Module:Arguments: Difference between revisions

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Module:Arguments (view source)

Revision as of 15:45, 2 February 2015

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-- 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')
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local arguments = {}
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.
-- 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)
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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
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luaArgs = frame
luaArgs = frame
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


-- 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.
-- Generate the tidyVal function. If it has been specified by the user, we
local args, metaArgs, metatable = {}, {}, {}
-- use that; if not, we choose one of four functions depending on the
setmetatable(args, metatable)
-- 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
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end
end
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)
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
local metaArgsVal = metaArgs[key]
if metaArgs[key] == nil then
if metaArgsVal == nil or metaArgsVal == nilArg then
local tidiedVal = tidyVal(key, val)
local tidiedVal = tidyVal(key, val)
if tidiedVal == nil then
if tidiedVal == nil then
metaArgs[key] = nilArg
nilArgs[key] = true
else
else
metaArgs[key] = tidiedVal
metaArgs[key] = tidiedVal
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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
-- 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. Fetching arguments
-- performance. Also, we keep a record in the metatable of when pairs and ipairs have been called, so we
-- from the argument tables is the most resource-intensive step in this
-- do not run pairs and ipairs on fargs and pargs more than once. We also do not run ipairs on fargs and
-- module, so we try and avoid it where possible. For this reason, nil
-- pargs if pairs has already been run, as all the arguments will already have been copied over.
-- 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 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)
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]
local val = metaArgs[key]
if val ~= nil then
if val ~= nil then
if val == nilArg then
return val
return nil
elseif metatable.donePairs or nilArgs[key] then
else
return nil
return val
end
end
end
for _, argTable in ipairs(argTables) do
for _, argTable in ipairs(argTables) do
local argTableVal = tidyVal(key, argTable[key])
local argTableVal = tidyVal(key, argTable[key])
if argTableVal == nil then
if argTableVal == nil then
metaArgs[key] = nilArg
nilArgs[key] = true
else
else
metaArgs[key] = argTableVal
metaArgs[key] = argTableVal
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metatable.__newindex = function (t, key, val)
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
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.
--[[
-- 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] = true -- Memoize nils.
else
else
metaArgs[key] = val
metaArgs[key] = val
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metatable.__pairs = function ()
metatable.__pairs = function ()
-- Called when pairs is run on the args table.
if not metatable.donePairs then
if not metatable.donePairs then
mergeArgs(pairs, argTables)
mergeArgs(pairs, argTables)
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metatable.doneIpairs = true
metatable.doneIpairs = true
end
end
return function (t, k)
return pairs(metaArgs)
local nk, val = next(metaArgs, k)
if val == nilArg then
val = nil
end
return nk, val
end
end
end


metatable.__ipairs = function ()
metatable.__ipairs = function ()
-- Called when ipairs is run on the args table.
if not metatable.doneIpairs then
if not metatable.doneIpairs then
mergeArgs(ipairs, argTables)
mergeArgs(ipairs, argTables)
metatable.doneIpairs = true
metatable.doneIpairs = true
end
end
return function (t, i)
return ipairs(metaArgs)
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
end


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