Roundrip fee on proportional remove

pkg/interfaces/contracts/test/IVaultMainMock.sol

@@ -277,6 +277,8 @@ interface IVaultMainMock {
 
     function manualFindTokenIndex(IERC20[] memory tokens, IERC20 token) external pure returns (uint256 index);
 
+    function manualSetAddLiquidityCalledFlag(address pool, bool flag) external;
+
     function manualSetPoolCreator(address pool, address newPoolCreator) external;
 
     function ensureValidTradeAmount(uint256 tradeAmount) external view;

pkg/interfaces/contracts/vault/IVaultExtension.sol

@@ -67,6 +67,12 @@ interface IVaultExtension {
      */
     function getReservesOf(IERC20 token) external view returns (uint256);
 
+    /**
+     * @notice Returns `true` if `addLiquidity` was called for the given pool in this transaction.
+     * @param pool Address of the pool to check.
+     */
+    function getAddLiquidityCalledFlag(address pool) external view returns (bool);
+
     /*******************************************************************************
                                     Pool Registration
     *******************************************************************************/

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - ERC4626 - BatchRouter] swapExactIn - no buffer liquidity - warm slots

@@ -1 +1 @@
-302.1k
+302.0k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - ERC4626 - BatchRouter] swapExactOut - no buffer liquidity - warm slots

@@ -1 +1 @@
-333.0k
+332.8k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - ERC4626 - BatchRouter] swapExactOut - with buffer liquidity - warm slots

@@ -1 +1 @@
-259.2k
+259.1k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard - BatchRouter] add liquidity unbalanced using swapExactIn - warm slots

@@ -1 +1 @@
-196.9k
+197.1k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard - BatchRouter] add liquidity using swapExactOur - warm slots

@@ -1 +1 @@
-181.5k
+181.7k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard - BatchRouter] swap exact in with one token and fees - cold slots

@@ -1 +1 @@
-195.5k
+195.4k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard] add liquidity proportional

@@ -1 +1 @@
-180.2k
+180.4k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard] add liquidity single token exact out - warm slots

@@ -1 +1 @@
-172.5k
+172.8k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard] add liquidity unbalanced - warm slots

@@ -1 +1 @@
-215.0k
+215.2k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - Standard] remove liquidity proportional

@@ -1 +1 @@
-168.2k
+168.3k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate - BatchRouter] add liquidity unbalanced using swapExactIn - warm slots

@@ -1 +1 @@
-218.6k
+218.8k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate - BatchRouter] add liquidity using swapExactOur - warm slots

@@ -1 +1 @@
-203.2k
+203.4k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate - BatchRouter] swap exact in with one token and fees - warm slots

@@ -1 +1 @@
-198.4k
+198.3k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate] add liquidity proportional

@@ -1 +1 @@
-235.6k
+235.8k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate] add liquidity single token exact out - warm slots

@@ -1 +1 @@
-194.3k
+194.5k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate] add liquidity unbalanced - warm slots

@@ -1 +1 @@
-231.4k
+231.6k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool - With rate] remove liquidity proportional

@@ -1 +1 @@
-223.4k
+223.5k

pkg/pool-stable/test/gas/.hardhat-snapshots/[StablePool] donation

@@ -1 +1 @@
-178.9k
+179.1k

pkg/pool-weighted/test/foundry/WeightedPoolLimits.t.sol

@@ -242,6 +242,9 @@ contract WeightedPoolLimitsTest is BaseVaultTest, WeightedPoolContractsDeployer
         startingBalances[daiIdx] = dai.balanceOf(bob);
         startingBalances[usdcIdx] = usdc.balanceOf(bob);
 
+        // Prevent roundtrip fee
+        vault.manualSetAddLiquidityCalledFlag(pool, false);
+
         uint256[] memory amountsOut = router.removeLiquidityProportional(
             address(weightedPool),
             bptAmountIn,

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - ERC4626 - BatchRouter] swapExactIn - no buffer liquidity - warm slots

