attr.validate() is not recursive
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Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 25/100
Research direction
Start with the documented behavior of attrs.validate and set_run_validators, then run the supplied nested Inner/Outer reproduction. Resolve whether the issue calls for clearer documentation or a recursive validation option; done means the selected behavior is clearly specified and demonstrated by the example.
Written by the indexing model from the issue text.
Description
I am using attrs to manage the configuration of a database system. I was hoping to use set_run_validators to temporarily disable validation during a multi-step evolution of a large data structure composed of nested attr classes, and deferring the validators until all the evolutions are complete.
It surprised me to see that attrs.validate is not recursive -- it only invokes the validators of the top-level fields of a class, and won't invoke the attr validators on any attr instances on that field.
The wording in the docs is technically correct but a rewording may be helpful.
Also, would there be any reason not to add something like a recursive=True option?
The script below illustrates the behavior.
def log_validation(cls, _, _2):
print(f"in log_validation for {cls}")
@attr.s(frozen=True)
class Inner:
vi: int = attr.ib(validator=log_validation)
@attr.s(frozen=True)
class Outer:
vo: str = attr.ib(validator=log_validation)
i: Inner = attr.ib()
attr.set_run_validators(False)
x = Outer(vo=None, i=Inner(vi=123))
attr.set_run_validators(True)
attr.validate(x)
# output:
# in log_validation for Inner(vi=123)
My assumption is that it would validate the entire tree, much as we would get if we serialized and deserialized the instance:
cattr.structure(cattr.unstructure(x), Outer)
# output:
# in log_validation for Inner(vi=123)
# in log_validation for Outer(vo='None', i=Inner(vi=123))
I'm using attrs 19.3.0.
Thanks!
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