Add a flag to simulateTransaction to use most recent blockhash (backport #17485)

client/src/rpc_config.rs

@@ -28,6 +28,8 @@ pub struct RpcSendTransactionConfig {
 pub struct RpcSimulateTransactionConfig {
     #[serde(default)]
     pub sig_verify: bool,
+    #[serde(default)]
+    pub replace_recent_blockhash: bool,
     #[serde(flatten)]
     pub commitment: Option<CommitmentConfig>,
     pub encoding: Option<UiTransactionEncoding>,

core/src/rpc.rs

@@ -3141,15 +3141,24 @@ pub mod rpc_full {
             debug!("simulate_transaction rpc request received");
             let config = config.unwrap_or_default();
             let encoding = config.encoding.unwrap_or(UiTransactionEncoding::Base58);
-            let (_, transaction) = deserialize_transaction(data, encoding)?;
+            let (_, mut transaction) = deserialize_transaction(data, encoding)?;
 
             if config.sig_verify {
+                if config.replace_recent_blockhash {
+                    return Err(Error::invalid_params(
+                        "sigVerify may not be used with replaceRecentBlockhash",
+                    ));
+                }
+
                 if let Err(e) = verify_transaction(&transaction) {
                     return Err(e);
                 }
             }
 
             let bank = &*meta.bank(config.commitment);
+            if config.replace_recent_blockhash {
+                transaction.message.recent_blockhash = bank.last_blockhash();
+            }
             let (result, logs) = bank.simulate_transaction(transaction);
 
             Ok(new_response(
@@ -4854,6 +4863,8 @@ pub mod tests {
         let tx_serialized_encoded = bs58::encode(serialize(&tx).unwrap()).into_string();
         tx.signatures[0] = Signature::default();
         let tx_badsig_serialized_encoded = bs58::encode(serialize(&tx).unwrap()).into_string();
+        tx.message.recent_blockhash = Hash::default();
+        let tx_invalid_recent_blockhash = bs58::encode(serialize(&tx).unwrap()).into_string();
 
         bank.freeze(); // Ensure the root bank is frozen, `start_rpc_handler_with_tx()` doesn't do this
 
@@ -4929,6 +4940,75 @@ pub mod tests {
             r#"{{"jsonrpc":"2.0","id":1,"method":"simulateTransaction","params":["{}"]}}"#,
             tx_serialized_encoded,
         );
+        let res = io.handle_request_sync(&req, meta.clone());
+        let expected = json!({
+            "jsonrpc": "2.0",
+            "result": {
+                "context":{"slot":0},
+                "value":{"err":null, "logs":[
+                    "Program 11111111111111111111111111111111 invoke [1]",
+                    "Program 11111111111111111111111111111111 success"
+                ]}
+            },
+            "id": 1,
+        });
+        let expected: Response =
+            serde_json::from_value(expected).expect("expected response deserialization");
+        let result: Response = serde_json::from_str(&res.expect("actual response"))
+            .expect("actual response deserialization");
+        assert_eq!(expected, result);
+
+        // Enabled both sigVerify=true and replaceRecentBlockhash=true
+        let req = format!(
+            r#"{{"jsonrpc":"2.0","id":1,"method":"simulateTransaction","params":["{}", {}]}}"#,
+            tx_serialized_encoded,
+            json!({
+                "sigVerify": true,
+                "replaceRecentBlockhash": true,
+            })
+            .to_string()
+        );
+        let res = io.handle_request_sync(&req, meta.clone());
+        let expected = json!({
+            "jsonrpc":"2.0",
+            "error": {
+                "code": ErrorCode::InvalidParams,
+                "message": "sigVerify may not be used with replaceRecentBlockhash"
+            },
+            "id":1
+        });
+        let expected: Response =
+            serde_json::from_value(expected).expect("expected response deserialization");
+        let result: Response = serde_json::from_str(&res.expect("actual response"))
+            .expect("actual response deserialization");
+        assert_eq!(expected, result);
+
+        // Bad recent blockhash with replaceRecentBlockhash=false
+        let req = format!(
+            r#"{{"jsonrpc":"2.0","id":1,"method":"simulateTransaction","params":["{}", {{"replaceRecentBlockhash": false}}]}}"#,
+            tx_invalid_recent_blockhash,
+        );
+        let res = io.handle_request_sync(&req, meta.clone());
+        let expected = json!({
+            "jsonrpc":"2.0",
+            "result": {
+                "context":{"slot":0},
+                "value":{"err": "BlockhashNotFound", "logs":[]}
+            },
+            "id":1
+        });
+
+        let expected: Response =
+            serde_json::from_value(expected).expect("expected response deserialization");
+        let result: Response = serde_json::from_str(&res.expect("actual response"))
+            .expect("actual response deserialization");
+        assert_eq!(expected, result);
+
+        // Bad recent blockhash with replaceRecentBlockhash=true
+        let req = format!(
+            r#"{{"jsonrpc":"2.0","id":1,"method":"simulateTransaction","params":["{}", {{"replaceRecentBlockhash": true}}]}}"#,
+            tx_invalid_recent_blockhash,
+        );
         let res = io.handle_request_sync(&req, meta);
         let expected = json!({
             "jsonrpc": "2.0",
@@ -4941,6 +5021,7 @@ pub mod tests {
             },
             "id": 1,
         });
+
         let expected: Response =
             serde_json::from_value(expected).expect("expected response deserialization");
         let result: Response = serde_json::from_str(&res.expect("actual response"))

docs/src/developing/clients/jsonrpc-api.md

@@ -3231,9 +3231,11 @@ Simulate sending a transaction
 
 - `<string>` - Transaction, as an encoded string. The transaction must have a valid blockhash, but is not required to be signed.
 - `<object>` - (optional) Configuration object containing the following field:
-  - `sigVerify: <bool>` - if true the transaction signatures will be verified (default: false)
+  - `sigVerify: <bool>` - if true the transaction signatures will be verified (default: false, conflicts with `replaceRecentBlockhash`)
   - `commitment: <string>` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment) level to simulate the transaction at (default: `"finalized"`).
   - `encoding: <string>` - (optional) Encoding used for the transaction data. Either `"base58"` (*slow*, **DEPRECATED**), or `"base64"`. (default: `"base58"`).
+  - `replaceRecentBlockhash: <bool>` - (optional) if true the transaction recent blockhash will be replaced with the most recent blockhash.
+  (default: false, conflicts with `sigVerify`)
 
 #### Results: