Errors for custom keywords / Sequence of initialization

[tjwoon]

Hello,

First of all, thank you for this library, and also for the main ajv library! :) I would just like to post this in order to save other people a few hours.

I discovered yesterday that it is important to add your keywords to your ajv instance before adding this ajv-errors plugin. Otherwise, customized error messages for your custom keywords will not appear, as your validators have not run by the time this plugin goes looking for custom error messages.

Example - if you init this plugin before adding your keywords:

const ajv = require('ajv')
const instance = new ajv({
  allErrors: true,
  jsonPointers: true
})

require('ajv-errors')(instance)

instance.addKeyword('testError', {
   validate: () => false
})

const validator = instance.compile({
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://workflow.rlscplatform.net/PPB_ASSAY",
  "type": "object",
  "properties": {
    "test": {
      "type": "string",
      "testError": true,
      "errorMessage": {
        "testError": "This is my custom error message"
      }
    }
  }
})

validator({
  test: "test"
})

console.log(validator.errors)

Outputs this:

[ { keyword: 'testError',
    dataPath: '/test',
    schemaPath: '#/properties/test/testError',
    params: { keyword: 'testError' },
    message: 'should pass "testError" keyword validation' } ]

But if you just put ajv-errors after your addKeyword:

instance.addKeyword('testError', {
   validate: () => false
})

require('ajv-errors')(instance)

The output becomes:

[ { keyword: 'errorMessage',
    dataPath: '/test',
    schemaPath: '#/properties/test/errorMessage',
    params: { errors: [Array] },
    message: 'This is my custom error message' } ]

Regards,
TJ

[epoberezkin]

Worth adding to docs