[RB Set V2] Add check for non-zero supply when starting a rebalance

contracts/core/tokens/rebalancing-v2/RebalancingStart.sol

@@ -17,6 +17,7 @@
 pragma solidity 0.5.7;
 pragma experimental "ABIEncoderV2";
 
+import { ERC20 } from "openzeppelin-solidity/contracts/token/ERC20/ERC20.sol";
 import { Math } from "openzeppelin-solidity/contracts/math/Math.sol";
 import { SafeMath } from "openzeppelin-solidity/contracts/math/SafeMath.sol";
 
@@ -32,6 +33,7 @@ import { RebalancingSetState } from "./RebalancingSetState.sol";
  * Implementation of Rebalancing Set Token V2 start rebalance functionality
  */
 contract RebalancingStart is 
+    ERC20,
     RebalancingSetState
 {
     using SafeMath for uint256;
@@ -62,6 +64,12 @@ contract RebalancingStart is
             "Interval not elapsed"
         );
 
+        // Must be a positive supply of the Set
+        require(
+            totalSupply() > 0,
+            "Invalid supply"
+        );
+
         // New proposed Set must be a valid Set created by Core
         require(
             core.validSets(address(_nextSet)),

test/contracts/core/tokens/rebalancing-v2/rebalancingSetState.spec.ts

@@ -140,13 +140,16 @@ contract('RebalancingSetState', accounts => {
 
     liquidatorMock = await liquidatorHelper.deployLiquidatorMockAsync();
     await coreHelper.addAddressToWhiteList(liquidatorMock.address, liquidatorWhitelist);
-
     [ initialSetToken, nextSetToken ] = await rebalancingHelper.createSetTokensAsync(
       coreMock,
       factory.address,
       transferProxy.address,
-      2
+      2,
+      undefined,
+      managerAccount,
     );
+
+
     manager = managerAccount;
     liquidator = liquidatorMock.address;
     initialUnitShares = DEFAULT_UNIT_SHARES;
@@ -181,6 +184,8 @@ contract('RebalancingSetState', accounts => {
         entryFee,
       ]
     );
+
+    await coreMock.addSet.sendTransactionAsync(rebalancingSetToken.address, txnFrom(deployerAccount));
   });
 
   afterEach(async () => {
@@ -625,16 +630,16 @@ contract('RebalancingSetState', accounts => {
 
     describe('when startRebalance is called from Rebalance State', async () => {
       beforeEach(async () => {
-      const nextSetTokenComponentAddresses = await nextSetToken.getComponents.callAsync();
-      await coreHelper.addTokensToWhiteList(nextSetTokenComponentAddresses, rebalancingComponentWhiteList);
-
-       await rebalancingHelper.transitionToRebalanceV2Async(
-         coreMock,
-         rebalancingComponentWhiteList,
-         rebalancingSetToken,
-         nextSetToken,
-         managerAccount
-       );
+        const nextSetTokenComponentAddresses = await nextSetToken.getComponents.callAsync();
+        await coreHelper.addTokensToWhiteList(nextSetTokenComponentAddresses, rebalancingComponentWhiteList);
+
+        await rebalancingHelper.transitionToRebalanceV2Async(
+          coreMock,
+          rebalancingComponentWhiteList,
+          rebalancingSetToken,
+          nextSetToken,
+          managerAccount
+        );
       });
 
       it('should revert', async () => {

test/contracts/core/tokens/rebalancing-v2/rebalancingStart.spec.ts

@@ -372,6 +372,20 @@ contract('StartRebalance', accounts => {
         });
       });
 
+      describe('when the rebalancing set supply is 0', async () => {
+        beforeEach(async () => {
+          // Redeem all supply
+          await coreMock.redeem.sendTransactionAsync(
+            rebalancingSetToken.address,
+            rebalancingSetQuantityToIssue
+          );
+        });
+
+        it('should revert', async () => {
+          await expectRevertError(subject());
+        });
+      });
+
       describe('when the rebalance interval has not elapsed', async () => {
         beforeEach(async () => {
           subjectTimeFastForward = ONE_DAY_IN_SECONDS.sub(10);

utils/helpers/rebalancingHelper.ts

@@ -153,8 +153,8 @@ export class RebalancingHelper {
     let naturalUnit: BigNumber;
     const setTokenArray: SetTokenContract[] = [];
 
-    const components = await this._erc20Helper.deployTokensAsync(tokenCount + 1, this._tokenOwnerAddress);
-    await this._erc20Helper.approveTransfersAsync(components, transferProxy);
+    const components = await this._erc20Helper.deployTokensAsync(tokenCount + 1, from);
+    await this._erc20Helper.approveTransfersAsync(components, transferProxy, from);
 
     const indexArray = _.times(tokenCount, Number);
     for (const index in indexArray) {
@@ -189,6 +189,12 @@ export class RebalancingHelper {
         naturalUnit,
       );
 
+      await setToken.approve.sendTransactionAsync(
+        transferProxy,
+        UNLIMITED_ALLOWANCE_IN_BASE_UNITS,
+        txnFrom(from)
+      );
+
       setTokenArray.push(setToken);
     }
 

utils/helpers/rebalancingSetV2Helper.ts

@@ -26,8 +26,8 @@ import {
   ZERO,
 } from '../constants';
 import { extractNewSetTokenAddressFromLogs } from '../contract_logs/core';
-
-import { getWeb3, getContractInstance } from '../web3Helper';
+import { ether } from '@utils/units';
+import { getWeb3, getContractInstance, txnFrom } from '../web3Helper';
 
 import { RebalancingHelper } from './rebalancingHelper';
 
@@ -172,6 +172,27 @@ export class RebalancingSetV2Helper extends RebalancingHelper {
     liquidatorData: string = EMPTY_BYTESTRING,
 
   ): Promise<void> {
+    const currentSupply = await rebalancingSetToken.totalSupply.callAsync();
+    if (currentSupply.eq(new BigNumber(0))) {
+      const currentSetMintQuantity = ether(8);
+      const currentSetToken = await rebalancingSetToken.currentSet.callAsync();
+
+      // Issue currentSetToken
+      await core.issue.sendTransactionAsync(
+        currentSetToken,
+        currentSetMintQuantity,
+        txnFrom(caller)
+      );
+
+      // Use issued currentSetToken to issue rebalancingSetToken
+      const rebalancingSetQuantityToIssue = ether(7);
+      await core.issue.sendTransactionAsync(
+        rebalancingSetToken.address,
+        rebalancingSetQuantityToIssue,
+        txnFrom(caller)
+      );
+    }
+
     const nextSetTokenComponentAddresses = await nextSetToken.getComponents.callAsync();
     await this._coreHelper.addTokensToWhiteList(
       nextSetTokenComponentAddresses,