Difference between revisions of "Module:Arguments"

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-- This module provides easy processing of arguments passed to Scribunto from
 
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-- #invoke. It is intended for use by other Lua modules, and should not be
 
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-- called from #invoke directly.
 
  
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local libraryUtil = require('libraryUtil')
 
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local checkType = libraryUtil.checkType
 
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local arguments = {}
 
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-- Generate four different tidyVal functions, so that we don't have to check the
 
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-- options every time we call it.
 
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local function tidyValDefault(key, val)
 
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if type(val) == 'string' then
 
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val = val:match('^%s*(.-)%s*$')
 
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if val == '' then
 
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return nil
 
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else
 
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return val
 
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end
 
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else
 
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return val
 
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end
 
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end
 
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local function tidyValTrimOnly(key, val)
 
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if type(val) == 'string' then
 
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return val:match('^%s*(.-)%s*$')
 
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else
 
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return val
 
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end
 
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end
 
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local function tidyValRemoveBlanksOnly(key, val)
 
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if type(val) == 'string' then
 
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if val:find('%S') then
 
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return val
 
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else
 
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return nil
 
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end
 
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else
 
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return val
 
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end
 
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end
 
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local function tidyValNoChange(key, val)
 
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return val
 
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end
 
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local function matchesTitle(given, title)
 
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local tp = type( given )
 
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return (tp == 'string' or tp == 'number') and mw.title.new( given ).prefixedText == title
 
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end
 
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local translate_mt = { __index = function(t, k) return k end }
 
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function arguments.getArgs(frame, options)
 
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checkType('getArgs', 1, frame, 'table', true)
 
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checkType('getArgs', 2, options, 'table', true)
 
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frame = frame or {}
 
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options = options or {}
 
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--[[
 
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-- Set up argument translation.
 
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--]]
 
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options.translate = options.translate or {}
 
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if getmetatable(options.translate) == nil then
 
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setmetatable(options.translate, translate_mt)
 
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end
 
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if options.backtranslate == nil then
 
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options.backtranslate = {}
 
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for k,v in pairs(options.translate) do
 
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options.backtranslate[v] = k
 
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end
 
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end
 
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if options.backtranslate and getmetatable(options.backtranslate) == nil then
 
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setmetatable(options.backtranslate, {
 
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__index = function(t, k)
 
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if options.translate[k] ~= k then
 
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return nil
 
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else
 
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return k
 
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end
 
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end
 
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})
 
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end
 
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--[[
 
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-- Get the argument tables. If we were passed a valid frame object, get the
 
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-- frame arguments (fargs) and the parent frame arguments (pargs), depending
 
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-- on the options set and on the parent frame's availability. If we weren't
 
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-- passed a valid frame object, we are being called from another Lua module
 
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-- or from the debug console, so assume that we were passed a table of args
 
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-- directly, and assign it to a new variable (luaArgs).
 
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--]]
 
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local fargs, pargs, luaArgs
 
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if type(frame.args) == 'table' and type(frame.getParent) == 'function' then
 
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if options.wrappers then
 
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--[[
 
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-- The wrappers option makes Module:Arguments look up arguments in
 
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-- either the frame argument table or the parent argument table, but
 
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-- not both. This means that users can use either the #invoke syntax
 
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-- or a wrapper template without the loss of performance associated
 
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-- with looking arguments up in both the frame and the parent frame.
 
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-- Module:Arguments will look up arguments in the parent frame
 
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-- if it finds the parent frame's title in options.wrapper;
 
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-- otherwise it will look up arguments in the frame object passed
 
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-- to getArgs.
 
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--]]
 
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local parent = frame:getParent()
 
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if not parent then
 
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fargs = frame.args
 
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else
 
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local title = parent:getTitle():gsub('/sandbox$', '')
 
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local found = false
 
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if matchesTitle(options.wrappers, title) then
 
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found = true
 
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elseif type(options.wrappers) == 'table' then
 
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for _,v in pairs(options.wrappers) do
 
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if matchesTitle(v, title) then
 
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found = true
 
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break
 
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end
 
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end
 
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end
 
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-- We test for false specifically here so that nil (the default) acts like true.
 
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if found or options.frameOnly == false then
 
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pargs = parent.args
 
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end
 
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if not found or options.parentOnly == false then
 
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fargs = frame.args
 
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end
 
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end
 
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else
 
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-- options.wrapper isn't set, so check the other options.
 
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if not options.parentOnly then
 
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fargs = frame.args
 
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end
 
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if not options.frameOnly then
 
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local parent = frame:getParent()
 
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pargs = parent and parent.args or nil
 
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end
 
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end
 
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if options.parentFirst then
 
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fargs, pargs = pargs, fargs
 
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end
 
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else
 
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luaArgs = frame
 
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end
 
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-- Set the order of precedence of the argument tables. If the variables are
 
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-- nil, nothing will be added to the table, which is how we avoid clashes
 
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-- between the frame/parent args and the Lua args.
 
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local argTables = {fargs}
 
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argTables[#argTables + 1] = pargs
 
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argTables[#argTables + 1] = luaArgs
 
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--[[
 
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-- Generate the tidyVal function. If it has been specified by the user, we
 
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-- use that; if not, we choose one of four functions depending on the
 
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-- options chosen. This is so that we don't have to call the options table
 
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-- every time the function is called.
 
