fix: Blockhash of current block should be zero

crates/zksync/core/src/vm/runner.rs

@@ -274,10 +274,10 @@ pub fn encode_create_params(
     signature.iter().copied().chain(params).collect()
 }
 
-/// Get last 256 block hashes mapped to block numbers
+/// Get last 256 block hashes mapped to block numbers. This excludes the current block.
 fn get_historical_block_hashes<DB: Database>(ecx: &mut EvmContext<DB>) -> HashMap<rU256, B256> {
     let mut block_hashes = HashMap::default();
-    for i in 0..256u32 {
+    for i in 1..=256u32 {
         let (block_number, overflow) = ecx.env.block.number.overflowing_sub(rU256::from(i));
         if overflow {
             break

crates/zksync/core/src/vm/tracer.rs

@@ -306,12 +306,13 @@ impl<S: Send, H: HistoryMode> DynTracer<S, SimpleMemory<H>> for CheatcodeTracer
                 calldata.starts_with(&SELECTOR_BLOCK_HASH)
             {
                 let block_number = U256::from(&calldata[4..36]);
-                if let Some(block_hash) =
-                    self.call_context.block_hashes.get(&block_number.to_ru256())
-                {
-                    self.farcall_handler.set_immediate_return(block_hash.to_vec());
-                    return;
-                }
+                let block_hash = self
+                    .call_context
+                    .block_hashes
+                    .get(&block_number.to_ru256())
+                    .unwrap_or_default();
+                self.farcall_handler.set_immediate_return(block_hash.to_vec());
+                return;
             }
         }
 

zk-tests/src/Basic.t.sol

@@ -16,7 +16,7 @@ contract BlockEnv {
         chainid = block.chainid;
     }
 
-    function ZkBlockhash(uint256 _blockNumber) public view returns (bytes32) {
+    function zkBlockhash(uint256 _blockNumber) public view returns (bytes32) {
         return blockhash(_blockNumber);
     }
 }
@@ -96,13 +96,21 @@ contract ZkBasicTest is Test {
             be.chainid() == block.chainid,
             "propagated block chainid is the same as current"
         );
+
         require(
-            be.ZkBlockhash(block.number) == blockhash(block.number),
-            "propagated blockhash is the same as current"
+            be.zkBlockhash(block.number) == blockhash(block.number),
+            "blockhash of the current block should be zero"
         );
+
+        // this corresponds to the the genesis block since the test runs in block #1
         require(
-            be.ZkBlockhash(block.number) == bytes32(0),
-            "blockhash mismatch"
+            be.zkBlockhash(block.number - 1) == blockhash(block.number - 1),
+            "blockhash of the previous block should be equal"
+        );
+
+        require(
+            be.zkBlockhash(0) == blockhash(0),
+            "blockhash of the genesis block should be equal"
         );
 
         be = new BlockEnv();
@@ -157,11 +165,11 @@ contract ZkBasicTest is Test {
         );
     }
 
-    function testZkBlockhashWithNewerBlocks() public {
+    function testzkBlockhashWithNewerBlocks() public {
         vm.selectFork(latestForkEth);
         BlockEnv be = new BlockEnv();
         require(
-            be.ZkBlockhash(block.number) == blockhash(block.number),
+            be.zkBlockhash(block.number) == blockhash(block.number),
             "blockhash mismatch"
         );
     }