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()) |
||
Line 7:
local arguments = {}
-- Generate four different tidyVal functions, so that we don't have to check the
Line 76 ⟶ 74:
luaArgs = frame
end
-- Set
--
--
local
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 tidiedVal = tidyVal(key, val)
if tidiedVal == nil then
else
metaArgs[key] = tidiedVal
Line 136 ⟶ 143:
end
end
▲ 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.
-- from the argument tables is the most resource-intensive step in this
--
-- arguments are also memoized, in the nilArgs table. Also, we keep a record
--
--
-- 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
elseif metatable.donePairs or nilArgs[key] then
▲ --]]
▲ return nil
else▼
end▼
end
for _, argTable in ipairs(argTables) do
local argTableVal = tidyVal(key, argTable[key])
if argTableVal == nil then
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
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.
metaArgs[key] = nil
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
▲ val = nil
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
end
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