Module:Arguments: Difference between revisions
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Latest revision as of 04:01, 30 April 2021
Documentation for this module may be created at Module:Arguments/doc
--- Arguments invocation argument extractor for Scribunto modules.
-- It is intended for use by other Lua modules, and should not be
-- called from an invocation (`#invoke`) directly.
--
-- This module supports the following features:
-- * Trimming and blank argument removal.
-- * Argument inheritance between child and parent frames.
-- * Argument extraction for external modules and console input.
-- * Options to customise argument extraction behaviour.
--
-- @script arguments
-- @release stable
-- @note The `args` table from the @{arguments.getArgs}
-- function is a metatable for performance reasons.
-- Thus, the table will not permit Lua table methods
-- such as `#args`, @{next|next(args)}, and @{table}
-- library functions.
-- @note This module will eventually be adapted as a
-- library in [[mw:gerrit:q/158323|MediaWiki
-- core]], called as `require('getArgs')`. The core
-- library will remove `options.parentOnly`.
-- @author [[wikipedia:User:Mr. Stradivarius|Mr. Stradivarius]] (Wikipedia)
-- @author [[wikipedia:User:Anomie|Anomie]] (Wikipedia)
-- @author [[wikipedia:User:Jackmcbarn|Jackmcbarn]] (Wikipedia)
-- @author [[User:Dessamator|Dessamator]]
-- @author [[User:DarthKitty|DarthKitty]]
-- @attribution [[wikipedia:Module:Arguments|Module:Arguments]] (Wikipedia)
-- @see [[wikipedia:Module:Arguments|Original module on Wikipedia]]
-- @see [[Module:Arguments/testcases|Test cases for this module]]
local arguments = {}
-- Module dependencies.
local i18n = require('Module:I18n').loadMessages('Arguments')
local util = require('libraryUtil')
local checkType = util.checkType
-- Four different value tidying functions.
-- This way, we don't have to check the options every time we call them.
--- Default value tidying function.
-- Trims parameter values automatically if they are defined strings.
-- Treats blank strings as `nil`.
-- @function tidyValDefault
-- @param {string|number} key MediaWiki parameter key.
-- @param {string|nil} val MediaWiki parameter value,
-- or nil if `key` is an empty string or nil.
-- @local
local function tidyValDefault(key, val)
if type(val) == 'string' then
val = val:match('^%s*(.-)%s*$')
if val == '' then
return nil
else
return val
end
else
return val
end
end
--- Value tidying function that trims values.
-- Trims parameter values automatically if they are defined strings.
-- @function tidyValTrimOnly
-- @param {string|number} key MediaWiki parameter key.
-- @param {string|nil} val MediaWiki parameter value.
-- @local
local function tidyValTrimOnly(key, val)
if type(val) == 'string' then
return val:match('^%s*(.-)%s*$')
else
return val
end
end
--- Value tidying function that removes blanks.
-- Removes blank values from the arguments table.
-- @function tidyValRemoveBlanksOnly
-- @param {string|number} key MediaWiki parameter key.
-- @param {string|nil} val MediaWiki parameter value,
-- or nil if `key` is whitespace or nil.
-- @local
local function tidyValRemoveBlanksOnly(key, val)
if type(val) == 'string' then
if val:find('%S') then
return val
else
return nil
end
else
return val
end
end
--- Value tidying function that returns original value.
-- Effectively a NOOP function that does no value processing.
-- @function tidyValNoChange
-- @param {string|number} key MediaWiki parameter key.
-- @param {string|nil} val MediaWiki parameter value.
-- @local
local function tidyValNoChange(key, val)
return val
end
--- Parent template title match checker.
-- @function matchesTitle
-- @param {string|number|nil} given Local prefixed page
-- title, or MediaWiki article ID (`wgArticleId`).
-- @param {string} title Title of parent template.
-- @return {boolean} Whether the `given` ID/title matches
-- the title of the parent template.
local function matchesTitle(given, title)
local tp = type( given )
return (tp == 'string' or tp == 'number') and mw.title.new( given ).prefixedText == title
end
--- Default argument translation metatable.
-- @table translate_mt
-- @local
local translate_mt = { __index = function(t, k) return k end }
--- Main argument extraction utility.
-- Arguments are memoized once fetched for optimal performance,
-- as with the `frame.args` metatable in Scribunto core.
--
-- The default argument lookup behaviour uses the child frame arguments
-- first, then the parent frame arguments. There are numerous frame
-- options to change this behaviour.
--
-- The default value tidying behaviour trims parameter values if they
-- are defined strings and treats blank strings as `nil`. This can be
-- customised in the `getArgs` options.
