stake-pool: Clarify stake deposit fee (#2520)

Author: joncinque

docs/src/stake-pool.md

@@ -807,6 +807,22 @@ $ spl-token balance BoNneHKDrX9BHjjvSpPfnQyRjsnc9WFH71v8wrgCd7LB
 10.00000000
 ```
 
+#### Note on stake deposit fee
+
+Stake pools have separate fees for stake and SOL, so the total fee from depositing
+a stake account is calculated from the rent-exempt reserve as SOL, and the delegation
+as stake.
+
+For example, if a stake pool has a stake deposit fee of 1%, and a SOL deposit fee
+of 5%, and you deposit a stake account with 10 SOL in stake, and .00228288 SOL
+in rent-exemption, the total fee charged is:
+
+```
+total_fee = stake_delegation * stake_deposit_fee + rent_exemption * sol_deposit_fee
+total_fee = 10 * 1% + .00228288 * 5%
+total_fee = 0.100114144
+```
+
 ### Update
 
 Every epoch, the network pays out rewards to stake accounts managed by the stake

stake-pool/program/src/processor.rs

@@ -1784,8 +1784,6 @@ impl Processor {
             return Err(StakePoolError::InvalidState.into());
         }
 
-        //Self::check_stake_activation(stake_info, clock, stake_history)?;
-
         stake_pool.check_authority_withdraw(
             withdraw_authority_info.key,
             program_id,
@@ -1836,16 +1834,6 @@ impl Processor {
             }
         }
 
-        let (meta, stake) = get_stake_state(stake_info)?;
-
-        // If the stake account is mergeable (full-activated), `meta.rent_exempt_reserve`
-        // will not be merged into `stake.delegation.stake`
-        let unactivated_stake_rent = if stake.delegation.activation_epoch < clock.epoch {
-            meta.rent_exempt_reserve
-        } else {
-            0
-        };
-
         let mut validator_stake_info = validator_list
             .find_mut::<ValidatorStakeInfo>(
                 vote_account_address.as_ref(),
@@ -1899,38 +1887,47 @@ impl Processor {
         let post_all_validator_lamports = validator_stake_account_info.lamports();
         msg!("Stake post merge {}", post_validator_stake.delegation.stake);
 
-        let all_deposit_lamports = post_all_validator_lamports
+        let total_deposit_lamports = post_all_validator_lamports
             .checked_sub(pre_all_validator_lamports)
             .ok_or(StakePoolError::CalculationFailure)?;
         let stake_deposit_lamports = post_validator_stake
             .delegation
             .stake
             .checked_sub(validator_stake.delegation.stake)
             .ok_or(StakePoolError::CalculationFailure)?;
-        let additional_lamports = all_deposit_lamports
+        let sol_deposit_lamports = total_deposit_lamports
             .checked_sub(stake_deposit_lamports)
             .ok_or(StakePoolError::CalculationFailure)?;
-        let credited_additional_lamports = additional_lamports.min(unactivated_stake_rent);
-        let credited_deposit_lamports =
-            stake_deposit_lamports.saturating_add(credited_additional_lamports);
 
         let new_pool_tokens = stake_pool
-            .calc_pool_tokens_for_deposit(credited_deposit_lamports)
+            .calc_pool_tokens_for_deposit(total_deposit_lamports)
+            .ok_or(StakePoolError::CalculationFailure)?;
+        let new_pool_tokens_from_stake = stake_pool
+            .calc_pool_tokens_for_deposit(stake_deposit_lamports)
+            .ok_or(StakePoolError::CalculationFailure)?;
+        let new_pool_tokens_from_sol = new_pool_tokens
+            .checked_sub(new_pool_tokens_from_stake)
             .ok_or(StakePoolError::CalculationFailure)?;
 
-        let pool_tokens_stake_deposit_fee = stake_pool
-            .calc_pool_tokens_stake_deposit_fee(new_pool_tokens)
+        let stake_deposit_fee = stake_pool
+            .calc_pool_tokens_stake_deposit_fee(new_pool_tokens_from_stake)
+            .ok_or(StakePoolError::CalculationFailure)?;
+        let sol_deposit_fee = stake_pool
+            .calc_pool_tokens_sol_deposit_fee(new_pool_tokens_from_sol)
             .ok_or(StakePoolError::CalculationFailure)?;
 
+        let total_fee = stake_deposit_fee
+            .checked_add(sol_deposit_fee)
+            .ok_or(StakePoolError::CalculationFailure)?;
         let pool_tokens_user = new_pool_tokens
-            .checked_sub(pool_tokens_stake_deposit_fee)
+            .checked_sub(total_fee)
             .ok_or(StakePoolError::CalculationFailure)?;
 
         let pool_tokens_referral_fee = stake_pool
-            .calc_pool_tokens_stake_referral_fee(pool_tokens_stake_deposit_fee)
+            .calc_pool_tokens_stake_referral_fee(total_fee)
             .ok_or(StakePoolError::CalculationFailure)?;
 
