Editing Module:Fallback

local p = {}

-- List the full fallback chain from a language to default (usually English)
function p.fblist(lang)
	local fbtable = mw.language.getFallbacksFor(lang)
	table.insert(fbtable, 1, lang)
	--[[
	Take a translation from "Mediawiki:<Message-ID>/<language-code>" namespace
	or from a loaded i18 resource bundle in MediaWiki for its UI messages (also
	used by the "{{Int:<Message-ID>}}" parser function), before using the
	provided default value. Requires args.message = 'Message-ID', instead of
	args.message = 'actual translated message'.
	--]]
	table.insert(fbtable, 'message')
	table.insert(fbtable, 'default')
	return fbtable
end

--[==[
Return an error if there is not default and no English version, otherwise
return the message in the most appropriate, plus the lang code as a second value.
--]==]
function p._langSwitch(args, lang)
	-- args: table of translations
	if not args.en and not args.default and not args.message and args.nocat ~= '1' then
		return error("langSwitch error: no default")
	end
	-- Get language (either stated one or user's default language).
	if not lang then
		return '<strong class="error">LangSwitch Error: no lang</strong>' -- must become proper error
	end
	-- Get the list of acceptable language (lang + those in lang's fallback chain) and check their content.
	for _, code in ipairs(p.fblist(lang)) do
		local msg = args[code]
		if msg then
			-- Trim the assigned message value before testing it.
			msg = mw.text.trim(msg)
			if msg ~= '' then
				if code == 'message' then
					-- If this is an UI message. See [[mw:Manual:Messages API]].
					msg = mw.message.new(args.message):inLanguage(lang)
					--[==[ If this message name does not exist, converting it to
					a string would not return an actual message, but this name
					within curved angle brackets U+29FC/U+29FD '⧼/⧽', 
					part of mathematical symbols). The UI message may also be
					disabled administratively if it causes problems.
					--]==]
					if msg:exists() and not msg:isDisabled() then
						--[==[FIXME: In which language is this message?
						This may be in some fallback language and not lang.
						Note that some UI messages may have placeholders like '%s'
						but there's no way to replace them here by actual values.
						--]==]
						return tostring(msg), lang
					end
				elseif msg == '~' then
					return nil, code
				else
					return msg, code
				end
			end
		end
	end
	return nil
end

--[==[
Version to be used from wikitext.
--]==]
function p.langSwitch(frame)
	local args = frame.args
	-- If no expected args provided than check parent template/module args.
	if not args.en and not args.default and not args.nocat then
		args = frame:getParent().args
	end
	local lang
	if args.lang and args.lang ~= '' then
		lang = args.lang
		args.lang = nil
	else -- Get user's chosen language.
		lang = frame:preprocess("{{Int:Lang}}")
	end
--[==[
	if args.zh ~= '' and args['zh-hans'] == '' and args['zh-hant'] == '' then
	else
	end
--]==]
	local str, language = p._langSwitch(args, lang)
	return str -- Get the first value of the langSwitch, (the text) not the second (the language).
end

function p.fallbackpage(base, lang, formatting)
	local languages = p.fblist(lang)
	for i, lng in ipairs(languages) do
		if mw.title.new(base .. '/' .. lng).exists then
			if formatting == 'table' then
				return {base .. '/' .. lng, lng} -- Returns name of the page + name of the language.
			else
				return base .. '/' .. lng -- Returns only the page.
			end
		end
	end
	return base
end

--[==[
Logic for [[Template:Autotranslate]].
]==]
function p.autotranslate(frame)
	local args = frame.args
	if not args.lang or args.lang == '' then
		args.lang = frame:preprocess("{{Int:Lang}}") -- Get user's chosen language.
	end
	-- Find base page.
	local base = args.base
	if not base or base == '' then
		return '<strong class="error">Base page not provided for autotranslate</strong>'
	end
	if string.sub(base, 2, 9) ~= 'emplate:' then
		base = 'Template:' .. base -- Base provided without 'Template:' part.
	end
	-- Find base template language subpage.
	local page = p.fallbackpage(base, args.lang) --
	if (not page and base ~= args.base) then
		-- Try the original args.base string. This case is only needed if base is not in template namespace.
		page = p.fallbackpage(args.base, args.lang)
	end
	if not page then
		return string.format('<strong class="error">no fallback page found for autotranslate (base=[[%s]], lang=%s)</strong>', args.base, args.lang)
	end
	-- Repack args in a standard table.
	local newargs = {}
	for field, value in pairs(args) do
		if field ~= 'base' then
			newargs[field] = value
		end
	end
	-- Transclude {{page |....}} with template arguments the same as the ones passed to {{autotranslate}} template.
	return frame:expandTemplate{ title = page, args = newargs }
end

--[==[
Translate data stored in a module.
]==]
function p.translate(page, key, lang)
	if type(page) == 'string' then -- If the requested translation table is not yet loaded.
		page = require('Module:' .. page)
	end
	local val
	if page[key] then
		val = page[key]
	elseif page.keys and page.keys[key] then -- Key 'keys" is an index of all keys, including redirects, see [[Module:i18n/datatype]].
		val = page.keys[key]
	end
	if not val then
		return '<' .. key .. '>'
	end
	return p._langSwitch(val, lang)
end

function p.translatelua(frame)
	local lang = frame.args.lang
	local page = require('Module:' .. mw.text.trim(frame.args[1])) -- Page should only contain a simple of translations.
	if not lang or mw.text.trim(lang) == '' then
		lang = frame:preprocess("{{Int:Lang}}")
	end
	if frame.args[2] then
		page = page[mw.text.trim(frame.args[2])]
	end
	return p._langSwitch(page, lang)
end

 -- This test does not work ('Module:Fallback/tests/fallbacks' is missing)
function p.runTests()
	local toFallbackTest = require('Module:Fallback/tests/fallbacks')
	local result = true
	mw.log('Testing fallback chains')
	for i, t in ipairs(toFallbackTest) do
		local fbtbl = table.concat(p.fblist(t.initial), ', ')
		local expected = table.concat(t.expected, ', ')
		local ret = (fbtbl == expected)
		mw.log(i, ret and 'passed' or 'FAILED', t.initial, (not ret) and ('FAILED\nis >>' .. fbtbl .. '<<\nbut should be >>' .. expected .. '<<\n') or '')
		result = result and ret
	end
	return result
end

--[==[
List all input arguments of the template that calls "{{#invoke:Fallback|showTemplateArguments}}"
]==]
function p.showTemplateArguments(frame)
	local str = ''
	for name, value in pairs( frame:getParent().args ) do
		if str == '' then
			str = string.format('%s=%s', name, value)          -- argument #1
		else
			str = string.format('%s, %s=%s', str, name, value) -- the rest
		end
	end
	return str
end

return p
Description	What you type	What you get
Italic	''Italic text''	Italic text
Bold	'''Bold text'''	Bold text
Bold & italic	'''''Bold & italic text'''''	*Bold & italic text*