Proposed commit message

This brings error-handling improvements.

• better error localisation in error snippets
• fixed handling of errors containing Go fmt verb syntax
• fix type signature of flatten extension
• recover internal panics to informative errors

If elastic/mito#71 is merged before this PR closes, I think it would be worth adding that into this change and bumping to v1.15.0. Now included in this change.

Note that runtime error handling is still not perfect. I will come back to this later. I've looked into this and what I was thinking was happening is happening; the _+_ call is returning an error type and there is no get overload for an error. It looks like the CEL runtime is not decorating/throwing when the _+_ call returns the error, so the next call is what gives error location annotation. There is not anything we can do about this at this level, and the error quality is reasonable. I may take another look at the runtime later.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

Related issues

Use cases

Screenshots

Logs