fix: rely less on foundry internals (#473)

* fix: rely less on foundry internals

* chore: update comments

Author: DaniPopes

src/StdChains.sol

@@ -159,10 +159,18 @@ abstract contract StdChains {
                 } else {
                     chain.rpcUrl = vm.envString(envName);
                 }
-                // distinguish 'not found' from 'cannot read'
-                bytes memory notFoundError =
+                // Distinguish 'not found' from 'cannot read'
+                // The upstream error thrown by forge for failing cheats changed so we check both the old and new versions
+                bytes memory oldNotFoundError =
                     abi.encodeWithSignature("CheatCodeError", string(abi.encodePacked("invalid rpc url ", chainAlias)));
-                if (keccak256(notFoundError) != keccak256(err) || bytes(chain.rpcUrl).length == 0) {
+                bytes memory newNotFoundError = abi.encodeWithSignature(
+                    "CheatcodeError(string)", string(abi.encodePacked("invalid rpc url: ", chainAlias))
+                );
+                bytes32 errHash = keccak256(err);
+                if (
+                    (errHash != keccak256(oldNotFoundError) && errHash != keccak256(newNotFoundError))
+                        || bytes(chain.rpcUrl).length == 0
+                ) {
                     /// @solidity memory-safe-assembly
                     assembly {
                         revert(add(32, err), mload(err))

test/StdChains.t.sol

@@ -208,13 +208,9 @@ contract StdChainsTest is Test {
 
         // Should error if default RPCs flag is set to false.
         stdChainsMock.exposed_setFallbackToDefaultRpcUrls(false);
-        vm.expectRevert(
-            "Failed to get environment variable `ANVIL_RPC_URL` as type `string`: environment variable not found"
-        );
+        vm.expectRevert();
         stdChainsMock.exposed_getChain(31337);
-        vm.expectRevert(
-            "Failed to get environment variable `SEPOLIA_RPC_URL` as type `string`: environment variable not found"
-        );
+        vm.expectRevert();
         stdChainsMock.exposed_getChain("sepolia");
     }
 }