[Question] Improving enum error messages

Question

Hello!

I’d like to improve the default error messages for enums to include the allowed values as defined in an enum class instead the of default value is not a valid enumeration member message without having to override Configs.error_msg_templates[type_error.enum] on the base model.

Is there a good way to parse the enum values from the Enum class?

Example:

class AllowedAWSInstanceTypesEnum(str, Enum):
    t2_medium = "t2.medium"
    t2_micro = "t2.micro"

class AWSBase(BaseModel):
  instance_size: AllowedAWSInstanceTypesEnum

Example Json

{
    "instance_size": "m4.xlarge"
}

This should generate an error similar to

value m4.xlarge is not valid. Must be one of ["t2.medium", "t2.micro"]

Thank you for your help!

[rodrigocaus]

Hello.

In Pydantic 1.6.1 the message to Enum ValidationError is in general: value is not a valid enumeration member; permitted: .... I’d like to know, in most cases, what value led to that error (not only in Enum types). The ValidationError ends up overlapping the ValueError message that usually informs such value. Is there any form of adding this in the message template or context field?

Thank you!

[samuelcolvin]

having a fixed error value, like value is not a valid enumeration member allows you to use it as the key of a dictionary, do str comparison, etc.

This is what the type attribute of errors is for. I would advise against using the msg of errors in a lookup as they’re like to change.