Module:Category handler

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This module implements the {{category handler}} template. The category handler template helps other templates to automate both categorization and category suppression. For information about using the category handler template in other templates, please see the template documentation. Keep reading for information about using the category handler module in other Lua modules, or for information on exporting this module to other wikis.

Use from other Lua modules

When not to use this module

For cases where a module only needs to categorise in one of the namespaces main (articles), file (images) or category, then using this module is overkill. Instead, you can simply get a title object using mw.title.getCurrentTitle and check the nsText field. For example: 

local title = mw.title.getCurrentTitle()
if title.nsText == 'File' then
    -- do something
end

However, if your module needs to categorize in any other namespace, then we recommend you use this module, since it provides proper category suppression and makes it easy to select how to categorize in the different namespaces.

Namespaces

This module detects and groups all the different namespaces used on Wikipedia into several types. These types are used as parameter names in this module.

main = Main/article space, as in normal Wikipedia articles.
talk = Any talk space, such as page names that start with "Talk:", "User talk:", "File talk:" and so on.
user, wikipedia, file ... = The other namespaces except the talk pages. Namespace aliases are also accepted. See the table below for the full list.
other = Any namespaces that were not specified as a parameter to the template. See examples below.
List of possible namespace parameters

(excluding talk and other)

Namespace Aliases
main
module
template
user
special
talk
project
help
category
media
file image
mediawiki

Basic usage

This module takes two or more parameters. Here's an example using a hello world program: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'Hello world!'
    local category = categoryHandler{
        '[[Category:Somecat]]',
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

The above example uses the default settings for the category handler module. That means the example module will categorize on pages in the following namespaces:

main, file, help, category, portal and book

But it will not categorize in any other namespaces, e.g.:

talk, user, wikipedia, mediawiki, template ...

And it will not categorize on blacklisted pages. (See section blacklist below.)

The reason the category handler module does not categorize in some of the namespaces is that in those namespaces most modules and templates are just demonstrated or listed, not used. Thus most modules and templates should not categorize in those namespaces.

Any module or template that is meant for one or more of the namespaces where this module categorizes can use the basic syntax as shown above.

Advanced usage

This module takes one or more parameters named after the different page types as listed in section namespaces above. By using those parameters you can specify exactly in which namespaces your template should categorize. Like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'This is a module meant for articles and talk pages.'
    local category = categoryHandler{
        main = '[[Category:Somecat1]]', -- Categorize in main (article) space
        talk = '[[Category:Somecat2]]', -- Categorize in talk space
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

The above module will only categorize in main and talk space. But it will not categorize on /archive pages since they are blacklisted. (See section blacklist below.) And if you need to demonstrate (discuss) the module on a talkpage, then you can feed "nocat='true'" to prevent that template from categorizing. (See section nocat below.) Like this: 

== My new module ==
Hey guys, have you seen my new module?
{{#invoke:mymodule|main|nocat=true}}
Nice, isn't it?
--~~~~

Sometimes we want to use the same category in several namespaces, then do like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'This is a module used in several namespaces.'
    local category = categoryHandler{
        main = '[[Category:Somecat1]]',
        [ 1 ] = '[[Category:Somecat2]]', -- For help and user space
        help = 1,
        user = 1,
        talk = '', -- No categories on talk pages
        other = '[[Category:Somecat3]]', -- For all other namespaces
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

In the above example we use a numbered parameter to feed one of the categories, and then we tell this module to use that numbered parameter for both the help and user space.

The category handler module understands an unlimited number of numbered parameters.

The other parameter defines what should be used in the remaining namespaces that have not explicitly been fed data.

Note the empty but defined talk parameter. That stops this module from showing what has been fed to the other parameter, when in talk space.

The category handler module also has a parameter called all. It works like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'This is a module used in all namespaces.'
    local category = categoryHandler{
        all = '[[Category:Somecat1]]', -- Categorize in all namespaces
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

The above example will categorize in all namespaces, but not on blacklisted pages. If you want to demonstrate that module on a page, then use "nocat=true" to prevent the template from categorizing.

We suggest avoiding the all parameter, since modules and templates should preferably only categorize in the namespaces they need to.

