TRUST QA-6/7: Optimizations in Distributor

contracts/facade/FacadeTest.sol

@@ -66,6 +66,7 @@ contract FacadeTest is IFacadeTest {
             erc20s
         );
         try main.rsrTrader().manageTokens(rsrERC20s, rsrKinds) {} catch {}
+        try main.rsrTrader().distributeTokenToBuy() {} catch {}
 
         // Start exact RToken auctions
         (IERC20[] memory rTokenERC20s, TradeKind[] memory rTokenKinds) = traderERC20s(
@@ -74,6 +75,7 @@ contract FacadeTest is IFacadeTest {
             erc20s
         );
         try main.rTokenTrader().manageTokens(rTokenERC20s, rTokenKinds) {} catch {}
+        try main.rTokenTrader().distributeTokenToBuy() {} catch {}
         // solhint-enable no-empty-blocks
     }
 
@@ -133,6 +135,7 @@ contract FacadeTest is IFacadeTest {
         IERC20[] memory traderERC20sAll = new IERC20[](erc20sAll.length);
         for (uint256 i = 0; i < erc20sAll.length; ++i) {
             if (
+                erc20sAll[i] != trader.tokenToBuy() &&
                 address(trader.trades(erc20sAll[i])) == address(0) &&
                 erc20sAll[i].balanceOf(address(trader)) > 1
             ) {

contracts/p0/Distributor.sol

@@ -63,8 +63,8 @@ contract DistributorP0 is ComponentP0, IDistributor {
         {
             RevenueTotals memory revTotals = totals();
             uint256 totalShares = isRSR ? revTotals.rsrTotal : revTotals.rTokenTotal;
-            require(totalShares > 0, "nothing to distribute");
-            tokensPerShare = amount / totalShares;
+            if (totalShares > 0) tokensPerShare = amount / totalShares;
+            require(tokensPerShare > 0, "nothing to distribute");
         }
 
         // Evenly distribute revenue tokens per distribution share.

contracts/p1/Distributor.sol

@@ -68,7 +68,6 @@ contract DistributorP1 is ComponentP1, IDistributor {
     }
 
     struct Transfer {
-        IERC20 erc20;
         address addrTo;
         uint256 amount;
     }
@@ -99,8 +98,8 @@ contract DistributorP1 is ComponentP1, IDistributor {
         {
             RevenueTotals memory revTotals = totals();
             uint256 totalShares = isRSR ? revTotals.rsrTotal : revTotals.rTokenTotal;
-            require(totalShares > 0, "nothing to distribute");
-            tokensPerShare = amount / totalShares;
+            if (totalShares > 0) tokensPerShare = amount / totalShares;
+            require(tokensPerShare > 0, "nothing to distribute");
         }
 
         // Evenly distribute revenue tokens per distribution share.
@@ -131,19 +130,15 @@ contract DistributorP1 is ComponentP1, IDistributor {
                 if (transferAmt > 0) accountRewards = true;
             }
 
-            transfers[numTransfers] = Transfer({
-                erc20: erc20,
-                addrTo: addrTo,
-                amount: transferAmt
-            });
+            transfers[numTransfers] = Transfer({ addrTo: addrTo, amount: transferAmt });
             numTransfers++;
         }
         emit RevenueDistributed(erc20, caller, amount);
 
         // == Interactions ==
         for (uint256 i = 0; i < numTransfers; i++) {
             Transfer memory t = transfers[i];
-            IERC20Upgradeable(address(t.erc20)).safeTransferFrom(caller, t.addrTo, t.amount);
+            IERC20Upgradeable(address(erc20)).safeTransferFrom(caller, t.addrTo, t.amount);
         }
 
         // Perform reward accounting

contracts/plugins/mocks/RevenueTraderBackComp.sol

@@ -14,8 +14,10 @@ contract RevenueTraderCompatibleV2 is RevenueTraderP1, IRevenueTraderComp {
         erc20s[0] = sell;
         TradeKind[] memory kinds = new TradeKind[](1);
         kinds[0] = TradeKind.DUTCH_AUCTION;
+
         // Mirror V3 logic (only the section relevant to tests)
-        this.manageTokens(erc20s, kinds);
+        // solhint-disable-next-line no-empty-blocks
+        try this.manageTokens(erc20s, kinds) {} catch {}
     }
 
     function version() public pure virtual override(Versioned, IVersioned) returns (string memory) {

test/Revenues.test.ts

@@ -705,6 +705,17 @@ describe(`Revenues - P${IMPLEMENTATION}`, () => {
         expect(newRTokenTotal).equal(bn(0))
       })
 
+      it('Should avoid zero transfers when distributing tokenToBuy', async () => {
+        // Distribute with no balance
+        await expect(rsrTrader.distributeTokenToBuy()).to.be.revertedWith('nothing to distribute')
+        expect(await rsr.balanceOf(stRSR.address)).to.equal(bn(0))
+
+        // Small amount which ends in zero distribution due to rounding
+        await rsr.connect(owner).mint(rsrTrader.address, bn(1))
+        await expect(rsrTrader.distributeTokenToBuy()).to.be.revertedWith('nothing to distribute')
+        expect(await rsr.balanceOf(stRSR.address)).to.equal(bn(0))
+      })
+
       it('Should account rewards when distributing tokenToBuy', async () => {
         // 1. StRSR.payoutRewards()
         const stRSRBal = await rsr.balanceOf(stRSR.address)