Module:parameters

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The following documentation is located at Module:parameters/documentation. [edit]
Useful links: subpage list • links • transclusions • testcases • sandbox (diff)

Exported functions

This module is used to standardize template argument processing and checking. A typical workflow is as follows (based on Module:translations): 

	...
	local parent_args = frame:getParent().args

	local params = {
		[1] = {required = true, default = "und"},
		[2] = {},
		[3] = {list = true},
		["alt"] = {},
		["sc"] = {},
		["tr"] = {},
	}

	local args = require("Module:parameters").process(parent_args, params)

	-- Do further processing of the parsed arguments in `args`.
	...

The params table should have the parameter names as the keys, and a (possibly empty) table of parameter tags as the value. An empty table as the value merely states that the parameter exists, but should not receive any special treatment. Possible parameter tags are listed below:

required = true
The parameter is required; an error is shown if it is not present. The template's page itself is an exception; no error is shown there.
default =
Specifies a default input value for the parameter, if it is absent or empty. This will be processed as though it were the input instead, so (for example) default = "und" with the type "language" will return a language object for Undetermined language if no language code is provided.
When used on list parameters, this specifies a default value for the first item in the list only. Note that it is not possible to generate a default that depends on the value of other parameters.
If used together with required = true, the default applies only to the template's page itself. This can be used to show an example text.
alias_of =
Treat the parameter as an alias of another. When arguments are specified for this parameter, they will automatically be renamed and stored under the alias name. This allows for parameters with multiple alternative names, while still treating them as if they had only one name.
Aliases cannot be required, as this prevents the other name or names of the parameter from being used. Parameters that are aliases and required at the same time cause an error to be thrown.
allow_empty = true
If the argument is an empty string value, it is not converted to nil, but kept as-is.
allow_whitespace = true
Spacing characters such as spaces and newlines at the beginning and end of a positional parameter are not removed. (MediaWiki itself automatically trims spaces and newlines at the edge of named parameters.)
type =
Specifies what value type to convert the argument into. The default is to leave it as a text string. Alternatives are:
type = "boolean"
The value is treated as a boolean value, either true or false. No value, the empty string, and the strings "0", "no", "n" and "false" are treated as false, all other values are considered true.
type = "number"
The value is converted into a number, or nil if the value is not parsable as a number.
type = "language"
The value is interpreted as a code (or language name, if method = "name") and converted into a language object. If the code is invalid, then an error is thrown. The additional settings etym_lang = true and/or family = true can be given to allow (respectively) Etymology-only language codes and/or language family codes to be considered valid and the corresponding object returned.
type = "wikimedia language"
The value is interpreted as a code and converted into a wikimedia language object. If the code is invalid, then an error is thrown.
type = "family"
The value is interpreted as a code (or language name, if method = "name") and converted into a language family object. If the code is invalid, then an error is thrown.
type = "script"
The value is interpreted as a code (or language name, if method = "name") and converted into a script object. If the code is invalid, then an error is thrown.
list =
Treat the parameter as a list of values, each having its own parameter name, rather than a single value. The parameters will have a number at the end, except optionally for the first (but see also require_index = true). For example, list = true on a parameter named "head" will include the parameters |head= (or |head1=), |head2=, |head3= and so on. If the parameter name is a number, another number doesn't get appended, but the counting simply continues, e.g. for parameter 3 the sequence is |3=, |4=, |5= etc. List parameters are returned as numbered lists, so for a template that is given the parameters |head=a|head2=b|head3=c, the processed value of the parameter "head" will be { "a", "b", "c" }}.
The value for list = can also be a string. This tells the module that parameters other than the first should have a different name, which is useful when the first parameter in a list is a number, but the remainder is named. An example would be for genders: list = "g" on a parameter named 1 would have parameters |1=, |g2=, |g3= etc.
If the number is not located at the end, it can be specified by putting "\1" at the number position. For example, parameters |f1accel=, |f2accel=, ... can be captured by using the parameter name "f\1accel", as is done in Module:headword/templates.
set =
Require that the value of the parameter be one of the specified list of values (or omitted, if required = true isn't given). The values in the specified list should be strings corresponding to the raw parameter values except when type = "number", in which case they should be numbers. The use of set is ignored if type = "boolean", as it doesn't make sense in this case.
sublist = true
The value of the parameter is a comma-separated list of individual values (possibly with whitespace on one or both sides of the comma, which is ignored). The resulting field in args will be a list of the converted values.
etym_lang = true
When used in conjunction with type = "language", allows etymology-only language codes to be returned. The returned objects are of the same type as those for full languages and for almost all purposes they can be used interchangeably. To check if a given object refers to an etymology-only language, use object:hasType("language", "etymology-only").
family = true
When used in conjunction with type = "language", allows language family codes to be returned. To check if a given object refers to a language family, use object:hasType("family").
method = "name"
When used in conjunction with type = "language", type = "family" or type = "script", checks for and parses a language, family or script name instead of a code.
allow_holes = true
This is used in conjunction with list-type parameters. By default, the values are tightly packed in the resulting list. This means that if, for example, an entry specified head=a|head3=c but not |head2=, the returned list will be {"a", "c"}}, with the values stored at the indices 1 and 2, not 1 and 3. If it is desirable to keep the numbering intact, for example if the numbers of several list parameters correlate with each other (like those of {{compound}}), then this tag should be specified.
If allow_holes = true is given, there may be nil values in between two real values, which makes many of Lua's table processing functions no longer work, like # or ipairs(). To remedy this, the resulting table will contain an additional named value, maxindex, which tells you the highest numeric index that is present in the table. In the example above, the resulting table will now be { "a", nil, "c", maxindex = 3}}. That way, you can iterate over the values from 1 to maxindex, while skipping nil values in between.
disallow_holes = true
This is used in conjunction with list-type parameters. As mentioned above, normally if there is a hole in the source arguments, e.g. head=a|head3=c but not |head2=, it will be removed in the returned list. If disallow_holes = true is specified, however, an error is thrown in such a case. This should be used whenever there are multiple list-type parameters that need to line up (e.g. both |head= and |tr= are available and |head3= lines up with |tr3=), unless allow_holes = true is given and you are prepared to handle the holes in the returned lists.
require_index = true
This is used in conjunction with list-type parameters. By default, the first parameter can have its index omitted. For example, a list parameter named head can have its first parameter specified as either |head= or |head1=. If require_index = true is specified, however, only |head1= is recognized, and |head= will be treated as an unknown parameter. {{affixusex}} (and variants {{suffixusex}}, {{prefixusex}}) use this, for example, on all list parameters.
separate_no_index = true
This is used to distinguish between |head= and |head1= as different parameters. For example, in {{affixusex}}, to distinguish between |sc= (a script code for all elements in the usex's language) and |sc1= (the script code of the first element, used when |lang1= is also specified to indicate that the first element is in a different language). When this is used, the resulting table will contain an additional named value, default, which contains the value for the indexless argument.

