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Difference between revisions of "Arguments"

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m (tweak one of the comments and make some beautification fixes, now that this is in the job queue)
(fix undefined next() behaviour bug by checking for metatable.donePairs in the __index metamethod; also, format the module so it fits into 80 characters)
Line 1: Line 1:
−
-- This module provides easy processing of arguments passed to Scribunto from #invoke.
+
-- This module provides easy processing of arguments passed to Scribunto from
−
-- It is intended for use by other Lua modules, and should not be called from #invoke directly.
+
-- #invoke. It is intended for use by other Lua modules, and should not be
 +
-- called from #invoke directly.
  
 
local libraryUtil = require('libraryUtil')
 
local libraryUtil = require('libraryUtil')
Line 9: Line 10:
 
local nilArg = {} -- Used for memoizing nil arguments in metaArgs.
 
local nilArg = {} -- Used for memoizing nil arguments in metaArgs.
  
−
-- Generate four different tidyVal functions, so that we don't have to check the options every time we call it.
+
-- 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)
 
local function tidyValDefault(key, val)
Line 54: Line 56:
 
options = options 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.
+
-- 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
 
local fargs, pargs, luaArgs
 
if type(frame.args) == 'table' and type(frame.getParent) == 'function' then
 
if type(frame.args) == 'table' and type(frame.getParent) == 'function' then
Line 71: Line 77:
 
end
 
end
  
−
-- Set up the args and metaArgs tables. args will be the one accessed from functions, and metaArgs will hold the actual arguments.
+
-- Set up the args and metaArgs tables. args will be the one accessed from
−
-- The metatable connects the two together.
+
-- functions, and metaArgs will hold the actual arguments. The metatable
 +
-- connects the two together.
 
local args, metaArgs, metatable = {}, {}, {}
 
local args, metaArgs, metatable = {}, {}, {}
 
setmetatable(args, metatable)
 
setmetatable(args, metatable)
  
−
-- 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.
+
-- 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
 
local tidyVal = options.valueFunc
 
if tidyVal then
 
if tidyVal then
 
if type(tidyVal) ~= 'function' then
 
if type(tidyVal) ~= 'function' then
−
error("bad value assigned to option 'valueFunc' (function expected, got " .. type(tidyVal) .. ')', 2)
+
error(
 +
"bad value assigned to option 'valueFunc'"
 +
.. '(function expected, got '
 +
.. type(tidyVal)
 +
.. ')',
 +
2
 +
)
 
end
 
end
 
elseif options.trim ~= false then
 
elseif options.trim ~= false then
Line 98: Line 115:
  
 
local function mergeArgs(iterator, tables)
 
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.
+
-- Accepts multiple tables as input and merges their keys and values
−
-- We are also memoizing nil values, but those values can be overwritten.
+
-- 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 _, t in ipairs(tables) do
 
for key, val in iterator(t) do
 
for key, val in iterator(t) do
Line 116: Line 137:
 
end
 
end
  
−
-- Set the order of precedence of the argument tables. If the variables are nil, nothing will be added to the table,
+
-- Set the order of precedence of the argument tables. If the variables are
−
-- which is how we avoid clashes between the frame/parent args and the Lua args.
+
-- 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}
 
local argTables = {fargs}
 
argTables[#argTables + 1] = pargs
 
argTables[#argTables + 1] = pargs
Line 123: Line 145:
  
 
--[[
 
--[[
−
-- Define metatable behaviour. Arguments are memoized in the metaArgs table, and are only fetched from the
+
-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
−
-- argument tables once. Nil arguments are also memoized using the nilArg variable in order to increase
+
-- and are only fetched from the argument tables once. Nil arguments are
−
-- performance. Also, we keep a record in the metatable of when pairs and ipairs have been called, so we
+
-- also memoized using the nilArg variable in order to increase performance.
−
-- do not run pairs and ipairs on fargs and pargs more than once. We also do not run ipairs on fargs and
+
-- Also, we keep a record in the metatable of when pairs and ipairs have
−
-- pargs if pairs has already been run, as all the arguments will already have been copied over.
+
-- 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)
 
metatable.__index = function (t, key)
 
local val = metaArgs[key]
 
local val = metaArgs[key]
−
if val ~= nil then
+
if metatable.donePairs or val ~= nil then
 +
--[[
 +
-- We have either memoized the argument already, or pairs has been
 +
-- called, meaning that mergeArgs has already copied all of the
 +
-- 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
 
if val == nilArg then
 
return nil
 
return nil
Line 153: Line 187:
 
metatable.__newindex = function (t, key, val)
 
metatable.__newindex = function (t, key, val)
 
if options.readOnly then
 
if options.readOnly then
−
error('could not write to argument table key "' .. tostring(key) .. '"; the table is read-only', 2)
+
error(
 +
'could not write to argument table key "'
 +
.. tostring(key)
 +
.. '"; the table is read-only',
 +
2
 +
)
 
elseif options.noOverwrite and args[key] ~= nil then
 
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)
+
error(
 +
'could not write to argument table key "'
 +
.. tostring(key)
 +
.. '"; overwriting existing arguments is not permitted',
 +
2
 +
)
 
elseif val == nil then
 
elseif val == nil then
 
metaArgs[key] = nilArg -- Memoize nils.
 
metaArgs[key] = nilArg -- Memoize nils.

Revision as of 02:10, 15 April 2014

Documentation for this module may be created at Module:Arguments/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 = {}

local nilArg = {} -- Used for memoizing nil arguments in metaArgs.

-- 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 up the args and metaArgs tables. args will be the one accessed from
	-- functions, and metaArgs will hold the actual arguments. The metatable
	-- connects the two together.
	local args, metaArgs, metatable = {}, {}, {}
	setmetatable(args, metatable)

	--[[
	-- 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

	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
				local metaArgsVal = metaArgs[key]
				if metaArgsVal == nil or metaArgsVal == nilArg then
					local tidiedVal = tidyVal(key, val)
					if tidiedVal == nil then
						metaArgs[key] = nilArg
					else
						metaArgs[key] = tidiedVal
					end
				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,
	-- and are only fetched from the argument tables once. Nil arguments are
	-- also memoized using the nilArg variable 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 metatable.donePairs or val ~= nil then
			--[[
			-- We have either memoized the argument already, or pairs has been
			-- called, meaning that mergeArgs has already copied all of the
			-- 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
		for _, argTable in ipairs(argTables) do
			local argTableVal = tidyVal(key, argTable[key])
			if argTableVal == nil then
				metaArgs[key] = nilArg
			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
			metaArgs[key] = nilArg -- 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 function (t, k)
			local nk, val = next(metaArgs, k)
			if val == nilArg then
				val = nil
			end
			return nk, val
		end
	end

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

	return args
end

return arguments
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