At the end of https://meta.wikimedia.org/wiki/Help:User_contributions and other pages using {{h:f}} on Meta, we see several pagefuls of Lua code and errors. Surely there's something wrong in the template, but this is not graceful degradation.
```
<p>--[=[ Not globally exposed. Internal function only.</p>
<p>language_subpages( frame, transform, options ) Parameters</p>
<pre>
frame: The frame that was passed to the method invoked. The first argument or the page argument will be respected.
transform: A transform function. Example: function( basepagename, subpagename, code, langname ) end
options: An object with options. Example: { abort= { on=function() end, time=0.8 } }
Following options are available:
abort: Aborts iterating over the subpages if one of the conditions is met. If the process is aborted, nil is returned!
on: Function to be called if an abort-condition was met.
cycles: The maximum number of subpages to run over.
time: Maximum time to spend running over the subpages.
</pre>
<p>]=] function language_subpages( frame, transform, options )</p>
<pre>
local args, pargs, options = frame.args, ( frame:getParent() or {} ).args or {}, options or {};
local title = args.page or args[1] or pargs.page or pargs[1] or "";
local abort = options.abort or {};
local at, clock = type( abort.on ), os.clock();
local ac = function()
if at == 'function' or ( at == 'table' and getmetatable(abort.on).__call ) then
abort.on();
end
end
local tt = type( transform );
local page = require( 'Module:Page' );
</pre>
<pre>
title = page.clean(title);
</pre>
<pre>
if tt == 'function' or ( tt == 'table' and getmetatable(transform).__call ) then
local fetch, pages, langcode, langname = mw.language.fetchLanguageName, {};
</pre>
<p>--[==[</p>
<pre>
/ \
/ | \
/ · \
¯¯¯¯¯¯¯
Page.subpages() no longer works because it attempted to parse the HTML content generated by
calling the parser function "Special:Prefixindex:" which is no longer expanded in Lua but
converted to a "stripped tag" (containing a unique identifier surrounded by ASCII DEL characters)
representing the tag name and its parameters.
The actual expansion of stripped tags can no longer be performed in Lua.
Now unstripping these tags just kills ALL these tags (except "wiki" tags) instead of performing
their expansion by running the extension code. Only MediaWiki can unstrip these tags in texts after
they have been returned by Lua.
For this reason, page.subpages() is now completely empty (Module:Page no longer works).
This cannot be bypassed, except by using a Scribunto extension library if lifting the limits set by mw.unstrip.
Note that "Special:Prefixindex:" is also costly, even if it just requires a single database query to
get all subpages, instead of one costly #ifexist or one costly mw.title() property reading per
tested subpage to know if it exists.
For now there's still no reliable way to get a list of subpages, or performing queries similar to
the <a href="/web/20150422111815/https://meta.wikimedia.org/wiki/Special:PrefixIndex" title="Special:PrefixIndex">Special:Prefixindex</a> page or list members of a category like when viewing a category page.
Ideally, there should exist a method for such queries on Title objects returned by the mw.title library;
but for now there's none.
In Lua now, the only expansion possible with an immediate effect is the expansion of standard templates,
all special tags or special pages, or parser function extensions do not work (Only the #expr parser
function is supported by using an external Scribunto library).
</pre>
<p>--]==]</p>
<pre>
for pg in page.subpages( title, { ignoreNS=true } ) do
if abort.cycles then
abort.cycles = abort.cycles - 1
if 0 == abort.cycles then return ac() end
end
if abort.time then
if (os.clock() - clock) > abort.time then return ac() end
end
if mw.ustring.len( pg ) <= 12 then
langcode = string.lower( pg );
langname = fetch( langcode );
if langname ~= <i> then</i>
table.insert( pages, transform( title, pg, langcode, langname ) );
end
end
end
return pages;
end
return {};
</pre>
<p>end</p>
<p>function cloneArgs(frame)</p>
<pre>
local args, pargs = {}, {}
for k,v in pairs( frame.args ) do args[k] = v end
if frame:getParent() then
for k,v in pairs( frame:getParent().args ) do pargs[k] = v end
end