export.process

function export.process(args, params, return_unknown)

Process arguments with a given list of parameters. Return a table containing the processed arguments. The args parameter specifies the arguments to be processed; they are the arguments you might retrieve from frame:getParent().args (the template arguments) or in some cases frame.args (the invocation arguments). The params parameter specifies a list of valid parameters, and consists of a table. If an argument is encountered that is not in the parameter table, an error is thrown.

The structure of the params table is as described above in the intro comment.

WARNING: The params table is destructively modified to save memory. Nonetheless, different keys can share the same value objects in memory without causing problems.

The return_unknown parameter, if set to true, prevents the function from triggering an error when it comes across an argument with a name that it doesn't recognise. Instead, the return value is a pair of values: the first is the processed arguments as usual, while the second contains all the unrecognised arguments that were left unprocessed. This allows you to do multi-stage processing, where the entire set of arguments that a template should accept is not known at once. For example, an inflection-table might do some generic processing on some arguments, but then defer processing of the remainder to the function that handles a specific inflectional type. 

local m_str_utils = require("Module:string utilities")

local require_when_needed = require("Module:utilities/require when needed")

local dump = mw.dumpObject
local floor = math.floor
local gsplit = mw.text.gsplit
local gsub = string.gsub
local huge = math.huge
local insert = table.insert
local list_to_set = require("Module:table").listToSet
local list_to_text = mw.text.listToText
local match = string.match
local max = math.max
local pairs = pairs
local pattern_escape = m_str_utils.pattern_escape
local remove_holes = require_when_needed("Module:parameters/remove holes")
local scribunto_param_key = m_str_utils.scribunto_param_key
local sort = table.sort
local trim = mw.text.trim
local type = type
local yesno = require_when_needed("Module:yesno")

local export = {}

--[==[ intro:
This module is used to standardize template argument processing and checking. A typical workflow is as follows (based
on [[Module:translations]]):

