Module:Template translation

 localthis={}

 functionthis.checkLanguage(subpage,default)
 --[[Check first if there's an any invalid character that would cause the
  mw.language.isKnownLanguageTag function() to throw an exception:
  - all ASCII controls in [000円-031円127円],
  - double quote ("), sharp sign (#), ampersand (&), apostrophe ('),
  - slash (/), colon (:), semicolon (;), lower than (<), greater than (>),
  - brackets and braces ([, ], {, }), pipe (|), backslash (\\)
  All other characters are accepted, including space and all non-ASCII
  characters (including 192,円 which is invalid in UTF-8).
  --]]
 ifmw.language.isValidCode(subpage)andmw.language.isKnownLanguageTag(subpage)
 --[[However "SupportedLanguages" are too restrictive, as they discard many
  valid BCP47 script variants (only because MediaWiki still does not
  define automatic transliterators for them, e.g. "en-dsrt" or
  "fr-brai" for French transliteration in Braille), and country variants,
  (useful in localized data, even if they are no longer used for
  translations, such as zh-cn, also useful for legacy codes).
  We want to avoid matching subpagenames containing any uppercase letter,
  (even if they are considered valid in BCP 47, in which they are
  case-insensitive; they are not "SupportedLanguages" for MediaWiki, so
  they are not "KnownLanguageTags" for MediaWiki).
  To be more restrictive, we exclude tags
  * for specific uses in template subpages and unusable as language tags;
  * that is not ASCII and not a lowercase letter, minus-hyphen, or digit,
  or does not start by a letter or does not finish by a letter or digit;
  * or that has subtags with more than 8 characters between hyphens;
  * or that has two hyphens.
  --]]
 orsubpage~="doc"
 andsubpage~="layout"
 andsubpage~="button"
 andsubpage~="buttons"
 andsubpage~="sandbox"
 andsubpage~="testcase"
 andsubpage~="testcases"
 andstring.find(subpage,"^[%l][%-%d%l]*[%d%l]$")~=nil
 andstring.find(subpage,"[%d%l][%d%l][%d%l][%d%l][%d%l][%d%l][%d%l][%d%l][%d%l]")==nil
 andstring.find(subpage,"%-%-")==nilthen
 returnsubpage
 end
 -- Otherwise there's currently no known language subpage
 returndefault
 end

 --[[Get the last subpage of an arbitrary page if it is a translation.
  To be used from templates.
  ]]
 functionthis.getLanguageSubpage(frame)
 localtitle=frameandframe.args[1]
 ifnottitleortitle==''then
 title=mw.title.getCurrentTitle()
 end
 returnthis._getLanguageSubpage(title)
 end

 --[[Get the last subpage of an arbitrary page if it is a translation.
  To be used from Lua.
  ]]
 functionthis._getLanguageSubpage(title)
 iftype(title)=='string'then
 title=mw.title.new(title)
 end
 ifnottitlethen
 -- invalid title
 returnnil
 end
 --[[This code does not work in all namespaces where the Translate tool works.
 	-- It works in the main namespace on Meta because it allows subpages there
 	-- It would not work in the main namespace of English Wikipedia (but the
 	-- articles are monolignual on that wiki).
 	-- On Meta-Wiki the main space uses subpages and its pages are translated.
 	-- The Translate tool allows translatng pages in all namespaces, even if
 	-- the namespace officially does not have subpages.
 	-- On Meta-Wiki the Category namespace still does not have subpages enabled,
 	-- even if they would be very useful for categorizing templates, that DO have
 	-- subpages (for documentatio and tstboxes pages). This is a misconfiguration
 	-- bug of Meta-Wiki. The work-around is to split the full title and then
 	-- get the last titlepart.
 	local subpage = title.subpageText
 	--]]
 localtitleparts=mw.text.split(title.fullText,'/')
 localsubpage=titleparts[#titleparts]
 returnthis.checkLanguage(subpage,'')
 end

 --[[Get the last subpage of the current page if it is a translation.
  ]]
 functionthis.getCurrentLanguageSubpage()
 returnthis._getLanguageSubpage(mw.title.getCurrentTitle())
 end

 --[[Get the first part of the language code of the subpage, before the '-'.
 --]]
 functionthis.getMainLanguageSubpage()
 parts=mw.text.split(this.getCurrentLanguageSubpage(),'-')
 returnparts[1]
 end

 --[[Get the last subpage of the current frame if it is a translation.
  Not used locally.
 --]]
 functionthis.getFrameLanguageSubpage(frame)
 returnthis._getLanguageSubpage(frame:getParent():getTitle())
 end

 --[[Get the language of the current page. Not used locally.
 --]]
 functionthis.getLanguage()
 localsubpage=mw.title.getCurrentTitle().subpageText
 returnthis.checkLanguage(subpage,mw.language.getContentLanguage():getCode())
 end

 --[[Get the language of the current frame. Not used locally.
 --]]
 functionthis.getFrameLanguage(frame)
 localtitleparts=mw.text.split(frame:getParent():getTitle(),'/')
 localsubpage=titleparts[#titleparts]
 returnthis.checkLanguage(subpage,mw.language.getContentLanguage():getCode())
 end

 functionthis.title(namespace,basepagename,subpage)
 localmessage,title
 localpagename=basepagename
 if(subpageor'')~=''then
 pagename=pagename..'/'..subpage
 end
 localvalid,title=xpcall(function()
 returnmw.title.new(pagename,namespace)-- costly
 end,function(msg)-- catch undocumented exception (!?)
 -- thrown when namespace does not exist. The doc still
 -- says it should return a title, even in that case...
 message=msg
 end)
 ifvalidandtitle~=niland(title.idor0)~=0then
 returntitle
 end
 return{-- "pseudo" mw.title object with id = nil in case of error
 prefixedText=pagename,-- the only property we need below
 message=message-- only for debugging
 }
 end

 --[[If on a translation subpage (like Foobar/de), this function returns
  a given template in the same language, if the translation is available.
  Otherwise, the template is returned in its default language, without
  modification.
  This is aimed at replacing the current implementation of Template:TNTN.