return args, pargs;
</pre>
<p>end</p>
<p><br /></p>
<p>local p = {};</p>
<p>--[=[ Usage: <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-0">Script error: The function "internal" does not exist.</span></strong> ]=] function p.internal(frame)</p>
<pre>
pages = language_subpages( frame, function( title, page, code, name )
return mw.ustring.format( '<span lang="%s" class="language lang-%s"><bdi><a href="/web/20150422111815/https://meta.wikimedia.org/w/index.php?title=%25s/%25s&action=edit&redlink=1" class="new" title="%s/%s (page does not exist)">%s</a></bdi></span>',
code, code, code, title, page, name
);
end);
return table.concat( pages, ' · ' );
</pre>
<p>end</p>
<p>--[=[ Usage: <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-1">Script error: The function "external" does not exist.</span></strong> ]=] function p.external(frame)</p>
<pre>
pages = language_subpages( frame, function( title, page, code, name )
return mw.ustring.format( '<span lang="%s" class="language lang-%s"><bdi>[%s/%s %s]</bdi></span>',
code, code, code, tostring( mw.uri.fullUrl( title ) ), page:gsub( ' ', '_' ), name
);
end);
return table.concat( pages, ' | ' );
</pre>
<p>end</p>
<p>--[=[ forEachLanguage</p>
<p>This function iterates over all language codes known to MediaWiki based on a maintained list replacing patterns in a pattern-string for each language</p>
<p>Usage: <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-2">Script error: The function "forEachLanguage" does not exist.</span></strong></p>
<p>Parameters</p>
<pre>
pattern: A pattern string which is processed for each language and which is concatenated at the end and returned as one string
before: A string that is inserted before the concatenated result
after: A string that is inserted after the concatenated result
sep: A string that is inserted between each line created from the pattern while iterating (like ProcessedPattern_sep_ProcessedPattern_sep_ProcessedPattern)
inLang: Langcode to use for $lnTrP and $lnTrUC1
</pre>
<p>Patterns:</p>
<pre>
$lc - language code such as en or de
$lnP - language name in own language (autonym)
$lnUC1 - language name in own language (autonym), first letter upper case
$lnTrP - language name translated to the language requested by language code passed to inLang
$lnTrUC1 - language name translated to the language requested by language code passed to inLang, first letter upper case
</pre>
<p>Example</p>
<pre>
<strong class="error"><span class="scribunto-error" id="mw-scribunto-error-3">Script error: The function "forEachLanguage" does not exist.</span></strong>
</pre>
<p>]=]</p>
<p>-- =p.forEachLanguage({ args= { pattern = "$lc - $lnTrP\n", inLang = "en" } }) function p.forEachLanguage(frame)</p>
<pre>
local l = require( "Module:Languages/List" )
</pre>
<pre>
local ret = {}
local lang = mw.language
local line
local pattern = frame.args.pattern or frame.args[1] or ""
local prefix = frame.args.before or frame.args[2] or ""
local postfix = frame.args.after or frame.args[3] or ""
local sep = frame.args.sep or frame.args.separator or frame.args[4] or ""
local inLang = frame.args.inLang or frame.args[5] or nil
</pre>
<pre>
local langNameUCFirstReq = not not pattern:find( "$lnUC1", 1, true )
local langNameReq = not not pattern:find( "$lnP", 1, true ) or langNameUCFirstReq
local langNameTranslatedUCFirstReq = not not pattern:find( "$lnTrUC1", 1, true )
local langNameTranslatedReq = not not pattern:find( "$lnTrP", 1, true ) or langNameTranslatedUCFirstReq
local contentLangInstance = mw.language.getContentLanguage()
local inLangLangInstance
local l = mw.language.fetchLanguageNames() -- autonyms
local lTr
local lcIdList = require( 'Module:Languages/List' ).getSortedList( l )
</pre>
<pre>
if langNameTranslatedReq then
inLangLangInstance = --[==[
mw.getLanguage( inLang ) -- Quota hit in :ucfirst() if using too many langInstances
--]==] contentLangInstance
lTr = mw.language.fetchLanguageNames( inLang ) -- translated names
end
</pre>
<pre>
for _, lcId in pairs( lcIdList ) do
local subst = lcId:gsub('%%', '%%%%')
line = pattern:gsub( "%$lc", subst )
local langName, langInstance
-- autonym (name of lcId in locale lcId)
if langNameReq then
langName = l[lcId]
subst = langName:gsub('%%', '%%%%')
line = line:gsub( "%$lnP", subst )
