Standard Validation Exception

[BEllis]

Currently validators seem to raise a plethora of exceptions of different types and often don't prove much structured info regarding the error.

When a validation exception is raised, I'd expect to be able to determine,

• data class type
• data class instance
• attribute (and/or path?)
• validiator instance/function
• value
• reason for the validation failure or caused by exception

So I can provide useful and structured validation errors to clients of my library/application.

This is partially covered with cattrs and the ClassValidationError exception (and related classes) perhaps porting those exceptions from cattrs or attrs would be a good start?

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[BEllis]

I've just found valid8 that fulfills my requirement. Would be nice if this was a first-class thing but happy to close if contributors disagree.

[hynek]

This is specifically what cattrs is for. With attrs we try to provide you with a toolkit that builds classes as close to what you'd write yourself and leave automation on top of our hooks and metadata to other packages – most famously cattrs. Some older bits and pieces are arguably past that line, but we're trying to keep the two planes separate.