From 6bc72b0dc5a255e0fec3b5ee9b59e5f80964dbcc Mon Sep 17 00:00:00 2001
From: Nikita Meshcheriakov <root@nikitam.io>
Date: Tue, 16 Sep 2025 15:58:13 +0300
Subject: [PATCH] Add comment and move isPostMerge

---
 consensus/beacon/consensus.go | 14 ++------------
 internal/ethapi/simulate.go   | 11 +++--------
 params/config.go              | 10 ++++++++++
 3 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/consensus/beacon/consensus.go b/consensus/beacon/consensus.go
index 196cbc857c..84926c3d0b 100644
--- a/consensus/beacon/consensus.go
+++ b/consensus/beacon/consensus.go
@@ -71,16 +71,6 @@ func New(ethone consensus.Engine) *Beacon {
 	return &Beacon{ethone: ethone}
 }
 
-// isPostMerge reports whether the given block number is assumed to be post-merge.
-// Here we check the MergeNetsplitBlock to allow configuring networks with a PoW or
-// PoA chain for unit testing purposes.
-func isPostMerge(config *params.ChainConfig, blockNum uint64, timestamp uint64) bool {
-	mergedAtGenesis := config.TerminalTotalDifficulty != nil && config.TerminalTotalDifficulty.Sign() == 0
-	return mergedAtGenesis ||
-		config.MergeNetsplitBlock != nil && blockNum >= config.MergeNetsplitBlock.Uint64() ||
-		config.ShanghaiTime != nil && timestamp >= *config.ShanghaiTime
-}
-
 // Author implements consensus.Engine, returning the verified author of the block.
 func (beacon *Beacon) Author(header *types.Header) (common.Address, error) {
 	if !beacon.IsPoSHeader(header) {
@@ -328,7 +318,7 @@ func (beacon *Beacon) verifyHeaders(chain consensus.ChainHeaderReader, headers [
 // Prepare implements consensus.Engine, initializing the difficulty field of a
 // header to conform to the beacon protocol. The changes are done inline.
 func (beacon *Beacon) Prepare(chain consensus.ChainHeaderReader, header *types.Header) error {
-	if !isPostMerge(chain.Config(), header.Number.Uint64(), header.Time) {
+	if !chain.Config().IsPostMerge(header.Number.Uint64(), header.Time) {
 		return beacon.ethone.Prepare(chain, header)
 	}
 	header.Difficulty = beaconDifficulty
@@ -442,7 +432,7 @@ func (beacon *Beacon) SealHash(header *types.Header) common.Hash {
 // the difficulty that a new block should have when created at time
 // given the parent block's time and difficulty.
 func (beacon *Beacon) CalcDifficulty(chain consensus.ChainHeaderReader, time uint64, parent *types.Header) *big.Int {
-	if !isPostMerge(chain.Config(), parent.Number.Uint64()+1, time) {
+	if !chain.Config().IsPostMerge(parent.Number.Uint64()+1, time) {
 		return beacon.ethone.CalcDifficulty(chain, time, parent)
 	}
 	return beaconDifficulty
diff --git a/internal/ethapi/simulate.go b/internal/ethapi/simulate.go
index 20be32b341..3545e8d043 100644
--- a/internal/ethapi/simulate.go
+++ b/internal/ethapi/simulate.go
@@ -458,13 +458,6 @@ func (sim *simulator) sanitizeChain(blocks []simBlock) ([]simBlock, error) {
 	return res, nil
 }
 
-func isPostMerge(config *params.ChainConfig, blockNum uint64, timestamp uint64) bool {
-	mergedAtGenesis := config.TerminalTotalDifficulty != nil && config.TerminalTotalDifficulty.Sign() == 0
-	return mergedAtGenesis ||
-		config.MergeNetsplitBlock != nil && blockNum >= config.MergeNetsplitBlock.Uint64() ||
-		config.ShanghaiTime != nil && timestamp >= *config.ShanghaiTime
-}
-
 // makeHeaders makes header object with preliminary fields based on a simulated block.
 // Some fields have to be filled post-execution.
 // It assumes blocks are in order and numbers have been validated.
@@ -493,8 +486,10 @@ func (sim *simulator) makeHeaders(blocks []simBlock) ([]*types.Header, error) {
 				parentBeaconRoot = overrides.BeaconRoot
 			}
 		}
+		// Set difficulty to zero if the given block is post-merge. Without this, all post-merge hardforks would remain inactive.
+		// For example, calling eth_simulateV1(..., blockParameter: 0x0) on hoodi network will cause all blocks to have a difficulty of 1 and be treated as pre-merge.
 		difficulty := header.Difficulty
-		if isPostMerge(sim.chainConfig, number.Uint64(), timestamp) {
+		if sim.chainConfig.IsPostMerge(number.Uint64(), timestamp) {
 			difficulty = big.NewInt(0)
 		}
 		header = overrides.MakeHeader(&types.Header{
diff --git a/params/config.go b/params/config.go
index b1297144c3..d5b2d4c1f2 100644
--- a/params/config.go
+++ b/params/config.go
@@ -654,6 +654,16 @@ func (c *ChainConfig) IsTerminalPoWBlock(parentTotalDiff *big.Int, totalDiff *bi
 	return parentTotalDiff.Cmp(c.TerminalTotalDifficulty) < 0 && totalDiff.Cmp(c.TerminalTotalDifficulty) >= 0
 }
 
+// IsPostMerge reports whether the given block number is assumed to be post-merge.
+// Here we check the MergeNetsplitBlock to allow configuring networks with a PoW or
+// PoA chain for unit testing purposes.
+func (c *ChainConfig) IsPostMerge(blockNum uint64, timestamp uint64) bool {
+	mergedAtGenesis := c.TerminalTotalDifficulty != nil && c.TerminalTotalDifficulty.Sign() == 0
+	return mergedAtGenesis ||
+		c.MergeNetsplitBlock != nil && blockNum >= c.MergeNetsplitBlock.Uint64() ||
+		c.ShanghaiTime != nil && timestamp >= *c.ShanghaiTime
+}
+
 // IsShanghai returns whether time is either equal to the Shanghai fork time or greater.
 func (c *ChainConfig) IsShanghai(num *big.Int, time uint64) bool {
 	return c.IsLondon(num) && isTimestampForked(c.ShanghaiTime, time)