Do you think names for bool values should end with a question mark?

I think it would help to explain why you see it as an anti-pattern. I personally really like it for variables, not so much for fields because it can cause issues with serialization (even though thanks to LiveView/OTP I haven’t had to work on a project that has a web API in a quite a while).

Perhaps I’m reading too much into your use of “should” here but my answer is that there is no “should” about it, it’s a question of style on a per-project basis.

I guess I mean “do you consider this a language idiom”

It honestly does not matter, if your functions get so long that a ? suffix on variables inside them actually matters then you have much bigger problems to worry about, and you should address those first.

As for function suffixes, why not. It helps express intent a little bit.

Nope.

IMO it’s a nice pattern that the language allows. You go to other languages codebases and you can always notice patterns like is_active all the time.

For values I would say I use it half the time, however I always use this pattern for functions, really helps to distinct them between simple functions and bang functions.

In that case I still don’t like any of the poll options, lol. No, it’s not an idiom and no, it’s not an anti-pattern. There is certainly no harm in it beyond personal preference. I personally really like the extra clarity and avoiding is_, has_ etc. And I don’t have an example off the top off my head but there are times where it’s awkward to come up with the correct English prefix or the correct one reads strangely. If I think of one I’ll post back.

Trailing ? is certainly not just a pattern for functions. E.g. ecto uses changeset.valid?.

Oh ya, that is an example of keys using it that I like.

For those who responded with “yes,” I have a question for you: Would you name your boolean database columns with a trailing question mark as well? I’m just curious to know the extent to which you would keep this naming convention in your apps.

PS.: I’m thinking in terms of keeping consistency with Ecto schemas (you can always specify the column source, but the mismatch might not be desirable)

Absolutely not, DB booleans will always be is_this_or_that on my watch. I have zero desire fighting with edge cases. Sticking to good old alpha-numeric strings for these things.

Notably you can have your cake and eat it too if you want by naming the database column via the is_ pattern and the Ecto schema via ? by using the source option.