refactor: change setMinimumFeeToZero to lowerMinimumFee

src/abstracts/SablierMerkleBase.sol

@@ -196,7 +196,7 @@ abstract contract SablierMerkleBase is
     }
 
     /// @inheritdoc ISablierMerkleBase
-    function setMinimumFeeToZero() external override {
+    function lowerMinimumFee(uint256 newFee) external override {
         // Retrieve the factory admin.
         address factoryAdmin = ISablierMerkleFactoryBase(FACTORY).admin();
 
@@ -205,13 +205,18 @@ abstract contract SablierMerkleBase is
             revert Errors.SablierMerkleBase_CallerNotFactoryAdmin(factoryAdmin, msg.sender);
         }
 
-        uint256 previousMinimumFee = minimumFee;
+        uint256 previousFee = minimumFee;
+
+        // Check: the new fee is less than the current fee.
+        if (newFee >= previousFee) {
+            revert Errors.SablierMerkleBase_NewFeeNotLower(previousFee, newFee);
+        }
 
         // Effect: set the minimum fee to zero.
-        minimumFee = 0;
+        minimumFee = newFee;
 
         // Log the event.
-        emit SetMinimumFeeToZero(factoryAdmin, previousMinimumFee);
+        emit LowerMinimumFee(factoryAdmin, newFee, previousFee);
     }
 
     /*//////////////////////////////////////////////////////////////////////////

src/interfaces/ISablierMerkleBase.sol

@@ -14,8 +14,8 @@ interface ISablierMerkleBase is IAdminable {
     /// @notice Emitted when the admin claws back the unclaimed tokens.
     event Clawback(address indexed admin, address indexed to, uint128 amount);
 
-    /// @notice Emitted when the minimum fee is set to zero.
-    event SetMinimumFeeToZero(address indexed factoryAdmin, uint256 previousFee);
+    /// @notice Emitted when the minimum fee is set to a lower value.
+    event LowerMinimumFee(address indexed factoryAdmin, uint256 newFee, uint256 previousFee);
 
     /*//////////////////////////////////////////////////////////////////////////
                                  CONSTANT FUNCTIONS
@@ -110,11 +110,12 @@ interface ISablierMerkleBase is IAdminable {
     /// @return feeAmount The amount of native tokens (e.g., ETH) collected as fees.
     function collectFees(address factoryAdmin) external returns (uint256 feeAmount);
 
-    /// @notice Sets the minimum fee required to claim the airdrop to zero.
+    /// @notice Sets the minimum fee to a lower value.
     ///
-    /// @dev Emits a {SetMinimumFeeToZero} event.
+    /// @dev Emits a {LowerMinimumFee} event.
     ///
     /// Requirements:
     /// - `msg.sender` must be the `FACTORY` admin.
-    function setMinimumFeeToZero() external;
+    /// - The new fee must be less than the current `minimumFee`.
+    function lowerMinimumFee(uint256 newFee) external;
 }

src/libraries/Errors.sol

@@ -30,6 +30,9 @@ library Errors {
     /// @notice Thrown when trying to claim with an invalid Merkle proof.
     error SablierMerkleBase_InvalidProof();
 
+    /// @notice Thrown when trying to set a fee that is not lower than the current fee.
+    error SablierMerkleBase_NewFeeNotLower(uint256 currentFee, uint256 newFee);
+
     /// @notice Thrown when trying to claim the same stream more than once.
     error SablierMerkleBase_StreamClaimed(uint256 index);
 

tests/integration/concrete/campaign/instant/MerkleInstant.t.sol

@@ -11,7 +11,7 @@ import { CollectFees_Integration_Test } from "./../shared/collect-fees/collectFe
 import { GetFirstClaimTime_Integration_Test } from "./../shared/get-first-claim-time/getFirstClaimTime.t.sol";
 import { HasClaimed_Integration_Test } from "./../shared/has-claimed/hasClaimed.t.sol";
 import { HasExpired_Integration_Test } from "./../shared/has-expired/hasExpired.t.sol";
-import { SetMinimumFeeToZero_Integration_Test } from "./../shared/set-minimum-fee-to-zero/setMinimumFeeToZero.t.sol";
+import { LowerMinimumFee_Integration_Test } from "./../shared/lower-minimum-fee/lowerMinimumFee.t.sol";
 
 /*//////////////////////////////////////////////////////////////////////////
                              NON-SHARED TESTS
@@ -84,9 +84,9 @@ contract HasExpired_MerkleInstant_Integration_Test is
     }
 }
 
