starknet_os_runner: virtual block executor

crates/blockifier_reexecution/src/state_reader/rpc_state_reader.rs

@@ -201,6 +201,16 @@ impl RpcStateReader {
         }
     }
 
+    /// Creates an RpcStateReader from a node URL, chain ID, and block number.
+    pub fn new_with_config_from_url(
+        node_url: String,
+        chain_id: ChainId,
+        block_number: BlockNumber,
+    ) -> Self {
+        let config = RpcStateReaderConfig::from_url(node_url);
+        Self::new(&config, chain_id, block_number, false)
+    }
+
     pub fn new_for_testing(block_number: BlockNumber) -> Self {
         RpcStateReader::new(&get_rpc_state_reader_config(), ChainId::Mainnet, block_number, false)
     }

crates/starknet_os_runner/Cargo.toml

@@ -7,6 +7,10 @@ license-file.workspace = true
 description = "Runs transactions through the Starknet OS and returns Cairo PIE and OS output."
 
 [dependencies]
+blockifier.workspace = true
+blockifier_reexecution.workspace = true
+starknet_api.workspace = true
+thiserror.workspace = true
 
 [lints]
 workspace = true

crates/starknet_os_runner/src/errors.rs

@@ -0,0 +1,18 @@
+use blockifier_reexecution::errors::ReexecutionError;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum VirtualBlockExecutorError {
+    #[error(transparent)]
+    // Boxed to reduce the size of Result on the stack (ReexecutionError is >128 bytes).
+    ReexecutionError(#[from] Box<ReexecutionError>),
+
+    #[error("Transaction execution failed: {0}")]
+    TransactionExecutionError(String),
+
+    #[error("Block state unavailable after execution")]
+    StateUnavailable,
+
+    #[error("Unsupported transaction type: only Invoke transactions are supported")]
+    UnsupportedTransactionType,
+}

crates/starknet_os_runner/src/lib.rs

@@ -1 +1,2 @@
-//! Starknet OS Runner - executes transactions through the OS and returns Cairo PIE and output.
+pub mod errors;
+pub mod virtual_block_executor;

