WIP Prevent zero shares being deposited

src/contracts/AbstractARM.sol

@@ -679,6 +679,7 @@ abstract contract AbstractARM is OwnableOperable, ERC20Upgradeable {
     function _deposit(uint256 assets, address receiver) internal returns (uint256 shares) {
         require(totalAssets() > MIN_TOTAL_SUPPLY || reservedWithdrawLiquidity == 0, "ARM: insolvent");
         shares = convertToShares(assets);
+        require(shares != 0, "ARM: zero shares");
 
         // Transfer liquidity from the depositor before minting LP shares.
         IERC20(liquidityAsset).transferFrom(msg.sender, address(this), assets);

test/invariants/LidoARM/TargetFunction.sol

@@ -93,8 +93,12 @@ abstract contract TargetFunction is Properties {
         // Select a random user
         address user = lps[account % lps.length];
 
-        amount = uint80(_bound(amount, 0, min(weth.balanceOf(user), type(uint80).max)));
-        vm.assume(amount > 0);
+        uint256 totalSupply = lidoARM.totalSupply();
+        uint256 totalAssets = lidoARM.totalAssets();
+        uint256 minAmount = totalAssets / totalSupply + 1;
+        uint256 maxAmount = min(weth.balanceOf(user), type(uint80).max);
+        vm.assume(minAmount <= maxAmount);
+        amount = uint80(_bound(amount, minAmount, maxAmount));
 
         // Cache preview deposit
         uint256 expectedShares = lidoARM.previewDeposit(amount);

test/invariants/OriginARM/TargetFunction.sol

@@ -86,6 +86,11 @@ abstract contract TargetFunction is Properties {
         if (CONSOLE_LOG) console.log("deposit() \t\t From: %s | \t Amount: %s", name(user), faa(amount));
 
         // Expected amount of shares
+        uint256 totalSupply = originARM.totalSupply();
+        uint256 totalAssets = originARM.totalAssets();
+        uint256 minAmount = totalAssets / totalSupply + 1;
+        vm.assume(minAmount <= type(uint88).max);
+        amount = uint88(_bound(amount, minAmount, type(uint88).max));
         uint256 previewDeposit = originARM.previewDeposit(amount);
 
         // Main call

test/unit/OriginARM/Deposit.sol

@@ -228,6 +228,18 @@ contract Unit_Concrete_OriginARM_Deposit_Test_ is Unit_Shared_Test {
         originARM.deposit(DEFAULT_AMOUNT);
     }
 
+    function test_RevertWhen_Deposit_Because_ZeroShares() public {
+        // Donating 1 wei increases assets per share enough for a 1 wei deposit to round down to 0 shares.
+        deal(address(weth), address(originARM), weth.balanceOf(address(originARM)) + 1);
+        assertEq(originARM.convertToShares(1), 0, "deposit should round to zero shares");
+
+        deal(address(weth), alice, 1);
+
+        vm.expectRevert("ARM: zero shares");
+        vm.prank(alice);
+        originARM.deposit(1);
+    }
+
     /// @notice Deposits remain priced from gross assets when escrowed redeem shares share a partial loss.
     function test_Deposit_When_OutstandingRequestSharesShareSmallLoss()
         public