Support __post_init__ for Struct types - #470
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A quick example: >>> import msgspec
>>> class Interval(msgspec.Struct):
... low: float
... high: float
...
... def __post_init__(self):
... if self.low > self.high:
... raise ValueError("`low` may not be greater than `high`")
>>> Interval(1, 2) # valid interval
Interval(low=1, high=2)
>>> Interval(2, 1) # invalid interval
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 6, in __post_init__
ValueError: `low` may not be greater than `high`
>>> msgspec.json.decode(b'{"low": 2, "high": 1}', type=Interval) # invalid interval from JSON
Traceback (most recent call last):
File "<stdin>", line 6, in __post_init__
ValueError: `low` may not be greater than `high`
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
msgspec.ValidationError: `low` may not be greater than `high` |
This adds support for an optional `__post_init__` hook method on `msgspec.Struct` types. If defined, this method is called at the end of the generated `__init__` method. It can be used to customize the builtin `__init__` as needed, as well as provides a spot to do some additional validation. As with `dec_hook` errors, any `ValueError` or `TypeError` raised in `__post_init__` will be wrapped in a `ValidationError` when decoding.
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Amazing, thank you! |
This was referenced Jul 12, 2023
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This adds support for an optional
__post_init__hook method onmsgspec.Structtypes. If defined, this method is called at the end of the generated__init__method. It can be used to customize the builtin__init__as needed, as well as provides a spot to do some additional validation.As with
dec_hookerrors, anyValueErrororTypeErrorraised in__post_init__will be wrapped in aValidationErrorwhen decoding. In the long run I plan to add support for more granular (and obviously named) custom validator support, but for now doing some validation in__post_init__is a fine and simple solution. There are other use cases for__post_init__besides validation, so we'd want to add this ability either way.Fixes #442.