Attribute Macro migration_validator 

#[migration_validator]

A procedural macro that lets you set up the migration validator. Right now, you can validate only the migration context, but using the set_context_validator for the whole context validation, and set_context_parameter_validator for per-parameter validation. For more information, check out these functions’ doc comments.

Example usage:

#[migration_validator]
pub fn migration_validator(mv: &mut picodata_plugin::plugin::interface::MigrationValidator) {
    mv.set_context_validator(|ctx| {
        if ctx.len() >= 3 {
            Err("this context is too long, man".into())
        } else {
            Ok(())
        }
    });
    mv.set_context_parameter_validator(|k, v| match k.as_str() {
        "always_ok_parameter" => Ok(()),
        "always_bad_parameter" => Err("don't use this parameter, please".into()),
        "short_parameter" => {
            if v.len() > 15 {
                Err("this parameter can't be that long!".into())
            } else {
                Ok(())
            }
        }
        _ => Ok(()),
    });
}