From 2e71e50b6bc6072ee72f13cc57443da935964f5c Mon Sep 17 00:00:00 2001
From: Manav Darji <manavdarji.india@gmail.com>
Date: Mon, 31 Mar 2025 12:02:19 +0530
Subject: [PATCH] core: emit sidechain event during reorg

---
 core/blockchain.go      | 6 +++++-
 core/blockchain_test.go | 7 +++----
 core/events.go          | 2 +-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/core/blockchain.go b/core/blockchain.go
index 06a84f4264..f124caee91 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -1993,7 +1993,7 @@ func (bc *BlockChain) writeBlockAndSetHead(block *types.Block, receipts []*types
 			// BOR
 		}
 	} else {
-		bc.chainSideFeed.Send(ChainSideEvent{Block: block})
+		bc.chainSideFeed.Send(ChainSideEvent{Header: block.Header()})
 
 		bc.chain2HeadFeed.Send(Chain2HeadEvent{
 			Type:     Chain2HeadForkEvent,
@@ -2994,6 +2994,10 @@ func (bc *BlockChain) reorg(oldHead *types.Header, newHead *types.Header) error
 	// TODO(karalabe): This should be nuked out, no idea how, deprecate some APIs?
 	{
 		for i := len(oldChain) - 1; i >= 0; i-- {
+			// Also send event for blocks removed from the canon chain. Note: Geth has removed
+			// the concept of side chains but we need them in bor.
+			bc.chainSideFeed.Send(ChainSideEvent{Header: oldChain[i]})
+
 			block := bc.GetBlock(oldChain[i].Hash(), oldChain[i].Number.Uint64())
 			if block == nil {
 				return errInvalidOldChain // Corrupt database, mostly here to avoid weird panics
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index d14e050baa..19a9975e5d 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -1513,7 +1513,6 @@ func checkLogEvents(t *testing.T, logsCh <-chan []*types.Log, rmLogsCh <-chan Re
 }
 
 func TestReorgSideEvent(t *testing.T) {
-	t.Skip("needs discussion")
 	testReorgSideEvent(t, rawdb.HashScheme)
 	testReorgSideEvent(t, rawdb.PathScheme)
 }
@@ -1575,9 +1574,9 @@ done:
 	for {
 		select {
 		case ev := <-chainSideCh:
-			block := ev.Block
-			if _, ok := expectedSideHashes[block.Hash()]; !ok {
-				t.Errorf("%d: didn't expect %x to be in side chain", i, block.Hash())
+			header := ev.Header
+			if _, ok := expectedSideHashes[header.Hash()]; !ok {
+				t.Errorf("%d: didn't expect %x to be in side chain", i, header.Hash())
 			}
 			i++
 
diff --git a/core/events.go b/core/events.go
index 62fb2d3cf5..ab8b2b5f84 100644
--- a/core/events.go
+++ b/core/events.go
@@ -34,7 +34,7 @@ type ChainEvent struct {
 }
 
 type ChainSideEvent struct {
-	Block *types.Block
+	Header *types.Header
 }
 
 type ChainHeadEvent struct {