{
	...
	local parent_args = frame:getParent().args

	local params = {
		[1] = {required = true, default = "und"},
		[2] = {},
		[3] = {list = true},
		["alt"] = {},
		["sc"] = {},
		["tr"] = {},
	}

	local args = require("Module:parameters").process(parent_args, params)

	-- Do further processing of the parsed arguments in `args`.
	...
}

The `params` table should have the parameter names as the keys, and a (possibly empty) table of parameter tags as the
value. An empty table as the value merely states that the parameter exists, but should not receive any special
treatment. Possible parameter tags are listed below:

; {required = true}
: The parameter is required; an error is shown if it is not present. The template's page itself is an exception; no error is shown there.
; {default =}
: Specifies a default input value for the parameter, if it is absent or empty. This will be processed as though it were the input instead, so (for example) {default = "und"} with the type {"language"} will return a language object for [[:Category:Undetermined language|Undetermined language]] if no language code is provided.
: When used on list parameters, this specifies a default value for the first item in the list only. Note that it is not possible to generate a default that depends on the value of other parameters.
: If used together with {required = true}, the default applies only to the template's page itself. This can be used to show an example text.
; {alias_of =}
: Treat the parameter as an alias of another. When arguments are specified for this parameter, they will automatically be renamed and stored under the alias name. This allows for parameters with multiple alternative names, while still treating them as if they had only one name.
: Aliases cannot be required, as this prevents the other name or names of the parameter from being used. Parameters that are aliases and required at the same time cause an error to be thrown.
; {allow_empty = true}
: If the argument is an empty string value, it is not converted to {nil}, but kept as-is.
; {allow_whitespace = true}
: Spacing characters such as spaces and newlines at the beginning and end of a positional parameter are not removed.
(MediaWiki itself automatically trims spaces and newlines at the edge of named parameters.)
; {type =}
: Specifies what value type to convert the argument into. The default is to leave it as a text string. Alternatives are:
:; {type = "boolean"}
:: The value is treated as a boolean value, either true or false. No value, the empty string, and the strings {"0"}, {"no"}, {"n"} and {"false"} are treated as {false}, all other values are considered {true}.
:; {type = "number"}
:: The value is converted into a number, or {nil} if the value is not parsable as a number.
:; {type = "language"}
:: The value is interpreted as a code (or language name, if {method = "name"}) and converted into a language object. If 
the code is invalid, then an error is thrown. The additional settings {etym_lang = true} and/or {family = true} can be
given to allow (respectively) [[Wiktionary:Languages#Etymology-only languages|Etymology-only language codes]] and/or
[[Wiktionary:Language families|language family codes]] to be considered valid and the
corresponding object returned.
:; {type = "wikimedia language"}
:: The value is interpreted as a code and converted into a wikimedia language object. If the code is invalid, then an error is thrown.
:; {type = "family"}
:: The value is interpreted as a code (or language name, if {method = "name"}) and converted into a language family
object. If the code is invalid, then an error is thrown.
:; {type = "script"}
:: The value is interpreted as a code (or language name, if {method = "name"}) and converted into a script object. If
the code is invalid, then an error is thrown.
; {list =}
: Treat the parameter as a list of values, each having its own parameter name, rather than a single value. The parameters will have a number at the end, except optionally for the first (but see also {require_index = true}). For example, {list = true} on a parameter named "head" will include the parameters {{para|head}} (or {{para|head1}}), {{para|head2}}, {{para|head3}} and so on. If the parameter name is a number, another number doesn't get appended, but the counting simply continues, e.g. for parameter {3} the sequence is {{para|3}}, {{para|4}}, {{para|5}} etc. List parameters are returned as numbered lists, so for a template that is given the parameters `|head=a|head2=b|head3=c`, the processed value of the parameter {"head"} will be { { "a", "b", "c" }}}.
: The value for {list =} can also be a string. This tells the module that parameters other than the first should have a different name, which is useful when the first parameter in a list is a number, but the remainder is named. An example would be for genders: {list = "g"} on a parameter named {1} would have parameters {{para|1}}, {{para|g2}}, {{para|g3}} etc.