-        let pool_tokens_manager_deposit_fee = pool_tokens_stake_deposit_fee
+        let pool_tokens_manager_deposit_fee = total_fee
             .checked_sub(pool_tokens_referral_fee)
             .ok_or(StakePoolError::CalculationFailure)?;
 
@@ -1946,18 +1943,16 @@ impl Processor {
             return Err(StakePoolError::DepositTooSmall.into());
         }
 
-        if pool_tokens_user > 0 {
-            Self::token_mint_to(
-                stake_pool_info.key,
-                token_program_info.clone(),
-                pool_mint_info.clone(),
-                dest_user_pool_info.clone(),
-                withdraw_authority_info.clone(),
-                AUTHORITY_WITHDRAW,
-                stake_pool.stake_withdraw_bump_seed,
-                pool_tokens_user,
-            )?;
-        }
+        Self::token_mint_to(
+            stake_pool_info.key,
+            token_program_info.clone(),
+            pool_mint_info.clone(),
+            dest_user_pool_info.clone(),
+            withdraw_authority_info.clone(),
+            AUTHORITY_WITHDRAW,
+            stake_pool.stake_withdraw_bump_seed,
+            pool_tokens_user,
+        )?;
         if pool_tokens_manager_deposit_fee > 0 {
             Self::token_mint_to(
                 stake_pool_info.key,
@@ -1984,8 +1979,7 @@ impl Processor {
         }
 
         // withdraw additional lamports to the reserve
-
-        if additional_lamports > 0 {
+        if sol_deposit_lamports > 0 {
             Self::stake_withdraw(
                 stake_pool_info.key,
                 validator_stake_account_info.clone(),
@@ -1996,7 +1990,7 @@ impl Processor {
                 clock_info.clone(),
                 stake_history_info.clone(),
                 stake_program_info.clone(),
-                additional_lamports,
+                sol_deposit_lamports,
             )?;
         }
 
@@ -2008,7 +2002,7 @@ impl Processor {
         // transferred directly to the reserve stake account.
         stake_pool.total_lamports = stake_pool
             .total_lamports
-            .checked_add(all_deposit_lamports)
+            .checked_add(total_deposit_lamports)
             .ok_or(StakePoolError::CalculationFailure)?;
         stake_pool.serialize(&mut *stake_pool_info.data.borrow_mut())?;
 

stake-pool/program/tests/deposit.rs

@@ -214,8 +214,13 @@ async fn success() {
     // Check minted tokens
     let user_token_balance =
         get_token_balance(&mut context.banks_client, &pool_token_account).await;
-    let tokens_issued_user =
-        tokens_issued - stake_pool_accounts.calculate_deposit_fee(tokens_issued);
+    let tokens_issued_user = tokens_issued
+        - post_stake_pool
+            .calc_pool_tokens_sol_deposit_fee(stake_rent)
+            .unwrap()
+        - post_stake_pool
+            .calc_pool_tokens_stake_deposit_fee(stake_lamports - stake_rent)
+            .unwrap();
     assert_eq!(user_token_balance, tokens_issued_user);
 
     // Check balances in validator stake account list storage
@@ -358,7 +363,7 @@ async fn success_with_extra_stake_lamports() {
         .expect("get_account")
         .is_none());
 
-    let tokens_issued = stake_lamports;
+    let tokens_issued = stake_lamports + extra_lamports;
     // For now tokens are 1:1 to stake
 
     // Stake pool should add its balance to the pool balance
@@ -386,22 +391,22 @@ async fn success_with_extra_stake_lamports() {
     let user_token_balance =
         get_token_balance(&mut context.banks_client, &pool_token_account).await;
 
-    let tokens_issued_user =
-        tokens_issued - stake_pool_accounts.calculate_deposit_fee(tokens_issued);
+    let fee_tokens = post_stake_pool
+        .calc_pool_tokens_sol_deposit_fee(extra_lamports + stake_rent)
+        .unwrap()
+        + post_stake_pool
+            .calc_pool_tokens_stake_deposit_fee(stake_lamports - stake_rent)
+            .unwrap();
+    let tokens_issued_user = tokens_issued - fee_tokens;
     assert_eq!(user_token_balance, tokens_issued_user);
 
     let referrer_balance_post =
         get_token_balance(&mut context.banks_client, &referrer_token_account.pubkey()).await;
 
-    let tokens_issued_fees = stake_pool_accounts.calculate_deposit_fee(tokens_issued);
-    let tokens_issued_referral_fee = stake_pool_accounts
-        .calculate_referral_fee(stake_pool_accounts.calculate_deposit_fee(tokens_issued));
-    let tokens_issued_manager_fee = tokens_issued_fees - tokens_issued_referral_fee;
+    let referral_fee = stake_pool_accounts.calculate_referral_fee(fee_tokens);
+    let manager_fee = fee_tokens - referral_fee;
 
-    assert_eq!(
-        referrer_balance_post - referrer_balance_pre,
