joi

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Context

• node version: 16.4.0
• module version: 17.5.0
• environment (e.g. node, browser, native): node
• used with (e.g. hapi application, another framework, standalone, ...): nestjs
• any other relevant information:

How can we help?

Is there a better way to set custom error messages for each validation? Similar to Yup, is it possible to add custom messages in the validation function itself .string().required('Custom required message'). I can see the point to add all custom messages for the schema in a separate property where all messages can be accessed, but having this feature could be easy for understanding validations and their error messages.

// Current implementation

const schema = Joi.object({
    username: Joi.string()
        .min(3)
        .max(30)
        .required()
        .messages({
          "string.min": "Must have at least 3 characters",
          "string.min": "Must have max 30 characters",
          "string.required": "This is required"
    })
};

// Is something like this possible?

const schema = Joi.object({
    username: Joi.string()
        .min(3, (len) => `Must have at least ${len} characters.`))
        .max(30, (len) => `Must have max ${len} characters.`))
        .required("This is required")
};

The second option looks more readable and clear to me. Is there an option to achieve this?

looks like you have a typo here "string.min": "Must have max 30 characters", :

    username: Joi.string()
        .min(3)
        .max(30)
        .required()
        .messages({
          "string.min": "Must have at least 3 characters",
          "string.max": "Must have max 30 characters",
          "string.required": "This is required"
    })
};