Honor modded bag capacity

docs/gameboy-hardware-limitations.md

@@ -12,7 +12,7 @@ this port.
 
 | # | Mechanic | Value | Why the Game Boy had this limit | Where it lives here |
 |---|---|---|---|---|
-| 1 | Bag capacity | 20 item slots | `wNumBagItems` save block was a fixed 20-entry id/quantity array in SRAM | `src/inventory/Bag.lua:8` (`Bag.CAPACITY = 20`) |
+| 1 | Bag capacity | 20 item slots by default | `wNumBagItems` save block was a fixed 20-entry id/quantity array in SRAM | `Data.constants.bagSize`, read by `src/inventory/Bag.lua` (`Bag.capacity`) |
 | 2 | Party size | 6 Pokémon | `wPartyMon1..6` were 6 fixed save-RAM slots | `src/pokemon/Party.lua:5` (`Party.MAX = 6`) |
 | 3 | PC storage | 12 boxes × 20 Pokémon | `wBoxDataStart` / Bill's PC allocated a fixed 12×20 SRAM block | `src/pokemon/Boxes.lua:7-8` |
 | 4 | Moves per Pokémon | 4 | Fixed 4-move-slot field in the party/box Pokémon struct | `src/pokemon/Pokemon.lua:20`, enforced again in `src/battle/BattleState.lua:1941` |
@@ -38,6 +38,10 @@ this port.
 
 ## Notes
 
+- Mods may patch `constants.bagSize` through the public content registry. The
+  native `save.lua` format keeps every existing item when the configured
+  limit changes; exporting to a cartridge `.sav` still writes only the first
+  20 bag slots because the original SRAM layout has no room for more.
 - PC Box **overflow handling** was deliberately changed even though the
   20×12 box *shape* was kept faithful: instead of Gen 1's "full box discards
   or blocks the deposit," this port spills into the next box with room.

docs/new-features.md

@@ -380,7 +380,8 @@ semantics - so the two windows read as one app. Six tabs:
   party dock, so deposit and withdraw live in one place. Empty slots are
   clickable and create a mon there.
 - **Items**: money, a searchable item picker (replacing the arrows that
-  cycled one id at a time through ~250 items), the 20-slot bag, PC storage
+  cycled one id at a time through ~250 items), the configurable bag (20 slots
+  by default), PC storage
   with no slot cap, and the eight badges as toggle chips.
 - **Events**: flags, defeated trainers, taken items and per-map object
   toggles, with a real filter field and a two-column paged grid.

mods/nuzlocke/main.lua

@@ -156,7 +156,7 @@ return function(mod)
           caughtAreas()[areaKey(self.game, self)] = "DUPES_LOST"
           mod.save:set("caught_areas", caughtAreas())
         end
-        Bag.add(self.game.save, ball, 1)
+        Bag.add(self.game.save, ball, 1, self.game.data)
         self:say(reason == "area" and "This area already\nhas a captured POKéMON!"
           or "You already have\nthis POKéMON family!")
         return

src/core/Data.lua

@@ -14,12 +14,12 @@ local MODULES = {
 -- Optional for compatibility with developer and stale caches.
 local OPTIONAL = { "audio", "palettes", "icons" }
 
--- The rules the engine still carries as literals.  The constants registry
+-- Vanilla defaults for rules exposed through the constants registry.  A
--- deep-merges over these, so a value has to exist before a mod can patch
+-- value has to exist before a mod can patch it; each one matches the
--- it; each one is the number the engine hard-codes today, so seeding them
+-- engine's no-mod behavior, so seeding them changes nothing on a vanilla
--- changes nothing on a mod-free boot.
+-- boot.
 local CONSTANT_DEFAULTS = {
-  bagSize = 20,                 -- BAG_ITEM_CAPACITY (src/inventory/Bag.lua)
+  bagSize = 20,                 -- BAG_ITEM_CAPACITY (Bag.capacity fallback)
   partyMax = 6,                 -- PARTY_LENGTH (src/pokemon/Party.lua)
   boxCount = 12, boxSize = 20,  -- Bill's PC (src/pokemon/Boxes.lua)
   moveMax = 4,

