schema-utils

What is schema-utils?

The schema-utils package is a utility library for validating options against a JSON Schema. It is commonly used in the context of webpack loaders and plugins to validate configuration objects. It provides functions to validate options, throw useful errors, and ensure that the configuration adheres to a specified schema.

What are schema-utils's main functionalities?

Validation of options

This feature allows users to validate an options object against a predefined JSON Schema. The 'validate' function takes a schema, options, and a configuration object that includes the name of the plugin or loader using the validation.

const { validate } = require('schema-utils');
const schema = {
  type: 'object',
  properties: {
    name: {
      type: 'string'
    }
  },
  required: ['name']
};
const options = { name: 'Example' };
validate(schema, options, { name: 'MyPlugin' });

Custom error messages

This feature allows users to provide custom error messages in the schema that will be displayed when validation fails. The 'validate' function will throw an error with these messages if the options do not match the schema.

const { validate } = require('schema-utils');
const schema = {
  type: 'object',
  properties: {
    age: {
      type: 'number',
      description: 'Age must be a number'
    }
  },
  required: ['age']
};
const options = { age: 'old' };
try {
  validate(schema, options, { name: 'AgeChecker' });
} catch (error) {
  // Custom error handling
}

Other packages similar to schema-utils

ajv

Ajv is a JSON schema validator that is fast and supports draft-06/07/2019 JSON Schema. It is more feature-rich and supports more JSON Schema features compared to schema-utils, which is more focused on webpack-related configuration validation.

joi

Joi is an object schema validation library that can validate objects based on a schema with a fluent API. It is different from schema-utils in that it is not specifically tied to JSON Schema and provides a more expressive way to define validation rules and constraints.

yup

Yup is a JavaScript schema builder for value parsing and validation. It defines a schema using a declarative API and is often used in the context of form validation. Unlike schema-utils, Yup is not specifically designed for webpack configurations and offers a different API for schema construction.

README

schema-utils

Package for validate options in loaders and plugins.

Getting Started

To begin, you'll need to install schema-utils:

npm install schema-utils

API

schema.json

{
  "type": "object",
  "properties": {
    "option": {
      "type": "boolean"
    }
  },
  "additionalProperties": false
}

import schema from "./path/to/schema.json";
import { validate } from "schema-utils";

const options = { option: true };
const configuration = { name: "Loader Name/Plugin Name/Name" };

validate(schema, options, configuration);

schema

Type: String

JSON schema.

Simple example of schema:

{
  "type": "object",
  "properties": {
    "name": {
      "description": "This is description of option.",
      "type": "string"
    }
  },
  "additionalProperties": false
}

options

Type: Object

Object with options.

import schema from "./path/to/schema.json";
import { validate } from "schema-utils";

const options = { foo: "bar" };

validate(schema, { name: 123 }, { name: "MyPlugin" });

configuration

Allow to configure validator.

There is an alternative method to configure the name andbaseDataPath options via the title property in the schema. For example:

{
  "title": "My Loader options",
  "type": "object",
  "properties": {
    "name": {
      "description": "This is description of option.",
      "type": "string"
    }
  },
  "additionalProperties": false
}

The last word used for the baseDataPath option, other words used for the name option. Based on the example above the name option equals My Loader, the baseDataPath option equals options.

name

Type: Object Default: "Object"

Allow to setup name in validation errors.

import schema from "./path/to/schema.json";
import { validate } from "schema-utils";

const options = { foo: "bar" };

validate(schema, options, { name: "MyPlugin" });

Invalid configuration object. MyPlugin has been initialised using a configuration object that does not match the API schema.
 - configuration.optionName should be a integer.

baseDataPath

Type: String Default: "configuration"

Allow to setup base data path in validation errors.

import schema from "./path/to/schema.json";
import { validate } from "schema-utils";

const options = { foo: "bar" };

validate(schema, options, { name: "MyPlugin", baseDataPath: "options" });

Invalid options object. MyPlugin has been initialised using an options object that does not match the API schema.
 - options.optionName should be a integer.

postFormatter

Type: Function Default: undefined

Allow to reformat errors.

import schema from "./path/to/schema.json";
import { validate } from "schema-utils";

const options = { foo: "bar" };

validate(schema, options, {
  name: "MyPlugin",
  postFormatter: (formattedError, error) => {
    if (error.keyword === "type") {
      return `${formattedError}\nAdditional Information.`;
    }

    return formattedError;
  },
});

Invalid options object. MyPlugin has been initialized using an options object that does not match the API schema.
 - options.optionName should be a integer.
   Additional Information.

Examples

schema.json

{
  "type": "object",
  "properties": {
    "name": {
      "type": "string"
    },
    "test": {
      "anyOf": [
        { "type": "array" },
        { "type": "string" },
        { "instanceof": "RegExp" }
      ]
    },
    "transform": {
      "instanceof": "Function"
    },
    "sourceMap": {
      "type": "boolean"
    }
  },
  "additionalProperties": false
}

Loader

import { getOptions } from "loader-utils";
import { validate } from "schema-utils";

import schema from "path/to/schema.json";

function loader(src, map) {
  const options = getOptions(this);

  validate(schema, options, {
    name: "Loader Name",
    baseDataPath: "options",
  });

  // Code...
}

export default loader;

Plugin

import { validate } from "schema-utils";

import schema from "path/to/schema.json";

class Plugin {
  constructor(options) {
    validate(schema, options, {
      name: "Plugin Name",
      baseDataPath: "options",
    });

    this.options = options;
  }

  apply(compiler) {
    // Code...
  }
}

export default Plugin;

Allow to disable and enable validation (the validate function do nothing)

This can be useful when you don't want to do validation for production builds.

import { disableValidation, enableValidation, validate } from "schema-utils";

// Disable validation
disableValidation();
// Do nothing
validate(schema, options);

// Enable validation
enableValidation();
// Will throw an error if schema is not valid
validate(schema, options);

// Allow to undestand do you need validation or not
const need = needValidate();

console.log(need);

Also you can enable/disable validation using the process.env.SKIP_VALIDATION env variable.

Supported values (case insensitive):

• yes/y/true/1/on
• no/n/false/0/off

Contributing

Please take a moment to read our contributing guidelines if you haven't yet done so.

CONTRIBUTING

License

MIT

Changelog

4.3.2 (2025-04-22)

Bug Fixes

• compatibility with old types (#198) (8e31ef3)