gatsby-plugin-utils/README.md

Gatsby utils that help creating plugins

# gatsby-plugin-utils

## Usage

```shell
npm install gatsby-plugin-utils
```

### `validateOptionsSchema`

The `validateOptionsSchema` function verifies that the proper data types of options were passed into a plugin from the `gatsby-config.js` file. It is called internally by Gatsby to validate each plugin's options when a site is started.

#### Example

```js
import { validateOptionsSchema } from "gatsby-plugin-utils"

await validateOptionsSchema(pluginName, pluginSchema, pluginOptions)
```

### `testPluginOptionsSchema`

Utility to validate and test plugin options schemas. An example of a plugin options schema implementation can be found in the [`gatsby-node.js` file of `gatsby-plugin-google-analytics`](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-google-analytics/src/gatsby-node.js).

#### Example

```js
// This is an example using Jest (https://jestjs.io/)
import { testPluginOptionsSchema } from "gatsby-plugin-utils"

it(`should partially validate one value of a schema`, async () => {
  const pluginSchema = ({ Joi }) =>
    Joi.object({
      someOtherValue: Joi.string(),
      toVerify: Joi.boolean(),
    })

  // Only the "toVerify" key of the schema will be verified in this test
  const { isValid, errors } = await testPluginOptionsSchema(pluginSchema, {
    toVerify: `abcd`,
  })

  expect(isValid).toBe(false)
  expect(errors).toEqual([`"toVerify" must be a boolean`])
})
```

### `isGatsbyNodeLifecycleSupported`

Utility to be used by plugins to do runtime check against `gatsby` core package checking wether particular `gatsby-node` lifecycle API is supported. Useful for plugins to be able to support multiple `gatsby` core versions.

#### Example

```js
const { isGatsbyNodeLifecycleSupported } = require(`gatsby-plugin-utils`)

// only use createSchemaCustomization lifecycle only when it's available.
if (isGatsbyNodeLifecycleSupported(`createSchemaCustomization`)) {
  exports.createSchemaCustomization = function createSchemaCustomization({
    actions,
  }) {
    // customize schema
  }
}
```