From a0b2dceb0cdefb7ce6935a52620a8c139b43d4c4 Mon Sep 17 00:00:00 2001
From: Zack Grannan <zgrannan@protonmail.com>
Date: Fri, 15 Nov 2024 09:49:23 -0800
Subject: [PATCH] ERC-721: Clear approval in `burn()` (#2099)

* ERC-721: Clear approval in burn()

* ERC-721: add changelog entry
---
 CHANGELOG.md                           |  1 +
 integration-tests/public/erc721/lib.rs | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b9571f37470..00048420213 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix outdated docs for `[ink_e2e::test]` ‒ [#2162](https://github.com/use-ink/ink/pull/2162)
 - [E2E] build contracts before initializing node rpc ‒ [#2168](https://github.com/use-ink/ink/pull/2162)
 - [E2E] `set_account_balance` now can't set balance below existential deposit - [#1983](https://github.com/paritytech/ink/pull/1983) (thanks [@0xLucca](https://github.com/0xLucca)!)
+- ERC-721: `burn()` clears token approval - [#2099](https://github.com/paritytech/ink/pull/2099)
 
 ## Version 5.0.0
 
diff --git a/integration-tests/public/erc721/lib.rs b/integration-tests/public/erc721/lib.rs
index 637836f934f..5b2cbafd944 100644
--- a/integration-tests/public/erc721/lib.rs
+++ b/integration-tests/public/erc721/lib.rs
@@ -226,6 +226,7 @@ mod erc721 {
                 .ok_or(Error::CannotFetchValue)?;
             owned_tokens_count.insert(caller, &count);
             token_owner.remove(id);
+            self.clear_approval(id);
 
             self.env().emit_event(Transfer {
                 from: Some(caller),
@@ -635,6 +636,31 @@ mod erc721 {
             assert_eq!(erc721.burn(1), Err(Error::NotOwner));
         }
 
+        #[ink::test]
+        fn burn_clears_approval() {
+            let accounts =
+                ink::env::test::default_accounts::<ink::env::DefaultEnvironment>();
+            // Create a new contract instance.
+            let mut erc721 = Erc721::new();
+            // Create token Id 1 for Alice
+            assert_eq!(erc721.mint(1), Ok(()));
+            // Alice gives approval to Bob to transfer token Id 1
+            assert_eq!(erc721.approve(accounts.bob, 1), Ok(()));
+            // Alice burns token
+            assert_eq!(erc721.burn(1), Ok(()));
+            // Set caller to Frank
+            set_caller(accounts.frank);
+            // Frank mints token Id 1
+            assert_eq!(erc721.mint(1), Ok(()));
+            // Set caller to Bob
+            set_caller(accounts.bob);
+            // Bob tries to transfer token Id 1 from Frank to himself
+            assert_eq!(
+                erc721.transfer_from(accounts.frank, accounts.bob, 1),
+                Err(Error::NotApproved)
+            );
+        }
+
         #[ink::test]
         fn transfer_from_fails_not_owner() {
             let accounts =