Modul:Arguments/dok

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:

• 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.
• Arguments are fetched as needed, which can help avoid (some) problems with<ref></ref>tags.
• Most features can be customized.

Basic use

First, you need to load the module. It contains one function, namedgetArgs.

localgetArgs=require('Module:Arguments').getArgs

In the most basic scenario, you can use getArgs inside your main function. The variableargsis a table containing the arguments from #invoke. (See below for details.)

localgetArgs=require('Module:Arguments').getArgs
localp={}

functionp.main(frame)
localargs=getArgs(frame)
-- Main module code goes here.
end

returnp

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.

localgetArgs=require('Module:Arguments').getArgs
localp={}

functionp.main(frame)
localargs=getArgs(frame)
returnp._main(args)
end

functionp._main(args)
-- Main module code goes here.
end

returnp

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.

localgetArgs=require('Module:Arguments').getArgs

localfunctionmakeInvokeFunc(funcName)
returnfunction(frame)
localargs=getArgs(frame)
returnp[funcName](args)
end
end

localp={}

p.func1=makeInvokeFunc('_func1')

functionp._func1(args)
-- Code for the first function goes here.
end

p.func2=makeInvokeFunc('_func2')

functionp._func2(args)
-- Code for the second function goes here.
end

returnp

Options

The following options are available. They are explained in the sections below.

localargs=getArgs(frame,{
trim=false,
removeBlanks=false,
valueFunc=function(key,value)
-- Code for processing one argument
end,
frameOnly=true,
parentOnly=true,
parentFirst=true,
readOnly=true,
noOverwrite=true
})

Trimming and removing blanks

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 thetrimandremoveBlanksarguments tofalse.

localargs=getArgs(frame,{
trim=false,
removeBlanks=false
})

Custom formatting of arguments

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 thevalueFuncoption. The input to this option must be a function that takes two parameters,keyandvalue,and returns a single value. This value is what you will get when you access the fieldkeyin theargstable.

Example 1: this function preserves whitespace for the first positional argument, but trims all other arguments and removes all other blank arguments.

localargs=getArgs(frame,{
valueFunc=function(key,value)
ifkey==1then
returnvalue
elseifvaluethen
value=mw.text.trim(value)
ifvalue~=''then
returnvalue
end
end
returnnil
end
})

Example 2: this function removes blank arguments and converts all arguments to lower case, but doesn't trim whitespace from positional parameters.

localargs=getArgs(frame,{
valueFunc=function(key,value)
ifnotvaluethen
returnnil
end
value=mw.ustring.lower(value)
ifmw.ustring.find(value,'%S')then
returnvalue
end
returnnil
end
})

Note: the above functions will fail if passed input that is not of typestringornil.This might be the case if you use thegetArgsfunction 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 havep.mainandp._mainfunctions, or something similar).

Examples 1 and 2 with type checking

Example 1:

localargs=getArgs(frame,{
valueFunc=function(key,value)
ifkey==1then
returnvalue
elseiftype(value)=='string'then
value=mw.text.trim(value)
ifvalue~=''then
returnvalue
else
returnnil
end
else
returnvalue
end
end
})

Example 2:

localargs=getArgs(frame,{
valueFunc=function(key,value)
iftype(value)=='string'then
value=mw.ustring.lower(value)
ifmw.ustring.find(value,'%S')then
returnvalue
else
returnnil
end
else
returnvalue
end
end
})

Also, please note that thevalueFuncfunction is called more or less every time an argument is requested from theargstable, so if you care about performance you should make sure you aren't doing anything inefficient with your code.

Frames and parent frames

Arguments in theargstable 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 calledModule:ExampleArgs.This module prints the first two positional arguments that it is passed.

Module:ExampleArgs code

localgetArgs=require('Module:Arguments').getArgs
localp={}

functionp.main(frame)
localargs=getArgs(frame)
returnp._main(args)
end

functionp._main(args)
localfirst=args[1]or''
localsecond=args[2]or''
returnfirst..' '..second
end

returnp

Module:ExampleArgsis then called byTemplate:ExampleArgs,which contains the code{{#invoke:ExampleArgs|main|firstInvokeArg}}.This produces the result "firstInvokeArg".

Now if we were to callTemplate:ExampleArgs,the following would happen:

Code	Result
{{ExampleArgs}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg}}	firstInvokeArg
{{ExampleArgs|firstTemplateArg|secondTemplateArg}}	firstInvokeArg secondTemplateArg

There are three options you can set to change this behaviour:frameOnly,parentOnlyandparentFirst.If you setframeOnlythen only arguments passed from the current frame will be accepted; if you setparentOnlythen only arguments passed from the parent frame will be accepted; and if you setparentFirstthen 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 ofTemplate: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

Note: if you set both theframeOnlyandparentOnlyoptions, the module won't fetch any arguments at all from #invoke. This is probably not what you want.

Writing to the args table

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 thereadOnlyandnoOverwriteoptions. IfreadOnlyis set then it is not possible to write any values to the args table at all. IfnoOverwriteis 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

This module usesmetatablesto fetch arguments from #invoke. This allows access to both the frame arguments and the parent frame arguments without using thepairs()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 no number that links to it. This has been a problem with modules that usepairs()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 usepairs(args)elsewhere in your module, however.

Known limitations

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, thenext()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.