From a193bd99de15057be85ea13988122ceea8584737 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 18 Jan 2024 16:47:15 +0100
Subject: [PATCH 01/11] Move ERC721 and ERC1155 receiver checks to dedicate
 libraries

---
 contracts/token/ERC1155/ERC1155.sol           | 72 +----------------
 .../token/ERC1155/utils/ERC1155Utils.sol      | 77 +++++++++++++++++++
 contracts/token/ERC721/ERC721.sol             | 36 +--------
 contracts/token/ERC721/utils/ERC721Utils.sol  | 39 ++++++++++
 4 files changed, 123 insertions(+), 101 deletions(-)
 create mode 100644 contracts/token/ERC1155/utils/ERC1155Utils.sol
 create mode 100644 contracts/token/ERC721/utils/ERC721Utils.sol

diff --git a/contracts/token/ERC1155/ERC1155.sol b/contracts/token/ERC1155/ERC1155.sol
index 2ec3ef7be86..5e05e4791dd 100644
--- a/contracts/token/ERC1155/ERC1155.sol
+++ b/contracts/token/ERC1155/ERC1155.sol
@@ -4,8 +4,8 @@
 pragma solidity ^0.8.20;
 
 import {IERC1155} from "./IERC1155.sol";
-import {IERC1155Receiver} from "./IERC1155Receiver.sol";
 import {IERC1155MetadataURI} from "./extensions/IERC1155MetadataURI.sol";
+import {ERC1155Utils} from "./utils/ERC1155Utils.sol";
 import {Context} from "../../utils/Context.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
 import {Arrays} from "../../utils/Arrays.sol";
@@ -203,9 +203,9 @@ abstract contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI, IER
             if (ids.length == 1) {
                 uint256 id = ids.unsafeMemoryAccess(0);
                 uint256 value = values.unsafeMemoryAccess(0);
-                _doSafeTransferAcceptanceCheck(operator, from, to, id, value, data);
+                ERC1155Utils.checkOnERC1155Received(operator, from, to, id, value, data);
             } else {
-                _doSafeBatchTransferAcceptanceCheck(operator, from, to, ids, values, data);
+                ERC1155Utils.checkOnERC1155BatchReceived(operator, from, to, ids, values, data);
             }
         }
     }
@@ -374,72 +374,6 @@ abstract contract ERC1155 is Context, ERC165, IERC1155, IERC1155MetadataURI, IER
         emit ApprovalForAll(owner, operator, approved);
     }
 
-    /**
-     * @dev Performs an acceptance check by calling {IERC1155-onERC1155Received} on the `to` address
-     * if it contains code at the moment of execution.
-     */
-    function _doSafeTransferAcceptanceCheck(
-        address operator,
-        address from,
-        address to,
-        uint256 id,
-        uint256 value,
-        bytes memory data
-    ) private {
-        if (to.code.length > 0) {
-            try IERC1155Receiver(to).onERC1155Received(operator, from, id, value, data) returns (bytes4 response) {
-                if (response != IERC1155Receiver.onERC1155Received.selector) {
-                    // Tokens rejected
-                    revert ERC1155InvalidReceiver(to);
-                }
-            } catch (bytes memory reason) {
-                if (reason.length == 0) {
-                    // non-IERC1155Receiver implementer
-                    revert ERC1155InvalidReceiver(to);
-                } else {
-                    /// @solidity memory-safe-assembly
-                    assembly {
-                        revert(add(32, reason), mload(reason))
-                    }
-                }
-            }
-        }
-    }
-
-    /**
-     * @dev Performs a batch acceptance check by calling {IERC1155-onERC1155BatchReceived} on the `to` address
-     * if it contains code at the moment of execution.
-     */
-    function _doSafeBatchTransferAcceptanceCheck(
-        address operator,
-        address from,
-        address to,
-        uint256[] memory ids,
-        uint256[] memory values,
-        bytes memory data
-    ) private {
-        if (to.code.length > 0) {
-            try IERC1155Receiver(to).onERC1155BatchReceived(operator, from, ids, values, data) returns (
-                bytes4 response
-            ) {
-                if (response != IERC1155Receiver.onERC1155BatchReceived.selector) {
-                    // Tokens rejected
-                    revert ERC1155InvalidReceiver(to);
-                }
-            } catch (bytes memory reason) {
-                if (reason.length == 0) {
-                    // non-IERC1155Receiver implementer
-                    revert ERC1155InvalidReceiver(to);
-                } else {
-                    /// @solidity memory-safe-assembly
-                    assembly {
-                        revert(add(32, reason), mload(reason))
-                    }
-                }
-            }
-        }
-    }
-
     /**
      * @dev Creates an array in memory with only one value for each of the elements provided.
      */
diff --git a/contracts/token/ERC1155/utils/ERC1155Utils.sol b/contracts/token/ERC1155/utils/ERC1155Utils.sol
new file mode 100644
index 00000000000..8af75fa1415
--- /dev/null
+++ b/contracts/token/ERC1155/utils/ERC1155Utils.sol
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {IERC1155Receiver} from "../IERC1155Receiver.sol";
+import {IERC1155Errors} from "../../../interfaces/draft-IERC6093.sol";
+
+/**
+ * @title ERC1155Utils
+ */
+library ERC1155Utils {
+    /**
+     * @dev Performs an acceptance check by calling {IERC1155-onERC1155Received} on the `to` address
+     * if it contains code at the moment of execution.
+     */
+    function checkOnERC1155Received(
+        address operator,
+        address from,
+        address to,
+        uint256 id,
+        uint256 value,
+        bytes memory data
+    ) internal {
+        if (to.code.length > 0) {
+            try IERC1155Receiver(to).onERC1155Received(operator, from, id, value, data) returns (bytes4 response) {
+                if (response != IERC1155Receiver.onERC1155Received.selector) {
+                    // Tokens rejected
+                    revert IERC1155Errors.ERC1155InvalidReceiver(to);
+                }
+            } catch (bytes memory reason) {
+                if (reason.length == 0) {
+                    // non-IERC1155Receiver implementer
+                    revert IERC1155Errors.ERC1155InvalidReceiver(to);
+                } else {
+                    /// @solidity memory-safe-assembly
+                    assembly {
+                        revert(add(32, reason), mload(reason))
+                    }
+                }
+            }
+        }
+    }
+
+    /**
+     * @dev Performs a batch acceptance check by calling {IERC1155-onERC1155BatchReceived} on the `to` address
+     * if it contains code at the moment of execution.
+     */
+    function checkOnERC1155BatchReceived(
+        address operator,
+        address from,
+        address to,
+        uint256[] memory ids,
+        uint256[] memory values,
+        bytes memory data
+    ) internal {
+        if (to.code.length > 0) {
+            try IERC1155Receiver(to).onERC1155BatchReceived(operator, from, ids, values, data) returns (
+                bytes4 response
+            ) {
+                if (response != IERC1155Receiver.onERC1155BatchReceived.selector) {
+                    // Tokens rejected
+                    revert IERC1155Errors.ERC1155InvalidReceiver(to);
+                }
+            } catch (bytes memory reason) {
+                if (reason.length == 0) {
+                    // non-IERC1155Receiver implementer
+                    revert IERC1155Errors.ERC1155InvalidReceiver(to);
+                } else {
+                    /// @solidity memory-safe-assembly
+                    assembly {
+                        revert(add(32, reason), mload(reason))
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/contracts/token/ERC721/ERC721.sol b/contracts/token/ERC721/ERC721.sol
index 1b38f06814e..62ff1def969 100644
--- a/contracts/token/ERC721/ERC721.sol
+++ b/contracts/token/ERC721/ERC721.sol
@@ -4,8 +4,8 @@
 pragma solidity ^0.8.20;
 
