WP_REST_Terms_Controller::create_item( WP_REST_Request $request )

	public function create_item( $request ) {
		if ( isset( $request['parent'] ) ) {
			if ( ! is_taxonomy_hierarchical( $this->taxonomy ) ) {
				return new WP_Error( 'rest_taxonomy_not_hierarchical', __( 'Cannot set parent term, taxonomy is not hierarchical.' ), array( 'status' => 400 ) );
			}

			$parent = get_term( (int) $request['parent'], $this->taxonomy );

			if ( ! $parent ) {
				return new WP_Error( 'rest_term_invalid', __( 'Parent term does not exist.' ), array( 'status' => 400 ) );
			}
		}

		$prepared_term = $this->prepare_item_for_database( $request );

		$term = wp_insert_term( wp_slash( $prepared_term->name ), $this->taxonomy, wp_slash( (array) $prepared_term ) );
		if ( is_wp_error( $term ) ) {
			/*
			 * If we're going to inform the client that the term already exists,
			 * give them the identifier for future use.
			 */
			if ( $term_id = $term->get_error_data( 'term_exists' ) ) {
				$existing_term = get_term( $term_id, $this->taxonomy );
				$term->add_data( $existing_term->term_id, 'term_exists' );
				$term->add_data( array( 'status' => 409, 'term_id' => $term_id ) );
			}

			return $term;
		}

		$term = get_term( $term['term_id'], $this->taxonomy );

		/**
		 * Fires after a single term is created or updated via the REST API.
		 *
		 * The dynamic portion of the hook name, `$this->taxonomy`, refers to the taxonomy slug.
		 *
		 * @since WP-4.7.0
		 *
		 * @param WP_Term         $term     Inserted or updated term object.
		 * @param WP_REST_Request $request  Request object.
		 * @param bool            $creating True when creating a term, false when updating.
		 */
		do_action( "rest_insert_{$this->taxonomy}", $term, $request, true );

		$schema = $this->get_item_schema();
		if ( ! empty( $schema['properties']['meta'] ) && isset( $request['meta'] ) ) {
			$meta_update = $this->meta->update_value( $request['meta'], $term->term_id );

			if ( is_wp_error( $meta_update ) ) {
				return $meta_update;
			}
		}

		$fields_update = $this->update_additional_fields_for_object( $term, $request );

		if ( is_wp_error( $fields_update ) ) {
			return $fields_update;
		}

		$request->set_param( 'context', 'view' );

		$response = $this->prepare_item_for_response( $term, $request );
		$response = rest_ensure_response( $response );

		$response->set_status( 201 );
		$response->header( 'Location', rest_url( $this->namespace . '/' . $this->rest_base . '/' . $term->term_id ) );

		return $response;
	}