: If the number is not located at the end, it can be specified by putting {"\1"} at the number position. For example, parameters {{para|f1accel}}, {{para|f2accel}}, ... can be captured by using the parameter name {"f\1accel"}, as is done in [[Module:headword/templates]].
; {set =}
: Require that the value of the parameter be one of the specified list of values (or omitted, if {required = true} isn't
given). The values in the specified list should be strings corresponding to the raw parameter values except when
{type = "number"}, in which case they should be numbers. The use of `set` is ignored if {type = "boolean"}, as it
doesn't make sense in this case.
; {sublist = true}
: The value of the parameter is a comma-separated list of individual values (possibly with whitespace on one or both
sides of the comma, which is ignored). The resulting field in `args` will be a list of the converted values.
; {etym_lang = true}
: When used in conjunction with {type = "language"}, allows [[Wiktionary:Languages#Etymology-only languages|etymology-only language codes]]
to be returned. The returned objects are of the same type as those for full languages and for almost all purposes they
can be used interchangeably. To check if a given object refers to an etymology-only language, use
{object:hasType("language", "etymology-only")}.
; {family = true}
: When used in conjunction with {type = "language"}, allows [[Wiktionary:Language families|language family codes]]
to be returned. To check if a given object refers to a language family, use {object:hasType("family")}.
; {method = "name"}
: When used in conjunction with {type = "language"}, {type = "family"} or {type = "script"}, checks for and parses a
language, family or script name instead of a code.
; {allow_holes = true}
: This is used in conjunction with list-type parameters. By default, the values are tightly packed in the resulting list. This means that if, for example, an entry specified `head=a|head3=c` but not {{para|head2}}, the returned list will be { {"a", "c"}}}, with the values stored at the indices {1} and {2}, not {1} and {3}. If it is desirable to keep the numbering intact, for example if the numbers of several list parameters correlate with each other (like those of {{tl|compound}}), then this tag should be specified.
: If {allow_holes = true} is given, there may be {nil} values in between two real values, which makes many of Lua's table processing functions no longer work, like {#} or {ipairs()}. To remedy this, the resulting table will contain an additional named value, `maxindex`, which tells you the highest numeric index that is present in the table. In the example above, the resulting table will now be { { "a", nil, "c", maxindex = 3}}}. That way, you can iterate over the values from {1} to `maxindex`, while skipping {nil} values in between.
; {disallow_holes = true}
: This is used in conjunction with list-type parameters. As mentioned above, normally if there is a hole in the source arguments, e.g. `head=a|head3=c` but not {{para|head2}}, it will be removed in the returned list. If {disallow_holes = true} is specified, however, an error is thrown in such a case. This should be used whenever there are multiple list-type parameters that need to line up (e.g. both {{para|head}} and {{para|tr}} are available and {{para|head3}} lines up with {{para|tr3}}), unless {allow_holes = true} is given and you are prepared to handle the holes in the returned lists.
; {require_index = true}
: This is used in conjunction with list-type parameters. By default, the first parameter can have its index omitted. For example, a list parameter named `head` can have its first parameter specified as either {{para|head}} or {{para|head1}}. If {require_index = true} is specified, however, only {{para|head1}} is recognized, and {{para|head}} will be treated as an unknown parameter. {{tl|affixusex}} (and variants {{tl|suffixusex}}, {{tl|prefixusex}}) use this, for example, on all list parameters.
; {separate_no_index = true}
: This is used to distinguish between {{para|head}} and {{para|head1}} as different parameters. For example, in {{tl|affixusex}}, to distinguish between {{para|sc}} (a script code for all elements in the usex's language) and {{para|sc1}} (the script code of the first element, used when {{para|lang1}} is also specified to indicate that the first element is in a different language). When this is used, the resulting table will contain an additional named value, `default`, which contains the value for the indexless argument.
]==]

local function track(page)
	require("Module:debug/track")("parameters/" .. page)
end

local function save_pattern(name, list_name, patterns)
	name = type(name) == "string" and gsub(name, "\1", "") or name
	if match(list_name, "\1") then
		patterns["^" .. gsub(pattern_escape(list_name), "\1", "([1-9]%%d*)") .. "$"] = name
	else
		patterns["^" .. pattern_escape(list_name) .. "([1-9]%d*)$"] = name
	end
end

