fix(peewee): QueryAjaxModelLoader.get_one() raises DoesNotExist for a stale/absent pk

Summary

QueryAjaxModelLoader.get_one() in the peewee backend calls self.model.get(...), which raises peewee's DoesNotExist when no row matches. Its caller, AjaxSelectField._get_data, guards with if model is not None — expecting None, not an exception — so a form referencing a since-deleted (or otherwise unmatched) pk crashes instead of rendering with no selection.

This is the autocomplete/ajax-select twin of the view-layer bug fixed in #2939 / #2924. That PR fixed ModelView.get_one(); this one was left deliberately out of scope there.

Location

flask_admin/contrib/peewee/ajax.py:57   get_one -> self.model.get(**{self.pk: pk})
flask_admin/model/fields.py:195          AjaxSelectField._get_data -> model = self.loader.get_one(...)
flask_admin/model/fields.py:197          if model is not None:   # expects None on miss

Other backends

Both sibling loaders already return None on a miss, so peewee is the only one that lets the exception escape:

• sqla — flask_admin/contrib/sqla/ajax.py:90: session.get(self.model, pk) returns None
• mongoengine — flask_admin/contrib/mongoengine/ajax.py:69: self.model.objects.filter(pk=pk).first() returns None

Proposed fix

Catch the module-level peewee.DoesNotExist in QueryAjaxModelLoader.get_one and return None, mirroring the fix in #2939:

def get_one(self, pk: t.Any) -> t.Any:
    try:
        return self.model.get(**{self.pk: pk})
    except DoesNotExist:
        return None

(Module-level DoesNotExist rather than self.model.DoesNotExist — each model subclasses it, and the module-level name is what passes mypy --strict.)

Scope note

As with #2939, a malformed pk against an integer primary key raises no error on sqlite (DoesNotExist covers it) but would raise a driver-specific DataError on Postgres. That's left out here too rather than importing driver exceptions into the backend.