTargetFromCatRedirect(content) -- Basic filtering: only in the relevant content shown on target page itself content = (content or '') :gsub('<!%-%-(.-)%-%->', '') -- discard HTML comments :gsub('(.-) ', '') -- discard 'includeonly' sections and their content :gsub('(.-)$', '') -- discard unclosed 'includeonly' sections :gsub('<[/]?onlyinclude>', '') -- discard 'onlyinclude' opening/closing tags :gsub('<[/]?noinclude>', '') -- discard 'noinclude' opening/closing tags :gsub('', '') -- discard nowiki opening/closing/selfclosed tags -- Locate the template transclusion, keep their parameters only -- Note: there may potentially be several instances, this should not occur content = content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() or		content:match() if not content then return nil end do -- Parse template parameters (they may be in arbitrary order) local params, n = {}, 0 for param in content:gmatch("([^|]+)") do			local key local pos = param:find('=') if pos then key = param:sub(1, pos - 1):match('^%s*(.-)%s*$') -- split then trim param = param:sub(pos + 1):match('^%s*(.-)%s*$') -- split then trim else n = n + 1 key = tostring(n) end params[key] = param end -- The target is in parameter ['1'] of the template transclusion content = params['1'] end -- Check there's an effective target parameter to the template if not content then return nil end content = content -- The target parameter may contain some known character entities -- (their validity in page names is not checked here, just parsed) :gsub('&([#%d%a]+);', function(entity)			if entity:sub(1,1) == '#' then				local codepoint				if entity:sub(2,2) == 'x' then					codepoint = tonumber(entity:sub(3), 16)				else					codepoint = tonumber(entity:sub(2))				end				if codepoint and ( codepoint >= 0x0009 and codepoint <= 0x000D or -- accept some whitespace C0 controls codepoint >= 0x0020 and codepoint <= 0x10FFFD -- normal range and (codepoint 0x009F) -- exclude C1 controls and (codepoint < 0xDC00 or codepoint > 0xDFFF) -- exclude surrogates and (codepoint < 0xFDD0 or codepoint > 0xFDEF) -- exclude non-characters in BMP and codepoint % 0x10000 <= 0xFFFD -- exclude non-characters at end of planes ) then					return char(codepoint)				end			else				if entity == 'amp' then return '&' end				if entity == 'gt' then return '>' end				if entity == 'lt' then return '<' end				if entity == 'quot' then return '"' end			end			return entity		end)		-- Normalize spaces in the target according to Mediawiki pagename rules		:gsub('[%s_]+', ' ')		-- The target parameter should be trimmed by the template		:match('^ ?(.-) ?$')	-- The target should not be empty and not contain tag delimiters or other character forbidden in full page names	-- Note: templates used inside the target parameter of the soft redirect are not expanded (there should be none)	-- as this is costly or memory intensive and slow (would require invoking a full mediawiki parser).	if content == '' or content:find('[<>%[%]{|}]') then		return nil	end	-- The 'Category:' namespace is implied (it will be prefixed by a ':' to create a link) return 'Category:' .. (		content:match('^:*[Cc][Aa][Tt][Ee][Gg][Oo][Rr][Yy] *: *(.-)$') or		content	) end

-- Get page name that a redirect leads to, or nil if it isn't a redirect. function p.getTargetFrom(obj) --	obj:getContent is intensive for large pages, but obj.redirectTarget returns directly	the target without needing to load and parse the text content of the wiki page.	This works for wiki pages that are hard redirects (content starting by ' local r = obj.isRedirect and obj.redirectTarget if not r then --		For pages using soft redirects (like categories), we must detect the template		used in the page content itself (this may be costly in memory and slow if not		loaded in the cache of page contents). if obj:inNamespace('Category') then r = p.getTargetFromCatRedirect(obj:getContent) if r then local obj2 = getTitle(r) if obj2 then -- getTitle may fail obj = obj2 -- true replacement withe the target -- special: the replacement may also be a hard redirect r = obj.isRedirect and obj.redirectTarget -- not done here: second soft redirect detection end end end if not r and obj.isRedirect then -- The page is a redirect, but matching failed, which may be a bug -- in redirect matching pattern, so throw an error. error(string.format( 'could not parse redirect on page "%s"', fulltext and obj.fullText or obj.prefixedText ))		end r = obj.fulltext and obj.fullText or obj.prefixedText end return r end

