Fix error while calling nonexistent entry point selector (#2606)

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

Closes #1812

The `Err` message chosen to be thrown by `safe-dispatcher` is intended
to replicate `cairo-test` behavior. These felts are taken explicitly
from
[`CairoHintProcessor`](https://github.com/starkware-libs/cairo/blob/2ad7718591a8d2896fec2b435c509ee5a3da9fad/crates/cairo-lang-runner/src/casm_run/mod.rs#L1055-L1057)

## Introduced changes

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

- Add proper regex to catch falling error message

## 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`

CHANGELOG.md

@@ -15,6 +15,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Forge
 
+#### Fixed
+
+- Calling contract functions via safe-dispatcher now returns an `Err` when attempting to invoke a non-existent entry point, instead of causing a panic.
+
 #### Changed
 
 - You can now pass arguments to `cairo-profiler` and `cairo-coverage`. Everything after `--` will be passed to underlying binary. E.g.

crates/cheatnet/src/runtime_extensions/call_to_blockifier_runtime_extension/panic_data.rs

@@ -10,6 +10,13 @@ pub fn try_extract_panic_data(err: &str) -> Option<Vec<Felt252>> {
     let re_string = Regex::new(r#"(?s)Execution failed\. Failure reason: "(.*?)"\."#)
         .expect("Could not create string panic_data matching regex");
 
+    // CairoVM returns felts padded to 64 characters after 0x, unlike the spec's 63.
+    // This regex (0x[a-fA-F0-9]{0,64}) handles the padded form and is different from the spec.
+    let re_entry_point = Regex::new(
+        r"Entry point EntryPointSelector\((0x[a-fA-F0-9]{0,64})\) not found in contract\.",
+    )
+    .expect("Could not create entry point panic_data matching regex");
+
     if let Some(captures) = re_felt_array.captures(err) {
         if let Some(panic_data_match) = captures.get(1) {
             let panic_data_felts: Vec<Felt252> = panic_data_match
@@ -31,6 +38,16 @@ pub fn try_extract_panic_data(err: &str) -> Option<Vec<Felt252>> {
         }
     }
 
+    // These felts were chosen from `CairoHintProcessor` in order to be consistent with `cairo-test`:
+    // https://github.com/starkware-libs/cairo/blob/2ad7718591a8d2896fec2b435c509ee5a3da9fad/crates/cairo-lang-runner/src/casm_run/mod.rs#L1055-L1057
+    if let Some(_captures) = re_entry_point.captures(err) {
+        let panic_data_felts = vec![
+            Felt252::from_bytes_be_slice("ENTRYPOINT_NOT_FOUND".as_bytes()),
+            Felt252::from_bytes_be_slice("ENTRYPOINT_FAILED".as_bytes()),
+        ];
+        return Some(panic_data_felts);
+    }
+
     None
 }
 

crates/forge/tests/data/nonexistent_selector/Scarb.toml

@@ -0,0 +1,18 @@
+[package]
+name = "nonexistent_selector"
+version = "0.1.0"
+edition = "2023_11"
+
+# See more keys and their definitions at https://docs.swmansion.com/scarb/docs/reference/manifest.html
+
+[dependencies]
+starknet = "2.4.0"
+
+[dev-dependencies]
+snforge_std = { path = "../../../../../snforge_std" }
+
+[[target.starknet-contract]]
+sierra = true
+
+[scripts]
+test = "snforge test"

crates/forge/tests/data/nonexistent_selector/src/lib.cairo

@@ -0,0 +1,24 @@
+#[starknet::interface]
+pub trait IMyContract<TState> {
+    fn my_function(self: @TState);
+}
+
+#[starknet::contract]
+pub mod MyContract {
+    use starknet::SyscallResultTrait;
+    use starknet::syscalls::call_contract_syscall;
+
+    #[storage]
+    pub struct Storage {}
+
+    #[abi(embed_v0)]
+    impl MyContract of super::IMyContract<ContractState> {
+        fn my_function(self: @ContractState) {
+            let this = starknet::get_contract_address();
+            let selector = selector!("nonexistent");
+            let calldata = array![].span();
+
+            call_contract_syscall(this, selector, calldata).unwrap_syscall();
+        }
+    }
+}

crates/forge/tests/data/nonexistent_selector/tests/test_contract.cairo

@@ -0,0 +1,23 @@
+use starknet::ContractAddress;
+
+use snforge_std::{declare, ContractClassTrait, DeclareResultTrait};
+
+use nonexistent_selector::IMyContractSafeDispatcher;
+use nonexistent_selector::IMyContractSafeDispatcherTrait;
+
+#[test]
+#[feature("safe_dispatcher")]
+fn test_unwrapped_call_contract_syscall() {
+    let contract = declare("MyContract").unwrap().contract_class();
+    let (contract_address, _) = contract.deploy(@array![]).unwrap();
+
+    let safe_dispatcher = IMyContractSafeDispatcher { contract_address };
+    let res = safe_dispatcher.my_function();
+    match res {
+        Result::Ok(_) => panic!("Expected an error"),
+        Result::Err(err_data) => {
+            assert(*err_data.at(0) == 'ENTRYPOINT_NOT_FOUND', *err_data.at(0));
+            assert(*err_data.at(1) == 'ENTRYPOINT_FAILED', *err_data.at(1));
+        },
+    };
+}

crates/forge/tests/e2e/running.rs

@@ -1100,3 +1100,21 @@ fn catch_runtime_errors() {
         ),
     );
 }
+
+#[test]
+fn call_nonexistent_selector() {
+    let temp = setup_package("nonexistent_selector");
+
+    let output = test_runner(&temp).assert().code(0);
+
+    assert_stdout_contains(
+        output,
+        indoc! {r"
+        Collected 1 test(s) from nonexistent_selector package
+        Running 1 test(s) from tests/
+        [PASS] nonexistent_selector_integrationtest::test_contract::test_unwrapped_call_contract_syscall (gas: ~103)
+        Running 0 test(s) from src/
+        Tests: 1 passed, 0 failed, 0 skipped, 0 ignored, 0 filtered out
+        "},
+    );
+}

crates/forge/tests/integration/dispatchers.rs

@@ -782,7 +782,7 @@ fn nonexistent_libcall_function() {
     assert_case_output_contains(
         &result,
         "nonexistent_libcall_function",
-        "Entry point EntryPointSelector(0x1fdb214e1495025fa4baf660d34f03c0d8b5037cf10311d2a3202a806aa9485) not found in contract"
+        "(0x454e545259504f494e545f4e4f545f464f554e44 ('ENTRYPOINT_NOT_FOUND'), 0x454e545259504f494e545f4641494c4544 ('ENTRYPOINT_FAILED'))"
     );
 }
 

crates/forge/tests/integration/test_state.rs

@@ -397,8 +397,8 @@ fn cant_call_test_contract() {
     let result = run_test_case(&test);
 
     assert_failed(&result);
-    assert_case_output_contains(&result, "cant_call_test_contract", "Entry point");
-    assert_case_output_contains(&result, "cant_call_test_contract", "not found in contract");
+    assert_case_output_contains(&result, "cant_call_test_contract", "ENTRYPOINT_NOT_FOUND");
+    assert_case_output_contains(&result, "cant_call_test_contract", "ENTRYPOINT_FAILED");
 }
 
 #[test]