 import {IERC721} from "./IERC721.sol";
-import {IERC721Receiver} from "./IERC721Receiver.sol";
 import {IERC721Metadata} from "./extensions/IERC721Metadata.sol";
+import {ERC721Utils} from "./utils/ERC721Utils.sol";
 import {Context} from "../../utils/Context.sol";
 import {Strings} from "../../utils/Strings.sol";
 import {IERC165, ERC165} from "../../utils/introspection/ERC165.sol";
@@ -158,7 +158,7 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
      */
     function safeTransferFrom(address from, address to, uint256 tokenId, bytes memory data) public virtual {
         transferFrom(from, to, tokenId);
-        _checkOnERC721Received(from, to, tokenId, data);
+        ERC721Utils.checkOnERC721Received(_msgSender(), from, to, tokenId, data);
     }
 
     /**
@@ -311,7 +311,7 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
      */
     function _safeMint(address to, uint256 tokenId, bytes memory data) internal virtual {
         _mint(to, tokenId);
-        _checkOnERC721Received(address(0), to, tokenId, data);
+        ERC721Utils.checkOnERC721Received(_msgSender(), address(0), to, tokenId, data);
     }
 
     /**
@@ -384,7 +384,7 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
      */
     function _safeTransfer(address from, address to, uint256 tokenId, bytes memory data) internal virtual {
         _transfer(from, to, tokenId);
-        _checkOnERC721Received(from, to, tokenId, data);
+        ERC721Utils.checkOnERC721Received(_msgSender(), from, to, tokenId, data);
     }
 