The all parameter can also be combined with the rest of the parameters. Like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'This is a module used in all namespaces.'
    local category = categoryHandler{
        all = '[[Category:Somecat1]]', -- Categorize in all namespaces
        main = '[[Category:Somecat2]]', -- And add this in main space
        other = '[[Category:Somecat3]]', -- And add this in all other namespaces
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

If the above module is placed on an article, then it will add the categories "Somecat1" and "Somecat2". But on all other types of pages it will instead add "Somecat1" and "Somecat3". As the example shows, the all parameter works independently of the rest of the parameters.

Subpages

The category handler module understands the subpage parameter. Like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'This is a module used in all namespaces.'
    local category = categoryHandler{
        subpage = 'no' -- Don't categorize on subpages
        wikipedia = '[[Category:Somecat]]',
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

If "subpage='no'" then this template will not categorize on subpages. For the rare occasion you only want to categorize on subpages, then use "subpage='only'". If subpage is empty or undefined then this template categorizes both on basepages and on subpages.

Blacklist

This module has a blacklist of the pages and page types where templates should not auto-categorize. Thus modules that use this meta-template will for instance not categorize on /archive pages and on the subpages of Wikipedia:Template messages.

If you want a template to categorize on a blacklisted page, then feed "nocat = false" to the module when you place it on the page, thus skipping the blacklist check. Note that this module only categorizes if it has data for the namespace. For instance, if the basic syntax is used (see basic usage above), then even if you set "nocat = false" the template will not categorize on a talk page, since it has no data for talk pages. But it has data for help space, so on a blacklisted help page it will categorize.

The blacklist is located in the configuration table cfg.blacklist near the top of the module code.

The "nocat" parameter

This module understands the nocat parameter:

  • If "nocat = true" then this template does not categorize.
  • If nocat is nil then this template categorizes as usual.
  • If "nocat = false" this template categorizes even when on blacklisted pages. (See section blacklist above.)
  • The nocat parameter also accepts aliases for true and false as defined by Module:Yesno, e.g. "yes", "y", "true", and 1 for true, and "no", "n", "false", and 0 for false.

Modules and templates that use {{category handler}} should forward nocat, so they too understand nocat. The code "nocat = frame.args.nocat" shown in the examples on this page does that.

The "categories" parameter

For backwards compatibility this module also understands the categories parameter. It works the same as nocat. Like this:

  • If "categories = false" then this template does not categorize.
  • If categories is empty or undefined then this template categorizes as usual.
  • If "categories = true" this template categorizes even when on blacklisted pages.
  • The categories parameter also accepts aliases for true and false as defined by Module:Yesno, e.g. "yes", "y", "true", and 1 for true, and "no", "n", "false", and 0 for false.

The "category2" parameter

For backwards compatibility this template kind of supports the old "category =" parameter. But the parameter name "category" is already used in this module to feed category data for when in category space. So instead this template uses category2 for the usage similar to nocat. Like this:

  • If "category2 = " (empty but defined), or "category2 = 'no'", or if category2 is fed any other data (except as described in the next two points), then this template does not categorize.
  • If category2 is undefined or if "category2 = '¬'", then this template categorizes as usual.
  • If "category2 = 'yes'" this template categorizes even when on blacklisted pages.

Categories and text

Besides from categories, you can feed anything else to this module, for instance some text. Like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local result = 'This is a module used on talk pages.'
    local category = categoryHandler{
        talk = '[[Category:Somecat]]',
        other = '<p class="error">This module should only be used on talk pages.</p>',
        nocat = frame.args.nocat -- So "nocat=true/false" works
    }
    category = category or '' -- Check that we don't have a nil value for the category variable.
    return result .. category
end
 
return p

When the template above is shown on anything else than a talk page, it will look like this:

This is a module used on talk pages.

This module should only be used on talk pages.

That text will not show on blacklisted pages, so don't use this method to show any important information. Feeding "nocat = 'true'" to the template hides the text, just as it suppresses any categories.

