Module:Arguments
 | This Lua module is used in system messages, and on approximately 36,500,000 pages, or roughly 56% of all pages. Changes to it can cause immediate changes to the Wikipedia user interface. To avoid major disruption and server load, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Please discuss changes on the talk page before implementing them. |
 | This module is rated as ready for general use. It has reached a mature state, is considered relatively stable and bug-free, and may be used wherever appropriate. It can be mentioned on help pages and other Wikipedia resources as an option for new users. To minimise server load and avoid disruptive output, improvements should be developed through sandbox testing rather than repeated trial-and-error editing. |
 | This module is currently protected from editing. See the protection policy and protection log for more details. Please discuss any changes on the talk page; you may submit an edit request to ask an administrator to make an edit if it is uncontroversial or supported by consensus. You may also request that this page be unprotected. |
 | This module can only be edited by administrators because it is transcluded onto one or more cascade-protected pages. |
This module provides easy processing of arguments passed from #invoke. It is a meta-module, meant for use by other modules, and should not be called from #invoke directly (for a module directly invocable by templates you might want to have a look at {{#invoke:params}}). Its features include:
- Easy trimming of arguments and removal of blank arguments.
- Arguments can be passed by both the current frame and by the parent frame at the same time. (More details below.)
- Arguments can be passed in directly from another Lua module or from the debug console.
- Most features can be customized.
Basic use
[edit]First, you need to load the module. It contains one function, named getArgs.
local getArgs = require('Module:Arguments').getArgs
In the most basic scenario, you can use getArgs inside your main function. The variable args is a table containing the arguments from #invoke. (See below for details.)
local getArgs = require('Module:Arguments').getArgs
local p = {}
function p.main(frame)
local args = getArgs(frame)
-- Main module code goes here.
end
return p
Recommended practice
[edit]However, the recommended practice is to use a separate function as the entry point from #invoke just for processing the arguments. This allows other Lua modules to call your core logic directly, improving performance by avoiding the overhead of interacting with the frame object.
local getArgs = require('Module:Arguments').getArgs
local p = {}
function p.main(frame)
local args = getArgs(frame)
return p._main(args)
end
function p._main(args)
-- Main module code goes here.
end
return p
The way this is called from a template is {{#invoke:Example|main}} (optionally with some parameters like {{#invoke:Example|main|arg1=value1|arg2=value2}}), and the way this is called from a module is require('Module:Example')._main({arg1 = 'value1', arg2 = value2, 'spaced arg3' = 'value3'}). What this second one does is construct a table with the arguments in it, then gives that table to the p._main(args) function, which uses it natively.
Multiple functions
[edit]If you want multiple functions to use the arguments, and you also want them to be accessible from #invoke, you can use a wrapper function.
local getArgs = require('Module:Arguments').getArgs
local p = {}
local function makeInvokeFunc(funcName)
return function (frame)
local args = getArgs(frame)
return p[funcName](args)
end
end
p.func1 = makeInvokeFunc('_func1')
function p._func1(args)
-- Code for the first function goes here.
end
p.func2 = makeInvokeFunc('_func2')
function p._func2(args)
-- Code for the second function goes here.
end
return p
Options
[edit]The following options are available. They are explained in the sections below.
local args = getArgs(frame, {
trim = false,
removeBlanks = false,
valueFunc = function (key, value)
-- Code for processing one argument
end,
frameOnly = true,
parentOnly = true,
parentFirst = true,
wrappers = {
'Template:A wrapper template',
'Template:Another wrapper template'
},
readOnly = true,
noOverwrite = true
})
Trimming whitespace
[edit]MediaWiki trims whitespace for named arguments coming from #invoke or a template call, but preserves whitespace for positional arguments. By default, this module helps trim whitespace also for position arguments. To preserve whitespace for positional arguments, set the trim option to false.
local args = getArgs(frame, {
trim = false
})
When the valueFunc option is given, the valueFunc function will be responsible for trimming whitespace, and the trim option will have no effect.
Removing blank arguments
[edit]"Blank arguments" are arguments from #invoke or template that are blank strings or consist of only whitespace. By default, this module removes all blank arguments. To preserve the blank arguments, set the removeBlanks option to false.
local args = getArgs(frame, {
removeBlanks = false
})
This might be necessary for some templates' operation.