src/core/SaveData.lua

@@ -1058,7 +1058,7 @@ local function reclaim(save, data, report)
     if type(entry) == "table" and known(data.items, entry.id) then
       table.remove(orphaned.items, i)
       if entry.from == "pcItems" or type(save.inventory) ~= "table"
-          or not Bag.add(save, entry.id, entry.count or 1) then
+          or not Bag.add(save, entry.id, entry.count or 1, data) then
         save.pcItems = save.pcItems or {}
         save.pcItems[entry.id] = (save.pcItems[entry.id] or 0) + (entry.count or 1)
       end

src/dev/Console.lua

@@ -214,7 +214,7 @@ function VERBS.give(self, rest)
     end
   elseif game.data.items and game.data.items[id] then
     local n = tonumber(count) or 1
-    if require("src.inventory.Bag").add(save, id, n) then
+    if require("src.inventory.Bag").add(save, id, n, game.data) then
       self:print(("%s x%d added"):format(id, n))
     else
       self:print("bag full")

src/inventory/Bag.lua

@@ -1,11 +1,26 @@
--- The 20-slot bag (BAG_ITEM_CAPACITY, constants/menu_constants.asm):
+-- The bag defaults to 20 slots (BAG_ITEM_CAPACITY,
--- a distinct item id occupies one slot regardless of quantity; badges
+-- constants/menu_constants.asm), but mods may replace that limit through
--- live in the inventory table but are not bag items.  save.bagOrder
+-- Data.constants.bagSize.  A distinct item id occupies one slot regardless
--- keeps acquisition order like wBagItems (SELECT can reorder it).
+-- of quantity; badges live in the inventory table but are not bag items.
+-- save.bagOrder keeps acquisition order like wBagItems (SELECT can reorder
+-- it).
 
 local Bag = {}
 
-Bag.CAPACITY = 20
+local DEFAULT_CAPACITY = 20
+
+-- `data` is injectable for the save editor and headless mod tests.  Normal
+-- gameplay may omit it because the loader merges mods into the Data
+-- singleton before any item can be added.  The fallback keeps old/stale
+-- generated caches and isolated callers at the vanilla limit.
+function Bag.capacity(data)
+  data = data or require("src.core.Data")
+  local configured = data and data.constants and data.constants.bagSize
+  if type(configured) == "number" and configured >= 1 then
+    return math.floor(configured)
+  end
+  return DEFAULT_CAPACITY
+end
 
 local function isBadge(id)
   return id:find("BADGE", 1, true) ~= nil
@@ -55,9 +70,10 @@ end
 -- Add qty of an item; returns false (and adds nothing) when a new slot
 -- is needed and the bag is full, or when the stack would pass 99
 -- (AddItemToInventory's per-slot quantity cap).
-function Bag.add(save, id, qty)
+function Bag.add(save, id, qty, data)
   local inv = save.inventory
-  if not inv[id] and not isBadge(id) and Bag.slots(save) >= Bag.CAPACITY then
+  if not inv[id] and not isBadge(id)
+      and Bag.slots(save) >= Bag.capacity(data) then
     return false
   end
   if not isBadge(id) and (inv[id] or 0) + (qty or 1) > 99 then

