inserting header without set head from engine api should also validate the header

nimbus/merge/mergeutils.nim

@@ -93,4 +93,6 @@ proc invalidStatus*(validHash: Hash256, msg: string): PayloadStatusV1 =
 
 proc toBlockBody*(payload: ExecutionPayloadV1): BlockBody =
   # TODO the transactions from the payload have to be converted here
-  discard payload.transactions
+  result.transactions.setLen(payload.transactions.len)
+  for i, tx in payload.transactions:
+    result.transactions[i] = rlp.decode(distinctBase tx, Transaction)

nimbus/p2p/chain/persist_blocks.nim

@@ -34,7 +34,7 @@ when not defined(release):
 # ------------------------------------------------------------------------------
 
 proc persistBlocksImpl(c: Chain; headers: openarray[BlockHeader];
-                       bodies: openarray[BlockBody]): ValidationResult
+                       bodies: openarray[BlockBody], setHead: bool = true): ValidationResult
                           # wildcard exception, wrapped below in public section
                           {.inline, raises: [Exception].} =
   c.db.highestBlock = headers[^1].blockNumber
@@ -98,7 +98,11 @@ proc persistBlocksImpl(c: Chain; headers: openarray[BlockHeader];
             msg = res.error
           return ValidationResult.Error
 
+    if setHead:
       discard c.db.persistHeaderToDb(header)
+    else:
+      c.db.persistHeaderToDbWithoutSetHead(header)
+
     discard c.db.persistTransactions(header.blockNumber, body.transactions)
     discard c.db.persistReceipts(vmState.receipts)
 
@@ -109,6 +113,17 @@ proc persistBlocksImpl(c: Chain; headers: openarray[BlockHeader];
 
   transaction.commit()
 
+# ------------------------------------------------------------------------------
+# Public `ChainDB` methods
+# ------------------------------------------------------------------------------
+
+proc insertBlockWithoutSetHead*(c: Chain, header: BlockHeader,
+                                body: BlockBody): ValidationResult
+                                {.gcsafe, raises: [Defect,CatchableError].} =
+
+  safeP2PChain("persistBlocks"):
+    result = c.persistBlocksImpl([header], [body], setHead = false)
+
 # ------------------------------------------------------------------------------
 # Public `AbstractChainDB` overload method
 # ------------------------------------------------------------------------------

nimbus/rpc/engine_api.nim

@@ -93,7 +93,10 @@ proc setupEngineAPI*(
 
     trace "Inserting block without sethead",
       hash = blockHash.data.toHex, number = header.blockNumber
-    db.persistHeaderToDbWithoutSetHead(header)
+    let body = toBlockBody(payload)
+    let vres = sealingEngine.chain.insertBlockWithoutSetHead(header, body)
+    if vres != ValidationResult.OK:
+      return invalidStatus(db.getCurrentBlockHash(), "Failed to insert block")
 
     # We've accepted a valid payload from the beacon client. Mark the local
     # chain transitions to notify other subsystems (e.g. downloader) of the