local function concat_list(list, conjunction, dump_vals)
	if dump_vals then
		for i = 1, #list do
			list[i] = dump(list[i])
		end
	end
	return list_to_text(list, nil, conjunction)
end

local function format_choice_list(typ)
	return (#typ > 1 and "either " or "") .. concat_list(typ, " or ")
end

local function convert_val_error(val, name, typ, seetext)
	if type(name) == "function" then
		if type(typ) == "table" then
			typ = "choice, must be " .. format_choice_list(typ)
		end
		name(("Invalid %s; the value %s is not valid%s"):format(typ, val, seetext and "; see " .. seetext or ""))
	else
		if type(typ) == "table" then
			typ = "must be " .. format_choice_list(typ)
		else
			typ = "should be a valid " .. typ
		end
		error(("Parameter %s %s; the value %s is not valid.%s"):format(name, typ, val,
			seetext and " See " .. seetext .. "." or ""))
	end
end

local function check_set(val, name, param)
	if not param.set[val] then
		local list = {}
		for k in pairs(param.set) do
			insert(list, dump(k))
		end
		sort(list)
		-- If the parameter is not required then put "or empty" at the end of the list, to avoid implying the parameter is actually required.
		if not param.required then
			insert(list, "empty")
		end
		convert_val_error(val, name, list)
	end
end

local convert_val = setmetatable({
	["boolean"] = function(val)
		-- Set makes no sense with booleans, so don't bother checking for it.
		return yesno(val, true)
	end,
	
	["family"] = function(val, name, param)
		if param.set then
			check_set(val, name, param)
		end
		return require("Module:families")[param.method == "name" and "getByCanonicalName" or "getByCode"](val) or
			convert_val_error(val, name, "family " .. (param.method == "name" and "name" or "code"), "[[WT:LOF]]")
	end,
	
	["language"] = function(val, name, param)
		if param.set then
			check_set(val, name, param)
		end
		local lang = require("Module:languages")[param.method == "name" and "getByCanonicalName" or "getByCode"](val, nil, param.etym_lang, param.family)
		if lang then
			return lang
		end
		local list = {"language"}
		local links = {"[[WT:LOL]]"}
		if param.etym_lang then
			insert(list, "etymology language")
			insert(links, "[[WT:LOL/E]]")
		end
		if param.family then
			insert(list, "family")
			insert(links, "[[WT:LOF]]")
		end
		convert_val_error(val, name, concat_list(list, " or ") .. " " .. (param.method == "name" and "name" or "code"),
			concat_list(links, " and "))
	end,
	
	["number"] = function(val, name, param)
		if type(val) == "number" then
			return val
		end
		-- Avoid converting inputs like "nan" or "inf".
		val = tonumber(val:match("^[+%-]?%d+%.?%d*")) or
			convert_val_error(val, name, "number")
		if param.set then
			check_set(val, name, param)
		end
		return val
	end,
	
	["script"] = function(val, name, param)
		if param.set then
			check_set(val, name, param)
		end
		return require("Module:scripts")[param.method == "name" and "getByCanonicalName" or "getByCode"](val) or
			convert_val_error(val, name, "script " .. (param.method == "name" and "name" or "code"), "[[WT:LOS]]")
	end,
	
	["string"] = function(val, name, param)
		if param.set then
			check_set(val, name, param)
		end
		return val
	end,
	
	["wikimedia language"] = function(val, name, param)
		if param.set then
			check_set(val, name, param)
		end
		return require("Module:wikimedia languages").getByCode(val) or
			convert_val_error(val, name, "wikimedia language code")
	end,
}, {
	__call = function(self, val, name, param)
		local func, sublist = self[param.type or "string"], param.sublist
		if not func then
			error("Internal error: " .. dump(param.type) .. " is not a recognized parameter type.")
		elseif sublist then
			local ret_val = {}
			if type(val) ~= "string" then
				error("Internal error: " .. dump(val) .. " is not a string.")
			end
			for v in gsplit(val, sublist == true and "%s*,%s*" or sublist) do
				insert(ret_val, func(v, name, param))
			end
			return ret_val
		else
			return func(val, name, param)
		end
	end
})
export.convert_val = convert_val -- used by [[Module:parameter utilities]]

local function process_error(fmt, ...)
	local args = {...}
	for i, val in ipairs(args) do
		args[i] = dump(val)
	end
	if type(fmt) == "table" then
		-- hacky signal that we're called from internal_process_error(), and not to omit stack frames
		return error(fmt[1]:format(unpack(args)))
	else
		return error(fmt:format(unpack(args)), 3)
	end
end

local function internal_process_error(fmt, ...)
	fmt = "Internal error in `params` table: " .. fmt
	process_error({fmt}, ...)
end