src/script/Commands.lua

@@ -210,11 +210,12 @@ end
 -- text (label or literal; {RAM:wStringBuffer} becomes the item name);
 -- pass false when the script shows its own received-text row.
 function Commands.give_item(ctx, itemId, count, gotText)
-  -- the 20-slot bag can refuse (BAG_ITEM_CAPACITY): say so and halt
+  -- the bag can refuse at its configured capacity (20 in vanilla): halt
   -- the script, so later set_flag rows don't burn the gift -- make
   -- room and talk again, like the original (pokered's `jr nc, .bag_full`
   -- skips the received text entirely when AddItemToInventory refuses)
-  if not require("src.inventory.Bag").add(ctx.save, itemId, count or 1) then
+  if not require("src.inventory.Bag").add(
+      ctx.save, itemId, count or 1, ctx.game.data) then
     Commands.show_text(ctx, ctx.game.data.text
       and ctx.game.data.text._BagFullText or Strings("You can't carry\nany more items!"))
     return math.huge

src/ui/PlayerPC.lua

@@ -76,7 +76,7 @@ local function withdraw(game)
     onChoose = function(item, list)
       askQuantity(game, list, pc[item.value] or 1, item.value, function(qty)
         local Bag = require("src.inventory.Bag")
-        if not Bag.add(game.save, item.value, qty) then
+        if not Bag.add(game.save, item.value, qty, game.data) then
           list.footer = Strings("You can't carry\nany more items.")
           return
         end

src/ui/ShopMenu.lua

@@ -67,7 +67,7 @@ local function buy(game, stock)
               list.footer = notEnough
               return
             end
-            if not Bag.add(game.save, item.value, qty) then
+            if not Bag.add(game.save, item.value, qty, game.data) then
               list.footer = txt(game, "_PokemartItemBagFullText",
                                 Strings("You can't carry\nany more items."))
               return

src/world/OverworldController.lua

@@ -1803,7 +1803,7 @@ function OverworldState:tryHiddenObject(fx, fy)
     if h.x == fx and h.y == fy then
       save.hiddenTaken = save.hiddenTaken or {}
       if save.hiddenTaken[key] then return false end
-      if not require("src.inventory.Bag").add(save, h.item, 1) then
+      if not require("src.inventory.Bag").add(save, h.item, 1, Game.data) then
         Game.stack:push(TextBox.new(Game, Strings("You can't carry\nany more items!")))
         return true
       end
@@ -2423,7 +2423,7 @@ function OverworldState:talkTo(npc)
   -- (e.g. Blue's House wall Town Map / walking Daisy, #11).  Lua treats
   -- the string "0" as truthy, so screen it out and fall through to text.
   if d.item and d.item ~= "0" and d.item ~= 0 then
-    if not require("src.inventory.Bag").add(Game.save, d.item, 1) then
+    if not require("src.inventory.Bag").add(Game.save, d.item, 1, Game.data) then
       Game.stack:push(TextBox.new(Game, Strings("You can't carry\nany more items!")))
       return
     end

tests/drivers/route.lua

@@ -2414,14 +2414,15 @@ local function sellItem(id)
   return sold
 end
 
--- Free up bag slots so `needed` NEW item kinds fit (Bag.CAPACITY is 20
+-- Free up bag slots so `needed` NEW item kinds fit (20 slots without a
--- slots; a stack of an item already held costs nothing). This is why
+-- capacity mod; a stack of an item already held costs nothing). This is why
 -- every restock had been reporting "HYPER_POTION x0": the buy list
 -- opened, the quantity was set, the engine said "no room" -- and the run
 -- walked into the Mansion with FULL_HEALs but not one HP restore.
 local function freeBagSlots(needed, where)
   local used = #(G.save.bagOrder or {})
-  local free = 20 - used
+  local capacity = require("src.inventory.Bag").capacity(G.data)
+  local free = capacity - used
   for _, id in ipairs(SELLABLE_JUNK) do
     if free >= needed then break end
     if ((G.save.inventory or {})[id] or 0) > 0 then
@@ -2632,7 +2633,8 @@ function ops.shop(s, where)
       end
     end
     local used = #(G.save.bagOrder or {})
-    if newKinds > 0 and 20 - used < newKinds then
+    local capacity = require("src.inventory.Bag").capacity(G.data)
+    if newKinds > 0 and capacity - used < newKinds then
       freeBagSlots(newKinds, where)
     end
   end

