Modul:Arguments
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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 variableargs
is 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 thetrim
andremoveBlanks
arguments 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 thevalueFunc
option. The input to this option must be a function that takes two parameters,key
andvalue
,and returns a single value. This value is what you will get when you access the fieldkey
in theargs
table.
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 typestring
ornil
.This might be the case if you use thegetArgs
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 havep.main
andp._main
functions, or something similar).
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 thevalueFunc
function is called more or less every time an argument is requested from theargs
table, 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 theargs
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 calledModule:ExampleArgs
.This module prints the first two positional arguments that it is passed.
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:ExampleArgs
is 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
,parentOnly
andparentFirst
.If you setframeOnly
then only arguments passed from the current frame will be accepted; if you setparentOnly
then only arguments passed from the parent frame will be accepted; and if you setparentFirst
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 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 theframeOnly
andparentOnly
options, 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 thereadOnly
andnoOverwrite
options. IfreadOnly
is set then it is not possible to write any values to the args table at all. IfnoOverwrite
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
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.
-- 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.
locallibraryUtil=require('libraryUtil')
localcheckType=libraryUtil.checkType
localarguments={}
-- Generate four different tidyVal functions, so that we don't have to check the
-- options every time we call it.
localfunctiontidyValDefault(key,val)
iftype(val)=='string'then
val=val:match('^%s*(.-)%s*$')
ifval==''then
returnnil
else
returnval
end
else
returnval
end
end
localfunctiontidyValTrimOnly(key,val)
iftype(val)=='string'then
returnval:match('^%s*(.-)%s*$')
else
returnval
end
end
localfunctiontidyValRemoveBlanksOnly(key,val)
iftype(val)=='string'then
ifval:find('%S')then
returnval
else
returnnil
end
else
returnval
end
end
localfunctiontidyValNoChange(key,val)
returnval
end
localfunctionmatchesTitle(given,title)
localtp=type(given)
return(tp=='string'ortp=='number')andmw.title.new(given).prefixedText==title
end
localtranslate_mt={__index=function(t,k)returnkend}
functionarguments.getArgs(frame,options)
checkType('getArgs',1,frame,'table',true)
checkType('getArgs',2,options,'table',true)
frame=frameor{}
options=optionsor{}
--[[
-- Set up argument translation.
--]]
options.translate=options.translateor{}
ifgetmetatable(options.translate)==nilthen
setmetatable(options.translate,translate_mt)
end
ifoptions.backtranslate==nilthen
options.backtranslate={}
fork,vinpairs(options.translate)do
options.backtranslate[v]=k
end
end
ifoptions.backtranslateandgetmetatable(options.backtranslate)==nilthen
setmetatable(options.backtranslate,{
__index=function(t,k)
ifoptions.translate[k]~=kthen
returnnil
else
returnk
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).
--]]
localfargs,pargs,luaArgs
iftype(frame.args)=='table'andtype(frame.getParent)=='function'then
ifoptions.wrappersthen
--[[
-- 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.
--]]
localparent=frame:getParent()
ifnotparentthen
fargs=frame.args
else
localtitle=parent:getTitle():gsub('/sandbox$','')
localfound=false
ifmatchesTitle(options.wrappers,title)then
found=true
elseiftype(options.wrappers)=='table'then
for_,vinpairs(options.wrappers)do
ifmatchesTitle(v,title)then
found=true
break
end
end
end
-- We test for false specifically here so that nil (the default) acts like true.
iffoundoroptions.frameOnly==falsethen
pargs=parent.args
end
ifnotfoundoroptions.parentOnly==falsethen
fargs=frame.args
end
end
else
-- options.wrapper isn't set, so check the other options.
ifnotoptions.parentOnlythen
fargs=frame.args
end
ifnotoptions.frameOnlythen
localparent=frame:getParent()
pargs=parentandparent.argsornil
end
end
ifoptions.parentFirstthen
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.
localargTables={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.
--]]
localtidyVal=options.valueFunc
iftidyValthen
iftype(tidyVal)~='function'then
error(
"bad value assigned to option 'valueFunc'"
..'(function expected, got '
..type(tidyVal)
..')',
2
)
end
elseifoptions.trim~=falsethen
ifoptions.removeBlanks~=falsethen
tidyVal=tidyValDefault
else
tidyVal=tidyValTrimOnly
end
else
ifoptions.removeBlanks~=falsethen
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.
--]]
localargs,metaArgs,nilArgs,metatable={},{},{},{}
setmetatable(args,metatable)
localfunctionmergeArgs(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_,tinipairs(tables)do
forkey,valinpairs(t)do
ifmetaArgs[key]==nilandnilArgs[key]~='h'then
localtidiedVal=tidyVal(key,val)
iftidiedVal==nilthen
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.
--]]
iftype(key)=='string'then
key=options.translate[key]
end
localval=metaArgs[key]
ifval~=nilthen
returnval
elseifmetatable.donePairsornilArgs[key]then
returnnil
end
for_,argTableinipairs(argTables)do
localargTableVal=tidyVal(key,argTable[key])
ifargTableVal~=nilthen
metaArgs[key]=argTableVal
returnargTableVal
end
end
nilArgs[key]='h'
returnnil
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.
iftype(key)=='string'then
key=options.translate[key]
end
ifoptions.readOnlythen
error(
'could not write to argument table key "'
..tostring(key)
..' "; the table is read-only',
2
)
elseifoptions.noOverwriteandargs[key]~=nilthen
error(
'could not write to argument table key "'
..tostring(key)
..' "; overwriting existing arguments is not permitted',
2
)
elseifval==nilthen
--[[
-- 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
localfunctiontranslatenext(invariant)
localk,v=next(invariant.t,invariant.k)
invariant.k=k
ifk==nilthen
returnnil
elseiftype(k)~='string'ornotoptions.backtranslatethen
returnk,v
else
localbacktranslate=options.backtranslate[k]
ifbacktranslate==nilthen
-- Skip this one. This is a tail call, so this won't cause stack overflow
returntranslatenext(invariant)
else
returnbacktranslate,v
end
end
end
metatable.__pairs=function()
-- Called when pairs is run on the args table.
ifnotmetatable.donePairsthen
mergeArgs(argTables)
metatable.donePairs=true
end
returntranslatenext,{t=metaArgs}
end
localfunctioninext(t,i)
-- This uses our __index metamethod
localv=t[i+1]
ifv~=nilthen
returni+1,v
end
end
metatable.__ipairs=function(t)
-- Called when ipairs is run on the args table.
returninext,t,0
end
returnargs
end
returnarguments