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fix(saveslot): persist the Continue pointer apart from the active slot #781

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fix(saveslot): persist the Continue pointer apart from the active slot #781

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20b696f
fix(saveslot): persist the Continue pointer apart from the active slot
Quenty Jul 30, 2026
2498164
Merge branch 'main' into users/jamesonnen/persist-continue-pointer
Quenty Jul 30, 2026
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172 changes: 110 additions & 62 deletions src/saveslot/src/Server/Binders/HasSaveSlots.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ local ObservableMap = require("ObservableMap")
local PlayerBinder = require("PlayerBinder")
local PlayerDataStoreService = require("PlayerDataStoreService")
local Promise = require("Promise")
local PromiseUtils = require("PromiseUtils")
local Remoting = require("Remoting")
local Rx = require("Rx")
local RxBrioUtils = require("RxBrioUtils")
Expand Down Expand Up @@ -74,6 +75,7 @@ export type HasSaveSlots =
_metadataStore: any,
_summaryProviders: ObservableMap.ObservableMap<string, SummaryProvider>,
_lastActiveSlotId: SaveSlotData.SlotId?,
_persistedActiveSlotId: SaveSlotData.SlotId?,
_teleportDataService: any,
_sharedSaveSlotDataStoreService: any,
_playSessionSlotId: SaveSlotData.SlotId?,
Expand Down Expand Up @@ -782,12 +784,15 @@ function HasSaveSlots.PromiseDeleteSlot(self: HasSaveSlots, slotId: SaveSlotData

self._maid[slotId] = nil

-- The continue pointer must not outlive its slot. When the deleted slot is the one the player
-- would resume on (e.g. the just-deselected active slot, or a never-reselected last-active),
-- clear the last-active memory so "Continue" stops offering a slot that no longer exists.
-- Neither pointer may outlive its slot, and they are checked apart: the persisted active slot
-- outlives the session that wrote it, so it can still name this slot while a different one is
-- selected now. Each is retired only when it is this slot that is going.
if slotId == self._lastActiveSlotId then
self._lastActiveSlotId = nil
self.LastActiveSlotId.Value = nil
self:_setContinueSlotId(nil)
end

if slotId == self._persistedActiveSlotId then
self:_setPersistedActiveSlotId(nil)
end

-- Wipe default slot
Expand Down Expand Up @@ -826,8 +831,11 @@ function HasSaveSlots.PromiseDeleteAllSlots(self: HasSaveSlots): Promise.Promise
return (self._loadPromise :: any):Then(function()
-- Clear the selection first so the previously active slot is deletable
self.ActiveSlotId.Value = nil
self._lastActiveSlotId = nil
self.LastActiveSlotId.Value = nil

-- Every slot is going, so both pointers are retired outright rather than left to the selection hook
-- above: it writes nothing when no slot was selected, and skips an ephemeral deselect.
self:_setContinueSlotId(nil)
self:_setPersistedActiveSlotId(nil)

local slotIds = {}
for slotId in self._slotMap do
Expand Down Expand Up @@ -898,8 +906,7 @@ function HasSaveSlots.PromiseResetSlot(
-- Non-active reset never reselects, so carry the resume pointer onto the fresh id
-- ourselves when this slot was the one "Continue" would resume.
if wasLastActive then
self._lastActiveSlotId = newSlotId
self.LastActiveSlotId.Value = newSlotId
self:_setContinueSlotId(newSlotId)
end

return newSlotId
Expand Down Expand Up @@ -1133,7 +1140,9 @@ function HasSaveSlots._promiseLoadSlots(self: HasSaveSlots): Promise.Promise<{}>
self._systemStore = dataStore:GetSubStore(SaveSlotConstants.SYSTEM_STORE_KEY)
self._metadataStore = self._systemStore:GetSubStore(SaveSlotConstants.METADATA_STORE_KEY)

