Changes
memoize nils using a separate nilArgs table; this fixes a bug where nil values were being iterated over with pairs()
local arguments = {}
-- Generate four different tidyVal functions, so that we don't have to check the
luaArgs = frame
end
-- Set up the args and metaArgs order of precedence of the argument tables. args will be If the one accessed fromvariables are -- functionsnil, and metaArgs nothing will hold be added to the actual arguments. The metatabletable, which is how we avoid clashes -- connects between the two togetherframe/parent args and the Lua args. local args, metaArgs, metatable argTables = {fargs}, {}, {} setmetatable(args, metatable)argTables[#argTables + 1] = pargs argTables[#argTables + 1] = luaArgs
--[[
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)
for _, t in ipairs(tables) do
for key, val in iterator(t) do
local tidiedVal = tidyVal(key, val)
if tidiedVal == nil then
else
metaArgs[key] = tidiedVal
end
end
--[[
-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
-- and are only fetched from the argument tables once. Nil Fetching arguments are -- also memoized using from the argument tables is the nilArg variable most resource-intensive step in order to increase performancethis -- 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 fargs and pargs 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.
--]]
local val = metaArgs[key]
if metatable.donePairs or val ~= nil then --[[return val -- We have either memoized the argument already, elseif metatable.donePairs 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. --]nilArgs[key]then 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
else
metaArgs[key] = argTableVal
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(
)
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] = nilArg true -- Memoize nils.
else
metaArgs[key] = val
metatable.__pairs = function ()
-- Called when pairs is run on the args table.
if not metatable.donePairs then
mergeArgs(pairs, argTables)
metatable.doneIpairs = true
end
return function (t, k) local nk, val = nextpairs(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