From Lojban
Revision as of 19:42, 28 February 2014 by Gleki (talk | contribs) (1 revision)
Jump to navigation Jump to search

-- 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 val = val:match('^%s*(.-)%s*$') if val == then return nil else return val end else return val end end

local function tidyValTrimOnly(key, val) if type(val) == 'string' then return val:match('^%s*(.-)%s*$') else return val end end

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

local function tidyValNoChange(key, val) return val end

function arguments.getArgs(frame, options) checkType('getArgs', 1, frame, 'table', true) checkType('getArgs', 2, options, 'table', true) 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 if not options.parentOnly then fargs = frame.args end if not options.frameOnly then pargs = frame:getParent().args end if options.parentFirst then fargs, pargs = pargs, fargs end else 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 if options.removeBlanks ~= false then tidyVal = tidyValDefault else tidyVal = tidyValTrimOnly end else if options.removeBlanks ~= false then tidyVal = tidyValRemoveBlanksOnly else tidyVal = tidyValNoChange 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 local metaArgsVal = metaArgs[key] if metaArgsVal == nil or metaArgsVal == nilArg then local tidiedVal = tidyVal(key, val) if tidiedVal == nil then metaArgs[key] = nilArg else metaArgs[key] = tidiedVal end 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 = {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 val ~= nil then if val == nilArg then return nil else return val end end for _, argTable in ipairs(argTables) do local argTableVal = tidyVal(key, argTable[key]) if argTableVal == nil then metaArgs[key] = nilArg else metaArgs[key] = argTableVal return argTableVal end end 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. else metaArgs[key] = val end end

metatable.__pairs = function () if not metatable.donePairs then mergeArgs(pairs, argTables) metatable.donePairs = true metatable.doneIpairs = true end return function (t, k) local nk, val = next(metaArgs, k) if val == nilArg then val = nil end return nk, val end end

metatable.__ipairs = function () if not metatable.doneIpairs then mergeArgs(ipairs, argTables) metatable.doneIpairs = true end return function (t, i) local val = metaArgs[i + 1] if val == nil then return nil elseif val == nilArg then val = nil end return i + 1, val end, nil, 0 end

return args end

return arguments