ValidatidationError .toString()

[sanex3339]

It would be nice to define .toString() method for ValidationError which will return ValidationError.constraints messages as string.

if (errors.length) {
    for (let error of errors) {
         console.log(error.toString());
    }
}

Format for message something like (formatted string with new lines):

PROPERTY_NAME errors
    length: "PROPERTY_NAME must be shorter than 10 characters"
    contains: "PROPERTY_NAME must contain a hello string"

or

PROPERTY_NAME errors
    - PROPERTY_NAME must be shorter than 10 characters
    - PROPERTY_NAME must contain a hello string

[sanex3339]

Use case:

Right now i do something like

if (errors.length) {
    throw new ReferenceError(`Validation failed. errors:\n${Options.formatErrors(errors)}`);
}

    private static formatErrors(validationErrors: ValidationError[]): string {
        let errorsArray: string[] = [];

        for (let error of validationErrors) {
            let errorsString: string = `\`${error.property}\` errors:\n`;

            for (let constraint in error.constraints) {
                if (!error.constraints.hasOwnProperty(constraint)) {
                    continue;
                }

                errorsString += `    - ${error.constraints[constraint]}\n`;
            }

            errorsArray.push(errorsString);
        }

        return errorsArray.join('\n');
    }

It will cool if i could simplify formatErrors method or completely remove them.

With simplification it will looks like:

 private static formatErrors(validationErrors: ValidationError[]): string {
        let errorsArray: string[] = [];

        for (let error of validationErrors) {
             errorsString += error.toString();
        }

        return errorsArray.join('\n');
    }

With completely removing of this method it is need to define .toString method for ValidationErrors[] array. Or replace ValidationErrors[] array on wrapper class with various methods like getErrorsAsString(optionalFormatterCallback), getErrorsCount, hasErrors. But this is breaking change.

[pleerock]

Custom arrays in javascript is more problem then solution, so its better to avoid it. Also regarding to ValidationErrors I would like to keep it as plain object - without additional methods defined. Regarding to your proposal, also I don't think such formatting generally needed. Who really needs this specifically defined string and for what purposes? - don't think lot of people need it

[sanex3339]

for example with Joi following code

        Joi.validate(obfuscatorOptions, this.schema, (error: Joi.ValidationError) => {
            if (error) {
                throw error;
            }
        });

output:

ValidationError: child "sourceMapMode" fails because ["sourceMapMode" must be one of [inline, separate]]

If we use validator in public packages, we expect that error messages will easy understandable by other people. Of course we can create custom formatter, but i think there must be a way to get that kind of messages from validator.

[MichalLytek]

It's a good task for learning functional programming - concate all with map to receive array of error string in format:

property 'x' must be shorter than 10 characters
property 'x.y.z' must contain a hello string

For humans it looks nice as Rest API response but the original error is better for mapping response to frontend's form inputs.

[pleerock]

for form inputs there is a "message" inside validation error object

[NoNameProvided]

Which one would be the preferred way?

The RootClass has failed the following constraints:
  - title (property) 
    - isString: {alias} must be a string 
	  - minLength: {alias} must be longer than or equal to 15 characters 
  - nestedObj (class)
    - name (property)
      - isString: {alias} must be a string
    - url (property)
      - isUrl: {alias} must be an URL address
    - insideNested (class)
      - name (property)
        - isString: {alias} must be a string
      - url (property)
        - isUrl: {alias} must be an URL address

vs

The RootClass has failed the following constraints:
	- property 'title' failed the 'minLength' constraint': title must be longer than or equal to 15 characters
	- property 'title' failed the 'isString' constraint': title must be a string
	- property 'nestedObj.name' failed the 'isString' constraint': name must be a string
	- property 'nestedObj.url' failed the 'isUrl' constraint': url must be an URL address
	- property 'nestedObj.insideNested.name' failed the 'isString' constraint': name must be a string
	- property 'nestedObj.insideNested.url' failed the 'isUrl' constraint': url must be an URL address
	- property 'nestedArr.0.name' failed the 'isString' constraint': name must be a string
	- property 'nestedArr.0.url' failed the 'isUrl' constraint': url must be an URL address
	- property 'nestedArr.1.name' failed the 'isString' constraint': name must be a string
	- property 'nestedArr.1.url' failed the 'isUrl' constraint': url must be an URL address

[sanex3339]

For me - second one

[NoNameProvided]

Added and released in 0.8.2.

You can simply call validationError.toString() from now. You can also pretty print it. (It just makes the property names bold for better readability.)

The format is slightly modified:

An instance of RootClass has failed the validation:
 - property title has failed the following constraints: minLength, isString 
An instance of RootClass has failed the validation:
 - property nestedObj.name has failed the following constraints: isString 
 - property nestedObj.url has failed the following constraints: isUrl 
 - property nestedObj.insideNested.name has failed the following constraints: isString 
 - property nestedObj.insideNested.url has failed the following constraints: isUrl 
An instance of RootClass has failed the validation:
 - property nestedArr[0].name has failed the following constraints: isString 
 - property nestedArr[0].url has failed the following constraints: isUrl 
 - property nestedArr[1].name has failed the following constraints: isString 
 - property nestedArr[1].url has failed the following constraints: isUrl 

(We have 3 item here because it uses the current error format, what returns an array. This will be reworked too, and eventually will return one error for the object.)

[sanex3339]

Wow, amazing!

[sanex3339]

In my tests it gives me [object Object] when i called validationError.toString()

Also in runtime it gives me an error when i used error.toString():

TypeError: Cannot read property 'constructor' of undefined
 return `An instance of ${boldStart}${this.target.constructor.name}${boldEnd} has failed the validation:\n` +
                                                             ^