     /**
@@ -452,32 +452,4 @@ abstract contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Er
         }
         return owner;
     }
-
-    /**
-     * @dev Private function to invoke {IERC721Receiver-onERC721Received} on a target address. This will revert if the
-     * recipient doesn't accept the token transfer. The call is not executed if the target address is not a contract.
-     *
-     * @param from address representing the previous owner of the given token ID
-     * @param to target address that will receive the tokens
-     * @param tokenId uint256 ID of the token to be transferred
-     * @param data bytes optional data to send along with the call
-     */
-    function _checkOnERC721Received(address from, address to, uint256 tokenId, bytes memory data) private {
-        if (to.code.length > 0) {
-            try IERC721Receiver(to).onERC721Received(_msgSender(), from, tokenId, data) returns (bytes4 retval) {
-                if (retval != IERC721Receiver.onERC721Received.selector) {
-                    revert ERC721InvalidReceiver(to);
-                }
-            } catch (bytes memory reason) {
-                if (reason.length == 0) {
-                    revert ERC721InvalidReceiver(to);
-                } else {
-                    /// @solidity memory-safe-assembly
-                    assembly {
-                        revert(add(32, reason), mload(reason))
-                    }
-                }
-            }
-        }
-    }
 }
diff --git a/contracts/token/ERC721/utils/ERC721Utils.sol b/contracts/token/ERC721/utils/ERC721Utils.sol
new file mode 100644
index 00000000000..774b20d00f9
--- /dev/null
+++ b/contracts/token/ERC721/utils/ERC721Utils.sol
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {IERC721Receiver} from "../IERC721Receiver.sol";
+import {IERC721Errors} from "../../../interfaces/draft-IERC6093.sol";
+
+/**
+ * @title ERC721Utils
+ */
+library ERC721Utils {
+    /**
+     * @dev Private function to invoke {IERC721Receiver-onERC721Received} on a target address. This will revert if the
+     * recipient doesn't accept the token transfer. The call is not executed if the target address is not a contract.
+     *
+     * @param from address representing the previous owner of the given token ID
+     * @param to target address that will receive the tokens
+     * @param tokenId uint256 ID of the token to be transferred
+     * @param data bytes optional data to send along with the call
+     */
+    function checkOnERC721Received(address operator, address from, address to, uint256 tokenId, bytes memory data) internal {
+        if (to.code.length > 0) {
+            try IERC721Receiver(to).onERC721Received(operator, from, tokenId, data) returns (bytes4 retval) {
+                if (retval != IERC721Receiver.onERC721Received.selector) {
+                    revert IERC721Errors.ERC721InvalidReceiver(to);
+                }
+            } catch (bytes memory reason) {
+                if (reason.length == 0) {
+                    revert IERC721Errors.ERC721InvalidReceiver(to);
+                } else {
+                    /// @solidity memory-safe-assembly
+                    assembly {
+                        revert(add(32, reason), mload(reason))
+                    }
+                }
+            }
+        }
+    }
+}

From 4eecf9f96fa71b0e9e8a86c0b4626583c1443ea4 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 18 Jan 2024 16:59:31 +0100
Subject: [PATCH 02/11] doc

---
 contracts/token/ERC1155/utils/ERC1155Utils.sol | 10 ++++++----
 contracts/token/ERC721/utils/ERC721Utils.sol   | 10 +++-------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/contracts/token/ERC1155/utils/ERC1155Utils.sol b/contracts/token/ERC1155/utils/ERC1155Utils.sol
index 8af75fa1415..15d38e8c535 100644
--- a/contracts/token/ERC1155/utils/ERC1155Utils.sol
+++ b/contracts/token/ERC1155/utils/ERC1155Utils.sol
@@ -10,8 +10,9 @@ import {IERC1155Errors} from "../../../interfaces/draft-IERC6093.sol";
  */
 library ERC1155Utils {
     /**
-     * @dev Performs an acceptance check by calling {IERC1155-onERC1155Received} on the `to` address
-     * if it contains code at the moment of execution.
+     * @dev Performs an acceptance check by calling {IERC1155-onERC1155Received} on the `to` address if it
+     * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
+     * The call is not executed if the target address is not a contract.
      */
     function checkOnERC1155Received(
         address operator,
@@ -42,8 +43,9 @@ library ERC1155Utils {
     }
 
     /**
-     * @dev Performs a batch acceptance check by calling {IERC1155-onERC1155BatchReceived} on the `to` address
-     * if it contains code at the moment of execution.
+     * @dev Performs a batch acceptance check by calling {IERC1155-onERC1155BatchReceived} on the `to` address if it
+     * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
+     * The call is not executed if the target address is not a contract.
      */
     function checkOnERC1155BatchReceived(
         address operator,
diff --git a/contracts/token/ERC721/utils/ERC721Utils.sol b/contracts/token/ERC721/utils/ERC721Utils.sol
index 774b20d00f9..3bfb1b290d2 100644
--- a/contracts/token/ERC721/utils/ERC721Utils.sol
+++ b/contracts/token/ERC721/utils/ERC721Utils.sol
@@ -10,13 +10,9 @@ import {IERC721Errors} from "../../../interfaces/draft-IERC6093.sol";
  */
 library ERC721Utils {
     /**
-     * @dev Private function to invoke {IERC721Receiver-onERC721Received} on a target address. This will revert if the
-     * recipient doesn't accept the token transfer. The call is not executed if the target address is not a contract.
-     *
-     * @param from address representing the previous owner of the given token ID
-     * @param to target address that will receive the tokens
-     * @param tokenId uint256 ID of the token to be transferred
-     * @param data bytes optional data to send along with the call
+     * @dev Performs an acceptance check by calling {IERC721Receiver-onERC721Received} on the `to` address if it
+     * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
+     * The call is not executed if the target address is not a contract.
      */
     function checkOnERC721Received(address operator, address from, address to, uint256 tokenId, bytes memory data) internal {
         if (to.code.length > 0) {

From f372e76739ffb1ae5778e1dccdb1b19ceccc7bd1 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 18 Jan 2024 17:00:33 +0100
Subject: [PATCH 03/11] doc

---
 contracts/token/ERC1155/utils/ERC1155Utils.sol | 3 ++-
 contracts/token/ERC721/utils/ERC721Utils.sol   | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/contracts/token/ERC1155/utils/ERC1155Utils.sol b/contracts/token/ERC1155/utils/ERC1155Utils.sol
index 15d38e8c535..6bdac5001b7 100644
--- a/contracts/token/ERC1155/utils/ERC1155Utils.sol
+++ b/contracts/token/ERC1155/utils/ERC1155Utils.sol
@@ -6,7 +6,8 @@ import {IERC1155Receiver} from "../IERC1155Receiver.sol";
 import {IERC1155Errors} from "../../../interfaces/draft-IERC6093.sol";
 
