Difference between revisions of "Module:Arguments"

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-- 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
 

Revision as of 17:13, 22 May 2016

Documentation for this module may be created at Module:Arguments/doc