Custom data validation producing AJV-style errors

[ilyutov]

I want to return detailed error messages from my custom validation rules.
If a property is marked @Required() AJV produces a nice detailed response like this:

{
  "errors": [
        {
            "instancePath": "",
            "schemaPath": "#/required",
            "keyword": "required",
            "params": {
                "missingProperty": "email"
            },
            "message": "must have required property 'email'",
            "modelName": "MyModel",
            "dataPath": ".email",
            "requestPath": "body"
        }
    ]
}

Now I want to validate that the email is unique. Since I need to call the database I can't use AJV and let it build the error object (as far as I understand).
I created a new decorator like @IsUnique((email: string) => inject(UserService).isUniqueEmail(email)) that uses AfterDeserialize and throws a ValidationError if the callback returns false. That works but I'm not getting the nice detailed error unless I build it manually and pass to the ValidationError constructor.
Is there something I can import that would build the error details for me? Or am I doing it completely wrong?

[Romakita]

Hello @ilyutov

You can use this code example:

import {nameOf} from "@tsed/core";
import {JsonParameterStore} from "@tsed/schema";

import {ValidationError} from "./ValidationError.js";

export class RequiredValidationError extends ValidationError {
  public name: string = "REQUIRED_VALIDATION_ERROR";

  static from(metadata: JsonParameterStore) {
    const name = nameOf(metadata.paramType);
    const expression = metadata.expression;
    const type = name.toLowerCase().replace(/parse|params|filter/gi, "");
    const message = `It should have required parameter '${expression}'`;

    const errors = [
      {
        dataPath: "",
        keyword: "required",
        message,
        modelName: type,
        params: {
          missingProperty: expression
        },
        schemaPath: "#/required"
      }
    ];

    return new RequiredValidationError(message, errors);
  }
}

Note: Ajv Support asynchronous validation. Look this section: https://ajv.js.org/guide/async-validation.html, Ts.ED await validate result, so it could be possible to explore this way!

See you ;)

[ilyutov]

Thanks!