Add mock_call (#385)

<!-- Reference any GitHub issues resolved by this PR -->

Closes #

## Introduced changes

<!-- A brief description of the changes -->

- Add `start_mock_call` cheatcode (with tests and docs)
- Add `stop_mock_call` cheatcode (with tests and docs)

## Breaking changes

<!-- List of all breaking changes, if applicable -->

## Checklist

<!-- Make sure all of these are complete -->

- [x] Linked relevant issue
- [x] Updated relevant documentation
- [x] Added relevant tests
- [x] Performed self-review of the code
- [x] Added changes to `CHANGELOG.md`

---------

Co-authored-by: Marcin Warchoł <[email protected]>
Co-authored-by: Maksymilian Demitraszek <[email protected]>
Co-authored-by: Piotr Magiera <[email protected]>

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Print support for basic numeric data types
 - Functions `parse_txt` and `TxtParser<T>::deserialize_txt` to load data from plain text files and serialize it
 - `get_class_hash` cheatcode
+- `mock_call` cheatcode
 
 #### Changed
 

crates/cheatnet/src/cheatcodes.rs

@@ -11,6 +11,7 @@ use thiserror::Error;
 pub mod declare;
 pub mod deploy;
 pub mod get_class_hash;
+pub mod mock_call;
 pub mod prank;
 pub mod roll;
 pub mod warp;

crates/cheatnet/src/cheatcodes/mock_call.rs

@@ -0,0 +1,36 @@
+use crate::CheatnetState;
+use starknet_api::core::{ContractAddress, EntryPointSelector};
+use starknet_api::hash::StarkFelt;
+use std::collections::HashMap;
+
+impl CheatnetState {
+    pub fn start_mock_call(
+        &mut self,
+        contract_address: ContractAddress,
+        function_name: EntryPointSelector,
+        ret_data: Vec<StarkFelt>,
+    ) {
+        let contract_mocked_functions = self
+            .cheatcode_state
+            .mocked_functions
+            .entry(contract_address)
+            .or_insert_with(HashMap::new);
+
+        contract_mocked_functions.insert(function_name, ret_data);
+    }
+
+    pub fn stop_mock_call(
+        &mut self,
+        contract_address: ContractAddress,
+        function_name: EntryPointSelector,
+    ) {
+        if let std::collections::hash_map::Entry::Occupied(mut e) = self
+            .cheatcode_state
+            .mocked_functions
+            .entry(contract_address)
+        {
+            let contract_mocked_functions = e.get_mut();
+            contract_mocked_functions.remove(&function_name);
+        }
+    }
+}

crates/cheatnet/src/rpc.rs

@@ -12,12 +12,15 @@ use cairo_vm::{
         vm_core::VirtualMachine,
     },
 };
+use std::collections::HashSet;
 use std::{any::Any, collections::HashMap, sync::Arc};
 
 use crate::{
     constants::{build_block_context, build_transaction_context, TEST_ACCOUNT_CONTRACT_ADDRESS},
     CheatnetState,
 };
+use blockifier::execution::entry_point::CallExecution;
+use blockifier::execution::entry_point::Retdata;
 use blockifier::{
     abi::constants,
     execution::{
@@ -56,6 +59,7 @@ use cairo_lang_casm::{
     hints::{Hint, StarknetHint},
     operand::{BinOpOperand, DerefOrImmediate, Operation, Register, ResOperand},
 };
+use cairo_vm::vm::runners::cairo_runner::ExecutionResources as VmExecutionResources;
 use starknet_api::{
     core::{ClassHash, ContractAddress, EntryPointSelector, PatriciaKey},
     deprecated_contract_class::EntryPointType,
@@ -693,6 +697,21 @@ pub fn execute_inner_call(
     Ok(retdata_segment)
 }
 
+fn get_ret_data_by_call_entry_point<'a>(
+    call: &CallEntryPoint,
+    cheatcode_state: &'a CheatcodeState,
+) -> Option<&'a Vec<StarkFelt>> {
+    if let Some(contract_address) = call.code_address {
+        if let Some(contract_functions) = cheatcode_state.mocked_functions.get(&contract_address) {
+            let entrypoint_selector = call.entry_point_selector;
+
+            let ret_data = contract_functions.get(&entrypoint_selector);
+            return ret_data;
+        }
+    }
+    None
+}
+
 /// Executes a specific call to a contract entry point and returns its output.
 fn execute_entry_point_call_cairo1(
     call: CallEntryPoint,
@@ -702,6 +721,23 @@ fn execute_entry_point_call_cairo1(
     resources: &mut ExecutionResources,
     context: &mut EntryPointExecutionContext,
 ) -> EntryPointExecutionResult<CallInfo> {
+    if let Some(ret_data) = get_ret_data_by_call_entry_point(&call, cheatcode_state) {
+        return Ok(CallInfo {
+            call,
+            execution: CallExecution {
+                retdata: Retdata(ret_data.clone()),
+                events: vec![],
+                l2_to_l1_messages: vec![],
+                failed: false,
+                gas_consumed: 0,
+            },
+            vm_resources: VmExecutionResources::default(),
+            inner_calls: vec![],
+            storage_read_values: vec![],
+            accessed_storage_keys: HashSet::new(),
+        });
+    }
+
     let VmExecutionContext {
         mut runner,
         mut vm,

