source: frontend/node_modules/webpack/hot/only-dev-server.js

/*
        MIT License http://www.opensource.org/licenses/mit-license.php
        Author Tobias Koppers @sokra
*/
/* globals __webpack_hash__ */
if (module.hot) {
        /** @type {undefined | string} */
        var lastHash;
        var upToDate = function upToDate() {
                return /** @type {string} */ (lastHash).indexOf(__webpack_hash__) >= 0;
        };
        var log = require("./log");
        var check = function check() {
                module.hot
                        .check()
                        .then(function (updatedModules) {
                                if (!updatedModules) {
                                        log("warning", "[HMR] Cannot find update. Need to do a full reload!");
                                        log(
                                                "warning",
                                                "[HMR] (Probably because of restarting the webpack-dev-server)"
                                        );
                                        return;
                                }

                                return module.hot
                                        .apply({
                                                ignoreUnaccepted: true,
                                                ignoreDeclined: true,
                                                ignoreErrored: true,
                                                onUnaccepted: function (data) {
                                                        log(
                                                                "warning",
                                                                "Ignored an update to unaccepted module " +
                                                                        data.chain.join(" -> ")
                                                        );
                                                },
                                                onDeclined: function (data) {
                                                        log(
                                                                "warning",
                                                                "Ignored an update to declined module " +
                                                                        data.chain.join(" -> ")
                                                        );
                                                },
                                                onErrored: function (data) {
                                                        log("error", data.error);
                                                        log(
                                                                "warning",
                                                                "Ignored an error while updating module " +
                                                                        data.moduleId +
                                                                        " (" +
                                                                        data.type +
                                                                        ")"
                                                        );
                                                }
                                        })
                                        .then(function (renewedModules) {
                                                if (!upToDate()) {
                                                        check();
                                                }

                                                require("./log-apply-result")(updatedModules, renewedModules);

                                                if (upToDate()) {
                                                        log("info", "[HMR] App is up to date.");
                                                }
                                        });
                        })
                        .catch(function (err) {
                                var status = module.hot.status();
                                if (["abort", "fail"].indexOf(status) >= 0) {
                                        log(
                                                "warning",
                                                "[HMR] Cannot check for update. Need to do a full reload!"
                                        );
                                        log("warning", "[HMR] " + log.formatError(err));
                                } else {
                                        log("warning", "[HMR] Update check failed: " + log.formatError(err));
                                }
                        });
        };
        /** @type {EventTarget | NodeJS.EventEmitter} */
        var hotEmitter = require("./emitter");
        /**
         * @param {CustomEvent<{ currentHash: string }>} event event or hash
         */
        var handler = function (event) {
                lastHash = typeof event === "string" ? event : event.detail.currentHash;
                if (!upToDate()) {
                        var status = module.hot.status();
                        if (status === "idle") {
                                log("info", "[HMR] Checking for updates on the server...");
                                check();
                        } else if (["abort", "fail"].indexOf(status) >= 0) {
                                log(
                                        "warning",
                                        "[HMR] Cannot apply update as a previous update " +
                                                status +
                                                "ed. Need to do a full reload!"
                                );
                        }
                }
        };

        if (typeof EventTarget !== "undefined" && hotEmitter instanceof EventTarget) {
                hotEmitter.addEventListener(
                        "webpackHotUpdate",
                        /** @type {EventListener} */
                        (handler)
                );
        } else {
                hotEmitter.on("webpackHotUpdate", handler);
        }

        log("info", "[HMR] Waiting for update signal from WDS...");
} else {
        throw new Error("[HMR] Hot Module Replacement is disabled.");
}