Add view function

contracts/SpokePool.sol

@@ -629,7 +629,7 @@ abstract contract SpokePool is
         // this is unlikely and we choose to not check it and incur the extra gas cost:
         // e.g. if (msg.sender == address(0)) revert InvalidUnsafeDepositor();
 
-        uint256 depositId = uint256(bytes32(abi.encodePacked(msg.sender, depositNonce)));
+        uint256 depositId = getUnsafeDepositId(msg.sender, depositNonce);
         _depositV3(
             depositor,
             recipient,
@@ -1107,6 +1107,17 @@ abstract contract SpokePool is
         return block.timestamp; // solhint-disable-line not-rely-on-time
     }
 
+    /**
+     * @notice Returns the deposit ID for an unsafe deposit. This function is used to compute the deposit ID
+     * in unsafeDepositV3 and is provided as a convenience.
+     * @param depositor The address used as input to produce the deposit ID.
+     * @param depositNonce The nonce used as input to produce the deposit ID.
+     * @return The deposit ID for the unsafe deposit.
+     */
+    function getUnsafeDepositId(address depositor, uint96 depositNonce) public pure returns (uint256) {
+        return uint256(bytes32(abi.encodePacked(depositor, depositNonce)));
+    }
+
     /**************************************
      *         INTERNAL FUNCTIONS         *
      **************************************/

test/evm/hardhat/SpokePool.Deposit.ts

@@ -603,6 +603,7 @@ describe("SpokePool Depositor Logic", async function () {
       // new deposit ID should be the uint256 equivalent of the keccak256 hash of packed {address, forcedDepositId}.
       const forcedDepositId = "99";
       const expectedDepositId = ethers.utils.solidityPack(["address", "uint96"], [depositor.address, forcedDepositId]);
+      expect(await spokePool.getUnsafeDepositId(depositor.address, forcedDepositId)).to.equal(expectedDepositId);
       await expect(
         spokePool
           .connect(depositor)