--[==[
Process arguments with a given list of parameters. Return a table containing the processed arguments. The `args`
parameter specifies the arguments to be processed; they are the arguments you might retrieve from
{frame:getParent().args} (the template arguments) or in some cases {frame.args} (the invocation arguments). The `params`
parameter specifies a list of valid parameters, and consists of a table. If an argument is encountered that is not in
the parameter table, an error is thrown.

The structure of the `params` table is as described above in the intro comment.

'''WARNING:''' The `params` table is destructively modified to save memory. Nonetheless, different keys can share the
same value objects in memory without causing problems.

The `return_unknown` parameter, if set to {true}, prevents the function from triggering an error when it comes across an
argument with a name that it doesn't recognise. Instead, the return value is a pair of values: the first is the
processed arguments as usual, while the second contains all the unrecognised arguments that were left unprocessed. This
allows you to do multi-stage processing, where the entire set of arguments that a template should accept is not known at
once. For example, an inflection-table might do some generic processing on some arguments, but then defer processing of
the remainder to the function that handles a specific inflectional type.
]==]
function export.process(args, params, return_unknown)
	-- Process parameters for specific properties
	local args_new = {}
	local required = {}
	local seen = {}
	local patterns = {}
	local names_with_equal_sign = {}
	local list_from_index
	
	for name, param in pairs(params) do
		-- Populate required table, and make sure aliases aren't set to required.
		if param.required then
			if param.alias_of then
				internal_process_error(
					"Parameter %s is an alias of %s, but is also set as a required parameter. Only %s should be set as required.",
					name, param.alias_of, name)
			end
			required[name] = true
		end
		
		-- Convert param.set from a list into a set.
		-- `seen` prevents double-conversion if multiple parameter keys share the same param table.
		local set = param.set
		if set and not seen[param] then
			param.set = list_to_set(set)
			seen[param] = true
		end
		
		local alias = param.alias_of
		if alias then
			-- Check that the alias_of is set to a valid parameter.
			if not params[alias] then
				internal_process_error("Parameter %s is an alias of an invalid parameter.", name)
			end
			-- Check that all the parameters in params are in the form Scribunto normalizes input argument keys into (e.g. 1 not "1", "foo" not " foo "). Otherwise, this function won't be able to normalize the input arguments in the expected way.
			local normalized = scribunto_param_key(alias)
			if alias ~= normalized then
				internal_process_error(
					"Parameter %s (a " .. type(alias) .. ") given in the alias_of field of parameter %s is not a normalized Scribunto parameter. Should be %s (a " .. type(normalized) .. ").",
					alias, name, normalized)
			-- Aliases can't be lists unless the canonical parameter is also a list.
			elseif param.list and not params[alias].list then
				internal_process_error(
					"The list parameter %s is set as an alias of %s, which is not a list parameter.", name, alias)
			-- Aliases can't be aliases of other aliases.
			elseif params[alias].alias_of then
				internal_process_error(
					"Alias_of cannot be set to another alias: parameter %s is set as an alias of %s, which is in turn an alias of %s. Set alias_of for %s to %s.",
					name, alias, params[alias].alias_of, name, params[alias].alias_of)
			end
		end
		
		local normalized = scribunto_param_key(name)
		if name ~= normalized then
			internal_process_error(
				"Parameter %s (a " .. type(name) .. ") is not a normalized Scribunto parameter. Should be %s (a " ..
				type(normalized) .. ").",
				name, normalized)
		end
		
		if param.list then
			if not param.alias_of then
				local key = name
				if type(name) == "string" then
					key = gsub(name, "\1", "")
				end
				-- _list is used as a temporary flag.
				args_new[key] = {maxindex = 0, _list = param.list}
			end
			
			if type(param.list) == "string" then
				-- If the list property is a string, then it represents the name
				-- to be used as the prefix for list items. This is for use with lists
				-- where the first item is a numbered parameter and the
				-- subsequent ones are named, such as 1, pl2, pl3.
				save_pattern(name, param.list, patterns)
			elseif type(name) == "number" then
				if list_from_index then
					internal_process_error(
						"Only one numeric parameter can be a list, unless the list property is a string.")
				end
				-- If the name is a number, then all indexed parameters from
				-- this number onwards go in the list.
				list_from_index = name
			else
				save_pattern(name, name, patterns)
			end
			
			if match(name, "\1") then
				insert(names_with_equal_sign, name)
			end
		end
	end
	
