Difference between revisions of "Module:Arguments/sandbox"

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blackwiki>Mr. Stradivarius
(add a comment to warn future coders about the pairs problem)
blackwiki>Mr. Stradivarius
(memoize nils to a separate nilArgs table)
Line 7: Line 7:
  
 
local arguments = {}
 
local arguments = {}
 
local nilArg = {} -- Used for memoizing nil arguments in metaArgs.
 
  
 
-- Generate four different tidyVal functions, so that we don't have to check the
 
-- Generate four different tidyVal functions, so that we don't have to check the
Line 76: Line 74:
 
luaArgs = frame
 
luaArgs = frame
 
end
 
end
 
+
-- Set up the args and metaArgs tables. args will be the one accessed from
+
-- Set the order of precedence of the argument tables. If the variables are
-- functions, and metaArgs will hold the actual arguments. The metatable
+
-- nil, nothing will be added to the table, which is how we avoid clashes
-- connects the two together.
+
-- between the frame/parent args and the Lua args.
local args, metaArgs, metatable = {}, {}, {}
+
local argTables = {fargs}
setmetatable(args, metatable)
+
argTables[#argTables + 1] = pargs
 +
argTables[#argTables + 1] = luaArgs
  
 
--[[
 
--[[
Line 113: Line 112:
 
end
 
end
 
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(iterator, tables)
 
local function mergeArgs(iterator, tables)
Line 124: Line 132:
 
for _, t in ipairs(tables) do
 
for _, t in ipairs(tables) do
 
for key, val in iterator(t) do
 
for key, val in iterator(t) do
local metaArgsVal = metaArgs[key]
+
if metaArgs[key] == nil then
if metaArgsVal == nil or metaArgsVal == nilArg then
 
 
local tidiedVal = tidyVal(key, val)
 
local tidiedVal = tidyVal(key, val)
 
if tidiedVal == nil then
 
if tidiedVal == nil then
metaArgs[key] = nilArg
+
nilArgs[key] = true
 
else
 
else
 
metaArgs[key] = tidiedVal
 
metaArgs[key] = tidiedVal
Line 136: Line 143:
 
end
 
end
 
end
 
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
 
  
 
--[[
 
--[[
 
-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
 
-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
 
-- and are only fetched from the argument tables once. Nil arguments are
 
-- and are only fetched from the argument tables once. Nil arguments are
-- also memoized using the nilArg variable in order to increase performance.
+
-- also memoized using the nilArgs table in order to increase performance.
 
-- Also, we keep a record in the metatable of when pairs and ipairs have
 
-- 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 fargs and pargs more
 
-- been called, so we do not run pairs and ipairs on fargs and pargs more
Line 157: Line 157:
 
metatable.__index = function (t, key)
 
metatable.__index = function (t, key)
 
local val = metaArgs[key]
 
local val = metaArgs[key]
if metatable.donePairs or val ~= nil then
+
if val ~= nil then
--[[
+
return val
-- We have either memoized the argument already, or pairs has been
+
elseif nilArgs[key] then
-- called, meaning that mergeArgs has already copied all of the
+
return nil
-- available arguments into the metaArgs table. We need to check for
 
-- pairs as we can't memoize nils to the metaArgs table while pairs
 
-- is iterating. Adding new instances of nilArg to the metaArgs
 
-- table while pairs is iterating over it produces undefined
 
-- behaviour in the next() function.
 
--]]
 
if val == nilArg then
 
return nil
 
else
 
return val
 
end
 
 
end
 
end
 
for _, argTable in ipairs(argTables) do
 
for _, argTable in ipairs(argTables) do
 
local argTableVal = tidyVal(key, argTable[key])
 
local argTableVal = tidyVal(key, argTable[key])
 
if argTableVal == nil then
 
if argTableVal == nil then
metaArgs[key] = nilArg
+
nilArgs[key] = true
 
else
 
else
 
metaArgs[key] = argTableVal
 
metaArgs[key] = argTableVal
Line 201: Line 190:
 
)
 
)
 
elseif val == nil then
 
elseif val == nil then
metaArgs[key] = nilArg -- Memoize nils.
+
nilArgs[key] = true -- Memoize nils.
 
else
 
else
 
metaArgs[key] = val
 
metaArgs[key] = val
Line 213: Line 202:
 
metatable.doneIpairs = true
 
metatable.doneIpairs = true
 
end
 
end
return function (t, k)
+
return pairs(metaArgs)
local nk, val = next(metaArgs, k)
 
if val == nilArg then
 
val = nil
 
end
 
return nk, val
 
end
 
 
end
 
end
  
Line 227: Line 210:
 
metatable.doneIpairs = true
 
metatable.doneIpairs = true
 
end
 
end
return function (t, i)
+
return ipairs(metaArgs)
local val = metaArgs[i + 1]
 
if val == nil then
 
return nil
 
elseif val == nilArg then
 
val = nil
 
end
 
return i + 1, val
 
end, nil, 0
 
 
end
 
end
  

Revision as of 20:10, 15 April 2014

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

-- 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

function arguments.getArgs(frame, options)
	checkType('getArgs', 1, frame, 'table', true)
	checkType('getArgs', 2, options, 'table', true)
	frame = frame or {}
	options = options or {}

	--[[
	-- Get the arguments from the frame object if available. If the frame object
	-- is not available, we are being called from another Lua module or from the
	-- debug console, so assign the args to a new variable so we can
	-- differentiate them.
	--]]
	local fargs, pargs, luaArgs
	if type(frame.args) == 'table' and type(frame.getParent) == 'function' then
		if not options.parentOnly then
			fargs = frame.args
		end
		if not options.frameOnly then
			pargs = frame:getParent().args
		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(iterator, tables)
		--[[
		-- Accepts multiple tables as input and merges their keys and values
		-- into one table using the specified iterator. If a value is already
		-- present it is not overwritten; tables listed earlier have precedence.
		-- We are also memoizing nil values, but those values can be
		-- overwritten.
		--]]
		for _, t in ipairs(tables) do
			for key, val in iterator(t) do
				if metaArgs[key] == nil then
					local tidiedVal = tidyVal(key, val)
					if tidiedVal == nil then
						nilArgs[key] = true
					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. Nil arguments are
	-- also memoized using the nilArgs table in order to increase performance.
	-- 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 fargs and pargs 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)
		local val = metaArgs[key]
		if val ~= nil then
			return val
		elseif nilArgs[key] then
			return nil
		end
		for _, argTable in ipairs(argTables) do
			local argTableVal = tidyVal(key, argTable[key])
			if argTableVal == nil then
				nilArgs[key] = true
			else
				metaArgs[key] = argTableVal
				return argTableVal
			end
		end
		return nil
	end

	metatable.__newindex = function (t, key, val)
		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
			nilArgs[key] = true -- Memoize nils.
		else
			metaArgs[key] = val
		end
	end

	metatable.__pairs = function ()
		if not metatable.donePairs then
			mergeArgs(pairs, argTables)
			metatable.donePairs = true
			metatable.doneIpairs = true
		end
		return pairs(metaArgs)
	end

	metatable.__ipairs = function ()
		if not metatable.doneIpairs then
			mergeArgs(ipairs, argTables)
			metatable.doneIpairs = true
		end
		return ipairs(metaArgs)
	end

	return args
end

return arguments