The "page" parameter

For testing and demonstration purposes this module can take a parameter named page. Like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local category = categoryHandler{
        main = 'Category:Some cat',
        talk = 'Category:Talk cat',
        nocat = frame.args.nocat, -- So "nocat=true/false" works
        page = 'User talk:Example'
    }
    return category
end
 
return p

In the above code we on purpose left out the brackets around the category names so we see the output on the page. No matter on what kind of page the code above is used it will return this:

Category:Talk cat

The page parameter makes this module behave exactly as if on that page. Even the blacklist works. The pagename doesn't have to be an existing page.

If the page parameter is empty or undefined, the name of the current page determines the result.

You can make it so your module also understands the page parameter. That means you can test how your template will categorize on different pages, without having to actually edit those pages. Then do like this: 

p = {}
local categoryHandler = require( 'Module:Category handler' ).main
 
function p.main( frame )
    local category = categoryHandler{
        main = 'Category:Some cat',
        talk = 'Category:Talk cat',
        nocat = frame.args.nocat, -- So "nocat=true/false" works
        page = frame.args.page -- For testing
    }
    return category
end
 
return p

Parameters

List of all parameters:

  • First positional parameter - for default settings
  • subpage = 'no' / 'only'
  • 1, 2, 3 ...
  • all = '[[Category:Somecat]]' / 'Text'
  • main = 1, 2, 3 ... / '[[Category:Somecat]]' / 'Text'
  • ...
  • other = 1, 2, 3 ... / '[[Category:Somecat]]' / 'Text'
  • nocat = frame.args.nocat / true / false / 'yes' / 'no' / 'y' / 'n' / 'true' / 'false' / 1 / 0
  • categories = frame.args.categories / false / true / 'no' / 'yes' / 'n' / 'y' / 'false' / 'true' / 0 / 1
  • category2 = frame.args.category or '¬' / / 'no' / not defined / '¬' / 'yes'
  • page = frame.args.page / 'User:Example'

Note that empty values to the "main" ... "other" parameters have special meaning (see examples above). The "all" parameter doesn't understand numbered parameters, since there should never be a need for that.

Exporting to other wikis

This module can be exported to other wikis by changing the configuration values in the cfg table. All the variable values are configurable, so after the configuration values have been set there should be no need to alter the main module code. Details of each configuration value are included in the module code comments. In addition, this module requires Module:Namespace detect to be available on the local wiki.

See also

----------------------------------------------------------------------------------------------------------
--                                                                                                      --
--                                          CATEGORY HANDLER                                            --
--                                                                                                      --
--      This module implements the {{category handler}} template in Lua, with a few improvements: all   --
--      namespaces and all namespace aliases are supported, and namespace names are detected            --
--      automatically for the local wiki. This module requires [[Module:Namespace detect]] and          --
--      [[Module:Yesno]] to be available on the local wiki. It can be configured for different wikis    --
--      by altering the values in the "cfg" table.                                                      --
--                                                                                                      --
----------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------
--                                          Configuration data                                          --
--                      Language-specific parameter names and values can be set here.                   --
----------------------------------------------------------------------------------------------------------

local cfg = {}

-- The following config values set the names of parameters that suppress categorisation. They are used
-- with Module:Yesno, and work as follows:
--
-- cfg.nocat:
-- Result of yesno(args[cfg.nocat])         Effect
-- true                                     Categorisation is suppressed
-- false                                    Categorisation is allowed, and the blacklist check is skipped
-- nil                                      Categorisation is allowed
--
-- cfg.categories:
-- Result of yesno(args[cfg.categories])    Effect
-- true                                     Categorisation is allowed, and the blacklist check is skipped
-- false                                    Categorisation is suppressed
-- nil                                      Categorisation is allowed
cfg.nocat = 'nocat'    
cfg.categories = 'categories'

-- The parameter name for the legacy "category2" parameter. This skips the blacklist if set to the
-- cfg.category2Yes value, and suppresses categorisation if present but equal to anything other than
-- cfg.category2Yes or cfg.category2Negative.
cfg.category2 = 'category2'
cfg.category2Yes = 'yes'
cfg.category2Negative = '¬'

-- cfg.subpage is the parameter name to specify how to behave on subpages. cfg.subpageNo is the value to
-- specify to not categorise on subpages; cfg.only is the value to specify to only categorise on subpages.
cfg.subpage = 'subpage'
cfg.subpageNo = 'no'
cfg.subpageOnly = 'only'

