feat: add an ERC4626 rate provider

contracts/ERC4626RateProvider.sol

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+pragma solidity ^0.8.0;
+
+import "./interfaces/IRateProvider.sol";
+import "@openzeppelin/contracts/interfaces/IERC4626.sol";
+
+/**
+ * @title ERC4626 Rate Provider
+ * @notice Returns the value of 1 share of an ERC4626 in terms of the underlying asset
+ */
+contract ERC4626RateProvider is IRateProvider {
+    IERC4626 public immutable erc4626;
+    uint256 public immutable baseDecimals;
+
+    constructor(IERC4626 _erc4626) {
+        erc4626 = _erc4626;
+        baseDecimals = 10**(_erc4626.decimals());
+    }
+
+    /**
+     * @return the value of 1 share of an ERC4626 in terms of the underlying asset
+     */
+    function getRate() external view override returns (uint256) {
+        return erc4626.convertToAssets(baseDecimals);
+    }
+}

package.json

@@ -44,7 +44,7 @@
     "@chainlink/contracts": "^0.2.1",
     "@nomiclabs/hardhat-ethers": "^2.0.1",
     "@nomiclabs/hardhat-waffle": "^2.0.0",
-    "@openzeppelin/contracts": "^4.3.0",
+    "@openzeppelin/contracts": "^4.7.3",
     "@types/chai": "^4.2.12",
     "@types/mocha": "^8.0.3",
     "@types/node": "^14.6.0",

yarn.lock

@@ -620,10 +620,10 @@
     "@types/sinon-chai" "^3.2.3"
     "@types/web3" "1.0.19"
 
-"@openzeppelin/contracts@^4.3.0":
-  version "4.3.0"
-  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-4.3.0.tgz#345236d4ec73ef381ab4907c6ef66fd55e5dedad"
-  integrity sha512-+uBDl/TrmR0Kch6mq3tuxMex/fK7huR6+fQMae+zJk1K5T+dp0pFl12Hbc+1L6oYMXoyDSBJ8zqhRIntrREDFA==
+"@openzeppelin/contracts@^4.7.3":
+  version "4.9.3"
+  resolved "https://registry.yarnpkg.com/@openzeppelin/contracts/-/contracts-4.9.3.tgz#00d7a8cf35a475b160b3f0293a6403c511099364"
+  integrity sha512-He3LieZ1pP2TNt5JbkPA4PNT9WC3gOTOlDcFGJW4Le4QKqwmiNJCRt44APfxMxvq7OugU/cqYuPcSBzOw38DAg==
 
 "@resolver-engine/core@^0.3.3":
   version "0.3.3"