 /**
- * @title ERC1155Utils
+ * @dev Implementation of the ERC-1155 acceptance checks used in safe transfers.
+ * See https://eips.ethereum.org/EIPS/eip-1155
  */
 library ERC1155Utils {
     /**
diff --git a/contracts/token/ERC721/utils/ERC721Utils.sol b/contracts/token/ERC721/utils/ERC721Utils.sol
index 3bfb1b290d2..9d0b776be7b 100644
--- a/contracts/token/ERC721/utils/ERC721Utils.sol
+++ b/contracts/token/ERC721/utils/ERC721Utils.sol
@@ -6,7 +6,8 @@ import {IERC721Receiver} from "../IERC721Receiver.sol";
 import {IERC721Errors} from "../../../interfaces/draft-IERC6093.sol";
 
 /**
- * @title ERC721Utils
+ * @dev Implementation of the ERC-721 acceptance checks used in safe transfers.
+ * See https://eips.ethereum.org/EIPS/eip-721
  */
 library ERC721Utils {
     /**

From 0e853c0d0cc9e8420cfae99eef4a4466bfdad37c Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 18 Jan 2024 17:00:47 +0100
Subject: [PATCH 04/11] doc

---
 .changeset/poor-chefs-cheat.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/poor-chefs-cheat.md

diff --git a/.changeset/poor-chefs-cheat.md b/.changeset/poor-chefs-cheat.md
new file mode 100644
index 00000000000..ace9600ffba
--- /dev/null
+++ b/.changeset/poor-chefs-cheat.md
@@ -0,0 +1,5 @@
+---
+'openzeppelin-solidity': minor
+---
+
+`ERC721Utils` and `ERC1155Utils`: reusable libraries for performing the acceptance checks (safeTransfer)

From 9c5e8275835ed721fa9fc81aaec8071e8c6416b2 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 18 Jan 2024 17:04:12 +0100
Subject: [PATCH 05/11] up

---
 contracts/token/ERC1155/utils/ERC1155Utils.sol | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/contracts/token/ERC1155/utils/ERC1155Utils.sol b/contracts/token/ERC1155/utils/ERC1155Utils.sol
index 6bdac5001b7..947dd349194 100644
--- a/contracts/token/ERC1155/utils/ERC1155Utils.sol
+++ b/contracts/token/ERC1155/utils/ERC1155Utils.sol
@@ -26,12 +26,10 @@ library ERC1155Utils {
         if (to.code.length > 0) {
             try IERC1155Receiver(to).onERC1155Received(operator, from, id, value, data) returns (bytes4 response) {
                 if (response != IERC1155Receiver.onERC1155Received.selector) {
-                    // Tokens rejected
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 }
             } catch (bytes memory reason) {
                 if (reason.length == 0) {
-                    // non-IERC1155Receiver implementer
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 } else {
                     /// @solidity memory-safe-assembly
@@ -61,12 +59,10 @@ library ERC1155Utils {
                 bytes4 response
             ) {
                 if (response != IERC1155Receiver.onERC1155BatchReceived.selector) {
-                    // Tokens rejected
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 }
             } catch (bytes memory reason) {
                 if (reason.length == 0) {
-                    // non-IERC1155Receiver implementer
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 } else {
                     /// @solidity memory-safe-assembly

From dc2f8f41397adf55c3bb039524bb05d0e7d10947 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Thu, 18 Jan 2024 21:51:55 +0100
Subject: [PATCH 06/11] fix lint

---
 contracts/token/ERC721/utils/ERC721Utils.sol | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/contracts/token/ERC721/utils/ERC721Utils.sol b/contracts/token/ERC721/utils/ERC721Utils.sol
index 9d0b776be7b..6be0aab640d 100644
--- a/contracts/token/ERC721/utils/ERC721Utils.sol
+++ b/contracts/token/ERC721/utils/ERC721Utils.sol
@@ -15,7 +15,13 @@ library ERC721Utils {
      * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
      * The call is not executed if the target address is not a contract.
      */
-    function checkOnERC721Received(address operator, address from, address to, uint256 tokenId, bytes memory data) internal {
+    function checkOnERC721Received(
+        address operator,
+        address from,
+        address to,
+        uint256 tokenId,
+        bytes memory data
+    ) internal {
         if (to.code.length > 0) {
             try IERC721Receiver(to).onERC721Received(operator, from, tokenId, data) returns (bytes4 retval) {
                 if (retval != IERC721Receiver.onERC721Received.selector) {

From 29f3b16f438a55233ae45665601acbfe1a66ff93 Mon Sep 17 00:00:00 2001
From: Hadrien Croubois <hadrien.croubois@gmail.com>
Date: Tue, 30 Jan 2024 14:33:24 +0100
Subject: [PATCH 07/11] Apply suggestions from code review
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Co-authored-by: Ernesto García <ernestognw@gmail.com>
---
 .changeset/poor-chefs-cheat.md                 | 2 +-
 contracts/token/ERC1155/utils/ERC1155Utils.sol | 4 ++++
 contracts/token/ERC721/utils/ERC721Utils.sol   | 2 ++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/.changeset/poor-chefs-cheat.md b/.changeset/poor-chefs-cheat.md
index ace9600ffba..8f48d61642e 100644
--- a/.changeset/poor-chefs-cheat.md
+++ b/.changeset/poor-chefs-cheat.md
@@ -2,4 +2,4 @@
 'openzeppelin-solidity': minor
 ---
 
