kitchensink/examples/node_modules/webpack-hot-middleware/process-update.js

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/**
 * Based heavily on https://github.com/webpack/webpack/blob/
 *  c0afdf9c6abc1dd70707c594e473802a566f7b6e/hot/only-dev-server.js
 * Original copyright Tobias Koppers @sokra (MIT license)
 */

/* global window __webpack_hash__ */

if (!module.hot) {
  throw new Error("[HMR] Hot Module Replacement is disabled.");
}

var hmrDocsUrl = "http://webpack.github.io/docs/hot-module-replacement-with-webpack.html"; // eslint-disable-line max-len

var lastHash;
var failureStatuses = { abort: 1, fail: 1 };
var applyOptions = { ignoreUnaccepted: true };

function upToDate(hash) {
  if (hash) lastHash = hash;
  return lastHash == __webpack_hash__;
}

module.exports = function(hash, moduleMap, options) {
  var reload = options.reload;
  if (!upToDate(hash) && module.hot.status() == "idle") {
    if (options.log) console.log("[HMR] Checking for updates on the server...");
    check();
  }

  function check() {
    var cb = function(err, updatedModules) {
      if (err) return handleError(err);

      if(!updatedModules) {
        if (options.warn) {
          console.warn("[HMR] Cannot find update (Full reload needed)");
          console.warn("[HMR] (Probably because of restarting the server)");
        }
        performReload();
        return null;
      }

      var applyCallback = function(applyErr, renewedModules) {
        if (applyErr) return handleError(applyErr);

        if (!upToDate()) check();

        logUpdates(updatedModules, renewedModules);
      };

      var applyResult = module.hot.apply(applyOptions, applyCallback);
      // webpack 2 promise
      if (applyResult && applyResult.then) {
        // HotModuleReplacement.runtime.js refers to the result as `outdatedModules`
        applyResult.then(function(outdatedModules) {
          applyCallback(null, outdatedModules);
        });
        applyResult.catch(applyCallback);
      }

    };

    var result = module.hot.check(false, cb);
    // webpack 2 promise
    if (result && result.then) {
        result.then(function(updatedModules) {
            cb(null, updatedModules);
        });
        result.catch(cb);
    }
  }

  function logUpdates(updatedModules, renewedModules) {
    var unacceptedModules = updatedModules.filter(function(moduleId) {
      return renewedModules && renewedModules.indexOf(moduleId) < 0;
    });

    if(unacceptedModules.length > 0) {
      if (options.warn) {
        console.warn(
          "[HMR] The following modules couldn't be hot updated: " +
          "(Full reload needed)\n" +
          "This is usually because the modules which have changed " +
          "(and their parents) do not know how to hot reload themselves. " +
          "See " + hmrDocsUrl + " for more details."
        );
        unacceptedModules.forEach(function(moduleId) {
          console.warn("[HMR]  - " + moduleMap[moduleId]);
        });
      }
      performReload();
      return;
    }

    if (options.log) {
      if(!renewedModules || renewedModules.length === 0) {
        console.log("[HMR] Nothing hot updated.");
      } else {
        console.log("[HMR] Updated modules:");
        renewedModules.forEach(function(moduleId) {
          console.log("[HMR]  - " + moduleMap[moduleId]);
        });
      }

      if (upToDate()) {
        console.log("[HMR] App is up to date.");
      }
    }
  }

  function handleError(err) {
    if (module.hot.status() in failureStatuses) {
      if (options.warn) {
        console.warn("[HMR] Cannot check for update (Full reload needed)");
        console.warn("[HMR] " + err.stack || err.message);
      }
      performReload();
      return;
    }
    if (options.warn) {
      console.warn("[HMR] Update check failed: " + err.stack || err.message);
    }
  }

  function performReload() {
    if (reload) {
      if (options.warn) console.warn("[HMR] Reloading page");
      window.location.reload();
    }
  }
};