@@ -1 +1 @@
-297.0k
+296.9k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - ERC4626 - BatchRouter] swapExactOut - no buffer liquidity - warm slots

@@ -1 +1 @@
-319.5k
+319.4k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard - BatchRouter] add liquidity unbalanced using swapExactIn - warm slots

@@ -1 +1 @@
-190.6k
+190.8k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard - BatchRouter] add liquidity using swapExactOur - warm slots

@@ -1 +1 @@
-168.2k
+168.4k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard] add liquidity proportional

@@ -1 +1 @@
-180.2k
+180.4k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard] add liquidity single token exact out - warm slots

@@ -1 +1 @@
-159.3k
+159.5k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard] add liquidity unbalanced - warm slots

@@ -1 +1 @@
-213.5k
+213.7k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard] remove liquidity proportional

@@ -1 +1 @@
-168.2k
+168.4k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard] swap single token exact in with fees - cold slots

@@ -1 +1 @@
-169.2k
+169.1k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - Standard] swap single token exact in with fees - warm slots

@@ -1 +1 @@
-152.1k
+152.0k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate - BatchRouter] add liquidity unbalanced using swapExactIn - warm slots

@@ -1 +1 @@
-212.5k
+212.7k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate - BatchRouter] add liquidity using swapExactOur - warm slots

@@ -1 +1 @@
-190.0k
+190.2k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate - BatchRouter] swap exact in with one token and fees - cold slots

@@ -1 +1 @@
-218.5k
+218.4k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate - BatchRouter] swap exact in with one token and fees - warm slots

@@ -1 +1 @@
-184.3k
+184.2k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate] add liquidity proportional

@@ -1 +1 @@
-235.6k
+235.8k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate] add liquidity single token exact out - warm slots

@@ -1 +1 @@
-181.0k
+181.3k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate] add liquidity unbalanced - warm slots

@@ -1 +1 @@
-230.3k
+230.5k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool - With rate] remove liquidity proportional

@@ -1 +1 @@
-223.4k
+223.6k

pkg/pool-weighted/test/gas/.hardhat-snapshots/[WeightedPool] donation

@@ -1 +1 @@
-178.9k
+179.2k

pkg/solidity-utils/contracts/helpers/TransientStorageHelpers.sol

@@ -8,7 +8,8 @@ import { SlotDerivation } from "../openzeppelin/SlotDerivation.sol";
 import { StorageSlotExtension } from "../openzeppelin/StorageSlotExtension.sol";
 
 type TokenDeltaMappingSlotType is bytes32;
-type AddressMappingSlot is bytes32;
+type AddressToUintMappingSlot is bytes32;
+type AddressToBooleanMappingSlot is bytes32;
 type AddressArraySlotType is bytes32;
 
 /**
@@ -46,21 +47,29 @@ library TransientStorageHelpers {
         TokenDeltaMappingSlotType.unwrap(slot).deriveMapping(address(k1)).asInt256().tstore(value);
     }
 
-    function tGet(AddressMappingSlot slot, address key) internal view returns (uint256) {
-        return AddressMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tload();
+    function tGet(AddressToUintMappingSlot slot, address key) internal view returns (uint256) {
+        return AddressToUintMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tload();
     }
 
-    function tSet(AddressMappingSlot slot, address key, uint256 value) internal {
-        AddressMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tstore(value);
+    function tSet(AddressToUintMappingSlot slot, address key, uint256 value) internal {
+        AddressToUintMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tstore(value);
+    }
+
+    function tGet(AddressToBooleanMappingSlot slot, address key) internal view returns (bool) {
+        return AddressToBooleanMappingSlot.unwrap(slot).deriveMapping(key).asBoolean().tload();
+    }
+
+    function tSet(AddressToBooleanMappingSlot slot, address key, bool value) internal {
+        AddressToBooleanMappingSlot.unwrap(slot).deriveMapping(key).asBoolean().tstore(value);
     }
 
