feat(experiments): improve "no results" diagnostics

[jurajmajerik]

Problem

When solving this ticket, I've noticed that the "no results" diagnostics weren't working entirely correctly. This user did have the required event, just was missing the feature flag information on them. Yet, the diagnostics popup showed "Metric events not received".

I'm a bit unsure why this used to work in the old code. We did have this filter condition, but the query must've returned counts for all events too (to be able to confirm their existence in the validation method). In the new HogQL implementation, this is not the case, and only the events having the feature flag variants get returned.

Changes

Rather than fixing this, I'm proposing the following change:

• Simplify the diagnostics list, where we only let the user know when there are no events with required variants, as opposed to no events whatsoever.
• In the popup, add links to the Activity tab where the user can:
  • Verify that there are indeed no said events
  • Play with the filter to see if they're able to find any events at all

This is simplifies the checklist and lets the user verify and debug missing events in a more interactive way.

Trends

Before	After

Funnels

Before	After

• Clicking the link takes you to the activity tab where you can verify missing events:

How did you test this code?

Manually tested that the Activity query is set up correctly for:

• Trends, default exposure
• Trends custom exposure
• Funnels

[github-actions]

Size Change: 0 B

Total Size: 1.16 MB

ℹ️ View Unchanged

Filename	Size
frontend/dist/toolbar.js	1.16 MB

_{compressed-size-action}

[andehen]

Great to have this checklist improved!

Tested an experiment with only control events and it looks like this then

Here is the error message from the query API in that example:

`[ErrorDetail(string='{"no-exposures": false, "no-control-variant": false, "no-test-variant": true, "no-flag-info": false}', code='invalid')]`

Also, I find the "double negation" in the messages a little confusing actually. I think it would be clearer to have the success text with a red cross, so without the not. Not a strong opinion, but my personal preference.

[jurajmajerik]

@andehen ah it's a cached response! Good catch, fixed here: d0868c9 (#27772)

I think it would be clearer to have the success text with a red cross, so without the not.

We had this discussion a few months ago. For some reason, either option seems slightly confusing to some people. This is what we went with at the end 😶