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< Module:Arguments
This is a documentation subpage for Module:Arguments.
It contains usage information, categories and other content that is not part of the original module page.
This Lua module is used in system messages, and on approximately 28,400,000 pages, or roughly 52% 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 subject to page protection. It is a highly visible module in use by a very large number of pages, or is substituted very frequently. Because vandalism or mistakes would affect many pages, and even trivial editing might cause substantial load on the servers, it is protected from editing.
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. Its features include:
1Basic use
1.1Recommended practice
1.2Multiple functions
1.4Trimming and removing blanks
1.5Custom formatting of arguments
1.6Frames and parent frames
1.8Writing to the args table
1.9Ref tags
1.10Known limitations
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 function just for processing arguments from #invoke. This means that if someone calls your module from another Lua module you don't have to have a frame object available, which improves performance.
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
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 and removing blanks​[​edit​]
Blank arguments often trip up coders new to converting MediaWiki templates to Lua. In template syntax, blank strings and strings consisting only of whitespace are considered false. However, in Lua, blank strings and strings consisting of whitespace are considered true. This means that if you don't pay attention to such arguments when you write your Lua modules, you might treat something as true that should actually be treated as false. To avoid this, by default this module removes all blank arguments.
Similarly, whitespace can cause problems when dealing with positional arguments. Although whitespace is trimmed for named arguments coming from #invoke, it is preserved for positional arguments. Most of the time this additional whitespace is not desired, so this module trims it off by default.
However, sometimes you want to use blank arguments as input, and sometimes you want to keep additional whitespace. This can be necessary to convert some templates exactly as they were written. If you want to do this, you can set the trim and removeBlanks arguments to false.
local args = getArgs​(​frame​, { trim = false, removeBlanks = false})
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, but trims all other arguments 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 arguments 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
Module:ExampleArgs is then called by Template:ExampleArgs​, which contains the code {{#invoke:ExampleArgs|main|firstInvokeArg}}​. This produces the result "firstInvokeArg".
Now if we were to call Template:ExampleArgs​, the following would happen:
{{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​:
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}firstTemplateArg secondTemplateArg
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}firstTemplateArg secondTemplateArg
  1. If you set both the frameOnly and parentOnly options, the module won't fetch any arguments at all from #invoke. This is probably not what you want.
  2. 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 parentFirst and frameOnly options will have no effect.
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. }})
  1. 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.
  2. The wrappers option effectively changes the default of the frameOnly and parentOnly options. If, for example, parentOnly were explicitly set to 0 with wrappers set, calls via wrapper templates would result in both frame and parent arguments being loaded, though calls not via wrapper templates would result in only frame arguments being loaded.
  3. 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.) = '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.
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.
This page was last edited on 21 April 2021, at 08:14 (UTC).
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