UserFlow budgets for timespan and snapshot

[BioPhoton]

Feature request summary

What is the motivation or use case for changing this?
As a performance engineer I want to be able to assert results from user flow reports.
At the moment this is only possible for "Navigation". From my current information it should be possible to enable a set of metrics for "Timespan" and "Snapshot"

How is this beneficial to Lighthouse?
It will bring more benefit to runtime analysis

[adamraine]

I think budgets can be useful for timespan metrics however it's important to make sure that the metrics are normalized so the length of the timespan does not influence the score. For instance, CLS is normalized but TBT, request counts, transfer sizes, etc. are not normalized.

That being said, budgets are an opt-in feature so I think we can at least enable budgets in timespan mode, maybe with a warning about budgets that are impacted by timespan length. In the future it might be useful to normalize the request counts / transfer sizes as well as the performance metrics.

I don't see how budgets would be useful in snapshot mode. There are no performance metrics available in snapshot mode and we don't track network requests. Is there a specific use case you had in mind @BioPhoton?

[BioPhoton]

Hi @adamraine thx for the helpful answer!

Budgets opt-in in timespans would be amazing. 😍

In a Snapshot I could see e.g. number of DOM nodes as metric.