Source

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

protected function get_plugin_data( $plugin ) {
		$plugins = get_plugins();

		if ( ! isset( $plugins[ $plugin ] ) ) {
			return new WP_Error( 'rest_plugin_not_found', __( 'Plugin not found.' ), array( 'status' => 404 ) );
		}

		$data          = $plugins[ $plugin ];
		$data['_file'] = $plugin;

		return $data;
	}