TEPwiki

Module:Arguments: Difference between revisions

Module Discussion

Module:Arguments (view source)

Revision as of 05:30, 18 April 2014

546 bytes added ,  10 years ago
memoize nils using a separate nilArgs table; this fixes a bug where nil values were being iterated over with pairs()
(fix undefined next() behaviour bug by checking for metatable.donePairs in the __index metamethod; also, format the module so it fits into 80 characters)
(memoize nils using a separate nilArgs table; this fixes a bug where nil values were being iterated over with pairs())
Line 7:
 
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
Line 76 ⟶ 74:
luaArgs = frame
end
 
-- Set up the argsorder andof metaArgsprecedence tables.of argsthe willargument betables. theIf onethe accessedvariables fromare
-- functionsnil, and metaArgsnothing will holdbe added to the actualtable, which is how arguments.we Theavoid metatableclashes
-- connectsbetween the twoframe/parent togetherargs and the Lua args.
local args, metaArgs, metatableargTables = {}, {}, {fargs}
argTables[#argTables + 1] = pargs▼
setmetatable(args, metatable)▼
argTables[#argTables + 1] = luaArgs▼
 
--[[
Line 113 ⟶ 112:
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)
Line 124 ⟶ 132:
for _, t in ipairs(tables) do
for key, val in iterator(t) do
local metaArgsVal =if metaArgs[key] == nil then
if metaArgsVal == nil or metaArgsVal == nilArg then
local tidiedVal = tidyVal(key, val)
if tidiedVal == nil then
metaArgsnilArgs[key] = nilArgtrue
else
metaArgs[key] = tidiedVal
Line 136 ⟶ 143:
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. NilFetching arguments are
-- from the argument tables is the most resource-intensive step in this
-- also memoized using the nilArg variable in order to increase performance.
-- Alsomodule, so we keeptry aand recordavoid init thewhere metatablepossible. ofFor whenthis pairs and ipairsreason, havenil
-- arguments are also memoized, in the nilArgs table. Also, we keep a record
-- been called, so we do not run pairs and ipairs on fargs and pargs more
-- thanin once.the Wemetatable alsoof dowhen notpairs runand ipairs onhave fargsbeen andcalled, pargsso ifwe pairsdo hasnot
-- alreadyrun beenpairs run,and asipairs allon the argumentsargument tables more willthan alreadyonce. haveWe beenalso copieddo
-- not run ipairs on fargs and pargs if pairs has already been run, as all
-- over.
-- 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.
--]]
local val = metaArgs[key]
if metatable.donePairs or val ~= nil then
--[[return val
elseif metatable.donePairs or nilArgs[key] then
-- We have either memoized the argument already, or pairs has been
return nil▼
-- 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
metaArgsnilArgs[key] = nilArgtrue
else
metaArgs[key] = argTableVal
Line 186 ⟶ 187:
 
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 options.readOnly then
error(
Line 201 ⟶ 204:
)
elseif val == nil then
▲ else--[[
metaArgs[key] = nilArg -- Memoize nils.▼
-- 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.
▲ end--]]
metaArgs[key] = nil
▲ metaArgsnilArgs[key] = nilArgtrue -- Memoize nils.
else
metaArgs[key] = val
Line 208 ⟶ 219:
 
metatable.__pairs = function ()
-- Called when pairs is run on the args table.
if not metatable.donePairs then
mergeArgs(pairs, argTables)
Line 213 ⟶ 225:
metatable.doneIpairs = true
end
return function pairs(t, kmetaArgs)
local nk, val = next(metaArgs, k)
if val == nilArg then
▲ val = nil
end
return nk, val
end
end
 
metatable.__ipairs = function ()
-- Called when ipairs is run on the args table.
if not metatable.doneIpairs then
mergeArgs(ipairs, argTables)
metatable.doneIpairs = true
end
return function ipairs(t, imetaArgs)
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
 
Anonymous user
Retrieved from "https://tep.wiki/wiki/Special:MobileDiff/6247"