Ignore types unrelated to the configuration in the summarize plugin

[dominiklohmann]

This fixes a segfault in the summarize transform step when its configuration caused all fields to be dropped from the table.

📝 Checklist

• All user-facing changes have changelog entries.
• The changes are reflected on docs.tenzir.com/vast, if necessary.
• The PR description contains instructions for the reviewer, if necessary.

🎯 Review Instructions

Run this on our testbed and check that we encountered that same issue there. The unit test this adds crashes without the additional changes to the plugin and to libvast.

[lava]

I'm currently deploying this to the testbed; but I'm not sure about including the complete rewrite of record_type::transform() into the release. Would it make sense to split this and get just the bugfix in?

[dominiklohmann]

Would it make sense to split this and get just the bugfix in?

This actually fixed another bug for record types like this:

type foo = record {
  a: record {
    b: record {
      c: count,
    },
  },
  d: count,
}

Where before this change when removing c we returned the invalid type

type foo = record {
  a: record {
  },
  d: count,
}

rather than the correct:

type foo = record {
  d: count,
}

So no, I think we actually need to get that fix in as well. Users were theoretically able to trigger it with carefully crafted data.

[lava]

Tbh, I didn't 100% read through the changed logic in record_type::transform, but approving anyways since unit test coverage seems good and it's definitely fixing the segfault that used to appear in the testbed.

EDIT: The second bugfix still needs a changelog entry, though.

[dominiklohmann]

The second bugfix still needs a changelog entry, though.

Good point. I've added a second one.

Thanks for testing on the testbed @lava.