Source

File: wp-includes/rest-api/endpoints/class-wp-rest-themes-controller.php

public function prepare_item_for_response( $theme, $request ) {
		$data   = array();
		$fields = $this->get_fields_for_response( $request );

		if ( rest_is_field_included( 'stylesheet', $fields ) ) {
			$data['stylesheet'] = $theme->get_stylesheet();
		}

		if ( rest_is_field_included( 'template', $fields ) ) {
			/**
			 * Use the get_template() method, not the 'Template' header, for finding the template.
			 * The 'Template' header is only good for what was written in the style.css, while
			 * get_template() takes into account where WordPress actually located the theme and
			 * whether it is actually valid.
			 */
			$data['template'] = $theme->get_template();
		}

		$plain_field_mappings = array(
			'requires_php' => 'RequiresPHP',
			'requires_wp'  => 'RequiresWP',
			'textdomain'   => 'TextDomain',
			'version'      => 'Version',
		);

		foreach ( $plain_field_mappings as $field => $header ) {
			if ( rest_is_field_included( $field, $fields ) ) {
				$data[ $field ] = $theme->get( $header );
			}
		}

		if ( rest_is_field_included( 'screenshot', $fields ) ) {
			// Using $theme->get_screenshot() with no args to get absolute URL.
			$data['screenshot'] = $theme->get_screenshot() ? $theme->get_screenshot() : '';
		}

		$rich_field_mappings = array(
			'author'      => 'Author',
			'author_uri'  => 'AuthorURI',
			'description' => 'Description',
			'name'        => 'Name',
			'tags'        => 'Tags',
			'theme_uri'   => 'ThemeURI',
		);

		foreach ( $rich_field_mappings as $field => $header ) {
			if ( rest_is_field_included( "{$field}.raw", $fields ) ) {
				$data[ $field ]['raw'] = $theme->display( $header, false, true );
			}

			if ( rest_is_field_included( "{$field}.rendered", $fields ) ) {
				$data[ $field ]['rendered'] = $theme->display( $header );
			}
		}

		if ( rest_is_field_included( 'theme_supports', $fields ) ) {
			foreach ( get_registered_theme_features() as $feature => $config ) {
				if ( ! is_array( $config['show_in_rest'] ) ) {
					continue;
				}

				$name = $config['show_in_rest']['name'];

				if ( ! rest_is_field_included( "theme_supports.{$name}", $fields ) ) {
					continue;
				}

				if ( ! current_theme_supports( $feature ) ) {
					$data['theme_supports'][ $name ] = $config['show_in_rest']['schema']['default'];
					continue;
				}

				$support = get_theme_support( $feature );

				if ( isset( $config['show_in_rest']['prepare_callback'] ) ) {
					$prepare = $config['show_in_rest']['prepare_callback'];
				} else {
					$prepare = array( $this, 'prepare_theme_support' );
				}

				$prepared = $prepare( $support, $config, $feature, $request );

				if ( is_wp_error( $prepared ) ) {
					continue;
				}

				$data['theme_supports'][ $name ] = $prepared;
			}
		}

		$data = $this->add_additional_fields_to_object( $data, $request );

		// Wrap the data in a response object.
		$response = rest_ensure_response( $data );

		/**
		 * Filters theme data returned from the REST API.
		 *
		 * @since 5.0.0
		 *
		 * @param WP_REST_Response $response The response object.
		 * @param WP_Theme         $theme    Theme object used to create response.
		 * @param WP_REST_Request  $request  Request object.
		 */
		return apply_filters( 'rest_prepare_theme', $response, $theme, $request );
	}