Wrap dec_hook errors in ValidationError - #460
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This modifies decoding of custom types to wrap errors raised by a `dec_hook` with `ValidationError`. Only `TypeError` or `ValueError` (and subclasses) exceptions are wrapped, all other exceptions are raised directly. If an exception is wrapped with a `ValidationError`, the original exception is set as the `__cause__` (and `__context__`). This means the original exception will still show up in tracebacks, and is available for introspection if needed. This also changes the recommendation for raising `TypeError` on unsupported types in `dec_hook`/`enc_hook` to raising a `NotImplementedError`. No previous functionality was based on this recommendation, so this isn't a breaking change in anyway, just a change in recommendation of how best to use `msgspec`.
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Demo of behavior In [1]: import msgspec, pydantic
In [2]: class Point(pydantic.BaseModel):
...: x: int
...: y: int
...:
In [3]: class Test(msgspec.Struct):
...: point: Point
...:
In [4]: def dec_hook(typ, val):
...: if issubclass(typ, pydantic.BaseModel):
...: return typ.model_validate(val)
...: raise NotImplementedError
...:
In [5]: dec = msgspec.json.Decoder(type=Test, dec_hook=dec_hook)
In [6]: dec.decode(b'{"point": {"x": 1, "y": 2}}') # works
Out[6]: Test(point=Point(x=1, y=2))
In [7]: try:
...: dec.decode(b'{"point": {"x": "a", "y": "b"}}')
...: except msgspec.ValidationError as exc:
...: error = exc # work around auto-del of exc
...:
In [8]: error
Out[8]: msgspec.ValidationError("2 validation errors for Point\nx\n Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='a', input_type=str]\n For further information visit https://errors.pydantic.dev/0.39.0/v/int_parsing\ny\n Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='b', input_type=str]\n For further information visit https://errors.pydantic.dev/0.39.0/v/int_parsing - at `$.point`")
In [9]: error.__cause__
Out[9]:
2 validation errors for Point
x
Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='a', input_type=str]
For further information visit https://errors.pydantic.dev/0.39.0/v/int_parsing
y
Input should be a valid integer, unable to parse string as an integer [type=int_parsing, input_value='b', input_type=str]
For further information visit https://errors.pydantic.dev/0.39.0/v/int_parsingIf the |
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This modifies decoding of custom types to wrap errors raised by a
dec_hookwithValidationError. OnlyTypeErrororValueError(and subclasses) exceptions are wrapped, all other exceptions are raised directly.If an exception is wrapped with a
ValidationError, the original exception is set as the__cause__(and__context__). This means the original exception will still show up in tracebacks, and is available for introspection if needed.This also changes the recommendation for raising
TypeErroron unsupported types indec_hook/enc_hookto raising aNotImplementedError. No previous functionality was based on this recommendation, so this isn't a breaking change in anyway, just a change in recommendation of how best to usemsgspec.Fixes #456.