fix(gen2): sell TMs at Poké Marts instead of opening the teach party

Selecting a TM in the mart's SELL pack (and the item PC's DEPOSIT pack) opened the teach-party screen: PackMenu:useSelected taught any item carrying `teaches`, even when the pack was built as a chooser (DepositSellPack, world = {}). On the cart that chooser's jumptable is four ScrollingMenus and never reaches tmhm.asm, so the row must hand back to the caller instead.

Gate the teach and field-NOUSE branches behind world.useFieldItem so only the real field PACK teaches; choosers now hand TMs to onChoose. Selling then prices a TM at half its ItemAttributes price -- exactly half of what the Goldenrod/Celadon TM shelves charge, and half of the hidden price for the rest, the way SelectQuantityToSell -> GetItemPrice -> Sell_HalvePrice does on the cart.

Closes #1243

src/ui/gen2/MartMenu.lua

@@ -780,6 +780,11 @@ function MartMenu:offerToSell(itemId, count)
   end
   -- ScrollingMenu's .a_button copies the row's own quantity into
   -- wItemQuantity, so the selector's ceiling is how many you hold.
+  -- The unit price is the item's own ItemAttributes price: GetItemPrice is
+  -- what SelectQuantityToSell halves AND what the buy list's
+  -- GetMartItemPrice charges, so a TM sells for exactly half of what the
+  -- Goldenrod/Celadon TM shelves ask for it, and half of its hidden price
+  -- (usually ¥1,500) anywhere else (issue #1243).
   self.qtyItem = { id = itemId, name = def.name or itemId,
     price = def.price or 0 }
   self.qty = 1

src/ui/gen2/PackMenu.lua

@@ -354,20 +354,23 @@ function PackMenu:useSelected()
     end
     return
   end
-  -- engine/items/tmhm.asm:73
-  local def = self.items and self.items[row.id]
-  if def and def.teaches then
-    self:openTeachParty(row)
-    return
-  end
-  -- UseItem's jumptable runs off ITEMATTR's field-menu nibble, and the first
-  -- four entries are all .Oak -- an X ATTACK or a POKé DOLL used from the
-  -- field PACK prints OakThisIsntTheTimeText and goes nowhere.  Only the
-  -- FIELD pack owns that refusal: the battle pack returned above, and the
-  -- catch tutorial's DUDE pack carries a stub world with no useFieldItem at
-  -- all -- its POKE BALL is field-NOUSE and must still reach the throw.
+  -- UseItem's FIELD-pack tail (engine/items/tmhm.asm:73): a TM/HM row opens
+  -- the party to teach, and a field-NOUSE item -- an X ATTACK or a POKé DOLL
+  -- used from the field PACK -- prints OakThisIsntTheTimeText and goes
+  -- nowhere (UseItem's jumptable's first four entries are all .Oak).  Both
+  -- checks live behind `world.useFieldItem` on purpose: DepositSellPack (the
+  -- mart's SELL, the item PC's DEPOSIT) is a chooser whose jumptable is four
+  -- ScrollingMenus and never reaches tmhm.asm, so a TM picked there hands
+  -- its row to onChoose like every other item instead of opening the teach
+  -- party.  The battle pack returned above, and the catch tutorial's DUDE
+  -- pack carries a stub world with no useFieldItem at all -- its POKE BALL
+  -- is field-NOUSE and must still reach the throw.
   if world and world.useFieldItem then
     local def = self.items and self.items[row.id]
+    if def and def.teaches then
+      self:openTeachParty(row)
+      return
+    end
     if def and def.fieldMenu == "ITEMMENU_NOUSE" then
       self.message = OAK_THIS_ISNT_THE_TIME
       return

tests/gen2_field_items_test.lua

@@ -549,6 +549,27 @@ do
   dudePack:useSelected()
   eq(thrown, "POKE_BALL", "the tutorial pack still throws")
   eq(dudePack.message, nil, "with no Oak line in the way")
+
+  -- DepositSellPack passes the same empty world (the mart's SELL and the
+  -- item PC's DEPOSIT both do): a TM row must hand its id back rather than
+  -- open the teach party, which is issue #1243's "Teach which PKMN?" in
+  -- the middle of a sale.
+  local sellGame = { input = newInput(), save = {
+    player = { name = "GOLD" },
+    inventory = { TM01 = 1 },
+    options = {},
+  }, data = DATA, stack = newStack() }
+  local sold
+  local sellPack = PackMenu.new(sellGame, {
+    save = sellGame.save, items = DATA.items, world = {},
+    onChoose = function(id) sold = id end,
+  })
+  sellPack.pocketIndex = 4 -- TM_HM
+  sellPack:rebuild()
+  sellPack:useSelected()
+  eq(sold, "TM01", "a chooser pack hands a TM to its caller")
+  eq(sellPack.message, nil, "with no teach refusal in the way")
+  eq(#sellGame.stack._items, 0, "and nothing pushed over the pack")
 end
 
