Filters REST authentication errors. This is used to pass a WP_Error from an authentication method back to the API.
Authentication methods should check first if they’re being used, as multiple authentication methods can be enabled on a site (cookies, HTTP basic auth, OAuth). If the authentication method hooked in is not actually being attempted, null should be returned to indicate another authentication method should check instead. Similarly, callbacks should ensure the value is `null` before checking for errors.
A WP_Error instance can be returned if an error occurs, and this should match the format used by API methods internally (that is, the `status` data should be used). A callback can return `true` to indicate that the authentication method was used, and it succeeded.
- ( 4.4.0 ) . .
- ( WP_Error|null|bool ) if authentication error, null if authentication method wasn’t used, true if authentication succeeded. . . .