async calculateConfigForFile(filePath) {
		if (!isNonEmptyString(filePath)) {
			throw new Error("'filePath' must be a non-empty string");
		}
		const options = privateMembers.get(this).options;
		const absolutePath = path.resolve(options.cwd, filePath);
		const configs =
			await this.#configLoader.loadConfigArrayForFile(absolutePath);

		if (!configs) {
			const error = new Error("Could not find config file.");

			error.messageTemplate = "config-file-missing";
			throw error;
		}

		return configs.getConfig(absolutePath);
	}
Returns a configuration object for the given file based on the CLI options.
This is the same logic used by the ESLint CLI executable to determine
configuration for each file it processes.
@param {string} filePath The path of the file to retrieve a config object for.
@returns {Promise<Config|undefined>} A configuration object for the file
     or `undefined` if there is no configuration data for the object.