schema-utils/README.md

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# schema-utils

Package for validate options in loaders and plugins.

## Getting Started

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

```console
npm install schema-utils
```

## API

**schema.json**

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

```js
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:

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

### `options`

Type: `Object`

Object with options.

```js
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` and`baseDataPath` options via the `title` property in the schema.
For example:

```json
{
  "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.

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

const options = { foo: "bar" };

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

```shell
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.

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

const options = { foo: "bar" };

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

```shell
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.

```js
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;
  },
});
```

```shell
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**

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

### `Loader`

```js
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`

```js
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;
```

## Contributing

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

[CONTRIBUTING](./.github/CONTRIBUTING.md)

## License

[MIT](./LICENSE)

[npm]: https://img.shields.io/npm/v/schema-utils.svg
[npm-url]: https://npmjs.com/package/schema-utils
[node]: https://img.shields.io/node/v/schema-utils.svg
[node-url]: https://nodejs.org
[deps]: https://david-dm.org/webpack/schema-utils.svg
[deps-url]: https://david-dm.org/webpack/schema-utils
[tests]: https://github.com/webpack/schema-utils/workflows/schema-utils/badge.svg
[tests-url]: https://github.com/webpack/schema-utils/actions
[cover]: https://codecov.io/gh/webpack/schema-utils/branch/master/graph/badge.svg
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