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perf: simplify mapped logic

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littensy 2025-05-06 17:07:30 -07:00
parent f704acce71
commit b61d0b3b86
2 changed files with 14 additions and 56 deletions
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68
pkgs/charm/src/mapped.luau
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@ -10,12 +10,12 @@ type Mapped =
& (<KI, VI, KO, VO>(selector: () -> { [KI]: VI }, mapper: (item: VI, key: KI) -> (VO, KO)) -> () -> { [KO]: VO })
& (<K, VI, VO>(selector: () -> { [K]: VI }, mapper: (item: VI, key: K) -> VO) -> () -> { [K]: VO })
local function ensureCanMutateOutput<KO, VO>(output: { [KO]: VO }, previous: { [KO]: VO }): { [KO]: VO }
local function ensureCanMutateOutput<KO, VO>(output: { [KO]: VO }, previous: { [KO]: VO }?): { [KO]: VO }
return if output == previous then table.clone(output) else output
end
local function mapped<KI, VI, KO, VO>(selector: () -> { [KI]: VI }, mapper: (item: VI, key: KI) -> (VO, KO)): () -> { [KO]: VO }
local currentData: { [KI]: VI }
local currentData: { [KI]: VI } = {}
local keyCache: { [KI]: KO } = {}
local function map(value: VI, key: KI): (VO, KO)
@ -31,75 +31,33 @@ local function mapped<KI, VI, KO, VO>(selector: () -> { [KI]: VI }, mapper: (ite
end
return computed(function(previousOutput)
local currentOutput: { [KO]: VO } = previousOutput or {}
local previousData = currentData
currentData = selector()
-- Only perform additions if this is the first run
if not previousOutput then
local output: { [KO]: VO } = {}
for key, value in currentData do
local valueOut, keyOut = map(value, key)
if valueOut ~= nil then
output[keyOut] = valueOut
keyCache[key] = keyOut
end
for key, cachedKey in keyCache do
if currentData[key] ~= nil then
continue
end
return output
currentOutput = ensureCanMutateOutput(currentOutput, previousOutput)
currentOutput[cachedKey] = nil
keyCache[key] = nil
end
local output = previousOutput
-- Check equality since the selector might not be a computed value
if currentData == previousData then
return output
end
-- Clear removed values from the output and key cache
for key in previousData do
if currentData[key] == nil then
local keyOut = keyCache[key]
if keyOut then
output = ensureCanMutateOutput(output, previousOutput)
output[keyOut] = nil
keyCache[key] = nil
end
end
end
-- Process new or changed values
for key, value in currentData do
if value == previousData[key] then
continue
end
local valueOut, keyOut = map(value, key)
local cachedKeyOut = keyCache[key]
if valueOut ~= nil then
-- Skip update if the key and value are the same
if keyOut == cachedKeyOut and valueOut == output[cachedKeyOut] then
continue
end
output = ensureCanMutateOutput(output, previousOutput)
output[keyOut] = valueOut
keyCache[key] = keyOut
-- Remove the old key if a new key is assigned
if cachedKeyOut ~= nil and keyOut ~= cachedKeyOut then
output[cachedKeyOut] = nil
end
elseif cachedKeyOut ~= nil then
-- Remove the cached key if the new value is nil
output = ensureCanMutateOutput(output, previousOutput)
output[cachedKeyOut] = nil
keyCache[key] = nil
end
currentOutput = ensureCanMutateOutput(currentOutput, previousOutput)
currentOutput[keyOut] = valueOut
keyCache[key] = keyOut
end
return output
return currentOutput
end)
end