crates/cheatnet/src/state.rs

@@ -7,6 +7,7 @@ use blockifier::{
     },
 };
 use cairo_felt::Felt252;
+use starknet_api::core::EntryPointSelector;
 use starknet_api::{
     core::{ClassHash, CompiledClassHash, ContractAddress, Nonce},
     hash::StarkFelt,
@@ -86,6 +87,7 @@ pub struct CheatcodeState {
     pub rolled_contracts: HashMap<ContractAddress, Felt252>,
     pub pranked_contracts: HashMap<ContractAddress, ContractAddress>,
     pub warped_contracts: HashMap<ContractAddress, Felt252>,
+    pub mocked_functions: HashMap<ContractAddress, HashMap<EntryPointSelector, Vec<StarkFelt>>>,
 }
 
 impl CheatcodeState {
@@ -95,6 +97,7 @@ impl CheatcodeState {
             rolled_contracts: HashMap::new(),
             pranked_contracts: HashMap::new(),
             warped_contracts: HashMap::new(),
+            mocked_functions: HashMap::new(),
         }
     }
 }

crates/forge/src/cheatcodes_hint_processor.rs

@@ -4,8 +4,8 @@ use std::path::PathBuf;
 
 use crate::scarb::StarknetContractArtifacts;
 use anyhow::{anyhow, Result};
+use blockifier::abi::abi_utils::selector_from_name;
 use blockifier::execution::execution_utils::{felt_to_stark_felt, stark_felt_to_felt};
-
 use cairo_felt::Felt252;
 use cairo_vm::hint_processor::hint_processor_definition::HintProcessorLogic;
 use cairo_vm::hint_processor::hint_processor_definition::HintReference;
@@ -226,7 +226,42 @@ impl CairoHintProcessor<'_> {
                 self.cheatnet_state.stop_prank(contract_address);
                 Ok(())
             }
-            "mock_call" => todo!(),
+            "start_mock_call" => {
+                let contract_address = ContractAddress(PatriciaKey::try_from(StarkFelt::new(
+                    inputs[0].clone().to_be_bytes(),
+                )?)?);
+                let function_name = inputs[1].clone();
+                let function_name = as_cairo_short_string(&function_name).unwrap_or_else(|| {
+                    panic!("Failed to convert {function_name:?} to Cairo short str")
+                });
+                let function_name = selector_from_name(function_name.as_str());
+
+                let ret_data_length = inputs[2]
+                    .to_usize()
+                    .expect("Missing ret_data len in inputs");
+                let mut ret_data = vec![];
+                for felt in inputs.iter().skip(3).take(ret_data_length) {
+                    ret_data.push(felt_to_stark_felt(&felt.clone()));
+                }
+
+                self.cheatnet_state
+                    .start_mock_call(contract_address, function_name, ret_data);
+                Ok(())
+            }
+            "stop_mock_call" => {
+                let contract_address = ContractAddress(PatriciaKey::try_from(StarkFelt::new(
+                    inputs[0].clone().to_be_bytes(),
+                )?)?);
+                let function_name = inputs[1].clone();
+                let function_name = as_cairo_short_string(&function_name).unwrap_or_else(|| {
+                    panic!("Failed to convert {function_name:?} to Cairo short str")
+                });
+                let function_name = selector_from_name(function_name.as_str());
+
+                self.cheatnet_state
+                    .stop_mock_call(contract_address, function_name);
+                Ok(())
+            }
             "declare" => {
                 let contract_name = inputs[0].clone();
 

crates/forge/tests/data/contracts/constructor_mock_checker.cairo

@@ -0,0 +1,34 @@
+use starknet::ContractAddress;
+
+#[starknet::interface]
+trait IConstructorMockChecker<TContractState> {
+    fn get_stored_thing(ref self: TContractState) -> felt252;
+    fn get_constant_thing(ref self: TContractState) -> felt252;
+}
+
+#[starknet::contract]
+mod ConstructorMockChecker {
+    use super::IConstructorMockChecker;
+
+    #[storage]
+    struct Storage {
+        stored_thing: felt252,
+    }
+
+    #[constructor]
+    fn constructor(ref self: ContractState) {
+        let const_thing = self.get_constant_thing();
+        self.stored_thing.write(const_thing);
+    }
+
+    #[external(v0)]
+    impl IConstructorMockCheckerImpl of super::IConstructorMockChecker<ContractState> {
+        fn get_constant_thing(ref self: ContractState) -> felt252 {
+            13
+        }
+
+        fn get_stored_thing(ref self: ContractState) -> felt252 {
+            self.stored_thing.read()
+        }
+    }
+}

