Use namespaced storage for upgradeable contracts

.changeset/wet-bears-heal.md

@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': major
+---
+
+Upgradeable contracts now use namespaced storage (EIP-7201).

.github/actions/setup/action.yml

@@ -5,7 +5,7 @@ runs:
   steps:
     - uses: actions/setup-node@v3
       with:
-        node-version: 14.x
+        node-version: 16.x
     - uses: actions/cache@v3
       id: cache
       with:

contracts/governance/Governor.sol

@@ -299,8 +299,8 @@ abstract contract Governor is Context, ERC165, EIP712, Nonces, IGovernor, IERC72
         bytes[] memory calldatas,
         string memory description,
         address proposer
-    ) internal virtual returns (uint256) {
-        uint256 proposalId = hashProposal(targets, values, calldatas, keccak256(bytes(description)));
+    ) internal virtual returns (uint256 proposalId) {
+        proposalId = hashProposal(targets, values, calldatas, keccak256(bytes(description)));
 
         if (targets.length != values.length || targets.length != calldatas.length || targets.length == 0) {
             revert GovernorInvalidProposalLength(targets.length, calldatas.length, values.length);
@@ -329,7 +329,7 @@ abstract contract Governor is Context, ERC165, EIP712, Nonces, IGovernor, IERC72
             description
         );
 
-        return proposalId;
+        // Using a named return variable to avoid stack too deep errors
     }
 
     /**

contracts/governance/extensions/GovernorVotes.sol

@@ -12,18 +12,25 @@ import {SafeCast} from "../../utils/math/SafeCast.sol";
  * @dev Extension of {Governor} for voting weight extraction from an {ERC20Votes} token, or since v4.5 an {ERC721Votes} token.
  */
 abstract contract GovernorVotes is Governor {
-    IERC5805 public immutable token;
+    IERC5805 private immutable _token;
 
     constructor(IVotes tokenAddress) {
-        token = IERC5805(address(tokenAddress));
+        _token = IERC5805(address(tokenAddress));
+    }
+
+    /**
+     * @dev The token that voting power is sourced from.
+     */
+    function token() public view virtual returns (IERC5805) {
+        return _token;
     }
 
     /**
      * @dev Clock (as specified in EIP-6372) is set to match the token's clock. Fallback to block numbers if the token
      * does not implement EIP-6372.
      */
     function clock() public view virtual override returns (uint48) {
-        try token.clock() returns (uint48 timepoint) {
+        try token().clock() returns (uint48 timepoint) {
             return timepoint;
         } catch {
             return SafeCast.toUint48(block.number);
@@ -35,7 +42,7 @@ abstract contract GovernorVotes is Governor {
      */
     // solhint-disable-next-line func-name-mixedcase
     function CLOCK_MODE() public view virtual override returns (string memory) {
-        try token.CLOCK_MODE() returns (string memory clockmode) {
+        try token().CLOCK_MODE() returns (string memory clockmode) {
             return clockmode;
         } catch {
             return "mode=blocknumber&from=default";
@@ -50,6 +57,6 @@ abstract contract GovernorVotes is Governor {
         uint256 timepoint,
         bytes memory /*params*/
     ) internal view virtual override returns (uint256) {
-        return token.getPastVotes(account, timepoint);
+        return token().getPastVotes(account, timepoint);
     }
 }

contracts/governance/extensions/GovernorVotesQuorumFraction.sol

@@ -69,7 +69,7 @@ abstract contract GovernorVotesQuorumFraction is GovernorVotes {
      * @dev Returns the quorum for a timepoint, in terms of number of votes: `supply * numerator / denominator`.
      */
     function quorum(uint256 timepoint) public view virtual override returns (uint256) {
-        return (token.getPastTotalSupply(timepoint) * quorumNumerator(timepoint)) / quorumDenominator();
+        return (token().getPastTotalSupply(timepoint) * quorumNumerator(timepoint)) / quorumDenominator();
     }
 
     /**

package.json

@@ -85,7 +85,7 @@
     "semver": "^7.3.5",
     "solhint": "^3.3.6",
     "solhint-plugin-openzeppelin": "file:scripts/solhint-custom",
-    "solidity-ast": "^0.4.25",
+    "solidity-ast": "^0.4.50",
     "solidity-coverage": "^0.8.0",
     "solidity-docgen": "^0.6.0-beta.29",
     "undici": "^5.22.1",

scripts/upgradeable/transpile.sh

@@ -22,6 +22,8 @@ fi
 # -i: use included Initializable
 # -x: exclude proxy-related contracts with a few exceptions
 # -p: emit public initializer
+# -n: use namespaces
+# -N: exclude from namespaces transformation
 npx @openzeppelin/upgrade-safe-transpiler@latest -D \
   -b "$build_info" \
   -i contracts/proxy/utils/Initializable.sol \
@@ -32,7 +34,9 @@ npx @openzeppelin/upgrade-safe-transpiler@latest -D \
   -x '!contracts/proxy/ERC1967/ERC1967Utils.sol' \
   -x '!contracts/proxy/utils/UUPSUpgradeable.sol' \
   -x '!contracts/proxy/beacon/IBeacon.sol' \
-  -p 'contracts/**/presets/**/*'
+  -p 'contracts/**/presets/**/*' \
+  -n \
+  -N 'contracts/mocks/**/*'
 
 # delete compilation artifacts of vanilla code
 npm run clean