Deprecating a field in the Schema

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.

// 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 );

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