end
if langNameUCFirstReq then
langInstance = --[==[
mw.getLanguage( lcId ) -- Quota hit in :ucfirst() if using too many langInstances
--]==] contentLangInstance
langName = langInstance:ucfirst( langName )
subst = langName:gsub('%%', '%%%%')
line = line:gsub( "%$lnUC1", subst )
end
</pre>
<pre>
-- translated name (name of lcId in locale inLang)
if langNameTranslatedReq then
langName = lTr[lcId]
subst = langName:gsub('%%', '%%%%')
line = line:gsub( "%$lnTrP", subst )
end
if langNameTranslatedUCFirstReq then
langName = inLangLangInstance:ucfirst( langName )
subst = langName:gsub('%%', '%%%%')
line = line:gsub( "%$lnTrUC1", subst )
end
</pre>
<pre>
table.insert(ret, line)
end
return prefix .. table.concat( ret, sep ) .. postfix
</pre>
<p>end</p>
<p>--[=[</p>
<pre>
Provide logic for <a href="/web/20150422111815/https://meta.wikimedia.org/w/index.php?title=Template:Lle&action=edit&redlink=1" class="new" title="Template:Lle (page does not exist)">Template:Lle</a> (Language Links external, to be substituted)
</pre>
<p>]=] function p.lle(frame)</p>
<pre>
local ret
local pattern = "{{subst:#ifexist:{{{1}}}/$lc|[{{fullurl:{{{1}}}/$lc}} $lnUC1] {{subst:!}} }}"
ret = p.forEachLanguage({ args= { pattern = pattern } })
ret = frame:preprocess(ret)
return ret
</pre>
<p>end</p>
<p>--[=[</p>
<pre>
Provide logic for <a href="/web/20150422111815/https://meta.wikimedia.org/wiki/Template:Ll" title="Template:Ll" class="mw-redirect">Template:Ll</a> (Language Links, to be substituted)
</pre>
<p>]=] function p.ll(frame)</p>
<pre>
local ret
local pattern = "{{subst:#ifexist:{{{1}}}/$lc|[[{{{1}}}/$lc{{subst:!}}$lnUC1]] {{subst:!}} }}"
ret = p.forEachLanguage({ args= { pattern = pattern } })
ret = frame:preprocess(ret)
return ret
</pre>
<p>end</p>
<p><br /></p>
<hr />
<p>--- Different approaches for <a href="/web/20150422111815/https://meta.wikimedia.org/wiki/Template:Lang_links" title="Template:Lang links">Template:Lang links</a> ---</p>
<hr />
<p>--[=[</p>
<pre>
Provide logic for <a href="/web/20150422111815/https://meta.wikimedia.org/wiki/Template:Lang_links" title="Template:Lang links">Template:Lang links</a>
Using a cute Hybrid-Method:
First check the subpages which is quite fast; if there are too many fall back to checking for each language page individually
</pre>
<p>]=]</p>
<p>-- =p.langLinksNonExpensive({ args= { page='Commons:Picture of the Year/2010' }, getParent=function() end }) -- =p.langLinksNonExpensive({ args= { page='Main Page' }, getParent=function() end }) -- =p.langLinksNonExpensive({ args= { page='Template:No_source_since' }, getParent=function() end }) -- =p.langLinksNonExpensive({ args= { page='MediaWiki:Gadget-HotCat' }, getParent=function() end }) function p.langLinksNonExpensive(frame)</p>
<pre>
local args, pargs = frame.args, ( frame:getParent() or {} ).args or {};
local title = args.page or args[1] or pargs.page or pargs[1] or "";
local contentLangInstance = mw.language.getContentLanguage();
local pages2
if frame.preprocess == nil then
frame = mw.getCurrentFrame()
end
--[==[
local options = { abort= { time=3.5, on=function()
pages2 = p.forEachLanguage({ args= { pattern = <i> } })</i>
end } }
local pages = language_subpages( frame, function( basepagename, subpagename, code, langname )
return mw.ustring.format( '<span lang="%s" class="language lang-%s" style="white-space:nowrap"><bdi><a href="/web/20150422111815/https://meta.wikimedia.org/w/index.php?title=%25s/%25s&action=edit&redlink=1" class="new" title="%s/%s (page does not exist)">%s</a></bdi></span> | ',
code, code, code, basepagename, subpagename, contentLangInstance:ucfirst( langname ) )
end, options );
return pages2 and frame:preprocess(pages2) or table.concat( pages, <i> );</i>
]==]
return frame:preprocess( p.forEachLanguage({ args= { pattern = <i> } }) )</i>
</pre>
<p>end</p>
<hr />
<hr />
<p><a href="/web/20150422111815/https://meta.wikimedia.org/w/index.php?title=Template:Autolang&action=edit&redlink=1" class="new" title="Template:Autolang (page does not exist)">Template:Autolang</a> -----------------</p>
<hr />
<p>--[[</p>
<pre>
Works like <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-4">Script error: No such module "fallback".</span></strong> just allowing an unlimited number of arguments, even named arguments.