return self._maid:GivePromise(self._metadataStore:LoadAll({})):Then(function(metadata)
-- Annotated because the branches differ: the liveness guard returns nil where the body returns the
-- seeding promise, and inferring from the first of those makes the other an error.
return self._maid:GivePromise(self._metadataStore:LoadAll({})):Then(function(metadata): any
if not self.Destroy then
return nil -- Destroyed
end
Expand All @@ -1142,62 +1151,101 @@ function HasSaveSlots._promiseLoadSlots(self: HasSaveSlots): Promise.Promise<{}>
self:_buildSlot(slotId, data)
end

return self._maid
:GivePromise(self._systemStore:Load("activeSlotId"))
:Then(function(activeId: SaveSlotData.SlotId?)
if not self.Destroy then
return nil -- Destroyed
end
return self:_promiseSeedSlotPointers()
end)
end)
end

self._lastActiveSlotId = activeId
self.LastActiveSlotId.Value = activeId

-- The persisted active-slot pointer and the replicated "Continue" target only ever track real
-- slots. This replaces StoreOnValueChange so an ephemeral selection is invisible to both:
-- entering one leaves them pinned to the real slot, and the ephemeral slot is torn down the
-- moment it stops being active. We track the id we are leaving to know which of those to do.
local previousActiveSlotId: SaveSlotData.SlotId? = activeId

self._maid:GiveTask(self.ActiveSlotId.Changed:Connect(function()
local active = self.ActiveSlotId.Value

-- Replicate the active transferable-ephemeral slot's shared-store key (nil otherwise) so a
-- client-initiated teleport can carry it forward (SaveSlotServiceClient's provider reads this).
self.ActiveTransferableEphemeralKey.Value = if active
then self._transferableEphemeralKeys[active]
else nil

local leftSlotId = previousActiveSlotId
-- Read before the retire below, while the outgoing slot is still in the map.
local leavingEphemeral = self:_isEphemeral(leftSlotId)
previousActiveSlotId = active

-- Persist the pointer + remember the Continue target only for real-slot transitions
-- (real -> real, real -> nil deselect, nil -> real). Skip both ephemeral cases: entering an
-- ephemeral slot must stay invisible to persistence, and leaving one back to no slot must
-- leave the real pointer pinned where it was.
local enteringEphemeral = self:_isEphemeral(active)
local leavingEphemeralToMenu = leavingEphemeral and active == nil
if not (enteringEphemeral or leavingEphemeralToMenu) then
self._systemStore:Store("activeSlotId", active)
if active ~= nil then
self._lastActiveSlotId = active
self.LastActiveSlotId.Value = active
end
end
-- Moves the "Continue" pointer: what this session reads, what replicates to the client, and what carries
-- to the next session. All three together, or a consumer reads one the others have retired.
function HasSaveSlots._setContinueSlotId(self: HasSaveSlots, slotId: SaveSlotData.SlotId?): ()
self._lastActiveSlotId = slotId
self.LastActiveSlotId.Value = slotId
self._systemStore:Store(SaveSlotConstants.LAST_ACTIVE_SLOT_ID_KEY, slotId)
end

-- An ephemeral slot exists only while it is the active slot; retire the one we just left.
if leavingEphemeral and leftSlotId ~= active then
self:_destroyEphemeralSlot(leftSlotId :: SaveSlotData.SlotId)
end
end))
-- Moves the persisted active slot, mirrored in memory so a delete can tell whether the key names the slot
-- going away. Only ever written for real-slot transitions -- see the selection hook below.
function HasSaveSlots._setPersistedActiveSlotId(self: HasSaveSlots, slotId: SaveSlotData.SlotId?): ()
self._persistedActiveSlotId = slotId
self._systemStore:Store(SaveSlotConstants.ACTIVE_SLOT_ID_KEY, slotId)
end