	--Process required changes to `params`.
	for i = 1, #names_with_equal_sign do
		local name = names_with_equal_sign[i]
		params[gsub(name, "\1", "")] = params[name]
		params[name] = nil
	end
	
	-- Process the arguments
	local args_unknown = {}
	local max_index
	
	for name, val in pairs(args) do
		local orig_name, raw_type, index, normalized = name, type(name)
		
		if raw_type == "number" then
			if list_from_index ~= nil and name >= list_from_index then
				index = name - list_from_index + 1
				name = list_from_index
			end
		else
			-- Does this argument name match a pattern?
			for pattern, pname in pairs(patterns) do
				index = match(name, pattern)
				-- It matches, so store the parameter name and the
				-- numeric index extracted from the argument name.
				if index then
					index = tonumber(index)
					name = pname
					break
				end
			end
		end
		
		local param = params[name]
		
		if param and param.require_index then
			-- Disallow require_index for numeric parameter names, as this doesn't make sense.
			if raw_type == "number" then
				internal_process_error("Cannot set require_index for numeric parameter %s.", name)
			-- If a parameter without the trailing index was found, and
			-- require_index is set on the param, set the param to nil to treat it
			-- as if it isn't recognized.
			elseif not index then
				param = nil
			end
		end
		
		-- If the argument is not in the list of parameters, trigger an error.
		-- return_unknown suppresses the error, and stores it in a separate list instead.
		if not param then
			if return_unknown then
				args_unknown[name] = val
			else
				process_error("Parameter %s is not used by this template.", name)
			end
		else
			-- Check that separate_no_index is not being used with a numeric parameter.
			if param.separate_no_index then
				if raw_type == "number" then
					internal_process_error("Cannot set separate_no_index for numeric parameter %s.", name)
				elseif type(param.alias_of) == "number" then
					internal_process_error(
						"Cannot set separate_no_index for parameter %s, as it is an alias of numeric parameter %s.",
						name, param.alias_of)
				end
			end
			
			-- If no index was found, use 1 as the default index.
			-- This makes list parameters like g, g2, g3 put g at index 1.
			-- If `separate_no_index` is set, then use 0 as the default instead.
			if param.list then
				index = index or param.separate_no_index and 0 or 1
			end
			
			-- Normalize to the canonical parameter name. If it's a list, but the alias is not, then determine the index.
			local raw_name = param.alias_of
			if param.alias_of then
				raw_type = type(raw_name)
				if raw_type == "number" then
					if params[raw_name].list then
						index = index or param.separate_no_index and 0 or 1
						normalized = raw_name + index - 1
					else
						normalized = raw_name
					end
					name = raw_name
				else
					name = gsub(raw_name, "\1", "")
					if params[name].list then
						index = index or param.separate_no_index and 0 or 1
					end
					if not index or index == 0 then
						normalized = name
					elseif name == raw_name then
						normalized = name .. index
					else
						normalized = gsub(raw_name, "\1", index)
					end
				end
			else
				normalized = orig_name
			end
			
			-- Remove leading and trailing whitespace unless allow_whitespace is true.
			if not param.allow_whitespace then
				val = trim(val)
			end
			
			-- Empty string is equivalent to nil unless allow_empty is true.
			if val == "" and not param.allow_empty then
				val = nil
				-- Track empty parameters, unless (1) allow_empty is set or (2) they're numbered parameters where a higher numbered parameter is also in use (e.g. track {{l|en|term|}}, but not {{l|en||term}}).
				if raw_type == "number" and not max_index then
					-- Find the highest numbered parameter that's in use/an empty string, as we don't want parameters like 500= to mean we can't track any empty parameters with a lower index than 500.
					local n = 0
					while args[n + 1] do
						n = n + 1
					end
					max_index = 0
					for n = n, 1, -1 do
						if args[n] ~= "" then
							max_index = n
							break
						end
					end
				end
				if raw_type ~= "number" or name > max_index then
					-- Disable this for now as it causes slowdowns on large pages like [[a]].
					-- track("empty parameter")
				end
			end
			
