feat: Add rate provider zero check to constructor (#35)

* feat: add rate provider check

* fix: update to reduce diff

* feat: update to get invariant test setup to work with new constructor

deploy/PSM3Deploy.sol

@@ -1,10 +1,10 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 pragma solidity ^0.8.13;
 
-import { PSM3 } from "src/PSM3.sol";
-
 import { IERC20 } from "erc20-helpers/interfaces/IERC20.sol";
 
+import { PSM3 } from "src/PSM3.sol";
+
 library PSM3Deploy {
 
     function deploy(

src/PSM3.sol

@@ -46,6 +46,11 @@ contract PSM3 is IPSM3 {
 
         rateProvider = rateProvider_;
 
+        require(
+            IRateProviderLike(rateProvider_).getConversionRate() != 0,
+            "PSM3/rate-provider-returns-zero"
+        );
+
         _asset0Precision = 10 ** IERC20(asset0_).decimals();
         _asset1Precision = 10 ** IERC20(asset1_).decimals();
         _asset2Precision = 10 ** IERC20(asset2_).decimals();

test/invariant/Invariants.t.sol

@@ -4,6 +4,7 @@ pragma solidity ^0.8.13;
 import "forge-std/Test.sol";
 
 import { DSRAuthOracle } from "lib/xchain-dsr-oracle/src/DSRAuthOracle.sol";
+import { IDSROracle }    from "lib/xchain-dsr-oracle/src/interfaces/IDSROracle.sol";
 
 import { PSM3 } from "src/PSM3.sol";
 
@@ -542,6 +543,16 @@ contract PSMInvariants_TimeBasedRateSetting_NoTransfer is PSMInvariantTestBase {
 
         DSRAuthOracle dsrOracle = new DSRAuthOracle();
 
+        // Workaround to initialize PSM with an oracle that does not return zero
+        // This gets overwritten by the handler
+        dsrOracle.grantRole(dsrOracle.DATA_PROVIDER_ROLE(), address(this));
+        dsrOracle.setPotData(IDSROracle.PotData({
+            dsr: uint96(1e27),
+            chi: uint120(1e27),
+            rho: uint40(block.timestamp)
+        }));
+        dsrOracle.revokeRole(dsrOracle.DATA_PROVIDER_ROLE(), address(this));
+
         // Redeploy PSM with new rate provider
         psm = new PSM3(address(dai), address(usdc), address(sDai), address(dsrOracle));
 
@@ -611,6 +622,16 @@ contract PSMInvariants_TimeBasedRateSetting_WithTransfers is PSMInvariantTestBas
 
         DSRAuthOracle dsrOracle = new DSRAuthOracle();
 
+        // Workaround to initialize PSM with an oracle that does not return zero
+        // This gets overwritten by the handler
+        dsrOracle.grantRole(dsrOracle.DATA_PROVIDER_ROLE(), address(this));
+        dsrOracle.setPotData(IDSROracle.PotData({
+            dsr: uint96(1e27),
+            chi: uint120(1e27),
+            rho: uint40(block.timestamp)
+        }));
+        dsrOracle.revokeRole(dsrOracle.DATA_PROVIDER_ROLE(), address(this));
+
         // Redeploy PSM with new rate provider
         psm = new PSM3(address(dai), address(usdc), address(sDai), address(dsrOracle));
 

test/invariant/handlers/TimeBasedRateHandler.sol

@@ -28,12 +28,9 @@ contract TimeBasedRateHandler is HandlerBase, StdCheats {
         // 1. Setup and bounds
         dsr = _bound(newDsr, 1e27, TWENTY_PCT_APY_DSR);
 
+        // Update rho to be current, update chi based on current rate
         uint256 rho = block.timestamp;
-
-        // If chi hasn't been set yet, set to 1e27, else recalculate it in the same way it would
-        // happen during a refresh at `rho`
-        uint256 rate = dsrOracle.getConversionRate(rho);
-        uint256 chi  = rate == 0 ? 1e27 : rate;
+        uint256 chi = dsrOracle.getConversionRate(rho);
 
         // 2. Cache starting state
         uint256 startingConversion = psm.convertToAssetValue(1e18);

test/unit/Constructor.t.sol

@@ -7,6 +7,8 @@ import { PSM3 } from "src/PSM3.sol";
 
 import { PSMTestBase } from "test/PSMTestBase.sol";
 
+import { MockRateProvider } from "test/mocks/MockRateProvider.sol";
+
 contract PSMConstructorTests is PSMTestBase {
 
     function test_constructor_invalidAsset0() public {
@@ -44,6 +46,12 @@ contract PSMConstructorTests is PSMTestBase {
         new PSM3(address(dai), address(usdc), address(usdc), address(rateProvider));
     }
 
+    function test_constructor_rateProviderZero() public {
+        MockRateProvider(address(rateProvider)).__setConversionRate(0);
+        vm.expectRevert("PSM3/rate-provider-returns-zero");
+        new PSM3(address(dai), address(usdc), address(sDai), address(rateProvider));
+    }
+
     function test_constructor() public {
         // Deploy new PSM to get test coverage
         psm = new PSM3(address(dai), address(usdc), address(sDai), address(rateProvider));