-- Matches the liveness-guard returns above, which make this callback's inferred return
-- type nil; falling off the end instead returns no values at all.
return nil
end)
-- Restores the Continue pointer from whichever key the last session left it in, then keeps both keys in
-- step with every selection this one makes. The active slot is deliberately not restored -- a session
-- starts at no slot however the last one ended.
--
-- The read is maid-owned and the continuation re-checks we are alive, for the same reason as the rest of the
-- load it is a hop of: see _promiseLoadSlots.
function HasSaveSlots._promiseSeedSlotPointers(self: HasSaveSlots): Promise.Promise<()>
return self._maid
:GivePromise(PromiseUtils.all({
self._systemStore:Load(SaveSlotConstants.ACTIVE_SLOT_ID_KEY),
self._systemStore:Load(SaveSlotConstants.LAST_ACTIVE_SLOT_ID_KEY),
}))
:Then(function(activeId: SaveSlotData.SlotId?, continueId: SaveSlotData.SlotId?)
if not self.Destroy then
return nil -- Destroyed
end

-- The active slot is read first because it is the only pointer data written before the Continue key
-- existed has -- that fallback is what keeps Continue for a player upgrading onto this build.
self._persistedActiveSlotId = activeId
self._lastActiveSlotId = activeId or continueId
self.LastActiveSlotId.Value = self._lastActiveSlotId

-- Every slot this player has is built above, so a pointer naming none of them names a slot that went
-- away -- deleted by another server, or by a session that left this key behind. Retire it on disk too:
-- now that the pointer outlives a deselect, nothing else ever would.
local seeded = self._lastActiveSlotId
if seeded ~= nil and (self._slotMap[seeded] :: Folder?) == nil then
self:_setContinueSlotId(nil)
self:_setPersistedActiveSlotId(nil)
end

-- The persisted active-slot pointer and the replicated "Continue" target only ever track real
-- slots. This replaces StoreOnValueChange so an ephemeral selection is invisible to both:
-- entering one leaves them pinned to the real slot, and the ephemeral slot is torn down the
-- moment it stops being active. We track the id we are leaving to know which of those to do.
local previousActiveSlotId: SaveSlotData.SlotId? = activeId

self._maid:GiveTask(self.ActiveSlotId.Changed:Connect(function()
local active = self.ActiveSlotId.Value

-- Replicate the active transferable-ephemeral slot's shared-store key (nil otherwise) so a
-- client-initiated teleport can carry it forward (SaveSlotServiceClient's provider reads this).
self.ActiveTransferableEphemeralKey.Value = if active
then self._transferableEphemeralKeys[active]
else nil

local leftSlotId = previousActiveSlotId
-- Read before the retire below, while the outgoing slot is still in the map.
local leavingEphemeral = self:_isEphemeral(leftSlotId)
previousActiveSlotId = active

-- Persist the pointer + remember the Continue target only for real-slot transitions
-- (real -> real, real -> nil deselect, nil -> real). Skip both ephemeral cases: entering an
-- ephemeral slot must stay invisible to persistence, and leaving one back to no slot must
-- leave the real pointer pinned where it was.
local enteringEphemeral = self:_isEphemeral(active)
local leavingEphemeralToMenu = leavingEphemeral and active == nil
if not (enteringEphemeral or leavingEphemeralToMenu) then
self:_setPersistedActiveSlotId(active)
if active ~= nil then
self:_setContinueSlotId(active)
end
end

-- An ephemeral slot exists only while it is the active slot; retire the one we just left.
if leavingEphemeral and leftSlotId ~= active then
self:_destroyEphemeralSlot(leftSlotId :: SaveSlotData.SlotId)
end
end))

-- Matches the liveness-guard return above, which makes this callback's inferred return type nil;
-- falling off the end instead returns no values at all.
return nil
end)
end)
end

function HasSaveSlots._getSlotStore(self: HasSaveSlots, slotId: SaveSlotData.SlotId): DataStoreStage.DataStoreStage
Expand Down
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