local function fmtTitle(target, fulltext, ensureTitleExists) local titleObj if type(target) == 'string' or type(target) == 'number' then titleObj = getTitle(target) elseif type(target) == 'table' and type(target.getContent) == 'function' then titleObj = target else error(string.format("bad argument #1 to 'fmtTitle' " .. "(string, number, or title object expected, got %s)", type(target) ), 2)	end if titleObj then if not ensureTitleExists or ensureTitleExists and titleObj.exists then return fulltext and titleObj.fullText or titleObj.prefixedText end end end

-- Gets the target of a redirect. If the page specified is not a redirect, -- returns nil. function p.getTarget(page, rname, fulltext, ensureTitleExists) -- Get the title object. Both page names and title objects are allowed -- as input. local titleObj if type(page) == 'string' or type(page) == 'number' then titleObj = getTitle(page) elseif type(page) == 'table' and type(page.getContent) == 'function' then titleObj = page else error(string.format("bad argument #1 to 'getTarget' " .. "(string, number, or title object expected, got %s)", type(page) ), 2)	end if titleObj and titleObj.exists and (titleObj.isRedirect or titleObj:inNamespace("Category")) then -- Find the target by using string matching on the page content. return fmtTitle(p.getTargetFrom(titleObj), fulltext, ensureTitleExists) end end

-- -- Given a single page name determines what page it redirects to and returns the -- target page name, or the passed page name when not a redirect. The passed -- page name can be given as plain text or as a page link. -- -- Returns page name as plain text, or when the bracket parameter is given, as a -- page link. Returns an error message when page does not exist or the redirect -- target cannot be determined for some reason. -- function p.luaMain(rname, bracket, fulltext, ensureTitleExists) if type(rname) ~= "string" or not rname:find("%S") then return nil end rname = rname:match("%[%[%s*([%]|]-)%s*%]%]") or rname local ret = p.getTarget(rname, fulltext, ensureTitleExists) or		fmtTitle(rname, fulltext, ensureTitleExists) link = bracket and (ret == rname and "%s" or "%s") or "%s" return ret and link:format(ret, rname) end

local function use(x) return x and (x == '1' or x == 't' or x == 'true' or x == 'y' or x == 'yes') or nil end

-- Provides access to the luaMain function from wikitext, may return redlinks, -- albeit page titles that do not exist in the wiki. -- Parameters alt, bracket, fulltext, ensureTitleExists are optional function p.main(frame) local args = getArgs(frame, {frameOnly = true}) local rname = args[1] local alt = args[2] or '' local bracket = use(args.bracket) local fulltext = use(args.fulltext) local ensureTitleExists = use(args.noredlinks)

return p.luaMain(rname, bracket, fulltext, ensureTitleExists) or alt end

-- main variant, returns empty string if a redlink would be returned otherwise. -- '|noredlinks=true' by default. function p.mainE(frame) local args = getArgs(frame, {frameOnly = true}) local rname = args[1] local alt = args[2] or '' local bracket = use(args.bracket) local fulltext = use(args.fulltext)

return p.luaMain(rname, bracket, fulltext, true) or alt end

-- main variant, returns args[2] if a redlink would be returned otherwise. -- '|bracket=true|noredlinks=true' by default function p.mainA(frame) local args = getArgs(frame, {frameOnly = true}) local rname = args[1] local alt = args[2] or '' local bracket = use(args.bracket)

return p.luaMain(rname, bracket, true, true) or alt end

-- Returns true if the specified page is a redirect, and false otherwise. function p.luaIsRedirect(page) local titleObj = getTitle(page) if not titleObj then return false end if titleObj.isRedirect then return true else return false end end

-- Provides access to the luaIsRedirect function from wikitext, returning 'yes' -- if the specified page is a redirect, and the blank string otherwise. function p.isRedirect(frame) local args = getArgs(frame, {frameOnly = true}) if p.luaIsRedirect(args[1]) then return 'yes' else return '' end end

return p