Sometimes it can be helpful to deprecate a field in the Schema without removing it altogether. 



This snippet shows how to deprecate the `Post.excerpt` field. 



You can use this technique to deprecate other fields. 



<pre class="wp-block-code lang-php"><code>// Filter the Object Fields
add_filter( 'graphql_object_fields', function( $fields, $type_name, $wp_object_type, $type_registry ) {

 // If the Object Type is not the "Post" Type
 // return the fields unaltered
	if ( 'Post' !== $type_name ) {
		return $fields;
	}

 // If the excerpt field doesn't exist 
 // (removed by another plugin, for example)
 // return the fields unaltered
	if ( ! isset( $fields['excerpt'] ) ) {
		return $fields;
	}

 // Add a deprecation reason to the excerpt field
	$fields['excerpt']['deprecationReason'] = __( 'Just showing how to deprecate an existing field', 'your-textdomain' );
	
 // return the modified
 return $fields;

}, 10, 4 );</code></pre>



After using this snippet, we can verify in the WPGraphQL Schema Docs that the field is indeed deprecated: 



<div class="wp-block-image"><figure class="aligncenter size-full is-resized"><img loading="lazy" decoding="async" src="https://content.wpgraphql.com/wp-content/uploads/2022/01/Screen-Shot-2022-01-19-at-11.02.58-AM.png" alt="" class="wp-image-828603" width="422" height="374"/><figcaption>Screenshot of the excerpt field showing deprecated in the GraphiQL IDE Schema Docs</figcaption></figure></div>

Deprecating a field in the Schema

This snippet shows how to register a basic GraphQL Mutation with a single input field, a single output field, and the input is simply returned as the value for the output. 



<pre class="wp-block-code lang-php"><code>add_action( 'graphql_register_types', function() {

	register_graphql_mutation( 'testMutation', [
		'inputFields' => [
			'phoneNumber' => [
				'type' => [ 'non_null' => 'String' ],
			],
		],
		'outputFields' => [
			'phoneNumber' => [
				'type' => 'String',
			],
		],
		'mutateAndGetPayload' => function( $input ) {

			return [
				'phoneNumber' => $input['phoneNumber'] ?? null,
			];

		}
	]);

} );</code></pre>

Schema Customization

Deprecating a field in the Schema

Register a basic Mutation