Serum deregister: Close index reservation account

Only safe because this is a testing-only instruction

programs/mango-v4/src/instructions/serum3_deregister_market.rs

@@ -20,6 +20,14 @@ pub struct Serum3DeregisterMarket<'info> {
     )]
     pub serum_market: AccountLoader<'info, Serum3Market>,
 
+    /// CHECK: Unused account
+    #[account(
+        mut,
+        seeds = [b"Serum3Index".as_ref(), group.key().as_ref(), &serum_market.load()?.market_index.to_le_bytes()],
+        bump
+    )]
+    pub index_reservation: UncheckedAccount<'info>,
+
     #[account(mut)]
     /// CHECK: target for account rent needs no checks
     pub sol_destination: UncheckedAccount<'info>,
@@ -27,6 +35,20 @@ pub struct Serum3DeregisterMarket<'info> {
     pub token_program: Program<'info, Token>,
 }
 
-pub fn serum3_deregister_market(_ctx: Context<Serum3DeregisterMarket>) -> Result<()> {
+pub fn serum3_deregister_market(ctx: Context<Serum3DeregisterMarket>) -> Result<()> {
+    close_unsafe(
+        ctx.accounts.index_reservation.to_account_info(),
+        ctx.accounts.sol_destination.to_account_info(),
+    );
     Ok(())
 }
+
+fn close_unsafe<'info>(info: AccountInfo<'info>, sol_destination: AccountInfo<'info>) {
+    // Transfer tokens from the account to the sol_destination.
+    let dest_starting_lamports = sol_destination.lamports();
+    **sol_destination.lamports.borrow_mut() =
+        dest_starting_lamports.checked_add(info.lamports()).unwrap();
+    **info.lamports.borrow_mut() = 0;
+
+    // Does NOT prevent reinit attacks in any way
+}

programs/mango-v4/tests/program_test/mango_client.rs

@@ -1387,7 +1387,7 @@ impl<'keypair> ClientInstruction for Serum3DeregisterMarketInstruction<'keypair>
     type Instruction = mango_v4::instruction::Serum3DeregisterMarket;
     async fn to_instruction(
         &self,
-        _account_loader: impl ClientAccountLoader + 'async_trait,
+        account_loader: impl ClientAccountLoader + 'async_trait,
     ) -> (Self::Accounts, instruction::Instruction) {
         let program_id = mango_v4::id();
         let instruction = Self::Instruction {};
@@ -1401,11 +1401,23 @@ impl<'keypair> ClientInstruction for Serum3DeregisterMarketInstruction<'keypair>
             &program_id,
         )
         .0;
+        let serum_market_data: Serum3Market = account_loader.load(&serum_market).await.unwrap();
+
+        let index_reservation = Pubkey::find_program_address(
+            &[
+                b"Serum3Index".as_ref(),
+                self.group.as_ref(),
+                &serum_market_data.market_index.to_le_bytes(),
+            ],
+            &program_id,
+        )
+        .0;
 
         let accounts = Self::Accounts {
             group: self.group,
             admin: self.admin.pubkey(),
             serum_market,
+            index_reservation,
             sol_destination: self.sol_destination,
             token_program: Token::id(),
         };

ts/client/src/mango_v4.ts

@@ -1394,6 +1394,30 @@ export type MangoV4 = {
           "isMut": true,
           "isSigner": false
         },
+        {
+          "name": "indexReservation",
+          "isMut": true,
+          "isSigner": false,
+          "pda": {
+            "seeds": [
+              {
+                "kind": "const",
+                "type": "string",
+                "value": "Serum3Index"
+              },
+              {
+                "kind": "account",
+                "type": "publicKey",
+                "path": "group"
+              },
+              {
+                "kind": "account",
+                "type": "publicKey",
+                "path": "serum_market"
+              }
+            ]
+          }
+        },
         {
           "name": "solDestination",
           "isMut": true,
@@ -6678,6 +6702,30 @@ export const IDL: MangoV4 = {
           "isMut": true,
           "isSigner": false
         },
+        {
+          "name": "indexReservation",
+          "isMut": true,
+          "isSigner": false,
+          "pda": {
+            "seeds": [
+              {
+                "kind": "const",
+                "type": "string",
+                "value": "Serum3Index"
+              },
+              {
+                "kind": "account",
+                "type": "publicKey",
+                "path": "group"
+              },
+              {
+                "kind": "account",
+                "type": "publicKey",
+                "path": "serum_market"
+              }
+            ]
+          }
+        },
         {
           "name": "solDestination",
           "isMut": true,