Parsing a UDT with a field not present in a struct results in a BadCqlType error

[merlleu]

Hello,

I've been using this driver for a few months in production but I have a little problem:
Some of our services need to read data from scylla but their cql schema is not up-to-date, so when a field is added to an UDT, any column containing this UDT would no longer be readable using this driver.

The cause behind this is this piece of code:

 if fields_iter.next().is_some() {
    return Err(FromCqlValError::BadCqlType);
}

That is why we're using our own version of scylla-macros, but I think it would be better letting the user choose if they want to allow this kind of behavior.

I think there could be two solutions:

1. The easiest would be just to duplicate this derive macro with a different name with the check disabled and a different name.

• Pros:
  • Easier
• Cons:
  • Duplicate Code
  • Less user-friendly

2. Add a #[scylla(non_exhaustive)] derive macro attribute at the struct level for FromUserType.

• Pros:
  • Easier to use
  • Cleaner code
• Cons:
  • A little bit harder to implement

What do you think of these two approaches ?
Do you think it would be worth adding them to this crate ?

[merlleu]

For those who have similar needs, you can use https://github.com/merlleu/scylla-macros-flex.

[wprzytula]

Ref: #962

[wprzytula]

The PR with new deserialization macros has been merged (#1024), but the new deserialization API they generate implementation for is not yet available in the driver. For tracking it, see #462.