Solana: solana-program-test fails to serialize account if optional field starts from “None” instead of “Some”

Solana Program Test: Serialization Issue with Optional Field

As a developer testing instructions on Solana, you’ve encountered an issue with program test serialization. Specifically, the solana-program-test tool fails to serialize account data when a field is set to None.

The problem lies in how the program-test library handles optional fields during serialization. In your specific case, it seems that setting a field to None instead of Some(value) causes the serialization failure.

Example Code

To demonstrate this issue, let’s create a simple example account struct:

struct MyAccount {

    name: String,

}


impl MyAccount {

    fn new(name: String) -> Self {

        MyAccount { name }

    }


    fn set_name(&mut self, name: String) {

        self.name = name;

    }

}

In this example, we define a MyAccount struct with an optional field name.

Test Code

To test the serialization issue, you can use the following code:

use solana_program_test::{run_test, account_key};

use solana_program_test::program_tests;


#[test]

fn my_account_serialization() {

    let mut accounts = vec![];

    let program_id = "your-program-id";

    let public_key = "public-key";


    // Create an optional field

    let name = Some("John Doe");


    // Initialize the account struct with a value for the name field (some value)

    let account = MyAccount::new(name);


    // Add the account to the accounts vector

    accounts.push(account);


    run_test(&program_id, &public_key, |_, ctx| {

        // Set the optional field to None instead of Some(value) and verify serialization failure

        program_tests::set_optional_field(ctx, program_id, "my_account", name, false).unwrap();


        // Verify that the serialization failed with code 3004 (code: 3004)

        assert!(ctx.read_data(&program_id, &public_key) == None);


        // Update the account to reflect changes in the serialized data

        accounts[0].set_name(name);

    });

}

Explanation

In this test, we create an optional field name and initialize it with a value. We then set the my_account variable to some value (which is Some("John Doe")), but instead of using that value, we use None. When running the program tests, the program_tests::set_optional_field function attempts to serialize the account data when the optional field is set to None, and it fails with code 3004. This error indicates a serialization issue.

Conclusion

The solana-program-test library has an issue that prevents setting an optional field to None from being serialized correctly, causing the specified error (code: 3004). To resolve this issue, you need to ensure that you’re using the correct value for the optional field when serializing account data. In your specific case, you can verify this by checking the serialization failure code and verifying that the correct value is being set for the optional field.

Recommendations

To fix this issue, I recommend adding a check for the None value in the program_tests::set_optional_field function before attempting to serialize the account data. You can do this by using the unwrap_or method or an alternative solution like using a default value if name is Some(()). Additionally, you may want to investigate why the serialization failure code is occurring and look for any related issues in other parts of your program.

I hope this helps clarify the issue! If you have any further questions or need additional guidance, feel free to ask.