Module:Ns has subpages/sandbox

 -- This module implements [[Template:Ns has subpages]].
 -- While the template is fairly simple, this information is made available to
 -- Lua directly, so using a module means that we don't have to update the
 -- template as new namespaces are added.

 localp={}

 functionp._main(ns,frame)
 -- Get the current namespace if we were not passed one.
 ifnotnsthen
 ns=mw.title.getCurrentTitle().namespace
 end

 -- Look up the namespace table from mw.site.namespaces. This should work
 -- for a majority of cases.
 localnsTable=mw.site.namespaces[ns]

 -- Try using string matching to get the namespace from page names.
 -- Do a quick and dirty bad title check to try and make sure we do the same
 -- thing as {{NAMESPACE}} in most cases.
 ifnotnsTableandtype(ns)=='string'andnotns:find('[<>|%[%]{}]')then
 localnsStripped=ns:gsub('^[_%s]*:','')
 nsStripped=nsStripped:gsub(':.*$','')
 nsTable=mw.site.namespaces[nsStripped]
 end

 -- If we still have no match then try the {{NAMESPACE}} parser function,
 -- which should catch the remainder of cases. Don't use a mw.title object,
 -- as this would increment the expensive function count for each new page
 -- tested.
 ifnotnsTablethen
 frame=frameormw.getCurrentFrame()
 localnsProcessed=frame:callParserFunction('NAMESPACE',ns)
 nsTable=nsProcessedandmw.site.namespaces[nsProcessed]
 end

 returnnsTableandnsTable.hasSubpages
 end

 functionp.main(frame)
 localns=frame:getParent().args[1]
 ifnsthen
 ns=ns:match('^%s*(.-)%s*$')-- trim whitespace
 ns=tonumber(ns)orns
 end
 localhasSubpages=p._main(ns,frame)
 returnhasSubpagesand'yes'or''
 end

 returnp