starknet_os_runner: contract class hints to casm hints (#11527)

Author: AvivYossef-starkware

crates/blockifier/src/execution/contract_class.rs

@@ -20,7 +20,7 @@ use cairo_vm::serde::deserialize_program::{
 };
 use cairo_vm::types::builtin_name::BuiltinName;
 use cairo_vm::types::errors::program_errors::ProgramError;
-use cairo_vm::types::program::Program;
+use cairo_vm::types::program::{HintsCollection, Program};
 use cairo_vm::types::relocatable::MaybeRelocatable;
 use cairo_vm::vm::runners::cairo_runner::ExecutionResources;
 use itertools::Itertools;
@@ -709,6 +709,29 @@ fn hint_to_hint_params(hint: &Hint) -> Result<HintParams, ProgramError> {
     })
 }
 
+/// Converts `HintParams` back to `Hint` by deserializing the JSON code.
+/// This is the reverse of `hint_to_hint_params`.
+fn hint_params_to_hint(hint_params: &HintParams) -> Result<Hint, ProgramError> {
+    Ok(serde_json::from_str(&hint_params.code)?)
+}
+
+/// Converts `BTreeMap<usize, Vec<HintParams>>` back to `Vec<(usize, Vec<Hint>)>`.
+/// This is the reverse of the conversion done in `TryFrom<VersionedCasm> for CompiledClassV1`.
+pub fn program_hints_to_casm_hints(
+    program_hints: &HintsCollection,
+) -> Result<Vec<(usize, Vec<Hint>)>, ProgramError> {
+    let program_hints: BTreeMap<usize, Vec<HintParams>> = program_hints.into();
+    let mut casm_hints: Vec<(usize, Vec<Hint>)> = Vec::new();
+    for (i, hint_params_list) in program_hints.iter() {
+        let hints: Vec<Hint> = hint_params_list
+            .iter()
+            .map(hint_params_to_hint)
+            .collect::<Result<Vec<Hint>, ProgramError>>()?;
+        casm_hints.push((*i, hints));
+    }
+    Ok(casm_hints)
+}
+
 fn convert_entry_points_v1(external: &[CasmContractEntryPoint]) -> Vec<EntryPointV1> {
     external
         .iter()

crates/blockifier/src/execution/contract_class_test.rs

@@ -19,6 +19,7 @@ use starknet_types_core::felt::Felt;
 use starknet_types_core::hash::Blake2Felt252;
 
 use crate::execution::contract_class::{
+    program_hints_to_casm_hints,
     CompiledClassV1,
     ContractClassV1Inner,
     EntryPointV1,
@@ -236,3 +237,32 @@ fn test_entry_points_round_trip(#[case] original: CasmContractEntryPoints) {
 
     assert_eq!(round_tripped, original);
 }
+
+#[rstest]
+fn test_hints_round_trip() {
+    // Get a test contract that has hints.
+    let feature_contract =
+        FeatureContract::TestContract(CairoVersion::Cairo1(RunnableCairo1::Casm));
+    let (casm, sierra_version) = match feature_contract.get_class() {
+        ContractClass::V1(versioned_casm) => versioned_casm,
+        _ => panic!("Expected ContractClass::V1"),
+    };
+
+    // Panic if the contract has no hints - we need hints to test the roundtrip.
+    assert!(!casm.hints.is_empty(), "Test contract must have hints for roundtrip test");
+
+    // Get original hints from the CasmContractClass.
+    let original_hints = casm.hints.clone();
+
+    // Forward conversion: Convert CasmContractClass convert the hints from Vec<(usize, Vec<Hint>)>
+    // to HashMap<usize, Vec<HintParams>>.
+    let compiled_class = CompiledClassV1::try_from((casm, sierra_version)).unwrap();
+
+    // Reverse conversion: Access the hints from the VM program and convert back.
+    // The program stores hints as a HintsCollection, which can be converted to BTreeMap.
+    let program_hints = &compiled_class.program.shared_program_data.hints_collection;
+    let round_tripped_hints = program_hints_to_casm_hints(program_hints).unwrap();
+
+    // Compare with original.
+    assert_eq!(round_tripped_hints, original_hints);
+}