Module:Arguments

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This is a meta module.

This module is meant to be used only by other modules. It should not be invoked in wikitext.

This module was adapted from Module:Arguments on Wikipedia.
Adaptation is noted for reference and attribution only. This module may differ from the original in function or in usage. The documentation on Wikipedia may be helpful in understanding this module.

The above documentation is transcluded from Module:Arguments/doc. (edit | history)
Editors can experiment in this module's sandbox (create | mirror) and testcases (create) pages.
Please add categories to the /doc subpage. Subpages of this module.

-- 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 arguments = {}

function arguments.getArgs(frame, options)
	options = type(options) == 'table' and 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 put the args in a special table so we can differentiate them.
	local fargs, pargs, luaArgs
	if frame == mw.getCurrentFrame() then
		fargs = frame.args
		pargs = frame:getParent().args
	else
		luaArgs = type(frame) == 'table' and frame or {}
	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)

	local function tidyVal(key, val)
		-- Processes a value according to the options given to getArguments. Can trim whitespace and remove blanks.
		-- Keys are not used here, but they can be used by user-generated functions, so defining it here to avoid breakage.
		if type(val) == 'string' then
			if options.trim ~= false then
				val = mw.text.trim(val)
			end
			if options.removeBlanks == false or mw.ustring.find(val, '%S') then
				return val
			end
		else
			return val
		end
	end

	-- Use a user-generated function to tidy the values if specified.
	local valueFunc = options.valueFunc
	if valueFunc then
		local valueFuncType = type(valueFunc)
		if valueFuncType == 'function' then
			tidyVal = valueFunc
		else
			error('type error in option "valueFunc": expected function, got ' .. valueFuncType, 2)
		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 precendence.
		for _, t in ipairs(tables) do
			for key, val in iterator(t) do
				if metaArgs[key] == nil then
					metaArgs[key] = tidyVal(key, val)
				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 = {}
	if options.parentFirst then
		table.insert(argTables, pargs)
		table.insert(argTables, fargs)
	else
		table.insert(argTables, fargs)
		table.insert(argTables, pargs)
	end
	table.insert(argTables, luaArgs)

	--[[
	-- Define metatable behaviour. Arguments are stored in the metaArgs table, and are only fetched from the
	-- argument tables once. 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 val ~= nil then
			return val
		else
			for i, argTable in ipairs(argTables) do
				local argTableVal = tidyVal(argTable[key])
				if argTableVal ~= nil then
					metaArgs[key] = argTableVal
					return argTableVal
				end
			end
		end
	end

	metatable.__newindex = function (t, key, val)
		if not options.readOnly and (not options.noOverwrite or args[key] == nil) then
			metaArgs[key] = val
		end
	end

	metatable.__pairs = function ()
		if not metatable.donePairs then
			mergeArgs(pairs, argTables)
			metatable.donePairs = true
			metatable.doneIpairs = true
		end
		return pairs(metaArgs)
	end

	metatable.__ipairs = function ()
		if not metatable.doneIpairs then
			mergeArgs(ipairs, argTables)
			metatable.doneIpairs = true
		end
		return ipairs(metaArgs)
	end
	
	return args
end

return arguments