-`ERC721Utils` and `ERC1155Utils`: reusable libraries for performing the acceptance checks (safeTransfer)
+`ERC721Utils` and `ERC1155Utils`: reusable libraries with functions to perform acceptance checks on `IERC721Receiver` and `IERC1155Receiver` implementers.
diff --git a/contracts/token/ERC1155/utils/ERC1155Utils.sol b/contracts/token/ERC1155/utils/ERC1155Utils.sol
index 947dd349194..6bdac5001b7 100644
--- a/contracts/token/ERC1155/utils/ERC1155Utils.sol
+++ b/contracts/token/ERC1155/utils/ERC1155Utils.sol
@@ -26,10 +26,12 @@ library ERC1155Utils {
         if (to.code.length > 0) {
             try IERC1155Receiver(to).onERC1155Received(operator, from, id, value, data) returns (bytes4 response) {
                 if (response != IERC1155Receiver.onERC1155Received.selector) {
+                    // Tokens rejected
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 }
             } catch (bytes memory reason) {
                 if (reason.length == 0) {
+                    // non-IERC1155Receiver implementer
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 } else {
                     /// @solidity memory-safe-assembly
@@ -59,10 +61,12 @@ library ERC1155Utils {
                 bytes4 response
             ) {
                 if (response != IERC1155Receiver.onERC1155BatchReceived.selector) {
+                    // Tokens rejected
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 }
             } catch (bytes memory reason) {
                 if (reason.length == 0) {
+                    // non-IERC1155Receiver implementer
                     revert IERC1155Errors.ERC1155InvalidReceiver(to);
                 } else {
                     /// @solidity memory-safe-assembly
diff --git a/contracts/token/ERC721/utils/ERC721Utils.sol b/contracts/token/ERC721/utils/ERC721Utils.sol
index 6be0aab640d..bc50b3c5b65 100644
--- a/contracts/token/ERC721/utils/ERC721Utils.sol
+++ b/contracts/token/ERC721/utils/ERC721Utils.sol
@@ -25,10 +25,12 @@ library ERC721Utils {
         if (to.code.length > 0) {
             try IERC721Receiver(to).onERC721Received(operator, from, tokenId, data) returns (bytes4 retval) {
                 if (retval != IERC721Receiver.onERC721Received.selector) {
+                    // Token rejected
                     revert IERC721Errors.ERC721InvalidReceiver(to);
                 }
             } catch (bytes memory reason) {
                 if (reason.length == 0) {
+                    // non-IERC721Receiver implementer
                     revert IERC721Errors.ERC721InvalidReceiver(to);
                 } else {
                     /// @solidity memory-safe-assembly

From d292276c8a570af9238ae6b25649d4c0ada49236 Mon Sep 17 00:00:00 2001
From: ernestognw <ernestognw@gmail.com>
Date: Tue, 30 Jan 2024 11:08:07 -0600
Subject: [PATCH 08/11] Nits

---
 .changeset/poor-chefs-cheat.md                |  2 +-
 .../token/ERC1155/utils/ERC1155Utils.sol      | 23 ++++++++++++-------
 contracts/token/ERC721/utils/ERC721Utils.sol  | 14 +++++++----
 3 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/.changeset/poor-chefs-cheat.md b/.changeset/poor-chefs-cheat.md
index 8f48d61642e..39db3d5139c 100644
--- a/.changeset/poor-chefs-cheat.md
+++ b/.changeset/poor-chefs-cheat.md
@@ -2,4 +2,4 @@
 'openzeppelin-solidity': minor
 ---
 
-`ERC721Utils` and `ERC1155Utils`: reusable libraries with functions to perform acceptance checks on `IERC721Receiver` and `IERC1155Receiver` implementers.
+`ERC721Utils` and `ERC1155Utils`: Add reusable libraries with functions to perform acceptance checks on `IERC721Receiver` and `IERC1155Receiver` implementers.
diff --git a/contracts/token/ERC1155/utils/ERC1155Utils.sol b/contracts/token/ERC1155/utils/ERC1155Utils.sol
index 6bdac5001b7..0ff2bf146a4 100644
--- a/contracts/token/ERC1155/utils/ERC1155Utils.sol
+++ b/contracts/token/ERC1155/utils/ERC1155Utils.sol
@@ -6,14 +6,18 @@ import {IERC1155Receiver} from "../IERC1155Receiver.sol";
 import {IERC1155Errors} from "../../../interfaces/draft-IERC6093.sol";
 