 -- ------------------------------------------------ say(): the teardown rule

tests/gen2_menus_test.lua

@@ -1481,6 +1481,11 @@ local martItems = {
     price = 100, canToss = true },
   NUGGET = { id = "NUGGET", name = "NUGGET", pocket = "ITEM", index = 36,
     price = 10000, canToss = true },
+  -- A TM carries the move it teaches; the SELL pack must hand it to the
+  -- mart rather than opening the teach party (issue #1243).
+  TM_HEADBUTT = { id = "TM_HEADBUTT", name = "TM02", pocket = "TM_HM",
+    index = 234, price = 2000, canToss = true, teaches = "HEADBUTT",
+    tmNumber = 2 },
   -- Every KEY ITEM carries CANT_TOSS, which is the flag SellMenu's
   -- _CheckTossableItem actually refuses on.
   BICYCLE = { id = "BICYCLE", name = "BICYCLE", pocket = "KEY_ITEM", index = 7,
@@ -1732,6 +1737,35 @@ sellInput:press("a") sell:update(0) -- YES
 check("the wallet clamps at MAX_MONEY", sellSave.player.money, 999999)
 check("and the nugget is gone", sellSave.inventory.NUGGET, nil)
 
+-- A TM is not a key item: DepositSellPack's jumptable is four ScrollingMenus
+-- and has no teach arm, so picking a TM from the SELL pack must ask "How
+-- many?" and price it at half of its ItemAttributes price -- never open the
+-- teach party (issue #1243).
+local tmSave = Save.newGame()
+tmSave.inventory = { TM_HEADBUTT = 1 }
+tmSave.player.money = 0
+local tm, tmInput = newMart(tmSave)
+tmInput:press("down") tm:update(0)
+tmInput:press("a") tm:update(0) -- SELL
+check("SELL builds the pack", tm.pack ~= nil, true)
+-- The PACK opens on the ITEM pocket; cross to TM/HM the way the player would.
+tm.pack.pocketIndex = 4
+tm.pack:rebuild()
+check("the TM is the TM pocket's row", tm.pack.rows[1].id, "TM_HEADBUTT")
+tmInput:press("a") tm:update(0)
+check("picking a TM asks how many", tm.phase, "sellQuantity")
+check("with no teach screen opened", #tm.game.stack._items, 0)
+check("and no pack refusal printed", tm.pack.message, nil)
+check("at the TM's own price", tm.qtyItem.price, 2000)
+check("and the ceiling is what you hold", tm.qtyMax, 1)
+tmInput:press("a") tm:update(0)
+check("the offer prices half of the TM", tm.confirm.pages[1][2],
+  "\xc2\xa51000.")
+tmInput:press("a") tm:update(0) -- page 2
+tmInput:press("a") tm:update(0) -- YES
+check("the TM leaves the bag", tmSave.inventory.TM_HEADBUTT, nil)
+check("and the money arrives", tmSave.player.money, 1000)
+
 -- ------------------------------------------------- PlayTransactionSound
 --
 -- engine/items/mart.asm rings SFX_TRANSACTION in exactly two places, both of

tests/gen2_pc_screens_test.lua

@@ -94,6 +94,8 @@ local ITEMS = {
     canToss = false },
   HM_CUT = { id = "HM_CUT", name = "HM01", pocket = "TM_HM", index = 0xf3,
     canToss = false },
+  TM_HEADBUTT = { id = "TM_HEADBUTT", name = "TM02", pocket = "TM_HM",
+    index = 0xea, canToss = true, teaches = "HEADBUTT" },
 }
 
 local function newGame(save, items)
@@ -291,6 +293,23 @@ do
   eq(pc.phase, "menu", "B drops back to the item PC menu")
 end
 
+-- The same DepositSellPack chooser holds a TM: it must reach the quantity
+-- selector like everything tossable, never the teach party (issue #1243).
+do
+  local save = newSave(1)
+  local game, input = newGame(save)
+  Bag.add(save, "TM_HEADBUTT", 1, game.data)
+  local pc = ItemPcMenu.new(game, { save = save, items = ITEMS })
+  press(pc, input, "down", "a")                 -- DEPOSIT ITEM
+  press(pc, input, "right", "right", "right")  -- ITEM -> BALL -> KEY_ITEM -> TM_HM
+  press(pc, input, "a")                         -- choose the TM
+  check(pc.qtyState ~= nil, "a TM asks how many to deposit")
+  eq(#game.stack._items, 0, "with no teach screen pushed over the pack")
+  press(pc, input, "a")                         -- deposit x1
+  eq(save.pcItems.TM_HEADBUTT, 1, "the TM lands in the PC")
+  eq(save.inventory.TM_HEADBUTT, nil, "and leaves the bag")
+end
+
 -- .TryDepositItem's .no_toss: a KEY ITEM stays in the bag, silently.
 do
   local save = newSave(1)