crates/forge/tests/data/contracts/mock_checker.cairo

@@ -0,0 +1,54 @@
+#[derive(Serde, Drop)]
+struct StructThing {
+    item_one: felt252,
+    item_two: felt252,
+}
+
+#[starknet::interface]
+trait IMockChecker<TContractState> {
+    fn get_thing(ref self: TContractState) -> felt252;
+    fn get_thing_wrapper(ref self: TContractState) -> felt252;
+    fn get_constant_thing(ref self: TContractState) -> felt252;
+    fn get_struct_thing(ref self: TContractState) -> StructThing;
+    fn get_arr_thing(ref self: TContractState) -> Array<StructThing>;
+}
+
+#[starknet::contract]
+mod MockChecker {
+    use super::IMockChecker;
+    use super::StructThing;
+    use array::ArrayTrait;
+
+    #[storage]
+    struct Storage {
+        stored_thing: felt252
+    }
+
+    #[constructor]
+    fn constructor(ref self: ContractState, arg1: felt252) {
+        self.stored_thing.write(arg1)
+    }
+
+    #[external(v0)]
+    impl IMockCheckerImpl of super::IMockChecker<ContractState> {
+        fn get_thing(ref self: ContractState) -> felt252 {
+            self.stored_thing.read()
+        }
+
+        fn get_thing_wrapper(ref self: ContractState) -> felt252 {
+            self.get_thing()
+        }
+
+        fn get_constant_thing(ref self: ContractState) -> felt252 {
+            13
+        }
+
+        fn get_struct_thing(ref self: ContractState) -> StructThing {
+            StructThing {item_one: 12, item_two: 21}
+        }
+
+        fn get_arr_thing(ref self: ContractState) -> Array<StructThing> {
+            array![StructThing {item_one: 12, item_two: 21}]
+        }
+    }
+}

crates/forge/tests/data/contracts/mock_checker_library_call.cairo

@@ -0,0 +1,28 @@
+use starknet::ClassHash;
+
+#[starknet::interface]
+trait IMockChecker<TContractState> {
+    fn get_constant_thing(ref self: TContractState) -> felt252;
+}
+
+#[starknet::interface]
+trait IMockCheckerLibCall<TContractState> {
+    fn get_constant_thing_with_lib_call(ref self: TContractState, class_hash: ClassHash) -> felt252;
+}
+
+#[starknet::contract]
+mod MockCheckerLibCall {
+    use super::{IMockCheckerDispatcherTrait, IMockCheckerLibraryDispatcher};
+    use starknet::ClassHash;
+
+    #[storage]
+    struct Storage {}
+
+    #[external(v0)]
+    impl IMockCheckerLibCall of super::IMockCheckerLibCall<ContractState> {
+        fn get_constant_thing_with_lib_call(ref self: ContractState, class_hash: ClassHash) -> felt252 {
+            let mock_checker = IMockCheckerLibraryDispatcher { class_hash };
+            mock_checker.get_constant_thing()
+        }
+    }
+}

crates/forge/tests/data/contracts/mock_checker_proxy.cairo

@@ -0,0 +1,49 @@
+use starknet::ContractAddress;
+
+#[starknet::interface]
+trait IMockChecker<TContractState> {
+    fn get_thing(ref self: TContractState) -> felt252;
+}
+
+
+#[starknet::interface]
+trait IMockCheckerProxy<TContractState> {
+    fn get_thing_from_contract(ref self: TContractState, address: ContractAddress) -> felt252;
+    fn get_thing_from_contract_and_emit_event(ref self: TContractState, address: ContractAddress) -> felt252;
+}
+
+#[starknet::contract]
+mod MockCheckerProxy {
+    use starknet::ContractAddress;
+    use super::IMockCheckerDispatcherTrait;
+    use super::IMockCheckerDispatcher;
+
+    #[storage]
+    struct Storage {}
+
+    #[event]
+    #[derive(Drop, starknet::Event)]
+    enum Event {
+        ThingEmitted: ThingEmitted
+    }
+
+    #[derive(Drop, starknet::Event)]
+    struct ThingEmitted {
+        thing: felt252
+    }
+
+    #[external(v0)]
+    impl IMockCheckerProxy of super::IMockCheckerProxy<ContractState> {
+        fn get_thing_from_contract(ref self: ContractState, address: ContractAddress) -> felt252 {
+            let dispatcher = IMockCheckerDispatcher { contract_address: address };
+            dispatcher.get_thing()
+        }
+
+        fn get_thing_from_contract_and_emit_event(ref self: ContractState, address: ContractAddress) -> felt252 {
+            let dispatcher = IMockCheckerDispatcher { contract_address: address };
+            let thing = dispatcher.get_thing();
+            self.emit(Event::ThingEmitted(ThingEmitted { thing }));
+            thing
+        }
+    }
+}