--
-- @param {frame|table} frame Scribunto frame object or
-- Lua arguments table, passed from an invocation
-- or Lua logic such as `frame:getParent()`.
-- If this parameter does not have an `args` field
-- and a `getParent` method, `frame` is assumed
-- to be a Lua arguments table, such as the
-- arguments from a named arguments call.
-- @param[opt] {table} options Extraction/processing options.
-- @param[opt] {boolean} options.trim
-- Whether to trim the blank arguments present in
-- the arguments table. Accepts `false` only.
-- Default: `true`.
-- @param[opt] {boolean} options.removeBlanks
-- Whether to remove blank arguments from the
-- arguments table. Does not shift sequential
-- arguments removed by the processing stage.
-- Accepts `false` only. Default: `true`.
-- @param[opt] {boolean} options.valueFunc
-- Custom value tidying function for use if the
-- `trim` and `removeBlanks` options don't cover
-- the developer's argument processing use case.
-- @param[opt] {boolean} options.frameOnly
-- Only read arguments from child frame (the
-- `frame` parameter - usually invocation frame).
-- @param[opt] {boolean} options.parentOnly
-- Only read arguments from `frame` parent (the
-- `frame` parameter - usually template frame).
-- @param[opt] {boolean} options.parentFirst
-- Argument lookup in the `frame` parent first,
-- prioritised over the invocation frame arguments.
-- @param[opt] {table} options.wrappers
-- Individual value or array of values, listing
-- wrapper title name(s) or article ID(s) to permit
-- parent argument lookup from.
-- @param[opt] {string|number} options.wrapper
-- Alias of `options.wrappers` - contains title
-- name or article ID to permit parent argument
-- lookup from.
-- @param[opt] {boolean} options.readOnly
-- Whether to restrict write permissions to the
-- arguments table. When set to a truthy value,
-- an error will be thrown on any write attempt.
-- @param[opt] {boolean} options.noOverwrite
-- Whether to restrict overwrite attempts on
-- existing argument keys in the arguments table.
-- When set to a truthy value, an error will be
-- thrown on any write attempt that would result
-- in an existing argument being overwritten.
-- @param[opt] {table} options.translate
-- Map of parameter name aliases to their canonical
-- argument parameter names.
-- @param[opt] {table} options.backtranslate
-- Map of canonical parameter names to their
-- argument parameter aliases.
-- Supersedes `options.translate` if both options
-- are in use.
-- @error[opt,317] 'bad value assigned to option "valueFunc"
-- (function expected, got $type)'
-- @error[opt,407] 'could not write to argument table key "$key";
-- the table is read-only'
-- @error[opt,409] 'could not write to argument table key "$key";
-- overwriting existing arguments is not permitted'
-- @return {table} Arguments extracted from invocation.
-- The argument data is embedded as a metatable in
-- the exported table and cannot be accessed with
-- the `#` operator or @{table} library methods.
-- However, the exported table can be written to if
-- the `options.readOnly` flag parameter is not
-- truthy.
-- @usage
--
-- local getArgs = require('Module:Arguments').getArgs
-- function p.main(frame)
-- local args = getArgs(frame, {
-- wrapper = 'Template:<TEMPLATE>'
-- })
-- -- Use the args table here.
-- -- A common paradigm is `return p._main(args)`.
-- -- This allows other Lua modules to access the
-- -- main logic in a performant manner without a
-- -- frame object.
-- end
--
-- @note Reference tags in the form of `<ref>` will
-- generate phantom references when calling the
-- @{pairs} iterator on the arguments table,
-- **IF** the `<ref>` tag does not appear in the
-- dependent module's wikitext output.
function arguments.getArgs(frame, options)
checkType('getArgs', 1, frame, 'table', true)
checkType('getArgs', 2, options, 'table', true)
frame = frame or {}
options = options or {}
-- Set up argument translation.
options.translate = options.translate or {}
if getmetatable(options.translate) == nil then
setmetatable(options.translate, translate_mt)
end
if options.backtranslate == nil then
options.backtranslate = {}
for k,v in pairs(options.translate) do
options.backtranslate[v] = k
end
end
if options.backtranslate and getmetatable(options.backtranslate) == nil then
setmetatable(options.backtranslate, {
__index = function(t, k)
if options.translate[k] ~= k then
return nil
else
return k
end
end
})
end
-- Get the argument tables. If we were passed a valid frame object,
-- get the frame arguments (fargs) and the parent frame arguments
-- (pargs), depending on the options set and on the parent frame's
-- availability. If we weren't passed a valid frame object, we are
-- being called from another Lua module or from the debug console,
-- so assume that we were passed a table of args directly, and
-- assign it to a new variable (luaArgs).
local fargs, pargs, luaArgs
options.wrappers = options.wrappers or options.wrapper
if
type(frame.args) == 'table' and
type(frame.getParent) == 'function'
then
-- The wrappers option makes Module:Arguments look up
-- arguments in either the frame argument table or the
-- parent argument table, but not both. This means that
-- users can use either the #invoke syntax or a wrapper
-- template without the loss of performance associated
-- with looking arguments up in both the frame and the
-- parent frame.