Note: When converting MediaWiki templates to Lua, keep in mind that in Lua, blank strings and strings consisting only of whitespace are considered true. If you don't pay attention to such blank arguments when you write your Lua modules, you might treat something as true that should actually be treated as false.
When the valueFunc option is given, the valueFunc function will be responsible for handling blank arguments, and the removeBlanks option will have no effect.
Custom formatting of arguments
[edit]Sometimes you want to remove some blank arguments but not others, or perhaps you might want to put all of the positional arguments in lower case. To do things like this you can use the valueFunc option. The input to this option must be a function that takes two parameters, key and value, and returns a single value. This value is what you will get when you access the field key in the args table.
Example 1: this function preserves whitespace for the first positional argument's value, but trims all other arguments' value and removes all other blank arguments.
local args = getArgs(frame, {
valueFunc = function (key, value)
if key == 1 then
return value
elseif value then
value = mw.text.trim(value)
if value ~= '' then
return value
end
end
return nil
end
})
Example 2: this function removes blank arguments and converts all argument values to lower case, but doesn't trim whitespace from positional parameters.
local args = getArgs(frame, {
valueFunc = function (key, value)
if not value then
return nil
end
value = mw.ustring.lower(value)
if mw.ustring.find(value, '%S') then
return value
end
return nil
end
})
Note: the above functions will fail if passed input that is not of type string or nil. This might be the case if you use the getArgs function in the main function of your module, and that function is called by another Lua module. In this case, you will need to check the type of your input. This is not a problem if you are using a function specially for arguments from #invoke (i.e. you have p.main and p._main functions, or something similar).
Examples 1 and 2 with type checking
|
|---|
|
Example 1: local args = getArgs(frame, {
valueFunc = function (key, value)
if key == 1 then
return value
elseif type(value) == 'string' then
value = mw.text.trim(value)
if value ~= '' then
return value
else
return nil
end
else
return value
end
end
})
Example 2: local args = getArgs(frame, {
valueFunc = function (key, value)
if type(value) == 'string' then
value = mw.ustring.lower(value)
if mw.ustring.find(value, '%S') then
return value
else
return nil
end
else
return value
end
end
})
|
Also, please note that the valueFunc function is called more or less every time an argument is requested from the args table, so if you care about performance you should make sure you aren't doing anything inefficient with your code.
Frames and parent frames
[edit]Arguments in the args table can be passed from the current frame or from its parent frame at the same time. To understand what this means, it is easiest to give an example. Let's say that we have a module called Module:ExampleArgs. This module prints the first two positional arguments that it is passed.
Module:ExampleArgs code
|
|---|
local getArgs = require('Module:Arguments').getArgs
local p = {}
function p.main(frame)
local args = getArgs(frame)
return p._main(args)
end
function p._main(args)
local first = args[1] or ''
local second = args[2] or ''
return first .. ' ' .. second
end
return p
|
Template:ExampleArgs contains the code {{#invoke:ExampleArgs|main|''firstInvokeArg''}}.
Now if we were to call Template:ExampleArgs, the following would happen:
| Code | Result |
|---|---|
{{#invoke:ExampleArgs|main|''firstInvokeArg''}}
(call #invoke directly without template)
|
firstInvokeArg
(call #invoke directly without template) |
{{ExampleArgs}}
|
firstInvokeArg |
{{ExampleArgs|firstTemplateArg}}
|
firstInvokeArg |
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}
|
firstInvokeArg secondTemplateArg |
There are three options you can set to change this behaviour: frameOnly, parentOnly and parentFirst. If you set frameOnly then only arguments passed from the current frame will be accepted; if you set parentOnly then only arguments passed from the parent frame will be accepted; and if you set parentFirst then arguments will be passed from both the current and parent frames, but the parent frame will have priority over the current frame. Here are the results in terms of Template:ExampleArgs:
- frameOnly
| Code | Result |
|---|---|
{{ExampleArgs}}
|
firstInvokeArg |
{{ExampleArgs|firstTemplateArg}}
|
firstInvokeArg |
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}
|
firstInvokeArg |
- parentOnly
| Code | Result |
|---|---|
{{ExampleArgs}}
|
|
{{ExampleArgs|firstTemplateArg}}
|
firstTemplateArg |
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}
|
firstTemplateArg secondTemplateArg |
- parentFirst
| Code | Result |
|---|---|
{{ExampleArgs}}
|
firstInvokeArg |
{{ExampleArgs|firstTemplateArg}}
|
firstTemplateArg |
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}
|
firstTemplateArg secondTemplateArg |
Notes:
- If you set both the
frameOnlyandparentOnlyoptions, the module won't fetch any arguments at all from #invoke. This is probably not what you want. - In some situations a parent frame may not be available, e.g. if getArgs is passed the parent frame rather than the current frame. In this case, only the frame arguments will be used (unless parentOnly is set, in which case no arguments will be used) and the
parentFirstandframeOnlyoptions will have no effect.