 /**
- * @dev Implementation of the ERC-1155 acceptance checks used in safe transfers.
- * See https://eips.ethereum.org/EIPS/eip-1155
+ * @dev Library that provide common ERC-1155 utility functions.
+ *
+ * See https://eips.ethereum.org/EIPS/eip-1155[ERC-1155].
  */
 library ERC1155Utils {
     /**
-     * @dev Performs an acceptance check by calling {IERC1155-onERC1155Received} on the `to` address if it
-     * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
-     * The call is not executed if the target address is not a contract.
+     * @dev Performs an acceptance check for the provided `operator` by calling {IERC1155-onERC1155Received}
+     * on the `to` address. The `operator` is generally the address that initiated the token transfer (i.e. `msg.sender`).
+     *
+     * The acceptance call is not executed and treated as a no-op if the target address is doesn't contain code (i.e. an EOA).
+     * Otherwise, the recipient must implement {IERC1155Receiver-onERC1155Received} and return the acceptance magic value to accept
+     * the transfer.
      */
     function checkOnERC1155Received(
         address operator,
@@ -44,9 +48,12 @@ library ERC1155Utils {
     }
 
     /**
-     * @dev Performs a batch acceptance check by calling {IERC1155-onERC1155BatchReceived} on the `to` address if it
-     * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
-     * The call is not executed if the target address is not a contract.
+     * @dev Performs a batch acceptance check for the provided `operator` by calling {IERC1155-onERC1155BatchReceived}
+     * on the `to` address. The `operator` is generally the address that initiated the token transfer (i.e. `msg.sender`).
+     *
+     * The acceptance call is not executed and treated as a no-op if the target address is doesn't contain code (i.e. an EOA).
+     * Otherwise, the recipient must implement {IERC1155Receiver-onERC1155Received} and return the acceptance magic value to accept
+     * the transfer.
      */
     function checkOnERC1155BatchReceived(
         address operator,
diff --git a/contracts/token/ERC721/utils/ERC721Utils.sol b/contracts/token/ERC721/utils/ERC721Utils.sol
index bc50b3c5b65..b923e403736 100644
--- a/contracts/token/ERC721/utils/ERC721Utils.sol
+++ b/contracts/token/ERC721/utils/ERC721Utils.sol
@@ -6,14 +6,18 @@ import {IERC721Receiver} from "../IERC721Receiver.sol";
 import {IERC721Errors} from "../../../interfaces/draft-IERC6093.sol";
 
 /**
- * @dev Implementation of the ERC-721 acceptance checks used in safe transfers.
- * See https://eips.ethereum.org/EIPS/eip-721
+ * @dev Library that provide common ERC-721 utility functions.
+ *
+ * See https://eips.ethereum.org/EIPS/eip-721[ERC-721].
  */
 library ERC721Utils {
     /**
-     * @dev Performs an acceptance check by calling {IERC721Receiver-onERC721Received} on the `to` address if it
-     * contains code at the moment of execution. This will revert if the recipient doesn't accept the token transfer.
-     * The call is not executed if the target address is not a contract.
+     * @dev Performs an acceptance check for the provided `operator` by calling {IERC721-onERC721Received}
+     * on the `to` address. The `operator` is generally the address that initiated the token transfer (i.e. `msg.sender`).
+     *
+     * The acceptance call is not executed and treated as a no-op if the target address is doesn't contain code (i.e. an EOA).
+     * Otherwise, the recipient must implement {IERC721Receiver-onERC721Received} and return the acceptance magic value to accept
+     * the transfer.
      */
     function checkOnERC721Received(
         address operator,

From aaf7cdae40e0b8a1f4629848fae64fe4b09e73e3 Mon Sep 17 00:00:00 2001
From: ernestognw <ernestognw@gmail.com>
Date: Tue, 30 Jan 2024 12:11:41 -0600
Subject: [PATCH 09/11] Add tests

---
 test/token/ERC1155/utils/ERC1155Utils.test.js | 299 ++++++++++++++++++
 test/token/ERC721/utils/ERC721Utils.test.js   |  93 ++++++
 2 files changed, 392 insertions(+)
 create mode 100644 test/token/ERC1155/utils/ERC1155Utils.test.js
 create mode 100644 test/token/ERC721/utils/ERC721Utils.test.js