-- The arguments will be fetched from the parent frame if
-- the parent frame's title is present in options.wrapper;
-- otherwise it will look up arguments in the frame object
-- passed to getArgs.
if options.wrappers then
local parent = frame:getParent()
if not parent then
fargs = frame.args
else
local title = parent:getTitle():gsub('/sandbox$', '')
local found = false
if matchesTitle(options.wrappers, title) then
found = true
elseif type(options.wrappers) == 'table' then
for _,v in pairs(options.wrappers) do
if matchesTitle(v, title) then
found = true
break
end
end
end
-- We test for false specifically here so that nil (the
-- default) acts like true.
if found or options.frameOnly == false then
pargs = parent.args
end
if not found or options.parentOnly == false then
fargs = frame.args
end
end
-- When options.wrapper isn't set, check the other options.
else
if not options.parentOnly then
fargs = frame.args
end
if not options.frameOnly then
local parent = frame:getParent()
pargs = parent and parent.args or nil
end
end
if options.parentFirst then
fargs, pargs = pargs, fargs
end
else
luaArgs = frame
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
-- 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(i18n:msg('error-value-func', type(tidyVal)), 2)
end
elseif options.trim ~= false then
if options.removeBlanks ~= false then
tidyVal = tidyValDefault
else
tidyVal = tidyValTrimOnly
end
else
if options.removeBlanks ~= false then
tidyVal = tidyValRemoveBlanksOnly
else
tidyVal = tidyValNoChange
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)
-- Accepts multiple tables as input and merges their keys and values
-- into one table. If a value is already present it is not overwritten;
-- tables listed earlier have precedence. We are also memoizing nil
-- values, which can be overwritten if they are 's' (soft).
local function mergeArgs(tables)
for _, t in ipairs(tables) do
for key, val in pairs(t) do
if metaArgs[key] == nil and nilArgs[key] ~= 'h' then
local tidiedVal = tidyVal(key, val)
if tidiedVal == nil then
nilArgs[key] = 's'
else
metaArgs[key] = tidiedVal
end
end
end
end
end
-- Define metatable behaviour. Arguments are memoized in the metaArgs table,
-- and are only fetched from the argument tables once. Fetching arguments
-- from the argument tables is the most resource-intensive step in this
-- module, so we try and avoid it where possible. For this reason, nil
-- 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.
-- 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.
metatable.__index = function (t, key)
if type(key) == 'string' then
key = options.translate[key]
end
local val = metaArgs[key]
if val ~= nil then
return val
elseif metatable.donePairs or nilArgs[key] then
return nil
end
for _, argTable in ipairs(argTables) do
local argTableVal = tidyVal(key, argTable[key])
if argTableVal ~= nil then
metaArgs[key] = argTableVal
return argTableVal
end
end
nilArgs[key] = 'h'
return nil
end
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 type(key) == 'string' then
key = options.translate[key]
end
if options.readOnly then
error(i18n:msg('error-write-permission', tostring(key)), 2)
elseif options.noOverwrite and args[key] ~= nil then
error(i18n:msg('error-overwrite-permission', tostring(key)), 2)
elseif val == nil then
-- 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] = 'h'
else
metaArgs[key] = val
end
end
local function translatenext(invariant)
local k, v = next(invariant.t, invariant.k)
invariant.k = k
if k == nil then
return nil
elseif type(k) ~= 'string' or not options.backtranslate then
return k, v
else
local backtranslate = options.backtranslate[k]
if backtranslate == nil then
-- Skip this one. This is a tail call, so this
-- won't cause stack overflow.
return translatenext(invariant)
else
return backtranslate, v
end
end
end
-- This metamethod is called when pairs is run on the args table.
metatable.__pairs = function ()
if not metatable.donePairs then
mergeArgs(argTables)
metatable.donePairs = true
end
return translatenext, { t = metaArgs }
end
-- This custom `ipairs`-style iterator uses our __index metamethod.
local function inext(t, i)
local v = t[i + 1]
if v ~= nil then
return i + 1, v
end
end
-- This metamethod is called when ipairs is run on the args table.
metatable.__ipairs = function (t)
return inext, t, 0
end
return args
end
return arguments