-- The parameter for data to return in all namespaces.
cfg.all = 'all'

-- The parameter name for data to return if no data is specified for the namespace that is detected. This
-- must be the same as the cfg.other parameter in [[Module:Namespace detect]].
cfg.other = 'other'

-- The parameter name used to specify a page other than the current page; used for testing and
-- demonstration. This must be the same as the cfg.page parameter in [[Module:Namespace detect]].
cfg.page = 'page'

-- The categorisation blacklist. Pages that match Lua patterns in this list will not be categorised.
-- (However, see the explanation of cfg.nocat, cfg.categories and cfg.category2 for some exceptions.)
-- If the namespace name has a space in, it must be written with an underscore, e.g. "Wikipedia_talk".
-- Other parts of the title can have either underscores or spaces.
cfg.blacklist = {
    '^Main Page$', -- don't categorise the main page.
    
    -- Don't categorise the following pages or their subpages.
    '^Wikipedia:Cascade%-protected items$',
    '^Wikipedia:Cascade%-protected items/.*$',
    '^User:UBX$', -- The userbox "template" space.
    '^User:UBX/.*$',
    '^User_talk:UBX$',
    '^User_talk:UBX/.*$',
    
    -- Don't categorise subpages of these pages, but allow
    -- categorisation of the base page.
    '^Wikipedia:Template messages/.+$',
    
    '/[aA]rchive' -- Don't categorise archives.
}

-- This is a table of namespaces to categorise by default. They should be in the format of parameter
-- names accepted by [[Module:Namespace detect]].
cfg.defaultNamespaces = {
    'main',
    'file',
    'help',
    'category'
}

----------------------------------------------------------------------------------------------------------
--                                          End configuration data                                      --
----------------------------------------------------------------------------------------------------------

-- Get dependent modules
local nsDetect = require('Module:Namespace detect')
local yesno = require('Module:Yesno')

----------------------------------------------------------------------------------------------------------
--                                          Local functions                                             --
--      The following are internal functions, which we do not want to be accessible from other modules. --
----------------------------------------------------------------------------------------------------------

-- Find whether we need to return a category or not.
local function needsCategory(pageObject, args)
    -- Don't categorise if the relevant options are set.
    if yesno(args[cfg.nocat])
        or yesno(args[cfg.categories]) == false
        or (
            args[cfg.category2] 
            and args[cfg.category2] ~= cfg.category2Yes 
            and args[cfg.category2] ~= cfg.category2Negative
        )
    then
        return false
    end
    -- If there is no pageObject available, then that either means that we are over
    -- the expensive function limit or that the title specified was invalid. Invalid
    -- titles will probably only be a problem during testing, so we choose the best
    -- fallback for being over the expensive function limit. The fallback behaviour
    -- of the old template was to assume the page was not a subpage, so we will do
    -- the same here.
    if args[cfg.subpage] == cfg.subpageNo and pageObject and pageObject.isSubpage then
        return false
    end
    if args[cfg.subpage] == cfg.subpageOnly 
        and (not pageObject or (pageObject and not pageObject.isSubpage))
    then
        return false
    end
    return true
end

-- Find whether we need to check the blacklist or not.
local function needsBlacklistCheck(args)
    if yesno(args[cfg.nocat]) == false
        or yesno(args[cfg.categories]) == true
        or args[cfg.category2] == cfg.category2Yes
    then
        return false
    else
        return true
    end
end

-- Find whether any namespace parameters have been specified.
-- Mappings is the table of parameter mappings taken from
-- [[Module:Namespace detect]].
local function nsParamsExist(mappings, args)
    if args[cfg.all] or args[cfg.other] then
        return true
    end
    for ns, params in pairs(mappings) do
        for i, param in ipairs(params) do
            if args[param] then
                return true
            end
        end
    end
    return false
end

----------------------------------------------------------------------------------------------------------
--                                          Global functions                                            --
--      The following functions are global, because we want them to be accessible from #invoke and      --
--      from other Lua modules.                                                                         --
----------------------------------------------------------------------------------------------------------

local p = {}

-- Find if a string matches the blacklist. Returns the match if one is found, or nil otherwise.
-- Input should be a page title with a namespace prefix, e.g. "Wikipedia talk:Articles for deletion".
function p.matchesBlacklist(page)
    if type(page) ~= 'string' then return end
    for i, pattern in ipairs(cfg.blacklist) do
        local match = mw.ustring.match(page, pattern)
        if match then
            return match
        end
    end
end