Wrappers
[edit]The wrappers option is used to specify a limited number of templates as wrapper templates, that is, templates whose only purpose is to call a module. If the module detects that it is being called from a wrapper template, it will only check for arguments in the parent frame; otherwise it will only check for arguments in the frame passed to getArgs. This allows modules to be called by either #invoke or through a wrapper template without the loss of performance associated with having to check both the frame and the parent frame for each argument lookup.
For example, the only content of Template:Side box (excluding content in <noinclude>...</noinclude> tags) is {{#invoke:Side box|main}}. There is no point in checking the arguments passed directly to the #invoke statement for this template, as no arguments will ever be specified there. We can avoid checking arguments passed to #invoke by using the parentOnly option, but if we do this then #invoke will not work from other pages either. If this were the case, the |text=Some text in the code {{#invoke:Side box|main|text=Some text}} would be ignored completely, no matter what page it was used from. By using the wrappers option to specify 'Template:Side box' as a wrapper, we can make {{#invoke:Side box|main|text=Some text}} work from most pages, while still not requiring that the module check for arguments on the Template:Side box page itself.
Wrappers can be specified either as a string, or as an array of strings.
local args = getArgs(frame, {
wrappers = 'Template:Wrapper template'
})
local args = getArgs(frame, {
wrappers = {
'Template:Wrapper 1',
'Template:Wrapper 2',
-- Any number of wrapper templates can be added here.
}
})
The wrappers option changes the default behaviors of the frameOnly and parentOnly options.
Behaviors of frameOnly and parentOnly in relations with wrapper templates
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
The frame arguments will not be used at all.
|
Notes:
- The module will automatically detect if it is being called from a wrapper template's /sandbox subpage, so there is no need to specify sandbox pages explicitly.
- If the wrappers option is set and no parent frame is available, the module will always get the arguments from the frame passed to
getArgs.
Writing to the args table
[edit]Sometimes it can be useful to write new values to the args table. This is possible with the default settings of this module. (However, bear in mind that it is usually better coding style to create a new table with your new values and copy arguments from the args table as needed.)
args.foo = 'some value'
It is possible to alter this behaviour with the readOnly and noOverwrite options. If readOnly is set then it is not possible to write any values to the args table at all. If noOverwrite is set, then it is possible to add new values to the table, but it is not possible to add a value if it would overwrite any arguments that are passed from #invoke.
Notes
[edit]Ref tags
[edit]This module uses metatables to fetch arguments from #invoke. This allows access to both the frame arguments and the parent frame arguments without using the pairs() function. This can help if your module might be passed <ref>...</ref> tags as input.
As soon as <ref>...</ref> tags are accessed from Lua, they are processed by the MediaWiki software and the reference will appear in the reference list at the bottom of the article. If your module proceeds to omit the reference tag from the output, you will end up with a phantom reference – a reference that appears in the reference list but without any number linking to it. This has been a problem with modules that use pairs() to detect whether to use the arguments from the frame or the parent frame, as those modules automatically process every available argument.
This module solves this problem by allowing access to both frame and parent frame arguments, while still only fetching those arguments when it is necessary. The problem will still occur if you use pairs(args) elsewhere in your module, however.
Known limitations
[edit]The use of metatables also has its downsides. Most of the normal Lua table tools won't work properly on the args table, including the # operator, the next() function, and the functions in the table library. If using these is important for your module, you should use your own argument processing function instead of this module.