-contract SetMinimumFeeToZero_MerkleInstant_Integration_Test is
+contract LowerMinimumFee_MerkleInstant_Integration_Test is
     MerkleInstant_Integration_Shared_Test,
-    SetMinimumFeeToZero_Integration_Test
+    LowerMinimumFee_Integration_Test
 {
     function setUp() public override(MerkleInstant_Integration_Shared_Test, Integration_Test) {
         MerkleInstant_Integration_Shared_Test.setUp();

tests/integration/concrete/campaign/ll/MerkleLL.t.sol

@@ -11,7 +11,7 @@ import { CollectFees_Integration_Test } from "./../shared/collect-fees/collectFe
 import { GetFirstClaimTime_Integration_Test } from "./../shared/get-first-claim-time/getFirstClaimTime.t.sol";
 import { HasClaimed_Integration_Test } from "./../shared/has-claimed/hasClaimed.t.sol";
 import { HasExpired_Integration_Test } from "./../shared/has-expired/hasExpired.t.sol";
-import { SetMinimumFeeToZero_Integration_Test } from "./../shared/set-minimum-fee-to-zero/setMinimumFeeToZero.t.sol";
+import { LowerMinimumFee_Integration_Test } from "./../shared/lower-minimum-fee/lowerMinimumFee.t.sol";
 
 /*//////////////////////////////////////////////////////////////////////////
                              NON-SHARED TESTS
@@ -75,9 +75,9 @@ contract HasExpired_MerkleLL_Integration_Test is MerkleLL_Integration_Shared_Tes
     }
 }
 
-contract SetMinimumFeeToZero_MerkleLL_Integration_Test is
+contract LowerMinimumFee_MerkleLL_Integration_Test is
     MerkleLL_Integration_Shared_Test,
-    SetMinimumFeeToZero_Integration_Test
+    LowerMinimumFee_Integration_Test
 {
     function setUp() public override(MerkleLL_Integration_Shared_Test, Integration_Test) {
         MerkleLL_Integration_Shared_Test.setUp();

tests/integration/concrete/campaign/lt/MerkleLT.t.sol

@@ -11,7 +11,7 @@ import { CollectFees_Integration_Test } from "./../shared/collect-fees/collectFe
 import { GetFirstClaimTime_Integration_Test } from "./../shared/get-first-claim-time/getFirstClaimTime.t.sol";
 import { HasClaimed_Integration_Test } from "./../shared/has-claimed/hasClaimed.t.sol";
 import { HasExpired_Integration_Test } from "./../shared/has-expired/hasExpired.t.sol";
-import { SetMinimumFeeToZero_Integration_Test } from "./../shared/set-minimum-fee-to-zero/setMinimumFeeToZero.t.sol";
+import { LowerMinimumFee_Integration_Test } from "./../shared/lower-minimum-fee/lowerMinimumFee.t.sol";
 
 /*//////////////////////////////////////////////////////////////////////////
                              NON-SHARED TESTS
@@ -75,9 +75,9 @@ contract HasExpired_MerkleLT_Integration_Test is MerkleLT_Integration_Shared_Tes
     }
 }
 
-contract SetMinimumFeeToZero_MerkleLT_Integration_Test is
+contract LowerMinimumFee_MerkleLT_Integration_Test is
     MerkleLT_Integration_Shared_Test,
-    SetMinimumFeeToZero_Integration_Test
+    LowerMinimumFee_Integration_Test
 {
     function setUp() public override(MerkleLT_Integration_Shared_Test, Integration_Test) {
         MerkleLT_Integration_Shared_Test.setUp();

tests/integration/concrete/campaign/shared/calculate-minimum-fee-in-wei/calculateMinimumFeeInWei.t.sol

@@ -33,7 +33,7 @@ abstract contract CalculateMinimumFeeInWei_Integration_Test is Integration_Test
 
     function test_GivenMinimumFeeZero() external givenPriceFeedAddressNotZero {
         resetPrank(users.admin);
-        merkleBase.setMinimumFeeToZero();
+        merkleBase.lowerMinimumFee(0);
         assertEq(merkleBase.calculateMinimumFeeInWei(), 0, "minimum fee in wei");
     }
 

tests/integration/concrete/campaign/shared/lower-minimum-fee/lowerMinimumFee.t.sol