-- The main structure of the module. Checks whether we need to categorise,
-- and then passes the relevant arguments to [[Module:Namespace detect]].
function p._main(args)
    -- Get the page object and argument mappings from
    -- [[Module:Namespace detect]], to save us from having to rewrite the
    -- code.
    local pageObject = nsDetect.getPageObject(args[cfg.page])
    local mappings = nsDetect.getParamMappings()
    
    if not needsCategory(pageObject, args) then return end
    
    local ret = ''
    -- Check blacklist if necessary.
    if not needsBlacklistCheck(args) or not p.matchesBlacklist(pageObject.prefixedText) then
        if not nsParamsExist(mappings, args) then
            -- No namespace parameters exist; basic usage. Pass args[1] to
            -- [[Module:Namespace detect]] using the default namespace
            -- parameters, and return the result.
            local ndargs = {}
            for _, ndarg in ipairs(cfg.defaultNamespaces) do
                ndargs[ndarg] = args[1]
            end
            ndargs.page = args.page
            ndargs.demospace = args.demospace
            local ndresult = nsDetect._main(ndargs)
            if ndresult then
                ret = ret .. ndresult
            end
        else
            -- Namespace parameters exist; advanced usage.
            -- If the all parameter is specified, return it.
            local all = args.all
            if type(all) == 'string' then
                ret = ret .. all
            end
            
            -- Get the arguments to pass to [[Module:Namespace detect]].
            local ndargs = {}
            for ns, params in pairs(mappings) do
                for _, param in ipairs(params) do
                    ndargs[param] = args[param] or args[cfg.other] or nil
                end
            end
            ndargs.other = args.other
            ndargs.page = args.page
            ndargs.demospace = args.demospace
            
            local data = nsDetect._main(ndargs)
            
            -- Work out what to return based on the result of the namespace detect call.
            local datanum = tonumber(data)
            if type(datanum) == 'number' then
                -- "data" is a number, so return that positional parameter.
                -- Remove non-positive integer values, as only positive integers
                -- from 1-10 were used with the old template.
                if datanum > 0 and math.floor(datanum) == datanum then
                    local dataArg = args[datanum]
                    if type(dataArg) == 'string' then
                        ret = ret .. dataArg
                    end
                end
            else
                -- "data" is not a number, so return it as it is.
                if type(data) == 'string' then
                    ret = ret .. data
                end
            end
        end
    end
    return ret
end

function p.main(frame)
    -- If called via #invoke, use the args passed into the invoking
    -- template, or the args passed to #invoke if any exist. Otherwise
    -- assume args are being passed directly in.
    local origArgs
    if frame == mw.getCurrentFrame() then
        origArgs = frame:getParent().args
        for k, v in pairs(frame.args) do
            origArgs = frame.args
            break
        end
    else
        origArgs = frame
    end

    -- Trim whitespace and remove blank arguments for the following args:
    -- 1, 2, 3 etc., "nocat", "categories", "subpage", and "page".
    local args = {}
    for k, v in pairs(origArgs) do
        if type(v) == 'string' then
            v = mw.text.trim(v) -- Trim whitespace.
        end
        if type(k) == 'number'
            or k == cfg.nocat
            or k == cfg.categories
            or k == cfg.subpage
            or k == cfg.page
        then
            if v ~= '' then
                args[k] = v
            end
        else
            args[k] = v
        end
    end
    
    -- Lower-case "nocat", "categories", "category2", and "subpage". These
    -- parameters are put in lower case whenever they appear in the old
    -- template, so we can just do it once here and save ourselves some work.
    local lowercase = {cfg.nocat, cfg.categories, cfg.category2, cfg.subpage}
    for _, v in ipairs(lowercase) do
        local argVal = args[v]
        if type(argVal) == 'string' then
            args[v] = mw.ustring.lower(argVal)
        end
    end
    
    return p._main(args)
end

return p
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