Split ERC-7821 executor into its own contract

contracts/account/Account.sol

@@ -6,16 +6,21 @@ import {ERC721Holder} from "@openzeppelin/contracts/token/ERC721/utils/ERC721Hol
 import {ERC1155Holder} from "@openzeppelin/contracts/token/ERC1155/utils/ERC1155Holder.sol";
 import {ERC7739Signer} from "../utils/cryptography/ERC7739Signer.sol";
 import {AccountCore} from "./AccountCore.sol";
-import {AccountERC7821} from "./extensions/AccountERC7821.sol";
+import {ERC7821} from "./extensions/ERC7821.sol";
 
 /**
  * @dev Extension of {AccountCore} with recommended feature that most account abstraction implementation will want:
  *
- * * {AccountERC7821} for performing external calls in batches.
+ * * {ERC7821} for performing external calls in batches.
  * * {ERC721Holder} and {ERC1155Holder} to accept ERC-712 and ERC-1155 token transfers transfers.
  * * {ERC7739Signer} for ERC-1271 signature support with ERC-7739 replay protection
  *
  * NOTE: To use this contract, the {ERC7739Signer-_rawSignatureValidation} function must be
  * implemented using a specific signature verification algorithm. See {SignerECDSA}, {SignerP256} or {SignerRSA}.
  */
-abstract contract Account is AccountCore, AccountERC7821, ERC721Holder, ERC1155Holder, ERC7739Signer {}
+abstract contract Account is AccountCore, ERC7821, ERC721Holder, ERC1155Holder, ERC7739Signer {
+    /// @inheritdoc ERC7821
+    function execute(bytes32 mode, bytes calldata executionData) public payable virtual override onlyEntryPointOrSelf {
+        super.execute(mode, executionData);
+    }
+}

contracts/account/README.adoc

@@ -2,7 +2,12 @@
 [.readme-notice]
 NOTE: This document is better viewed at https://docs.openzeppelin.com/community-contracts/api/account
 
-This directory includes contracts to build accounts for ERC-4337.
+This directory includes contracts to build accounts for ERC-4337. These include:
+
+ * {AccountCore}: An ERC-4337 smart account implementation that includes the core logic to process user operations.
+ * {Account}: An extension of `AccountCore` that implements the recommended features for ERC-4337 smart accounts.
+ * {AccountSignerERC7702}: An account implementation with low-level signature validation performed by an EOA.
+ * {ERC7821}: Minimal batch executor implementation whose contracts can delegate to. Useful to enable easy batch execution for smart contracts. 
 
 == Core
 
@@ -14,4 +19,4 @@ This directory includes contracts to build accounts for ERC-4337.
 
 {{AccountSignerERC7702}}
 
-{{AccountERC7821}}
+{{ERC7821}}

contracts/account/extensions/AccountERC7821.sol → contracts/account/extensions/ERC7821.sol

@@ -4,18 +4,25 @@ pragma solidity ^0.8.20;
 
 import {ERC7579Utils, Mode, CallType, ExecType, ModeSelector} from "@openzeppelin/contracts/account/utils/draft-ERC7579Utils.sol";
 import {IERC7821} from "../../interfaces/IERC7821.sol";
-import {AccountCore} from "../AccountCore.sol";
 
 /**
- * @dev Minimal batch executor following ERC7821. Only supports basic mode (no optional "opData").
+ * @dev Minimal batch executor following ERC-7821. Only supports basic mode (no optional "opData").
  */
-abstract contract AccountERC7821 is AccountCore, IERC7821 {
+abstract contract ERC7821 is IERC7821 {
     using ERC7579Utils for *;
 
     error UnsupportedExecutionMode();
 
-    /// @inheritdoc IERC7821
-    function execute(bytes32 mode, bytes calldata executionData) public payable virtual onlyEntryPointOrSelf {
+    /**
+     * @dev Executes the calls in `executionData` with no optional `opData` support.
+     *
+     * NOTE: When using with an {Account}, make sure to use wrap this function with
+     * an authorization check that ensures the caller is the account itself or
+     * the entrypoint.
+     *
+     * Reverts and bubbles up error if any call fails.
+     */
+    function execute(bytes32 mode, bytes calldata executionData) public payable virtual {
         if (!supportsExecutionMode(mode)) revert UnsupportedExecutionMode();
         executionData.execBatch(ERC7579Utils.EXECTYPE_DEFAULT);
     }
@@ -28,4 +35,12 @@ abstract contract AccountERC7821 is AccountCore, IERC7821 {
             execType == ERC7579Utils.EXECTYPE_DEFAULT &&
             modeSelector == ModeSelector.wrap(0x00000000);
     }
+
+    // slither-disable-next-line write-after-write
+    function _emptyCalldataBytes() private pure returns (bytes calldata result) {
+        assembly ("memory-safe") {
+            result.offset := 0
+            result.length := 0
+        }
+    }
 }