diff --git a/test/token/ERC1155/utils/ERC1155Utils.test.js b/test/token/ERC1155/utils/ERC1155Utils.test.js
new file mode 100644
index 00000000000..5687568d341
--- /dev/null
+++ b/test/token/ERC1155/utils/ERC1155Utils.test.js
@@ -0,0 +1,299 @@
+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+const { RevertType } = require('../../../helpers/enums');
+const { PANIC_CODES } = require('@nomicfoundation/hardhat-chai-matchers/panic');
+
+const firstTokenId = 1n;
+const secondTokenId = 2n;
+const firstTokenValue = 1000n;
+const secondTokenValue = 1000n;
+
+const RECEIVER_SINGLE_MAGIC_VALUE = '0xf23a6e61';
+const RECEIVER_BATCH_MAGIC_VALUE = '0xbc197c81';
+
+const deployReceiver = (
+  revertType,
+  returnValueSingle = RECEIVER_SINGLE_MAGIC_VALUE,
+  returnValueBatched = RECEIVER_BATCH_MAGIC_VALUE,
+) => ethers.deployContract('$ERC1155ReceiverMock', [returnValueSingle, returnValueBatched, revertType]);
+
+const fixture = async () => {
+  const [eoa, operator, owner] = await ethers.getSigners();
+  const utils = await ethers.deployContract('$ERC1155Utils');
+
+  const receivers = {
+    correct: await deployReceiver(RevertType.None),
+    invalid: await deployReceiver(RevertType.None, '0xdeadbeef', '0xdeadbeef'),
+    message: await deployReceiver(RevertType.RevertWithMessage),
+    empty: await deployReceiver(RevertType.RevertWithoutMessage),
+    customError: await deployReceiver(RevertType.RevertWithCustomError),
+    panic: await deployReceiver(RevertType.Panic),
+    nonReceiver: await ethers.deployContract('CallReceiverMock'),
+    eoa,
+  };
+
+  return { operator, owner, utils, receivers };
+};
+
+describe('ERC1155Utils', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  describe('onERC1155Received', function () {
+    it('succeeds when called by an EOA', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.eoa,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      ).to.not.be.reverted;
+    });
+
+    it('succeeds when data is passed', async function () {
+      const data = '0x12345678';
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.correct,
+          firstTokenId,
+          firstTokenValue,
+          data,
+        ),
+      ).to.not.be.reverted;
+    });
+
+    it('succeeds when data is empty', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.correct,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      ).to.not.be.reverted;
+    });
+
+    it('reverts when receiver returns invalid value', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.invalid,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC1155InvalidReceiver')
+        .withArgs(this.receivers.invalid);
+    });
+
+    it('reverts when receiver reverts with message', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.message,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      ).to.be.revertedWith('ERC1155ReceiverMock: reverting on receive');
+    });
+
+    it('reverts when receiver reverts without message', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.empty,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC1155InvalidReceiver')
+        .withArgs(this.receivers.empty);
+    });
+
+    it('reverts when receiver reverts with custom error', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.customError,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.receivers.customError, 'CustomError')
+        .withArgs(RECEIVER_SINGLE_MAGIC_VALUE);
+    });
+
+    it('reverts when receiver panics', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.panic,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      ).to.be.revertedWithPanic(PANIC_CODES.DIVISION_BY_ZERO);
+    });
+
+    it('reverts when receiver does not implement onERC1155Received', async function () {
+      await expect(
+        this.utils.$checkOnERC1155Received(
+          this.operator,
+          this.owner,
+          this.receivers.nonReceiver,
+          firstTokenId,
+          firstTokenValue,
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC1155InvalidReceiver')
+        .withArgs(this.receivers.nonReceiver);
+    });
+  });
+
+  describe('onERC1155BatchReceived', function () {
+    it('succeeds when called by an EOA', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.eoa,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      ).to.not.be.reverted;
+    });
+
+    it('succeeds when data is passed', async function () {
+      const data = '0x12345678';
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.correct,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          data,
+        ),
+      ).to.not.be.reverted;
+    });
+
+    it('succeeds when data is empty', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.correct,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      ).to.not.be.reverted;
+    });
+
+    it('reverts when receiver returns invalid value', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.invalid,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC1155InvalidReceiver')
+        .withArgs(this.receivers.invalid);
+    });
+
+    it('reverts when receiver reverts with message', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.message,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      ).to.be.revertedWith('ERC1155ReceiverMock: reverting on batch receive');
+    });
+
+    it('reverts when receiver reverts without message', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.empty,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC1155InvalidReceiver')
+        .withArgs(this.receivers.empty);
+    });
+
+    it('reverts when receiver reverts with custom error', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.customError,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.receivers.customError, 'CustomError')
+        .withArgs(RECEIVER_SINGLE_MAGIC_VALUE);
+    });
+
+    it('reverts when receiver panics', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.panic,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      ).to.be.revertedWithPanic(PANIC_CODES.DIVISION_BY_ZERO);
+    });
+
+    it('reverts when receiver does not implement onERC1155BatchReceived', async function () {
+      await expect(
+        this.utils.$checkOnERC1155BatchReceived(
+          this.operator,
+          this.owner,
+          this.receivers.nonReceiver,
+          [firstTokenId, secondTokenId],
+          [firstTokenValue, secondTokenValue],
+          '0x',
+        ),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC1155InvalidReceiver')
+        .withArgs(this.receivers.nonReceiver);
+    });
+  });
+});
diff --git a/test/token/ERC721/utils/ERC721Utils.test.js b/test/token/ERC721/utils/ERC721Utils.test.js
new file mode 100644
index 00000000000..2ebfb95e3ee
--- /dev/null
+++ b/test/token/ERC721/utils/ERC721Utils.test.js
@@ -0,0 +1,93 @@
+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+const { loadFixture } = require('@nomicfoundation/hardhat-network-helpers');
+const { RevertType } = require('../../../helpers/enums');
+const { PANIC_CODES } = require('@nomicfoundation/hardhat-chai-matchers/panic');
+
+const tokenId = 1n;
+
+const RECEIVER_MAGIC_VALUE = '0x150b7a02';
+
+const deployReceiver = (revertType, returnValue = RECEIVER_MAGIC_VALUE) =>
+  ethers.deployContract('$ERC721ReceiverMock', [returnValue, revertType]);
+
+const fixture = async () => {
+  const [operator, owner] = await ethers.getSigners();
+  const utils = await ethers.deployContract('$ERC721Utils');
+
+  const receivers = {
+    correct: await deployReceiver(RevertType.None),
+    invalid: await deployReceiver(RevertType.None, '0xdeadbeef'),
+    message: await deployReceiver(RevertType.RevertWithMessage),
+    empty: await deployReceiver(RevertType.RevertWithoutMessage),
+    customError: await deployReceiver(RevertType.RevertWithCustomError),
+    panic: await deployReceiver(RevertType.Panic),
+    nonReceiver: await ethers.deployContract('CallReceiverMock'),
+  };
+
+  return { operator, owner, utils, receivers };
+};
+
+describe('ERC721Utils', function () {
+  beforeEach(async function () {
+    Object.assign(this, await loadFixture(fixture));
+  });
+
+  describe('onERC721Received', function () {
+    it('succeeds when called by an EOA', async function () {
+      await expect(this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.eoa, tokenId, '0x')).to
+        .not.be.reverted;
+    });
+
+    it('succeeds when data is passed', async function () {
+      const data = '0x12345678';
+      await expect(this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.correct, tokenId, data))
+        .to.not.be.reverted;
+    });
+
+    it('succeeds when data is empty', async function () {
+      await expect(this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.correct, tokenId, '0x'))
+        .to.not.be.reverted;
+    });
+
+    it('reverts when receiver returns invalid value', async function () {
+      await expect(this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.invalid, tokenId, '0x'))
+        .to.be.revertedWithCustomError(this.utils, 'ERC721InvalidReceiver')
+        .withArgs(this.receivers.invalid);
+    });
+
+    it('reverts when receiver reverts with message', async function () {
+      await expect(
+        this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.message, tokenId, '0x'),
+      ).to.be.revertedWith('ERC721ReceiverMock: reverting');
+    });
+
+    it('reverts when receiver reverts without message', async function () {
+      await expect(this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.empty, tokenId, '0x'))
+        .to.be.revertedWithCustomError(this.utils, 'ERC721InvalidReceiver')
+        .withArgs(this.receivers.empty);
+    });
+
+    it('reverts when receiver reverts with custom error', async function () {
+      await expect(
+        this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.customError, tokenId, '0x'),
+      )
+        .to.be.revertedWithCustomError(this.receivers.customError, 'CustomError')
+        .withArgs(RECEIVER_MAGIC_VALUE);
+    });
+
+    it('reverts when receiver panics', async function () {
+      await expect(
+        this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.panic, tokenId, '0x'),
+      ).to.be.revertedWithPanic(PANIC_CODES.DIVISION_BY_ZERO);
+    });
+
+    it('reverts when receiver does not implement onERC721Received', async function () {
+      await expect(
+        this.utils.$checkOnERC721Received(this.operator, this.owner, this.receivers.nonReceiver, tokenId, '0x'),
+      )
+        .to.be.revertedWithCustomError(this.utils, 'ERC721InvalidReceiver')
+        .withArgs(this.receivers.nonReceiver);
+    });
+  });
+});

