Module:Fallback

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This documentation is transcluded from Module:Fallback/doc.

This module is rated as ready for general use. It has reached a mature form and is thought to be bug-free and ready for use wherever appropriate. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

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.

Dependencies

• Module:Fallbacklist catalogs old fallback chains for each language as it was set up on Commons a decade ago. Lua allows now to access the default MediaWiki fallback chains which are used by most templates.

local p = {}

local langlist = require('Module:Fallbacklist')


--[[
_langSwitch
 
This function is the core part of the LangSwitch template. 
 
Example usage from Lua:
text = _langSwitch({en='text in english', pl='tekst po polsku'}, lang)
 
Parameters:
  args - table with translations by language
  lang - desired language (often user's native language)

 Error Handling:

]]

function p._langSwitch(args, lang) -- args: table of translations
	-- Return error if there is not default and no english version
	if not args.en and not args.default then
		if args.nocat == '1' then
			return '<strong class="error">LangSwitch Error: no default</strong>' 
		else
			return '<strong class="error">LangSwitch Error: no default</strong>[[Category:LangSwitch template without default version]]' 
		end
	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 accepetable language (lang + those in lang's fallback chain) and check their content
	local langList = mw.language.getFallbacksFor(lang)
	table.insert(langList,1,lang)
	table.insert(langList, 'default')
	for _, language  in ipairs(langList) do 
		if args[language ] == '~' then 
			return ''
		elseif args[language] and args[language] ~= '' then 
			return args[language] 
		end
	end
end

--[[
langSwitch
 
This function is the core part of the LangSwitch template. 
 
Example Usage from a template:
{{#invoke:fallback|langSwitch|en=text in english|pl=tekst po polsku|lang={{int:lang}} }}
 
Parameters:
  frame.args - table with translations by language
  frame.args.lang - desired language (often user's native language)

 Error Handling:

]]
function p.langSwitch(frame) -- version to be used from wikitext
	args = frame.args
	-- if no expected args provided than check parent template/module args
	if args.en==nil and args.default==nil and args.nocat==nil then
		args = mw.getCurrentFrame():getParent().args 
	end
	if args.lang and args.lang ~= '' then
		lang = args.lang
	else -- get user's chosen language 
		lang = frame:callParserFunction( "int", "lang" )
	end
	args.lang = nil
	return p._langSwitch(args, lang)
end

--[[
autotranslate
 
This function is the core part of the Autotranslate template. 
 
Usage from a template:
{{#invoke:fallback|autotranslate|base=|lang= }}
 
Parameters:
  frame.args.base - base page name
  frame.args.lang - desired language (often user's native language)

 Error Handling:

]]
function p.autotranslate(frame) 
	local args = frame.args
	if not args.lang or args.lang == '' then
		args.lang = frame:callParserFunction( "int", "lang" )           -- get user's chosen language 
	end
	local langList = mw.language.getFallbacksFor(args.lang)
	table.insert(langList,1,args.lang)
 
	-- 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 not mw.ustring.find(base,':') then -- if base page does not indicate namespace
		base = 'Template:' .. base          -- than assume it is a template 
	end
 
	-- find base template language subpage
	local page = nil
	for _, language in ipairs(langList) do
		if mw.title.new(base .. '/' .. language).exists then
			page =  base .. '/' .. language -- returns only the page
			break
		end
	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 inArgs = {}
	for field, value in pairs(args) do
		inArgs[field] = value;
	end
 
	-- Transclude {{page |....}} with template arguments the same as the ones passed to {{autotranslate}} template.
	inArgs.base = nil
	return frame:expandTemplate{ title = page, args = inArgs }
end

--[[
fblist
 
Similar to  mw.language.getFallbacksFor(lang) but uses Commons old fallback chain 
 
Parameters:
  lang - desired language (often user's native language)

 Error Handling:

]]
function p.fblist(lang) -- list the full fallback chain from a language to en
	local fbtable = p.fallbackloop{ lang:lower() }
	table.insert(fbtable, 'default')
	table.insert(fbtable, 'en')
	return fbtable
end

function _inArray(x, t)
	for i, v in ipairs(t) do
		if v == x then return i end
	end
	return -1
end

function p.fallbackloop(fbtable)  --list of fallback languages in string format (more convenient than tables)
	local changes = false
	for i, j in ipairs(fbtable) do
		local seq = langlist[j]
		if seq then
			for k, l in ipairs(seq) do
				if _inArray(l, fbtable) == -1 then
					table.insert(fbtable, l)
					changes = true
				end
			end
		end
	end
	if changes then
		return p.fallbackloop(fbtable)
	end
	return fbtable
end

return p