[ES|QL] improve function validation

[drewdaemon]

Summary

Closes #180518

Part of #221230

This is a full rewrite of our function validation logic. The primary goal is to simplify our code, though the algorithm has also been simplified and some user-facing validation messages have been changed.

For reviewers

I know... it looks big 😞 But most of it is updating tests! ✨

The place to start is src/platform/packages/shared/kbn-esql-ast/src/definitions/utils/validation/function.ts. All the other changes stem from this rewrite.

I did come across test suites that weren't worth updating and I removed those. I've tried to leave comments where I felt that was the case. I did significantly extend our test coverage in the functions.test.ts file where most of our function tests should live.

I tried to be careful, but I wouldn't be surprised if there are some regressions. I have included a list of things I thought about during the refactor below... it would be a good place to start testing. I've noted the ones I didn't test at all yet.

Cases to consider

• optional params
• minParams
• function_named_arguments
• nulls
• implicit string casts
• inline_casts
• conflict fields
• unsupported fields
• dashboard params
• licensing
• in / not in

User facing changes

Checks removed

Several checks we used to do are gone now

• function-specific validation checks
  • full-text search function validation
  • warnings for log functions and division by zero
• making sure literals matched acceptedValues
• making sure fields weren't in arguments where they shouldn't be (constantOnly)

Messages changed

Some error messages have been changed as well.

Wrong argument types

Most significantly, we no longer attempt to give per-parameter feedback. Instead, we list all the available signatures of the function, leaving the users to do the diffing themselves. This removes confusing messages like

Argument of [+] must be [date], found value [1] type [integer]

for

from a_index | eval 1 + "2".

It also largely follows the behavior of the TypeScript interpreter, though TypeScript goes further and I'm sure we could too.

Optional param

Variable length params

Wrong arity

Validation ends if a child function generates errors

Screen.Recording.2025-08-01.at.2.04.54.PM.mov

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[stratoula]

ok everything looks fine except for the ts command bug. Let's fix it and I will do a final testing and approve! Thanx for addressing my feedback Drew!

[stratoula]

yeah this is still broken

[stratoula]

👍

[stratoula]

Last bug fixed! LGTM! Thanx for the effort Drew, I am very excited about this change!

(Btw at the end of our effort let's also check the issue with validation bugs, we might have fixed everything. In that case we can also close the issue. I am hoping that we will have less and less bugs and we can create individual issues for those)

[afharo]

I cannot find where this new method is used in this PR.

Are we planning to use it in a follow-up, or was this an oversight?

[drewdaemon]

Take a look at https://github.com/elastic/kibana/pull/230139/files#diff-f2bc682842bdad261b0deb8dbbcf37ee8c7b5f7624eb81c552d2ed6c09d3f1f3R79

[afharo]

Thank you! I don't know why I couldn't find it! All good on my end.

Still, I'd like to rely on @Bamieh for the final approval

[Bamieh]

Looks good to me :elasticheart:

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: a7c7545

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
onechat	438	440	+2
unifiedSearch	440	442	+2
total			+4

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
@kbn/esql-ast	517	516	-1
@kbn/i18n	27	30	+3
total			+2

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
esql	265.5KB	265.6KB	+26.0B
onechat	788.7KB	788.3KB	-441.0B
total			-415.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
kbnUiSharedDeps-srcJs	3.8MB	3.8MB	-3.3KB

Unknown metric groups

API count

id	before	after	diff
@kbn/esql-ast	638	636	-2
@kbn/i18n	38	41	+3
total			+1

References to deprecated APIs

id	before	after	diff
@kbn/esql-validation-autocomplete	20	19	-1

[Bamieh]

i18n addition of formatList LGTM