crates/starknet_os_runner/src/virtual_block_executor.rs

@@ -0,0 +1,206 @@
+use blockifier::blockifier::config::TransactionExecutorConfig;
+use blockifier::blockifier::transaction_executor::{
+    TransactionExecutionOutput,
+    TransactionExecutor,
+};
+use blockifier::context::BlockContext;
+use blockifier::state::cached_state::{CachedState, StateMaps};
+use blockifier::state::contract_class_manager::ContractClassManager;
+use blockifier::state::state_reader_and_contract_manager::StateReaderAndContractManager;
+use blockifier::transaction::account_transaction::ExecutionFlags;
+use blockifier::transaction::transaction_execution::Transaction as BlockifierTransaction;
+use blockifier_reexecution::state_reader::rpc_state_reader::RpcStateReader;
+use starknet_api::block::BlockNumber;
+use starknet_api::core::ChainId;
+use starknet_api::transaction::{Transaction, TransactionHash};
+
+use crate::errors::VirtualBlockExecutorError;
+
+/// Captures execution data for a virtual block (multiple transactions).
+///
+/// A virtual block is a set of transactions executed together without block preprocessing,
+/// useful for OS input generation and proving. This struct contains all the transaction execution
+/// outputs, block context, and initial state reads needed for proof generation.
+pub struct VirtualBlockExecutionData {
+    /// Execution outputs for all transactions in the virtual block.
+    pub execution_outputs: Vec<TransactionExecutionOutput>,
+    /// The block context in which the transactions were executed.
+    pub block_context: BlockContext,
+    /// The initial state reads (accessed state) during execution.
+    pub initial_reads: StateMaps,
+}
+
+/// Executes a virtual block of transactions.
+///
+/// A virtual block executor runs transactions without block preprocessing
+/// (`pre_process_block`), which is useful for simulating execution or generating
+/// OS input for proving.
+///
+/// Implementations can fetch state from different sources (RPC nodes, local state,
+/// mocked data, etc.).
+///
+/// # Note
+///
+/// - Currently only Invoke transactions are supported.
+/// - fee charging and nonce check are always skipped (useful for simulation/proving).
+///
+/// # Examples
+///
+/// ```text
+/// let executor = RpcVirtualBlockExecutor::new(
+///     "http://localhost:9545".to_string(),
+///     ChainId::Mainnet,
+///     contract_class_manager,
+/// );
+///
+/// let execution_data = executor.execute(block_number, transactions)?;
+/// // Use execution_data to build OS input for proving...
+/// ```
+pub trait VirtualBlockExecutor {
+    /// Executes a virtual block based on the state and context at the given block number.
+    ///
+    /// # Arguments
+    ///
+    /// * `block_number` - The block number to use for state and context
+    /// * `txs` - Invoke transactions to execute (with their hashes)
+    ///
+    /// # Returns
+    ///
+    /// Returns `VirtualBlockExecutionData` containing execution outputs for all
+    /// transactions, or an error if any transaction fails or is not an Invoke.
+    fn execute(
+        &self,
+        block_number: BlockNumber,
+        txs: Vec<(Transaction, TransactionHash)>,
+    ) -> Result<VirtualBlockExecutionData, VirtualBlockExecutorError> {
+        let blockifier_txs = Self::convert_invoke_txs(txs)?;
+        self.execute_inner(block_number, blockifier_txs)
+    }
+
+    fn execute_inner(
+        &self,
+        block_number: BlockNumber,
+        txs: Vec<BlockifierTransaction>,
+    ) -> Result<VirtualBlockExecutionData, VirtualBlockExecutorError>;
+
+    /// Converts Invoke transactions to blockifier transactions.
+    ///
+    /// Uses execution flags that skip fee charging and nonce check.
+    /// Returns an error if any transaction is not an Invoke.
+    fn convert_invoke_txs(
+        txs: Vec<(Transaction, TransactionHash)>,
+    ) -> Result<Vec<BlockifierTransaction>, VirtualBlockExecutorError> {
+        // Skip validation, fee charging, and nonce check for virtual block execution.
+        let execution_flags = ExecutionFlags {
+            validate: true,
+            charge_fee: false,
+            strict_nonce_check: false,
+            only_query: false,
+        };
+
+        txs.into_iter()
+            .map(|(tx, tx_hash)| {
+                if !matches!(tx, Transaction::Invoke(_)) {
+                    return Err(VirtualBlockExecutorError::UnsupportedTransactionType);
+                }
+
+                BlockifierTransaction::from_api(
+                    tx,
+                    tx_hash,
+                    None, // class_info - not needed for Invoke.
+                    None, // paid_fee_on_l1 - not needed for Invoke.
+                    None, // deployed_contract_address - not needed for Invoke.
+                    execution_flags.clone(),
+                )
+                .map_err(|e| VirtualBlockExecutorError::TransactionExecutionError(e.to_string()))
+            })
+            .collect()
+    }
+}
+
+/// RPC-based virtual block executor.
+///
+/// This executor fetches historical state from an RPC node and executes transactions
+/// without block preprocessing. Validation and fee charging are always skipped,
+/// making it suitable for simulation and OS input generation.
+pub struct RpcVirtualBlockExecutor {
+    node_url: String,
+    chain_id: ChainId,
+    contract_class_manager: ContractClassManager,
+}
+
+impl RpcVirtualBlockExecutor {
+    /// Creates a new RPC-based virtual block executor.
+    ///
+    /// # Arguments
+    ///
+    /// * `node_url` - URL of the RPC node to fetch state from
+    /// * `chain_id` - The chain ID for transaction hash computation
+    /// * `contract_class_manager` - Manager for compiled contract classes
+    pub fn new(
+        node_url: String,
+        chain_id: ChainId,
+        contract_class_manager: ContractClassManager,
+    ) -> Self {
+        Self { node_url, chain_id, contract_class_manager }
+    }
+}
+
+impl VirtualBlockExecutor for RpcVirtualBlockExecutor {
+    fn execute_inner(
+        &self,
+        block_number: BlockNumber,
+        txs: Vec<BlockifierTransaction>,
+    ) -> Result<VirtualBlockExecutionData, VirtualBlockExecutorError> {
+        // Create RPC state reader for the given block.
+        let rpc_state_reader = RpcStateReader::new_with_config_from_url(
+            self.node_url.clone(),
+            self.chain_id.clone(),
+            block_number,
+        );
+
+        // Get block context from RPC.
+        let block_context = rpc_state_reader
+            .get_block_context()
+            .map_err(|e| VirtualBlockExecutorError::ReexecutionError(Box::new(e)))?;
+
+        // Create state reader with contract manager.
+        let state_reader_and_contract_manager = StateReaderAndContractManager::new(
+            rpc_state_reader,
+            self.contract_class_manager.clone(),
+            None,
+        );
+
+        let block_state = CachedState::new(state_reader_and_contract_manager);
+
+        // Create executor WITHOUT preprocessing (no pre_process_block call).
+        let mut transaction_executor = TransactionExecutor::new(
+            block_state,
+            block_context.clone(),
+            TransactionExecutorConfig::default(),
+        );
+
+        // Execute all transactions.
+        let execution_results = transaction_executor.execute_txs(&txs, None);
+
+        // Collect results, returning error if any transaction fails.
+        let execution_outputs: Vec<TransactionExecutionOutput> = execution_results
+            .into_iter()
+            .map(|result| {
+                result.map_err(|e| {
+                    VirtualBlockExecutorError::TransactionExecutionError(e.to_string())
+                })
+            })
+            .collect::<Result<Vec<_>, _>>()?;
+
+        // Get initial state reads.
+        let initial_reads = transaction_executor
+            .block_state
+            .as_ref()
+            .ok_or(VirtualBlockExecutorError::StateUnavailable)?
+            .get_initial_reads()
+            .map_err(|e| VirtualBlockExecutorError::ReexecutionError(Box::new(e.into())))?;
+
+        Ok(VirtualBlockExecutionData { execution_outputs, block_context, initial_reads })
+    }
+}