From d551d5c2c12c9c701cb10f25b169606004af81f8 Mon Sep 17 00:00:00 2001
From: ernestognw <ernestognw@gmail.com>
Date: Tue, 30 Jan 2024 12:16:52 -0600
Subject: [PATCH 10/11] Fix tests

---
 test/token/ERC721/utils/ERC721Utils.test.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/test/token/ERC721/utils/ERC721Utils.test.js b/test/token/ERC721/utils/ERC721Utils.test.js
index 2ebfb95e3ee..e90c18e4f26 100644
--- a/test/token/ERC721/utils/ERC721Utils.test.js
+++ b/test/token/ERC721/utils/ERC721Utils.test.js
@@ -12,7 +12,7 @@ const deployReceiver = (revertType, returnValue = RECEIVER_MAGIC_VALUE) =>
   ethers.deployContract('$ERC721ReceiverMock', [returnValue, revertType]);
 
 const fixture = async () => {
-  const [operator, owner] = await ethers.getSigners();
+  const [eoa, operator, owner] = await ethers.getSigners();
   const utils = await ethers.deployContract('$ERC721Utils');
 
   const receivers = {
@@ -23,12 +23,13 @@ const fixture = async () => {
     customError: await deployReceiver(RevertType.RevertWithCustomError),
     panic: await deployReceiver(RevertType.Panic),
     nonReceiver: await ethers.deployContract('CallReceiverMock'),
+    eoa,
   };
 
   return { operator, owner, utils, receivers };
 };
 
-describe('ERC721Utils', function () {
+describe.only('ERC721Utils', function () {
   beforeEach(async function () {
     Object.assign(this, await loadFixture(fixture));
   });

From ed00c2ac8c943fd4c8114a8b52ff05093b6a5682 Mon Sep 17 00:00:00 2001
From: ernestognw <ernestognw@gmail.com>
Date: Tue, 30 Jan 2024 12:22:25 -0600
Subject: [PATCH 11/11] Remove unnecessary .only

---
 test/token/ERC721/utils/ERC721Utils.test.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/token/ERC721/utils/ERC721Utils.test.js b/test/token/ERC721/utils/ERC721Utils.test.js
index e90c18e4f26..2327d1ac7da 100644
--- a/test/token/ERC721/utils/ERC721Utils.test.js
+++ b/test/token/ERC721/utils/ERC721Utils.test.js
@@ -29,7 +29,7 @@ const fixture = async () => {
   return { operator, owner, utils, receivers };
 };
 
-describe.only('ERC721Utils', function () {
+describe('ERC721Utils', function () {
   beforeEach(async function () {
     Object.assign(this, await loadFixture(fixture));
   });