Settings Checker for Extensions

[andkay]

As a follow on from ActivitySim PR 950, this pull request demonstrates a pattern for building a settings checker for extensions.

The key requirements are that users create a checker module in their extensions directory. This must be called settings_checker.py and contain a (dict) registry of settings called EXTENSION_SETTER_CHECKINGS. The general pattern established in core repository should be followed.

[jpn--]

@andkay please merge in latest changes from main to use uv for tests. I don't seem to have write access to your fork so I can't do it for you.

[andkay]

@jpn-- I've forked and rebased this branch to main.

[jpn--]

I looked over the code changes here. Conceptually, it looks good. It passes the tests now, which is good. But to really test it I tried writing another test that would intentionally break an extension settings file:

https://github.com/driftlesslabs/sandag-abm3-example/blob/37804001bc12096a0e75278829a7438a6eeaeaff/test/test_sandag_abm3.py#L181-L246

In short, we make a copy of the settings, break the av_ownership.yaml file, and run with the broken settings. It should raise a validation error before it gets to the av_ownership model. But it doesn't: https://github.com/driftlesslabs/sandag-abm3-example/actions/runs/17132819984/job/48601266109

Can we figure out why, and fix it?

[andkay]

@jpn-- that is odd.

AvOwnershipSettings inherits from LogitComponentSettings, which is explicit about the allowable values for LOGIT_TYPE. So this should be caught upon loading the model. I'll have a look.

[andkay]

@jpn-- Smoke testing the settings checker with a bad value against the LOGIT_TYPE key in the av_ownership.yaml yielded the expected error:

[00:26.24] ERROR:       Error checking settings for av_ownership using files av_ownership.yaml: 1 validation error for AVOwnershipSettings
LOGIT_TYPE
  Input should be 'MNL' or 'NL' [type=literal_error, input_value='NOT_A_LOGIT', input_type=str]

Reading through your test in more detail, I don' think the settings checker is invoked at all. It's not called on a per-step basis. Its done once for all models before an ActivitySim run. https://github.com/ActivitySim/activitysim/blob/e345f9774e14d0eac7fe01b2e22aeca28c2b821f/activitysim/cli/run.py#L388

This does make it hard to test - and there may well be better way to code it in.