See also
[edit]
-- This module provides easy processing of arguments passed to Scribunto from
-- #invoke. It is intended for use by other Lua modules, and should not be
-- called from #invoke directly.
local libraryUtil = require('libraryUtil')
local checkType = libraryUtil.checkType
local arguments = {}
-- Generate four different tidyVal functions, so that we don't have to check the
-- options every time we call it.
local function tidyValDefault(key, val)
if type(val) == 'string' then
val = val:match('^%s*(.-)%s*$')
if val == '' then
return nil
else
return val
end
else
return val
end
end
local function tidyValTrimOnly(key, val)
if type(val) == 'string' then
return val:match('^%s*(.-)%s*$')
else
return val
end
end
local function tidyValRemoveBlanksOnly(key, val)
if type(val) == 'string' then
if val:find('%S') then
return val
else
return nil
end
else
return val
end
end
local function tidyValNoChange(key, val)
return val
end
local function matchesTitle(given, title)
local tp = type( given )
return (tp == 'string' or tp == 'number') and mw.title.new( given ).prefixedText == title
end
local translate_mt = { __index = function(t, k) return k end }
function arguments.getArgs(frame, options)
checkType('getArgs', 1, frame, 'table', true)
checkType('getArgs', 2, options, 'table', true)
frame = frame or {}
options = options or {}
--[[
-- Set up argument translation.
--]]
options.translate = options.translate or {}
if getmetatable(options.translate) == nil then
setmetatable(options.translate, translate_mt)
end
if options.backtranslate == nil then
options.backtranslate = {}
for k,v in pairs(options.translate) do
options.backtranslate[v] = k
end
end
if options.backtranslate and getmetatable(options.backtranslate) == nil then
setmetatable(options.backtranslate, {
__index = function(t, k)
if options.translate[k] ~= k then
return nil
else
return k
end
end
})
end
--[[
-- Get the argument tables. If we were passed a valid frame object, get the
-- frame arguments (fargs) and the parent frame arguments (pargs), depending
-- on the options set and on the parent frame's availability. If we weren't
-- passed a valid frame object, we are being called from another Lua module
-- or from the debug console, so assume that we were passed a table of args
-- directly, and assign it to a new variable (luaArgs).
--]]
local fargs, pargs, luaArgs
if type(frame.args) == 'table' and type(frame.getParent) == 'function' then
if options.wrappers then
--[[
-- The wrappers option makes Module:Arguments look up arguments in
-- either the frame argument table or the parent argument table, but
-- not both. This means that users can use either the #invoke syntax
-- or a wrapper template without the loss of performance associated
-- with looking arguments up in both the frame and the parent frame.
-- Module:Arguments will look up arguments in the parent frame
-- if it finds the parent frame's title in options.wrapper;
-- otherwise it will look up arguments in the frame object passed
-- to getArgs.
--]]
local parent = frame:getParent()
if not parent then
fargs = frame.args
else
local title = parent:getTitle():gsub('/sandbox$', '')
local found = false
if matchesTitle(options.wrappers, title) then
found = true
elseif type(options.wrappers) == 'table' then
for _,v in pairs(options.wrappers) do
if matchesTitle(v, title) then
found = true
break
end
end
end
-- We test for false specifically here so that nil (the default) acts like true.
if found or options.frameOnly == false then
pargs = parent.args
end
if not found or options.parentOnly == false then
fargs = frame.args
end
end
else
-- options.wrapper isn't set, so check the other options.
if not options.parentOnly then
fargs = frame.args
end
if not options.frameOnly then
local parent = frame:getParent()
pargs = parent and parent.args or nil
end
end
if options.parentFirst then
fargs, pargs = pargs, fargs
end
else
luaArgs = frame
end
-- Set the order of precedence of the argument tables. If the variables are
-- nil, nothing will be added to the table, which is how we avoid clashes
-- between the frame/parent args and the Lua args.
local argTables = {fargs}
argTables[#argTables + 1] = pargs
argTables[#argTables + 1] = luaArgs
--[[
-- Generate the tidyVal function. If it has been specified by the user, we
-- use that; if not, we choose one of four functions depending on the
-- options chosen. This is so that we don't have to call the options table
-- every time the function is called.
--]]
local tidyVal = options.valueFunc
if tidyVal then
if type(tidyVal) ~= 'function' then
error(
"bad value assigned to option 'valueFunc'"
.. '(function expected, got '
.. type(tidyVal)
.. ')',
2
)
end
elseif options.trim ~= false then
if options.removeBlanks ~= false then
tidyVal = tidyValDefault
else
tidyVal = tidyValTrimOnly
end
else
if options.removeBlanks ~= false then
tidyVal = tidyValRemoveBlanksOnly
else
tidyVal = tidyValNoChange
end
end
--[[
-- Set up the args, metaArgs and nilArgs tables. args will be the one
-- accessed from functions, and metaArgs will hold the actual arguments. Nil
-- arguments are memoized in nilArgs, and the metatable connects all of them
-- together.
