fix(chain_spec): Set correct paris block and chain difficulty (#7111)

Signed-off-by: Danil <deniallugo@gmail.com>

crates/primitives/src/chain/spec.rs

@@ -890,15 +890,20 @@ impl From<Genesis> for ChainSpec {
             .collect::<BTreeMap<_, _>>();
 
         // Paris
-        if let Some(ttd) = genesis.config.terminal_total_difficulty {
-            hardforks.insert(
-                Hardfork::Paris,
-                ForkCondition::TTD {
-                    total_difficulty: ttd,
-                    fork_block: genesis.config.merge_netsplit_block,
-                },
-            );
-        }
+        let paris_block_and_final_difficulty =
+            if let Some(ttd) = genesis.config.terminal_total_difficulty {
+                hardforks.insert(
+                    Hardfork::Paris,
+                    ForkCondition::TTD {
+                        total_difficulty: ttd,
+                        fork_block: genesis.config.merge_netsplit_block,
+                    },
+                );
+
+                genesis.config.merge_netsplit_block.map(|block| (block, ttd))
+            } else {
+                None
+            };
 
         // Time-based hardforks
         let time_hardfork_opts = [
@@ -921,7 +926,7 @@ impl From<Genesis> for ChainSpec {
             genesis_hash: None,
             fork_timestamps: ForkTimestamps::from_hardforks(&hardforks),
             hardforks,
-            paris_block_and_final_difficulty: None,
+            paris_block_and_final_difficulty,
             deposit_contract: None,
             ..Default::default()
         }
@@ -1229,13 +1234,22 @@ impl ChainSpecBuilder {
     /// This function panics if the chain ID and genesis is not set ([`Self::chain`] and
     /// [`Self::genesis`])
     pub fn build(self) -> ChainSpec {
+        let paris_block_and_final_difficulty = {
+            self.hardforks.get(&Hardfork::Paris).and_then(|cond| {
+                if let ForkCondition::TTD { fork_block, total_difficulty } = cond {
+                    fork_block.map(|fork_block| (fork_block, *total_difficulty))
+                } else {
+                    None
+                }
+            })
+        };
         ChainSpec {
             chain: self.chain.expect("The chain is required"),
             genesis: self.genesis.expect("The genesis is required"),
             genesis_hash: None,
             fork_timestamps: ForkTimestamps::from_hardforks(&self.hardforks),
             hardforks: self.hardforks,
-            paris_block_and_final_difficulty: None,
+            paris_block_and_final_difficulty,
             deposit_contract: None,
             ..Default::default()
         }
@@ -2833,6 +2847,8 @@ Post-merge hard forks (timestamp based):
 
         // check that they're the same
         assert_eq!(got_forkid, expected_forkid);
+        // Check that paris block and final difficulty are set correctly
+        assert_eq!(chainspec.paris_block_and_final_difficulty, Some((72, U256::from(9454784))));
     }
 
     #[test]
@@ -2881,6 +2897,17 @@ Post-merge hard forks (timestamp based):
         assert_eq!(genesis.config.cancun_time, Some(4661));
     }
 
+    #[test]
+    fn test_paris_block_and_total_difficulty() {
+        let genesis = Genesis { gas_limit: 0x2fefd8u64, ..Default::default() };
+        let paris_chainspec = ChainSpecBuilder::default()
+            .chain(Chain::from_id(1337))
+            .genesis(genesis)
+            .paris_activated()
+            .build();
+        assert_eq!(paris_chainspec.paris_block_and_final_difficulty, Some((0, U256::ZERO)));
+    }
+
     #[test]
     fn test_default_cancun_header_forkhash() {
         // set the gas limit from the hive test genesis according to the hash