It's doing Magic! No arguments should be passed to <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-5">Script error: You must specify a function to call.</span></strong>
</pre>
<p>]]</p>
<p>function p.autolang(frame)</p>
<pre>
local args, pargs = cloneArgs( frame )
if nil == args.useargs then
if not args.base then args = pargs end
elseif 'both' == args.useargs then
for k,v in pairs(args) do pargs[k] = v end
args = pargs
elseif 'parent' == args.useargs then
args = pargs
if pargs.base and not args.base then
args.base = pargs.base
end
end
local base = args.base
local userlang = frame:preprocess( 'en' )
local tl, tlns = 'Template:', 10
local tlb, fallback1, currenttemplate
local fallback, contentlang = mw.text.split( userlang, '-', true )[1], mw.language.getContentLanguage():getCode()
</pre>
<pre>
local createReturn = function(title)
local ret
local tlargs = {}
-- When LUA is invoked, templates are already expanded. This must be respected.
return frame:expandTemplate{ title = title, args = args }
end
</pre>
<pre>
if not base then
return ("'autolang' in <a href="/web/20150422111815/https://meta.wikimedia.org/wiki/Module:Languages" title="Module:Languages">Module:Languages</a> was called but the 'base' parameter could not be found." ..
"The base parameter specifies the template that's subpages will be sought for a suitable translation.")
end
tlb = tl .. base .. '/'
</pre>
<pre>
currenttemplate = tlb .. userlang
local ok, exists = pcall( function()
return mw.title.new( currenttemplate, tlns ).exists
end )
if ok and exists then
return createReturn(currenttemplate)
end
</pre>
<pre>
fallback1 = frame:preprocess( 'en' )
if fallback1 ~= contentlang then
return createReturn(tlb .. fallback1)
end
</pre>
<pre>
currenttemplate = tlb .. fallback
local ok, exists = pcall( function()
return mw.title.new( currenttemplate, tlns ).exists
end )
if ok and exists then
return createReturn(currenttemplate)
end
</pre>
<pre>
currenttemplate = tlb .. contentlang
local ok, exists = pcall( function()
return mw.title.new( currenttemplate, tlns ).exists
end )
if ok and exists then
return createReturn(currenttemplate)
end
return createReturn(tl .. base)
</pre>
<p>end</p>
<p>--[=[ Usage: <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-6">Script error: The function "isKnownLanguageTag" does not exist.</span></strong> -> 1 <strong class="error"><span class="scribunto-error" id="mw-scribunto-error-7">Script error: The function "isKnownLanguageTag" does not exist.</span></strong> -> ]=] function p.isKnownLanguageTag(frame)</p>
<pre>
return mw.language.isKnownLanguageTag( frame.args[1] or frame.args.tag or frame.args.code or <i> ) and '1' or </i>
</pre>
<p>end</p>
<p>function p.file_languages(frame)</p>
<pre>
local M_link = require( 'Module:Link' )
local contentLangInstance = mw.language.getContentLanguage()
local pattern = frame.args.pattern or '%s (%s)'
local original = frame.args.original or mw.title.getCurrentTitle().text
local ext_start, _ = string.find( original, '\.%w+$' )
local file_ext = string.sub( original, ext_start )
original = string.sub( original, 0, ext_start-1 )
</pre>
<p>return frame:preprocess('</p>
<ul class="gallery mw-gallery-traditional">
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Function(linkInfo)</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Local filename = mw.ustring.format( pattern, original, linkInfo.text ) .. file ext</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Local ok, exists = pcall( function()</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Return mw.title.new( filename, 6 ).exists</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">End )</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">If ok and exists then</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Return mw.ustring.format( '%s</div>
<div class="gallerytext">
<p>%s', filename, contentLangInstance:ucfirst( mw.language.fetchLanguageName( linkInfo.text ) ) )</p>
</div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Else</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">Return nil</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">End</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">End</div>
<div class="gallerytext"></div>
</div>
</li>
<li class="gallerybox" style="width: 155px">
<div style="width: 155px">
<div class="thumb" style="height: 150px;">), '\n'))..'\n</div>
<div class="gallerytext"></div>
</div>
</li>
</ul>
<p>')</p>
<p>end</p>
<p>function p.runTests()</p>
<pre>
return p.langLinksNonExpensive({ args= { page='Module:Languages/testcases/test' }, getParent=function() end }) == "<a href="/web/20150422111815/https://meta.wikimedia.org/w/index.php?title=Module:Languages/testcases/test/de&action=edit&redlink=1" class="new" title="Module:Languages/testcases/test/de (page does not exist)">Deutsch</a> | <a href="/web/20150422111815/https://meta.wikimedia.org/w/index.php?title=Module:Languages/testcases/test/en&action=edit&redlink=1" class="new" title="Module:Languages/testcases/test/en (page does not exist)">English</a> | "
</pre>
<p>end</p>
<p>return p;</p>
```