Convenience decorators for promoting functions to attrs-compatible validators about attrs HOT 4 OPEN

First, thanks for an amazing project! Words can't express how much attrs has changed my programming career for the better.

Thank you! ❤️

I have found that I often write some validation function which has to check something about some value. In most cases, the inbuilt validators are perfect, in some I still have to write something custom and that is where the question begins.

Oof man, this is a topic that's almost as old as attrs: #146

Giving up on my hopes and dreams of my youth, I guess we could replicate here something we've done to __attrs_pre_init__ recently: look at the number of arguments and wrap the validator if it has exactly one.

However, skimming your example you seem to have a much bigger need for customization?

from attrs.

Oof man, this is a topic that's almost as old as attrs: #146

Ah I see. I had a look through that but have to admit I didn't read far enough to see the exact parallels. You've thought about it much more than me, so happy to close this and let you work it out elsewhere!

However, skimming your example you seem to have a much bigger need for customization?

Not necessarily. If there was a built in way to do this in atttrs, I'd probably just use that. Because I wrote it myself, I added some extra info so I got slightly more verbose error messages, but ultimately it just boils down to what you discussed above, except in reverse I guess. I.e. rather than attrs doing the wrapping automatically, it would just provide a utility so users could explicitly 'upcast' their own functions if they wanted. That would mean you don't have to modify the attrs API as it stands, but could provide a convenient way for people to work around this problem if they want (rather than rolling their own solution and getting it wrong multiple times, like I did :)).

from attrs.

Oof man, this is a topic that's almost as old as attrs: #146
Ah I see. I had a look through that but have to admit I didn't read far enough to see the exact parallels. You've thought about it much more than me, so happy to close this and let you work it out elsewhere!

That's not what I meant at all – as you can see I've been thinking about it for 7 years and never came up with anything good. Given PEP 712 (converters for dataclass transforms) and #1267 – I don't think the unification will ever happen.

However, skimming your example you seem to have a much bigger need for customization?
Not necessarily. If there was a built in way to do this in atttrs, I'd probably just use that. Because I wrote it myself, I added some extra info so I got slightly more verbose error messages, but ultimately it just boils down to what you discussed above, except in reverse I guess. I.e. rather than attrs doing the wrapping automatically, it would just provide a utility so users could explicitly 'upcast' their own functions if they wanted. That would mean you don't have to modify the attrs API as it stands, but could provide a convenient way for people to work around this problem if they want (rather than rolling their own solution and getting it wrong multiple times, like I did :)).

I think this could be made to fit the approach in #1267 by introducing a Validator class?

from attrs.

I think this could be made to fit the approach in #1267 by introducing a Validator class?

Yep, if there were a Validator class that had the same idea as the Converter in #1267 I would just use that!

from attrs.