-        tokens_issued_referral_fee
-    );
+    assert_eq!(referrer_balance_post - referrer_balance_pre, referral_fee);
 
     let manager_pool_balance_post = get_token_balance(
         &mut context.banks_client,
@@ -410,7 +415,7 @@ async fn success_with_extra_stake_lamports() {
     .await;
     assert_eq!(
         manager_pool_balance_post - manager_pool_balance_pre,
-        tokens_issued_manager_fee
+        manager_fee
     );
 
     // Check balances in validator stake account list storage
@@ -1114,8 +1119,22 @@ async fn success_with_referral_fee() {
 
     let referrer_balance_post =
         get_token_balance(&mut context.banks_client, &referrer_token_account.pubkey()).await;
-    let referral_fee = stake_pool_accounts
-        .calculate_referral_fee(stake_pool_accounts.calculate_deposit_fee(stake_lamports));
+    let stake_pool = get_account(
+        &mut context.banks_client,
+        &stake_pool_accounts.stake_pool.pubkey(),
+    )
+    .await;
+    let stake_pool =
+        try_from_slice_unchecked::<state::StakePool>(stake_pool.data.as_slice()).unwrap();
+    let rent = context.banks_client.get_rent().await.unwrap();
+    let stake_rent = rent.minimum_balance(std::mem::size_of::<stake_program::StakeState>());
+    let fee_tokens = stake_pool
+        .calc_pool_tokens_sol_deposit_fee(stake_rent)
+        .unwrap()
+        + stake_pool
+            .calc_pool_tokens_stake_deposit_fee(stake_lamports - stake_rent)
+            .unwrap();
+    let referral_fee = stake_pool_accounts.calculate_referral_fee(fee_tokens);
     assert!(referral_fee > 0);
     assert_eq!(referrer_balance_pre + referral_fee, referrer_balance_post);
 }

stake-pool/program/tests/helpers/mod.rs

@@ -685,10 +685,6 @@ impl StakePoolAccounts {
         pool_tokens * self.withdrawal_fee.numerator / self.withdrawal_fee.denominator
     }
 
-    pub fn calculate_deposit_fee(&self, pool_tokens: u64) -> u64 {
-        pool_tokens * self.deposit_fee.numerator / self.deposit_fee.denominator
-    }
-
     pub fn calculate_referral_fee(&self, deposit_fee_collected: u64) -> u64 {
         deposit_fee_collected * self.referral_fee as u64 / 100
     }

stake-pool/program/tests/withdraw.rs

@@ -994,15 +994,30 @@ async fn success_with_reserve() {
     assert!(error.is_none());
 
     // first and only deposit, lamports:pool 1:1
-    let tokens_deposit_fee =
-        stake_pool_accounts.calculate_deposit_fee(deposit_info.stake_lamports + stake_rent);
-    let tokens_withdrawal_fee =
-        stake_pool_accounts.calculate_withdrawal_fee(deposit_info.pool_tokens);
+    let stake_pool = get_account(
+        &mut context.banks_client,
+        &stake_pool_accounts.stake_pool.pubkey(),
+    )
+    .await;
+    let stake_pool =
+        try_from_slice_unchecked::<state::StakePool>(stake_pool.data.as_slice()).unwrap();
+    // the entire deposit is actually stake since it isn't activated, so only
+    // the stake deposit fee is charged
+    let deposit_fee = stake_pool
+        .calc_pool_tokens_stake_deposit_fee(stake_rent + deposit_info.stake_lamports)
+        .unwrap();
     assert_eq!(
-        deposit_info.stake_lamports + stake_rent - tokens_deposit_fee,
+        deposit_info.stake_lamports + stake_rent - deposit_fee,
         deposit_info.pool_tokens,
+        "stake {} rent {} deposit fee {} pool tokens {}",
+        deposit_info.stake_lamports,
+        stake_rent,
+        deposit_fee,
+        deposit_info.pool_tokens
     );
 
+    let withdrawal_fee = stake_pool_accounts.calculate_withdrawal_fee(deposit_info.pool_tokens);
+
     // Check tokens used
     let user_token_balance = get_token_balance(
         &mut context.banks_client,
@@ -1020,12 +1035,8 @@ async fn success_with_reserve() {
     let stake_state =
         deserialize::<stake_program::StakeState>(&reserve_stake_account.data).unwrap();
     let meta = stake_state.meta().unwrap();
-    // TODO: these numbers dont add up even with +tokens_deposit_fee
     assert_eq!(
-        initial_reserve_lamports
-            + meta.rent_exempt_reserve
-            + tokens_withdrawal_fee
-            + tokens_deposit_fee,
+        initial_reserve_lamports + meta.rent_exempt_reserve + withdrawal_fee + deposit_fee,
         reserve_stake_account.lamports
     );
 
@@ -1035,8 +1046,8 @@ async fn success_with_reserve() {
     assert_eq!(
         user_stake_recipient_account.lamports,
         initial_stake_lamports + deposit_info.stake_lamports + stake_rent
-            - tokens_withdrawal_fee
-            - tokens_deposit_fee
+            - withdrawal_fee
+            - deposit_fee
     );
 }