tests/modkit/cases/bag_capacity.lua

@@ -0,0 +1,69 @@
+-- T4: constants.bagSize controls the bag through the public mod API while
+-- vanilla and existing-save behavior remain unchanged.
+
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+local T = require("tests.modkit")
+local Bag = require("src.inventory.Bag")
+
+local CAPACITY_MOD = {
+  ["mods/fix_small_bag/manifest.json"] = [[{
+    "id": "fix_small_bag",
+    "name": "Fixture Small Bag",
+    "version": "1.0.0",
+    "entry": "main.lua",
+    "api": 2
+  }]],
+  ["mods/fix_small_bag/main.lua"] = [[
+    local mod = ...
+    mod.content.constants:patch("bagSize", 2)
+  ]],
+}
+
+-- No-mod parity: the new lookup keeps the cartridge's 20-slot limit.
+do
+  local data = T.fixtures.fresh()
+  local run = T.sdk.loadNone({ data = data })
+  T.eq(#run.errors, 0, "the no-mod baseline loads cleanly")
+  T.eq(Bag.capacity(data), 20, "the vanilla bag still has 20 slots")
+  T.eq(Bag.capacity({}), 20, "a stale dataset without bagSize falls back to 20")
+  run.release()
+end
+
+-- The public constants registry changes both the reported and enforced cap.
+do
+  local data = T.fixtures.fresh()
+  local run = T.sdk.loadMods({ "mods/fix_small_bag" },
+    { data = data, fs = T.sdk.memfs(CAPACITY_MOD) })
+  T.eq(#run.errors, 0, "the capacity mod loads cleanly")
+  T.eq(Bag.capacity(data), 2, "Bag.capacity reads merged constants.bagSize")
+
+  local save = { inventory = {} }
+  T.check(Bag.add(save, "FIX_POTION", 1, data), "the first item fits")
+  T.check(Bag.add(save, "FIX_BALL", 1, data), "the second item fits")
+  T.check(not Bag.add(save, "FIX_TM", 1, data),
+    "a new item is refused at the modded limit")
+  T.eq(Bag.slots(save), 2, "a refused add does not change the bag")
+  run.release()
+end
+
+-- Saves are dictionaries, not fixed arrays: lowering the active cap never
+-- truncates an older or modded save. Existing stacks remain usable while a
+-- new item waits until the player makes enough room.
+do
+  local data = T.fixtures.fresh()
+  data.constants.bagSize = 1
+  local save = {
+    inventory = { FIX_POTION = 1, FIX_BALL = 1 },
+    bagOrder = { "FIX_POTION", "FIX_BALL" },
+  }
+  T.eq(Bag.slots(save), 2, "an over-cap save keeps all existing slots")
+  T.check(Bag.add(save, "FIX_POTION", 1, data),
+    "an over-cap save can still add to an existing stack")
+  T.eq(save.inventory.FIX_POTION, 2, "the existing stack is updated")
+  T.check(not Bag.add(save, "FIX_TM", 1, data),
+    "an over-cap save cannot add another item kind")
+  T.eq(Bag.slots(save), 2, "the compatibility path never drops items")
+end
+
+T.finish("bag_capacity")

tests/save_editor_task6_tests.lua

@@ -181,12 +181,13 @@ end
 do
   -- the bag has a hard slot cap; the picker must refuse past it
   local S = newState()
+  local capacity = Bag.capacity(S.data)
   local added = 0
   for _, id in ipairs(S.cat.items) do
     if not Ops.isBadgeId(id) and Ops.addToBag(S, id) then added = added + 1 end
-    if added >= Bag.CAPACITY then break end
+    if added >= capacity then break end
   end
-  eq(Bag.slots(S.save), Bag.CAPACITY, "the bag filled to its cap")
+  eq(Bag.slots(S.save), capacity, "the bag filled to its cap")
   S.dirty = false
   local spare
   for _, id in ipairs(S.cat.items) do