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity >=0.8.22 <0.9.0;
+
+import { ISablierMerkleBase } from "src/interfaces/ISablierMerkleBase.sol";
+import { Errors } from "src/libraries/Errors.sol";
+
+import { Integration_Test } from "../../../../Integration.t.sol";
+
+abstract contract LowerMinimumFee_Integration_Test is Integration_Test {
+    function test_RevertWhen_CallerNotFactoryAdmin() external {
+        resetPrank({ msgSender: users.eve });
+        vm.expectRevert(
+            abi.encodeWithSelector(Errors.SablierMerkleBase_CallerNotFactoryAdmin.selector, users.admin, users.eve)
+        );
+        merkleBase.lowerMinimumFee(MINIMUM_FEE - 1);
+    }
+
+    function test_RevertWhen_NewFeeNotLower() external whenCallerFactoryAdmin {
+        uint256 newFee = MINIMUM_FEE + 1;
+        resetPrank(users.admin);
+        vm.expectRevert(abi.encodeWithSelector(Errors.SablierMerkleBase_NewFeeNotLower.selector, MINIMUM_FEE, newFee));
+        merkleBase.lowerMinimumFee(newFee);
+    }
+
+    function test_WhenNewFeeNotZero() external whenCallerFactoryAdmin whenNewFeeLower {
+        uint256 newFee = MINIMUM_FEE - 1;
+        resetPrank(users.admin);
+        vm.expectEmit({ emitter: address(merkleBase) });
+        emit ISablierMerkleBase.LowerMinimumFee(users.admin, newFee, MINIMUM_FEE);
+        merkleBase.lowerMinimumFee(newFee);
+        assertEq(merkleBase.minimumFee(), newFee);
+    }
+
+    function test_WhenNewFeeZero() external whenCallerFactoryAdmin whenNewFeeLower {
+        uint256 newFee = 0;
+        resetPrank(users.admin);
+        vm.expectEmit({ emitter: address(merkleBase) });
+        emit ISablierMerkleBase.LowerMinimumFee(users.admin, newFee, MINIMUM_FEE);
+        merkleBase.lowerMinimumFee(newFee);
+        assertEq(merkleBase.minimumFee(), newFee);
+    }
+}

tests/integration/concrete/campaign/shared/lower-minimum-fee/lowerMinimumFee.tree

@@ -0,0 +1,13 @@
+LowerMinimumFee_Integration_Test
+├── when caller not factory admin
+│  └── it should revert
+└── when caller factory admin
+   ├── when new fee not lower
+   │  └── it should revert
+   └── when new fee lower
+      ├── when new fee not zero
+      │  ├── it should set minimum fee to new fee
+      │  └── it should emit event LowerMinimumFee
+      └── when new fee zero
+         ├── it should set minimum fee to zero   
+         └── it should emit event LowerMinimumFee

tests/integration/concrete/campaign/vca/MerkleVCA.t.sol

@@ -11,7 +11,7 @@ import { CollectFees_Integration_Test } from "./../shared/collect-fees/collectFe
 import { GetFirstClaimTime_Integration_Test } from "./../shared/get-first-claim-time/getFirstClaimTime.t.sol";
 import { HasClaimed_Integration_Test } from "./../shared/has-claimed/hasClaimed.t.sol";
 import { HasExpired_Integration_Test } from "./../shared/has-expired/hasExpired.t.sol";
-import { SetMinimumFeeToZero_Integration_Test } from "./../shared/set-minimum-fee-to-zero/setMinimumFeeToZero.t.sol";
+import { LowerMinimumFee_Integration_Test } from "./../shared/lower-minimum-fee/lowerMinimumFee.t.sol";
 
 /*//////////////////////////////////////////////////////////////////////////
                              NON-SHARED TESTS
@@ -75,9 +75,9 @@ contract HasExpired_MerkleVCA_Integration_Test is MerkleVCA_Integration_Shared_T
     }
 }
 
-contract SetMinimumFeeToZero_MerkleVCA_Integration_Test is
+contract LowerMinimumFee_MerkleVCA_Integration_Test is
     MerkleVCA_Integration_Shared_Test,
-    SetMinimumFeeToZero_Integration_Test
+    LowerMinimumFee_Integration_Test
 {
     function setUp() public override(MerkleVCA_Integration_Shared_Test, Integration_Test) {
         MerkleVCA_Integration_Shared_Test.setUp();

tests/utils/Modifiers.sol

@@ -19,6 +19,10 @@ abstract contract Modifiers is EvmUtilsBase {
                                        GIVEN
     //////////////////////////////////////////////////////////////////////////*/
 
+    modifier whenCallerFactoryAdmin() {
+        _;
+    }
+
     modifier givenCampaignNotExists() {
         _;
     }
@@ -95,6 +99,10 @@ abstract contract Modifiers is EvmUtilsBase {
         _;
     }
 
+    modifier whenNewFeeLower() {
+        _;
+    }
+
     modifier whenNewFeeDoesNotExceedTheMaximumFee() {
         _;
     }