Module:Languages/error

Documentation for this module may be created at Module:Languages/error/doc

--[=[
Throw an error for an invalid language code or script code.

`lang_code` (required) is the bad code and can be nil or a non-string.

`param` (required) is the name of the parameter in which the code was contained. It can be a string, a number
	(for a numeric param, in which case the param will show up in the error message as an ordinal such as
	"first" or "second"), or `true` if no parameter can be clearly identified.

`code_desc` (optional) is text describing what the code is; by default, "language code".

`template_text` (optional) is a string specifying the template that generated the error, or a function
	to generate this string. If given, it will be displayed in the error message.

`not_real_lang` (optional), if given, indicates that the code is not in the form of a language code
	(e.g. it's a script code). Normally, this function checks for things that could plausibly be a language code:
	two or three lowercase letters, two or three groups of three lowercase letters with hyphens between them.
	If such a pattern is found, a different error message is displayed (indicating an invalid code) than otherwise
	(indicating a missing code). If `not_real_lang` is given, this check is suppressed.
]=]

return function (lang_code, param, code_desc, template_tag, not_real_lang)
	local ordinals = {
		"first", "second", "third", "fourth", "fifth", "sixth",
		"seventh", "eighth", "ninth", "tenth", "eleventh", "twelfth",
		"thirteenth", "fourteenth", "fifteenth", "sixteenth", "seventeenth",
		"eighteenth", "nineteenth", "twentieth"
	}
	
	code_desc = code_desc or "language code"
	
	if not template_tag then
		template_tag = ""
	else
		if type(template_tag) ~= "string" then
			template_tag = template_tag()
		end
		template_tag = " (Original template: " .. template_tag .. ")"
	end
	local function err(msg)
		error(msg .. template_tag, 3)
	end
	local param_type = type(param)
	local in_the_param
	if param == true then
		-- handled specially below
		in_the_param = ""
	else
		if param_type == "number" then
			param = ordinals[param] .. " parameter"
		elseif param_type == "string" then
			param = 'parameter "' .. param .. '"'
		else
			err("The parameter name is "
					.. (param_type == "table" and "a table" or tostring(param))
					.. ", but it should be a number or a string.")
		end
		in_the_param = " in the " .. param
	end
	
	if not lang_code or lang_code == "" then
		if param == true then
			err("The " .. code_desc .. " is missing.")
		else
			err("The " .. param .. " (" .. code_desc .. ") is missing.")
		end
	elseif type(lang_code) ~= "string" then
		err("The " .. code_desc .. in_the_param .. " is supposed to be a string but is a " .. type(lang_code) .. ".")
	-- Can use string.find because language codes only contain ASCII.
	elseif not_real_lang or lang_code:find("^%l%l%l?$")
			or lang_code:find("^%l%l%l%-%l%l%l$")
			or lang_code:find("^%l%l%l%-%l%l%l%-%l%l%l$") then
		err("The " .. code_desc .. " \"" .. lang_code .. "\"" .. in_the_param .. " is not valid. See [[Wiktionary:List of languages]].")
	else
		err("Please specify a " .. code_desc .. in_the_param .. ". The value \"" .. lang_code .. "\" is not valid. See [[Wiktionary:List of languages]].")
	end
end