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Module:Arguments: Difference between revisions
fix undefined next() behaviour bug by checking for metatable.donePairs in the __index metamethod; also, format the module so it fits into 80 characters
(Created page with "-- This module provides easy processing of arguments passed to Scribunto from #invoke. -- It is intended for use by other Lua modules, and should not be called from #invoke di...") |
(fix undefined next() behaviour bug by checking for metatable.donePairs in the __index metamethod; also, format the module so it fits into 80 characters) |
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Line 1:
-- This module provides easy processing of arguments passed to Scribunto from
-- #invoke. It is intended for use by other Lua modules, and should not be
-- called from #invoke directly.
local libraryUtil = require('libraryUtil')
local checkType = libraryUtil.checkType
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.
local function tidyValDefault(key, val)
if type(val) == 'string' then
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end
end
local function tidyValTrimOnly(key, val)
if type(val) == 'string' then
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end
end
local function tidyValRemoveBlanksOnly(key, val)
if type(val) == 'string' then
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end
end
local function tidyValNoChange(key, val)
return val
end
function arguments.getArgs(frame, options)
checkType('getArgs', 1, frame, 'table', true)
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frame = frame 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.
--]]
local fargs, pargs, luaArgs
if type(frame.args) == 'table' and type(frame.getParent) == 'function' then
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luaArgs = frame
end
-- 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.
local args, metaArgs, metatable = {}, {}, {}
setmetatable(args, metatable)
--[[
-- 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
if tidyVal then
if type(tidyVal) ~= 'function' then
error(
"bad value assigned to option 'valueFunc'"
.. '(function expected, got '
.. type(tidyVal)
.. ')',
2
)
end
elseif options.trim ~= false then
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end
end
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.
-- We are also memoizing nil values, but those values can be
-- overwritten.
--]]
for _, t in ipairs(tables) do
for key, val in iterator(t) do
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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. Nil arguments are
-- also memoized using the nilArg variable in order to increase performance.
-- 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 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)
local val = metaArgs[key]
if metatable.donePairs or val ~= nil then
--[[
-- We have either memoized the argument already, 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.
--]]
if val == nilArg then
return nil
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return nil
end
metatable.__newindex = function (t, key, val)
if options.readOnly then
error(
'could not write to argument table key "'
.. tostring(key)
.. '"; the table is read-only',
2
)
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
)
elseif val == nil then
metaArgs[key] = nilArg -- Memoize nils.
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end
end
metatable.__pairs = function ()
if not metatable.donePairs then
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end
end
metatable.__ipairs = function ()
if not metatable.doneIpairs then
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end, nil, 0
end
return args
end
return arguments
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