Add attr.validators.in_()

[dieb]

Hello there!

I wrote this for one of my projects and I thought it could be useful to others too. This is a validator called in_(options) that allows you to check if the value is within the allowed values. In my particular case it was useful to test things like in_(POSSIBLE_CHOICES), in_(Animals), etc.

Example:

US_STATES = ['AB', 'AG', 'AK', ...]

@attr(slots=True)
class Location(object):
    city = attr.ib(validator=instance_of(str))
    state = attr.ib(validator=in_(US_STATES))

I was wondering if you had any thoughts and whether it would make sense to add it to attrs. If that's the case, I'd be more than happy to adjust the code with your suggestions.

Thanks!

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[codecov]

Codecov Report

Merging #181 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #181   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           9      9           
  Lines         579    589   +10     
  Branches      126    128    +2     
=====================================
+ Hits          579    589   +10

Impacted Files	Coverage Δ
src/attr/validators.py	100% <100%> (ø)	⬆️

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[hynek]

This seems like a good idea however the naming (and docstring) seems too restrictive given the implementation. Something like is_in(possible_values) seems more natural to me?

[dieb]

is_in sounds good. Given that other validators are single words (e.g. optional), what do you think about within?

[hynek]

@glyph try to talk me out of calling it in_() please. We have precedents in sqlchemistry. ;)

[glyph]

found_in?

[hynek]

Since we’re going for and_() in #186 and ppl are used to them from sqlalchemy, please go for in_().

[hynek]

(I cannot promise this will make it into 17.1 b/c I need to get it out ASAP but it’s possible. If you want to raise your chances, please double check CONTRIBUTING.rst; especially re: test docstrings.)

[dieb]

Just updated it to in_().

[hynek]

Thanks, I’ve made some small adjustments.

[dieb]

Thanks!

[dieb]

I just noticed I forgot to add in_() to __all__, I'll submit a PR later on.