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--]]
 
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local tidyVal = options.valueFunc
 
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if tidyVal then
 
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if type(tidyVal) ~= 'function' then
 
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error(
 
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"bad value assigned to option 'valueFunc'"
 
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.. '(function expected, got '
 
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.. type(tidyVal)
 
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.. ')',
 
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2
 
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)
 
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end
 
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elseif options.trim ~= false then
 
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if options.removeBlanks ~= false then
 
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tidyVal = tidyValDefault
 
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else
 
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tidyVal = tidyValTrimOnly
 
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end
 
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else
 
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if options.removeBlanks ~= false then
 
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tidyVal = tidyValRemoveBlanksOnly
 
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else
 
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tidyVal = tidyValNoChange
 
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end
 
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end
 
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--[[
 
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-- Set up the args, metaArgs and nilArgs tables. args will be the one
 
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-- accessed from functions, and metaArgs will hold the actual arguments. Nil
 
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-- arguments are memoized in nilArgs, and the metatable connects all of them
 
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-- together.
 
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--]]
 
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local args, metaArgs, nilArgs, metatable = {}, {}, {}, {}
 
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setmetatable(args, metatable)
 
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local function mergeArgs(tables)
 
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--[[
 
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-- Accepts multiple tables as input and merges their keys and values
 
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-- into one table. If a value is already present it is not overwritten;
 
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-- tables listed earlier have precedence. We are also memoizing nil
 
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-- values, which can be overwritten if they are 's' (soft).
 
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--]]
 
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for _, t in ipairs(tables) do
 
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for key, val in pairs(t) do
 
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if metaArgs[key] == nil and nilArgs[key] ~= 'h' then
 
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local tidiedVal = tidyVal(key, val)
 
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if tidiedVal == nil then
 
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nilArgs[key] = 's'
 
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else
 
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metaArgs[key] = tidiedVal
 
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end
 
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end
 
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end
 
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end
 
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end
 
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--[[
 
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-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
 
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-- and are only fetched from the argument tables once. Fetching arguments
 
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-- from the argument tables is the most resource-intensive step in this
 
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-- module, so we try and avoid it where possible. For this reason, nil
 
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-- arguments are also memoized, in the nilArgs table. Also, we keep a record
 
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-- in the metatable of when pairs and ipairs have been called, so we do not
 
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-- run pairs and ipairs on the argument tables more than once. We also do
 
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-- not run ipairs on fargs and pargs if pairs has already been run, as all
 
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-- the arguments will already have been copied over.
 
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--]]
 
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metatable.__index = function (t, key)
 
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--[[
 
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-- Fetches an argument when the args table is indexed. First we check
 
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-- to see if the value is memoized, and if not we try and fetch it from
 
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-- the argument tables. When we check memoization, we need to check
 
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-- metaArgs before nilArgs, as both can be non-nil at the same time.
 
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-- If the argument is not present in metaArgs, we also check whether
 
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-- pairs has been run yet. If pairs has already been run, we return nil.
 
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-- This is because all the arguments will have already been copied into
 
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-- metaArgs by the mergeArgs function, meaning that any other arguments
 
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-- must be nil.
 
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--]]
 
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if type(key) == 'string' then
 
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key = options.translate[key]
 
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end
 
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local val = metaArgs[key]
 
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if val ~= nil then
 
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return val
 
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elseif metatable.donePairs or nilArgs[key] then
 
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return nil
 
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end
 
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for _, argTable in ipairs(argTables) do
 
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local argTableVal = tidyVal(key, argTable[key])
 
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if argTableVal ~= nil then
 
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metaArgs[key] = argTableVal
 
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return argTableVal
 
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end
 
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end
 
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nilArgs[key] = 'h'
 
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return nil
 
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end
 
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metatable.__newindex = function (t, key, val)
 
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-- This function is called when a module tries to add a new value to the
 
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-- args table, or tries to change an existing value.
 
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if type(key) == 'string' then
 
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key = options.translate[key]
 
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end
 
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if options.readOnly then
 
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error(
 
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'could not write to argument table key "'
 
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.. tostring(key)
 
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.. '"; the table is read-only',
 
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2
 
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)
 
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elseif options.noOverwrite and args[key] ~= nil then
 
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error(
 
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'could not write to argument table key "'
 
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.. tostring(key)
 
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.. '"; overwriting existing arguments is not permitted',
 
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2
 
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)
 
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elseif val == nil then
 
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--[[
 
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-- If the argument is to be overwritten with nil, we need to erase
 
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-- the value in metaArgs, so that __index, __pairs and __ipairs do
 
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-- not use a previous existing value, if present; and we also need
 
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-- to memoize the nil in nilArgs, so that the value isn't looked
 
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-- up in the argument tables if it is accessed again.
 
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--]]
 
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metaArgs[key] = nil
 
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nilArgs[key] = 'h'
 
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else
 
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metaArgs[key] = val
 
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end
 
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end
 
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local function translatenext(invariant)
 
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local k, v = next(invariant.t, invariant.k)
 
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invariant.k = k
 
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if k == nil then
 
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return nil
 
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elseif type(k) ~= 'string' or not options.backtranslate then
 
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return k, v
 
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else
 
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local backtranslate = options.backtranslate[k]
 
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if backtranslate == nil then
 
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-- Skip this one. This is a tail call, so this won't cause stack overflow
 
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return translatenext(invariant)
 
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else
 
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return backtranslate, v
 
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end
 
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end
 
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end
 
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metatable.__pairs = function ()
 
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-- Called when pairs is run on the args table.
 
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if not metatable.donePairs then
 
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mergeArgs(argTables)
 
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metatable.donePairs = true
 
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end
 
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return translatenext, { t = metaArgs }
 
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end
 
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local function inext(t, i)
 
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-- This uses our __index metamethod
 
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local v = t[i + 1]
 
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if v ~= nil then
 
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return i + 1, v
 
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end
 
−
end
 
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metatable.__ipairs = function (t)
 
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-- Called when ipairs is run on the args table.
 
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return inext, t, 0
 
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end
 
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return args
 
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end
 
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return arguments
 

Revision as of 10:13, 22 May 2016

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