  This version does not expand the returned template name: this solves the
  problem of self-recursion in TNT when translatable templates need themselves
  to transclude other translable templates (such as Tnavbar).
 --]]
 functionthis.getTranslatedTemplate(frame,withStatus)
 localargs=frame.args
 localpagename=args['template']
 --[[Check whether the pagename is actually in the Template namespace, or
  if we're transcluding a main-namespace page.
  (added for backward compatibility of Template:TNT)
  ]]
 localnamespace,title=args['tntns']or''
 ifnamespace~=''then-- Checks for tntns parameter for custom ns.
 title=this.title(namespace,pagename)-- Costly
 else-- Supposes that set page is in ns10.
 namespace='Template'
 title=this.title(namespace,pagename)-- Costly
 iftitle.id==nilthen-- not found in the Template namespace, assume the main namespace (for backward compatibility)
 namespace=''
 title=this.title(namespace,pagename)-- Costly
 end
 end
 -- Get the last subpage and check if it matches a known language code.
 localsubpage=args['uselang']or''
 ifsubpage==''then
 subpage=this.getCurrentLanguageSubpage()
 end
 ifsubpage==''then
 -- Check if a translation of the pagename exists in English
 localnewtitle=this.title(namespace,pagename,'en')-- Costly
 -- Use the translation when it exists
 ifnewtitle.id~=nilthen
 title=newtitle
 end
 else
 -- Check if a translation of the pagename exists in that language
 localnewtitle=this.title(namespace,pagename,subpage)-- Costly
 ifnewtitle.id==nilthen
 -- Check if a translation of the pagename exists in English
 newtitle=this.title(namespace,pagename,'en')-- Costly
 end
 -- Use the translation when it exists
 ifnewtitle.id~=nilthen
 title=newtitle
 end
 end
 -- At this point the title should exist
 ifwithStatusthen
 -- status returned to Lua function below
 returntitle.prefixedText,title.id~=nil
 else
 -- returned directly to MediaWiki
 returntitle.prefixedText
 end
 end

 --[[If on a translation subpage (like Foobar/de), this function renders
  a given template in the same language, if the translation is available.
  Otherwise, the template is rendered in its default language, without
  modification.
  This is aimed at replacing the current implementation of Template:TNT.

  Note that translatable templates cannot transclude themselves other
  translatable templates, as it will recurse on TNT. Use TNTN instead
  to return only the effective template name to expand externally, with
  template parameters also provided externally.
 --]]
 functionthis.renderTranslatedTemplate(frame)
 localtitle,found=this.getTranslatedTemplate(frame,true)
 -- At this point the title should exist prior to performing the expansion
 -- of the template, otherwise render a red link to the missing page
 -- (resolved in its assumed namespace). If we don't tet this here, a
 -- script error would be thrown. Returning a red link is consistant with
 -- MediaWiki behavior when attempting to transclude inexistant templates.
 ifnotfoundthen
 return'[['..title..']]'
 end
 -- Copy args pseudo-table to a proper table so we can feed it to expandTemplate.
 -- Then render the pagename.
 localargs=frame.args
 localpargs=(frame:getParent()or{}).args
 localarguments={}
 if(args['noshift']or'')==''then
 fork,vinpairs(pargs)do
 localn=tonumber(k)or0
 ifn<=0then-- unnumbered args
 arguments[k]=v
 elseifn>=2then-- numbered args >= 2 need to be shifted
 arguments[n-1]=v
 end
 end
 else-- special case where TNT is used as autotranslate
 -- (don't shift again what is shifted in the invokation)
 fork,vinpairs(pargs)do
 arguments[k]=v
 end
 end
 arguments['template']=title-- override the existing parameter of the base template name supplied with the full name of the actual template expanded
 arguments['tntns']=nil-- discard the specified namespace override
 arguments['uselang']=args['uselang']-- argument forwarded into parent frame
 arguments['noshift']=args['noshift']-- argument forwarded into parent frame
 returnframe:expandTemplate{title=':'..title,args=arguments}
 end

 --[[A helper for mocking TNT in Special:TemplateSandbox. TNT breaks
  TemplateSandbox; mocking it with this method means templates won't be
  localized but at least TemplateSandbox substitutions will work properly.
  Won't work with complex uses.
 --]]
 functionthis.mockTNT(frame)
 localpargs=(frame:getParent()or{}).args
 localarguments={}
 fork,vinpairs(pargs)do
 localn=tonumber(k)or0
 ifn<=0then-- unnumbered args
 arguments[k]=v
 elseifn>=2then-- numbered args >= 2 need to be shifted
 arguments[n-1]=v
 end
 end
 ifnotpargs[1]then
 return''
 end
 returnframe:expandTemplate{title='Template:'..pargs[1],args=arguments}
 end

 returnthis