tools/save-editor/App.lua

@@ -427,7 +427,7 @@ local function tabCount(id)
     return tostring(n)
   elseif id == "items" then
     local Bag = require("src.inventory.Bag")
-    return ("%d/%d"):format(Bag.slots(S.save), Bag.CAPACITY)
+    return ("%d/%d"):format(Bag.slots(S.save), Bag.capacity(S.data))
   elseif id == "events" then
     local n = 0
     for _ in pairs(S.save.flags or {}) do n = n + 1 end

tools/save-editor/Ops.lua

@@ -8,7 +8,8 @@
 --
 -- Clamps mirror the running game, not the UI: level 1-100, DV 0-15, party 6
 -- (src/pokemon/Party), box 20 x 12 (src/pokemon/Boxes), money 0-999999,
--- item stack 99 and 20 bag slots (src/inventory/Bag).
+-- item stack 99 and the configured bag capacity (20 by default;
+-- src/inventory/Bag).
 
 local Pokemon = require("src.pokemon.Pokemon")
 local PartyMod = require("src.pokemon.Party")
@@ -338,11 +339,13 @@ end
 
 function Ops.addToBag(S, id)
   if not id then return Ops.say(S, "Pick an item first") end
-  if Bag.add(S.save, id, 1) then
+  local capacity = Bag.capacity(S.data)
+  if Bag.add(S.save, id, 1, S.data) then
     return Ops.mark(S, ("Added %s to the bag (%d/%d slots)")
-      :format(id, Bag.slots(S.save), Bag.CAPACITY))
+      :format(id, Bag.slots(S.save), capacity))
   end
-  return Ops.say(S, ("Bag is full (%d/%d slots)"):format(Bag.slots(S.save), Bag.CAPACITY))
+  return Ops.say(S, ("Bag is full (%d/%d slots)")
+    :format(Bag.slots(S.save), capacity))
 end
 
 function Ops.bagAdjust(S, id, delta)
@@ -352,7 +355,7 @@ function Ops.bagAdjust(S, id, delta)
     if have >= Ops.STACK_MAX then
       return Ops.say(S, ("%s is already at x%d"):format(id, Ops.STACK_MAX))
     end
-    Bag.add(S.save, id, delta)
+    Bag.add(S.save, id, delta, S.data)
   else
     Bag.remove(S.save, id, -delta)
     if not S.save.inventory[id] then

tools/save-editor/panels/Items.lua

@@ -1,4 +1,4 @@
--- Items panel: money, the shared item picker, badges, the 20-slot bag
+-- Items panel: money, the shared item picker, badges, the configurable bag
 -- (Bag.add/remove, ordered by Bag.order) and PC item storage (a plain
 -- S.save.pcItems dict with no slot cap).
 --
@@ -178,12 +178,13 @@ function M.draw(S, Kit, x, y, w, h)
 
   -- --------------------------------------------------------------- bag
   local order = Bag.order(S.save)
+  local capacity = Bag.capacity(S.data)
   Kit.card(bagX, y, listW, h)
   Kit.caption(bagX + pad, y + pad, "BAG")
-  Kit.textRight("mono", ("%d/%d slots"):format(Bag.slots(S.save), Bag.CAPACITY),
+  Kit.textRight("mono", ("%d/%d slots"):format(Bag.slots(S.save), capacity),
     bagX + listW - pad, y + pad, PAL.caption)
   local barY = y + pad + Kit.textHeight("caption") + 8 * s
-  local slotFrac = Bag.slots(S.save) / Bag.CAPACITY
+  local slotFrac = Bag.slots(S.save) / capacity
   Kit.meter(bagX + pad, barY, listW - 2 * pad, 5 * s, slotFrac * 100,
     slotFrac >= 1 and PAL.yellow or PAL.blue)