--]]
local args, metaArgs, nilArgs, metatable = {}, {}, {}, {}
setmetatable(args, metatable)
local function mergeArgs(tables)
--[[
-- Accepts multiple tables as input and merges their keys and values
-- into one table. If a value is already present it is not overwritten;
-- tables listed earlier have precedence. We are also memoizing nil
-- values, which can be overwritten if they are 's' (soft).
--]]
for _, t in ipairs(tables) do
for key, val in pairs(t) do
if metaArgs[key] == nil and nilArgs[key] ~= 'h' then
local tidiedVal = tidyVal(key, val)
if tidiedVal == nil then
nilArgs[key] = 's'
else
metaArgs[key] = tidiedVal
end
end
end
end
end
--[[
-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
-- and are only fetched from the argument tables once. Fetching arguments
-- from the argument tables is the most resource-intensive step in this
-- module, so we try and avoid it where possible. For this reason, nil
-- arguments are also memoized, in the nilArgs table. Also, we keep a record
-- in the metatable of when pairs and ipairs have been called, so we do not
-- run pairs and ipairs on the argument tables more than once. We also do
-- not run ipairs on fargs and pargs if pairs has already been run, as all
-- the arguments will already have been copied over.
--]]
metatable.__index = function (t, key)
--[[
-- Fetches an argument when the args table is indexed. First we check
-- to see if the value is memoized, and if not we try and fetch it from
-- the argument tables. When we check memoization, we need to check
-- metaArgs before nilArgs, as both can be non-nil at the same time.
-- If the argument is not present in metaArgs, we also check whether
-- pairs has been run yet. If pairs has already been run, we return nil.
-- This is because all the arguments will have already been copied into
-- metaArgs by the mergeArgs function, meaning that any other arguments
-- must be nil.
--]]
if type(key) == 'string' then
key = options.translate[key]
end
local val = metaArgs[key]
if val ~= nil then
return val
elseif metatable.donePairs or nilArgs[key] then
return nil
end
for _, argTable in ipairs(argTables) do
local argTableVal = tidyVal(key, argTable[key])
if argTableVal ~= nil then
metaArgs[key] = argTableVal
return argTableVal
end
end
nilArgs[key] = 'h'
return nil
end
metatable.__newindex = function (t, key, val)
-- This function is called when a module tries to add a new value to the
-- args table, or tries to change an existing value.
if type(key) == 'string' then
key = options.translate[key]
end
if options.readOnly then
error(
'could not write to argument table key "'
.. tostring(key)
.. '"; the table is read-only',
2
)
elseif options.noOverwrite and args[key] ~= nil then
error(
'could not write to argument table key "'
.. tostring(key)
.. '"; overwriting existing arguments is not permitted',
2
)
elseif val == nil then
--[[
-- If the argument is to be overwritten with nil, we need to erase
-- the value in metaArgs, so that __index, __pairs and __ipairs do
-- not use a previous existing value, if present; and we also need
-- to memoize the nil in nilArgs, so that the value isn't looked
-- up in the argument tables if it is accessed again.
--]]
metaArgs[key] = nil
nilArgs[key] = 'h'
else
metaArgs[key] = val
end
end
local function translatenext(invariant)
local k, v = next(invariant.t, invariant.k)
invariant.k = k
if k == nil then
return nil
elseif type(k) ~= 'string' or not options.backtranslate then
return k, v
else
local backtranslate = options.backtranslate[k]
if backtranslate == nil then
-- Skip this one. This is a tail call, so this won't cause stack overflow
return translatenext(invariant)
else
return backtranslate, v
end
end
end
metatable.__pairs = function ()
-- Called when pairs is run on the args table.
if not metatable.donePairs then
mergeArgs(argTables)
metatable.donePairs = true
end
return translatenext, { t = metaArgs }
end
local function inext(t, i)
-- This uses our __index metamethod
local v = t[i + 1]
if v ~= nil then
return i + 1, v
end
end
metatable.__ipairs = function (t)
-- Called when ipairs is run on the args table.
return inext, t, 0
end
return args
end
return arguments