Module:Sandbox/Artoria2e5/Fallback: Difference between revisions

Revision as of 14:20, 13 October 2016

Latest revision as of 17:16, 2 April 2020

(4 intermediate revisions by one other user not shown)

Line 6:

local oldArgsMeta = getmetatable(args) or {}

local newArgsMeta = {}

-- Forget about thread-safety.

-- States kept to avoid strange loops.

local referencedKeys = {} -- dataType:Set/hashtable-impl

local attemptDepth = 0 -- useful for "last nil" case

-- Start the new metatable as a copy of the old metatable.

for k, v in ipairs(oldArgsMeta) do

newArgsMeta[k] = v

end

-- Change the __index metamethod to our implementation.

-- See https://www.lua.org/pil/13.4.1.html.

newArgsMeta.__index = function (t, k)

-- My friend, why are you here again?

-- Try the old metamethod first.

if referencedKeys[k] then

-- Thanks to closures, this whole oldArgsMeta object will stay.

-- You have to be drunk. Go home.

if oldArgsMeta.__index ~= nil then

return valnil

local val = oldArgsMeta.__index(t, k)

end

if val ~= nil then

referencedKeys[k] = true

return val

end

end

-- Try the old metamethod first.

-- Thanks to closures, this whole oldArgsMeta object will stay.

if oldArgsMeta.__index ~= nil then

local val = oldArgsMeta.__index(t, k)

if val ~= nil then

referencedKeys = {}

return val

end

end

attemptDepth = attemptDepth + 1

-- Now try use the aliases given.

for _, v in ipairs(arg_aliases[k] or {}) do

-- If a working value is found, use it.

-- Note: mw-argument-specific empty str chk.

if t[v] ~= nil and t[v] ~= '' then

if t[v] ~= nil returnand t[v] ~= '' then

referencedKeys = {}

end

return t[v]

end

end

attemptDepth = attemptDepth - 1

if attemptDepth == 0 then

referencedKeys = {}

end

return nil

Line 38 ⟶ 59:

return makeFallback

--[[

P.S. Don't blame me for writing these obj-states. Sure, we can use an

accumulator and do some "index with acc" ourselves, but that sounds like too

much work done just to avoid states.

Here is that custom index function in case anyone is curious about it:

function index_w_acc(t, k, acc)

local v = rawget(t, k)

if v ~= nil

endreturn v

else

return getmetatable(t).__index(k, acc)

end

end

My guess is that it will certainly be slower than the native t[k] one. Perhaps

not getting the metatable every time will help a bit.

]]--