     // Implement the common "+=" operation: map[key] += value.
-    function tAdd(AddressMappingSlot slot, address key, uint256 value) internal {
-        AddressMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tstore(tGet(slot, key) + value);
+    function tAdd(AddressToUintMappingSlot slot, address key, uint256 value) internal {
+        AddressToUintMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tstore(tGet(slot, key) + value);
     }
 
-    function tSub(AddressMappingSlot slot, address key, uint256 value) internal {
-        AddressMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tstore(tGet(slot, key) - value);
+    function tSub(AddressToUintMappingSlot slot, address key, uint256 value) internal {
+        AddressToUintMappingSlot.unwrap(slot).deriveMapping(key).asUint256().tstore(tGet(slot, key) - value);
     }
 
     /***************************************************************************

pkg/solidity-utils/contracts/openzeppelin/TransientEnumerableSet.sol

@@ -5,7 +5,7 @@ pragma solidity ^0.8.24;
 import { StorageSlotExtension } from "./StorageSlotExtension.sol";
 import {
     AddressArraySlotType,
-    AddressMappingSlot,
+    AddressToUintMappingSlot,
     TransientStorageHelpers
 } from "../helpers/TransientStorageHelpers.sol";
 
@@ -212,7 +212,7 @@ library TransientEnumerableSet {
         }
     }
 
-    function _indexes(AddressSet storage set) private view returns (AddressMappingSlot slot) {
+    function _indexes(AddressSet storage set) private view returns (AddressToUintMappingSlot slot) {
         mapping(address addressKey => uint256 indexValue) storage indexes = set.__indexes;
 
         assembly ("memory-safe") {

pkg/vault/contracts/BatchRouterCommon.sol

@@ -13,7 +13,7 @@ import {
 } from "@balancer-labs/v3-solidity-utils/contracts/openzeppelin/TransientEnumerableSet.sol";
 import {
     TransientStorageHelpers,
-    AddressMappingSlot
+    AddressToUintMappingSlot
 } from "@balancer-labs/v3-solidity-utils/contracts/helpers/TransientStorageHelpers.sol";
 
 import { RouterCommon } from "./RouterCommon.sol";
@@ -61,21 +61,21 @@ contract BatchRouterCommon is RouterCommon {
     }
 
     // token in -> amount: tracks token in amounts within a batch swap.
-    function _currentSwapTokenInAmounts() internal view returns (AddressMappingSlot slot) {
-        return AddressMappingSlot.wrap(_CURRENT_SWAP_TOKEN_IN_AMOUNTS_SLOT);
+    function _currentSwapTokenInAmounts() internal view returns (AddressToUintMappingSlot slot) {
+        return AddressToUintMappingSlot.wrap(_CURRENT_SWAP_TOKEN_IN_AMOUNTS_SLOT);
     }
 
     // token out -> amount: tracks token out amounts within a batch swap.
-    function _currentSwapTokenOutAmounts() internal view returns (AddressMappingSlot slot) {
-        return AddressMappingSlot.wrap(_CURRENT_SWAP_TOKEN_OUT_AMOUNTS_SLOT);
+    function _currentSwapTokenOutAmounts() internal view returns (AddressToUintMappingSlot slot) {
+        return AddressToUintMappingSlot.wrap(_CURRENT_SWAP_TOKEN_OUT_AMOUNTS_SLOT);
     }
 
     // token -> amount that is part of the current input / output amounts, but is settled preemptively.
     // This situation happens whenever there is BPT involved in the operation, which is minted and burned instantly.
     // Since those amounts are not tracked in the inputs / outputs to settle, we need to track them elsewhere
     // to return the correct total amounts in and out for each token involved in the operation.
-    function _settledTokenAmounts() internal view returns (AddressMappingSlot slot) {
-        return AddressMappingSlot.wrap(_SETTLED_TOKEN_AMOUNTS_SLOT);
+    function _settledTokenAmounts() internal view returns (AddressToUintMappingSlot slot) {
+        return AddressToUintMappingSlot.wrap(_SETTLED_TOKEN_AMOUNTS_SLOT);
     }
 
     function _calculateBatchRouterStorageSlot(string memory key) internal pure returns (bytes32) {

pkg/vault/contracts/Vault.sol

@@ -500,6 +500,7 @@ contract Vault is IVaultMain, VaultCommon, Proxy {
         // bptOut = supply * (ratio - 1), so lower ratio = less bptOut, favoring the pool.
 
