ActiveRecord: Always use NestedError in association validation

[c960657]

Summary

When an association record about to be auto-saved fails validation, the validation error is wrapped in a NestedError, but only if the association is defined with autosave: true (see ActiveRecord::AutosaveAssociation#association_valid?). Otherwise just a plain error is created without additional context. So if you are interested in the detailed NestedErrors, you have to enable autosave: true – validate: true is not enough.

I don't see any good reason for this difference. The logic was originally added in 5cda000bf0f6d85d1a1efedf9fa4d0b6eaf988a1 but without any explanation. A NestedError with full context seems useful in any case.

Steps to reproduce

Test case based on bug report template: https://gist.github.com/c960657/3d4667bfd9709c86bfb4c732d718d6e6

Other Information

If one prefers just a single validation error, the validates_association validator still just creates one error for any number of invalidation errors on associated objects, possible with a custom message. If a message is supplied, it doesn't seem useful to create a NestedError for each invalidation error, because they would all have the same message.

One might consider modifying Errors#messages_for, Errors#added? etc. to do a prefix search, i.e. so that Errors#messages_for("foo") would match errors with attribute foo as well as foo.bar and foo[1].bar. This would provide the best of both worlds for the two different ways of handling errors .

[rails-bot[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[febeling]

This looks like a reasonable PR to me that deserves consideration. I can't think of a reason why the result of validation should depend on whether :autosave behavior has been declared for an association.

Superficially one might argue, plain and :autosave associations behave differently, or even inconsistently wrt persisting. But validation is a concern unrelated to the pragmatics of persisting, and not a consequence of this same tradeoff.

I think it makes sense and is probably closer to user expectations if :autosave is transparent with regard to validation.

[c960657]

I have created a test case that shows this bug/issue: https://gist.github.com/c960657/3d4667bfd9709c86bfb4c732d718d6e6