			-- Can't use "if val" alone, because val may be a boolean false.
			if val ~= nil then
				-- Convert to proper type if necessary.
				val = convert_val(val, orig_name, params[raw_name] or param)
				
				-- Mark it as no longer required, as it is present.
				required[name] = nil
				
				-- Store the argument value.
				if index then
					-- If the parameter is duplicated, throw an error.
					if args_new[name][index] ~= nil then
						process_error(
							"Parameter %s has been entered more than once. This is probably because a list parameter has been entered without an index and with index 1 at the same time, or because a parameter alias has been used.",
							normalized)
					end
					args_new[name][index] = val
					
					-- Store the highest index we find.
					args_new[name].maxindex = max(index, args_new[name].maxindex)
					if args_new[name][0] ~= nil then
						args_new[name].default = args_new[name][0]
						if args_new[name].maxindex == 0 then
							args_new[name].maxindex = 1
						end
						args_new[name][0] = nil
						
					end
					
					if params[name].list then
						-- Don't store index 0, as it's a proxy for the default.
						if index > 0 then
							args_new[name][index] = val
							-- Store the highest index we find.
							args_new[name].maxindex = max(index, args_new[name].maxindex)
						end
					else
						args_new[name] = val
					end
				else
					-- If the parameter is duplicated, throw an error.
					if args_new[name] ~= nil then
						process_error(
							"Parameter %s has been entered more than once. This is probably because a parameter alias has been used.",
							normalized)
					end
					
					if not param.alias_of then
						args_new[name] = val
					else
						if params[param.alias_of].list then
							args_new[param.alias_of][1] = val
							
							-- Store the highest index we find.
							args_new[param.alias_of].maxindex = max(1, args_new[param.alias_of].maxindex)
						else
							args_new[param.alias_of] = val
						end
					end
				end
			end
		end
	end
	
	-- Remove holes in any list parameters if needed.
	for name, val in pairs(args_new) do
		if type(val) == "table" then
			local listname = val._list
			if listname then
				if params[name].disallow_holes then
					local highest = 0
					for num, _ in pairs(val) do
						if type(num) == "number" and num > 0 and num < huge and floor(num) == num then
							highest = max(highest, num)
						end
					end
					for i = 1, highest do
						if val[i] == nil then
							if type(listname) == "string" then
								listname = dump(listname)
							elseif type(name) == "number" then
								i = i + name - 1 -- Absolute index.
								listname = "numeric"
							else
								listname = dump(name)
							end
							process_error(
								"Item %s in the list of " .. listname .. " parameters cannot be empty, because the list must be contiguous.",
								i)
						end
					end
					-- Some code depends on only numeric params being present
					-- when no holes are allowed (e.g. by checking for the
					-- presence of arguments using next()), so remove
					-- `maxindex`.
					val.maxindex = nil
				elseif not params[name].allow_holes then
					args_new[name] = remove_holes(val)
				end
			end
		end
	end
	
	-- Handle defaults.
	for name, param in pairs(params) do
		if param.default ~= nil then
			local arg_new = args_new[name]
			if type(arg_new) == "table" and arg_new._list then
				if arg_new[1] == nil then
					arg_new[1] = convert_val(param.default, name, param)
				end
				if arg_new.maxindex == 0 then
					arg_new.maxindex = 1
				end
				arg_new._list = nil
			elseif arg_new == nil then
				args_new[name] = convert_val(param.default, name, param)
			end
		end
	end
	
	-- The required table should now be empty.
	-- If any entry remains, trigger an error, unless we're in the template namespace.
	if mw.title.getCurrentTitle().namespace ~= 10 then
		local list = {}
		for name in pairs(required) do
			insert(list, dump(name))
		end
		local n = #list
		if n > 0 then
			process_error("Parameter" .. (
				n == 1 and (" " .. list[1] .. " is") or
				("s " .. concat_list(list, " and ", true) .. " are")
			) .. " required.")
		end
	end
	
	-- Remove the temporary _list flag.
	for _, arg_new in pairs(args_new) do
		if type(arg_new) == "table" then
			arg_new._list = nil
		end
	end
	
	if return_unknown then
		return args_new, args_unknown
	else
		return args_new
	end
end

return export
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