         _ensureUnpaused(params.pool);
+        _addLiquidityCalled().tSet(params.pool, true);
 
         // `_loadPoolDataUpdatingBalancesAndYieldFees` is non-reentrant, as it updates storage as well
         // as filling in poolData in memory. Since the add liquidity hooks are reentrant and could do anything,
@@ -878,6 +879,15 @@ contract Vault is IVaultMain, VaultCommon, Proxy {
                 _totalSupply(params.pool),
                 bptAmountIn
             );
+
+            // Charge roundtrip fee.
+            if (_addLiquidityCalled().tGet(params.pool)) {
+                uint256 swapFeePercentage = poolData.poolConfigBits.getStaticSwapFeePercentage();
+                for (uint256 i = 0; i < locals.numTokens; ++i) {
+                    swapFeeAmounts[i] = amountsOutScaled18[i].mulUp(swapFeePercentage);
+                    amountsOutScaled18[i] -= swapFeeAmounts[i];
+                }
+            }
         } else if (params.kind == RemoveLiquidityKind.SINGLE_TOKEN_EXACT_IN) {
             poolData.poolConfigBits.requireUnbalancedLiquidityEnabled();
             bptAmountIn = params.maxBptAmountIn;

pkg/vault/contracts/VaultExtension.sol

@@ -126,6 +126,11 @@ contract VaultExtension is IVaultExtension, VaultCommon, Proxy {
         return _reservesOf[token];
     }
 
+    /// @inheritdoc IVaultExtension
+    function getAddLiquidityCalledFlag(address pool) external view onlyVaultDelegateCall returns (bool) {
+        return _addLiquidityCalled().tGet(pool);
+    }
+
     /*******************************************************************************
                                     Pool Registration
     *******************************************************************************/

pkg/vault/contracts/VaultStorage.sol

@@ -13,8 +13,8 @@ import "@balancer-labs/v3-interfaces/contracts/vault/VaultTypes.sol";
 import { StorageSlotExtension } from "@balancer-labs/v3-solidity-utils/contracts/openzeppelin/StorageSlotExtension.sol";
 import {
     TransientStorageHelpers,
-    AddressArraySlotType,
-    TokenDeltaMappingSlotType
+    TokenDeltaMappingSlotType,
+    AddressToBooleanMappingSlot
 } from "@balancer-labs/v3-solidity-utils/contracts/helpers/TransientStorageHelpers.sol";
 
 import { VaultStateBits } from "./lib/VaultStateLib.sol";
@@ -66,6 +66,7 @@ contract VaultStorage {
     bytes32 private immutable _IS_UNLOCKED_SLOT = _calculateVaultStorageSlot("isUnlocked");
     bytes32 private immutable _NON_ZERO_DELTA_COUNT_SLOT = _calculateVaultStorageSlot("nonZeroDeltaCount");
     bytes32 private immutable _TOKEN_DELTAS_SLOT = _calculateVaultStorageSlot("tokenDeltas");
+    bytes32 private immutable _ADD_LIQUIDITY_CALLED_SLOT = _calculateVaultStorageSlot("addLiquidityCalled");
     // solhint-enable var-name-mixedcase
 
     /***************************************************************************
@@ -173,6 +174,10 @@ contract VaultStorage {
         return TokenDeltaMappingSlotType.wrap(_TOKEN_DELTAS_SLOT);
     }
 
+    function _addLiquidityCalled() internal view returns (AddressToBooleanMappingSlot slot) {
+        return AddressToBooleanMappingSlot.wrap(_ADD_LIQUIDITY_CALLED_SLOT);
+    }
+
     function _calculateVaultStorageSlot(string memory key) private pure returns (bytes32) {
         return TransientStorageHelpers.calculateSlot(type(VaultStorage).name, key);
     }