updated remove dust logic to return dust to the sender

Author: 0xIryna

.solcover.js

@@ -1,3 +1,3 @@
 module.exports = {	
-	skipFiles: ["interfaces", "test"]
+	skipFiles: ["interfaces", "test", "wrappedTokens"]
 };

contracts/OriginalTokenBridge.sol

@@ -74,25 +74,29 @@ contract OriginalTokenBridge is TokenBridgeBase {
     /// @dev Locks an ERC20 on the source chain and sends LZ message to the remote chain to mint a wrapped token
     function bridge(address token, uint amountLD, address to, LzLib.CallParams calldata callParams, bytes memory adapterParams) external payable nonReentrant {
         require(supportedTokens[token], "OriginalTokenBridge: token is not supported");
-        amountLD = _removeDust(token, amountLD);
-
+   
         // Supports tokens with transfer fee
         uint balanceBefore = IERC20(token).balanceOf(address(this));
         IERC20(token).safeTransferFrom(msg.sender, address(this), amountLD);
         uint balanceAfter = IERC20(token).balanceOf(address(this));
-        amountLD = balanceAfter - balanceBefore;
+        (uint amountWithoutDustLD, uint dust) = _removeDust(token, balanceAfter - balanceBefore);
+
+        // return dust to the sender
+        if (dust > 0) {
+            IERC20(token).safeTransfer(msg.sender, dust);
+        }
 
-        _bridge(token, amountLD, to, msg.value, callParams, adapterParams);
+        _bridge(token, amountWithoutDustLD, to, msg.value, callParams, adapterParams);
     }
 
     /// @notice Bridges ETH to the remote chain
     /// @dev Locks WETH on the source chain and sends LZ message to the remote chain to mint a wrapped token
     function bridgeETH(uint amountLD, address to, LzLib.CallParams calldata callParams, bytes memory adapterParams) external payable nonReentrant {
         require(supportedTokens[weth], "OriginalTokenBridge: token is not supported");
         require(msg.value >= amountLD, "OriginalTokenBridge: not enough value sent");
-        amountLD = _removeDust(weth, amountLD);
+        (uint amountWithoutDustLD, ) = _removeDust(weth, amountLD);
         IWETH(weth).deposit{value: amountLD}();
-        _bridge(weth, amountLD, to, msg.value - amountLD, callParams, adapterParams);
+        _bridge(weth, amountLD, to, msg.value - amountWithoutDustLD, callParams, adapterParams);
     }
 
     function _bridge(address token, uint amountLD, address to, uint nativeFee, LzLib.CallParams calldata callParams, bytes memory adapterParams) private {
@@ -153,8 +157,9 @@ contract OriginalTokenBridge is TokenBridgeBase {
         return amountLD / LDtoSDConversionRate[token];
     }
 
-    function _removeDust(address token, uint amountLD) internal view returns (uint) {
-        return _amountSDtoLD(token, _amountLDtoSD(token, amountLD));
+    function _removeDust(address token, uint amountLD) internal view returns (uint amountWithoutDustLD, uint dust) {
+        dust = amountLD % LDtoSDConversionRate[token];
+        amountWithoutDustLD = amountLD - dust;
     }
 
     /// @dev Allows receiving ETH when calling WETH.withdraw()

test/OriginalTokenBridge.test.js

@@ -1,6 +1,6 @@
 const { expect } = require("chai")
 const { ethers } = require("hardhat")
-const { utils, constants } = require("ethers")
+const { utils, constants, BigNumber } = require("ethers")
 
 describe("OriginalTokenBridge", () => {
     const originalTokenChainId = 0
@@ -146,6 +146,21 @@ describe("OriginalTokenBridge", () => {
             expect(await originalToken.balanceOf(originalTokenBridge.address)).to.be.eq(amount)
             expect(await originalToken.balanceOf(user.address)).to.be.eq(0)
         })
+
+        it("locks tokens in the contract and returns dust to the sender", async () => {
+            const dust = BigNumber.from("12345")
+            const amountWithDust = amount.add(dust)
+
+            await originalTokenBridge.registerToken(originalToken.address, sharedDecimals)
+            await originalToken.mint(user.address, dust)
+            await originalToken.connect(user).approve(originalTokenBridge.address, amountWithDust)
+            await originalTokenBridge.connect(user).bridge(originalToken.address, amountWithDust, user.address, callParams, adapterParams, { value: fee })
+            const LDtoSD = await originalTokenBridge.LDtoSDConversionRate(originalToken.address)
+
+            expect(await originalTokenBridge.totalValueLockedSD(originalToken.address)).to.be.eq(amount.div(LDtoSD))
+            expect(await originalToken.balanceOf(originalTokenBridge.address)).to.be.eq(amount)
+            expect(await originalToken.balanceOf(user.address)).to.be.eq(dust)
+        })
     })
 
     describe("bridgeETH", () => {