Module:Arguments: Difference between revisions
From Roses, Tulips, & Liberty
Content added Content deleted
(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()) |
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Line 7: | Line 7: | ||
local arguments = {} |
local arguments = {} |
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local nilArg = {} -- Used for memoizing nil arguments in metaArgs. |
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-- 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 |
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luaArgs = frame |
luaArgs = frame |
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end |
end |
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-- Set |
-- 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 |
local argTables = {fargs} |
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⚫ | |||
⚫ | |||
⚫ | |||
--[[ |
--[[ |
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end |
end |
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end |
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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⚫ | |||
local args, metaArgs, nilArgs, metatable = {}, {}, {}, {} |
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⚫ | |||
local function mergeArgs(iterator, tables) |
local function mergeArgs(iterator, tables) |
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for _, t in ipairs(tables) do |
for _, t in ipairs(tables) do |
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for key, val in iterator(t) do |
for key, val in iterator(t) do |
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if metaArgs[key] == nil then |
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if metaArgsVal == nil or metaArgsVal == nilArg then |
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local tidiedVal = tidyVal(key, val) |
local tidiedVal = tidyVal(key, val) |
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if tidiedVal == nil then |
if tidiedVal == nil then |
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nilArgs[key] = true |
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else |
else |
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metaArgs[key] = tidiedVal |
metaArgs[key] = tidiedVal |
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Line 136: | Line 143: | ||
end |
end |
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end |
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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⚫ | |||
⚫ | |||
--[[ |
--[[ |
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-- Define metatable behaviour. Arguments are memoized in the metaArgs table, |
-- Define metatable behaviour. Arguments are memoized in the metaArgs table, |
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-- and are only fetched from the argument tables once. |
-- 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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-- also memoized using the nilArg variable in order to increase performance. |
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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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-- been called, so we do not run pairs and ipairs on fargs and pargs more |
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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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-- over. |
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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) |
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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local val = metaArgs[key] |
local val = metaArgs[key] |
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if |
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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-- We have either memoized the argument already, or pairs has been |
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⚫ | |||
-- called, meaning that mergeArgs has already copied all of the |
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-- available arguments into the metaArgs table. We need to check for |
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-- pairs as we can't memoize nils to the metaArgs table while pairs |
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-- is iterating. Adding new instances of nilArg to the metaArgs |
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-- table while pairs is iterating over it produces undefined |
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-- behaviour in the next() function. |
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⚫ | |||
if val == nilArg then |
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⚫ | |||
⚫ | |||
return val |
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⚫ | |||
end |
end |
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for _, argTable in ipairs(argTables) do |
for _, argTable in ipairs(argTables) do |
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local argTableVal = tidyVal(key, argTable[key]) |
local argTableVal = tidyVal(key, argTable[key]) |
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if argTableVal == nil then |
if argTableVal == nil then |
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nilArgs[key] = true |
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else |
else |
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metaArgs[key] = argTableVal |
metaArgs[key] = argTableVal |
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Line 186: | Line 187: | ||
metatable.__newindex = function (t, key, val) |
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 options.readOnly then |
if options.readOnly then |
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error( |
error( |
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Line 201: | Line 204: | ||
) |
) |
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elseif val == nil then |
elseif val == nil then |
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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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⚫ | |||
metaArgs[key] = nil |
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else |
else |
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metaArgs[key] = val |
metaArgs[key] = val |
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Line 208: | Line 219: | ||
metatable.__pairs = function () |
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 |
if not metatable.donePairs then |
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mergeArgs(pairs, argTables) |
mergeArgs(pairs, argTables) |
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metatable.doneIpairs = true |
metatable.doneIpairs = true |
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end |
end |
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return |
return pairs(metaArgs) |
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local nk, val = next(metaArgs, k) |
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if val == nilArg then |
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⚫ | |||
end |
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return nk, val |
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end |
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end |
end |
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metatable.__ipairs = function () |
metatable.__ipairs = function () |
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-- Called when ipairs is run on the args table. |
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if not metatable.doneIpairs then |
if not metatable.doneIpairs then |
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mergeArgs(ipairs, argTables) |
mergeArgs(ipairs, argTables) |
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metatable.doneIpairs = true |
metatable.doneIpairs = true |
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end |
end |
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return |
return ipairs(metaArgs) |
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local val = metaArgs[i + 1] |
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if val == nil then |
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return nil |
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elseif val == nilArg then |
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val = nil |
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end |
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return i + 1, val |
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end, nil, 0 |
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end |
end |
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