Rust ink, cross contract call returns ConctractTrapped error

Question

As the title suggests, I'm trying to call a function on already deployed contract with a very simple String return function.

Deployed contract1 function:

#[ink(message)]
#[ink(selector = 0xDEADBEEF)]
pub fn test(&self) -> String {
            return "TEST".to_string()
}

The following code snippet is the contract2 function, to return the value from contract1:

        #[ink(message)]
        pub fn test1(&self,token_contract: AccountId) -> String {
            
            let my_return_value: String =  ink_env::call::build_call::<ink_env::DefaultEnvironment>()
            .callee(token_contract)
            .gas_limit(50000)
            .transferred_value(0)
            .exec_input(
                ink_env::call::ExecutionInput::new(ink_env::call::Selector::new([0xDE, 0xAD, 0xBE, 0xEF]))
                

            )
            .returns::<ink_env::call::utils::ReturnType<String>>()
            .fire()
            .unwrap();
            my_return_value
        }

Answer 1

This means that your sub contract, the one that is holding "pub fn test" has panicked.

The way to debug this is to start your substrate node with:

RUST_LOG=runtime=debug

This way you'll get the exact panic error in the substrate logs.

If you wish to handle the error in your caller contract build_call has map_err function. You can check their multisig example for code reference: https://github.com/paritytech/ink/blob/master/examples/multisig/lib.rs