react-native/local-cli/server/util/attachHMRServer.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
'use strict';

const querystring = require('querystring');
const url = require('url');

/**
 * Attaches a WebSocket based connection to the Packager to expose
 * Hot Module Replacement updates to the simulator.
 */
function attachHMRServer({httpServer, path, packagerServer}) {
  let client = null;

  function disconnect() {
    client = null;
    packagerServer.setHMRFileChangeListener(null);
  }

  // Returns a promise with the full list of dependencies and the shallow
  // dependencies each file on the dependency list has for the give platform
  // and entry file.
  function getDependencies(platform, bundleEntry) {
    return packagerServer.getDependencies({
      platform: platform,
      dev: true,
      entryFile: bundleEntry,
    }).then(response => {
      // for each dependency builds the object:
      // `{path: '/a/b/c.js', deps: ['modA', 'modB', ...]}`
      return Promise.all(Object.values(response.dependencies).map(dep => {
        return dep.getName().then(depName => {
          if (dep.isAsset() || dep.isAsset_DEPRECATED() || dep.isJSON()) {
            return Promise.resolve({path: dep.path, deps: []});
          }
          return packagerServer.getShallowDependencies(dep.path)
            .then(deps => {
              return {
                path: dep.path,
                name: depName,
                deps,
              };
            });
        });
      }))
      .then(deps => {
        // list with all the dependencies' filenames the bundle entry has
        const dependenciesCache = response.dependencies.map(dep => dep.path);

        // map from module name to path
        const moduleToFilenameCache = Object.create(null);
        deps.forEach(dep => moduleToFilenameCache[dep.name] = dep.path);

        // map that indicates the shallow dependency each file included on the
        // bundle has
        const shallowDependencies = Object.create(null);
        deps.forEach(dep => shallowDependencies[dep.path] = dep.deps);

        // map from module name to the modules' dependencies the bundle entry
        // has
        const dependenciesModulesCache = Object.create(null);
        return Promise.all(response.dependencies.map(dep => {
          return dep.getName().then(depName => {
            dependenciesModulesCache[depName] = dep;
          });
        })).then(() => {
          return {
            dependenciesCache,
            dependenciesModulesCache,
            shallowDependencies,
          };
        });
      });
    });
  }

  const WebSocketServer = require('ws').Server;
  const wss = new WebSocketServer({
    server: httpServer,
    path: path,
  });

  console.log('[Hot Module Replacement] Server listening on', path);
  wss.on('connection', ws => {
    console.log('[Hot Module Replacement] Client connected');
    const params = querystring.parse(url.parse(ws.upgradeReq.url).query);

    getDependencies(params.platform, params.bundleEntry)
      .then(({
        dependenciesCache,
        dependenciesModulesCache,
        shallowDependencies,
      }) => {
        client = {
          ws,
          platform: params.platform,
          bundleEntry: params.bundleEntry,
          dependenciesCache,
          dependenciesModulesCache,
          shallowDependencies,
        };

        packagerServer.setHMRFileChangeListener((filename, stat) => {
          if (!client) {
            return Promise.resolve();
          }

          return stat.then(() => {
            return packagerServer.getShallowDependencies(filename)
              .then(deps => {
                if (!client) {
                  return [];
                }

                // if the file dependencies have change we need to invalidate the
                // dependencies caches because the list of files we need to send
                // to the client may have changed
                const oldDependencies = client.shallowDependencies[filename];
                if (arrayEquals(deps, oldDependencies)) {
                  return [packagerServer.getModuleForPath(filename)];
                }

                // if there're new dependencies compare the full list of
                // dependencies we used to have with the one we now have
                return getDependencies(client.platform, client.bundleEntry)
                  .then(({
                    dependenciesCache,
                    dependenciesModulesCache,
                    shallowDependencies,
                  }) => {
                    if (!client) {
                      return [];
                    }

                    // build list of modules for which we'll send HMR updates
                    const modulesToUpdate = [];
                    Object.keys(dependenciesModulesCache).forEach(module => {
                      if (!client.dependenciesModulesCache[module]) {
                        modulesToUpdate.push(dependenciesModulesCache[module]);
                      }
                    });

                    // invalidate caches
                    client.dependenciesCache = dependenciesCache;
                    client.dependenciesModulesCache = dependenciesModulesCache;
                    client.shallowDependencies = shallowDependencies;

                    return modulesToUpdate;
                  });
              })
              .then(modulesToUpdate => {
                if (!client) {
                  return;
                }

                // make sure the file was modified is part of the bundle
                if (!client.shallowDependencies[filename]) {
                  return;
                }

                return packagerServer.buildBundleForHMR({
                  entryFile: client.bundleEntry,
                  platform: client.platform,
                  modules: modulesToUpdate,
                });
              })
              .then(bundle => {
                if (!client) {
                  return;
                }

                // check we actually want to send an HMR update
                if (bundle) {
                  client.ws.send(bundle);
                }
              });
            },
            () => {
              // do nothing, file was removed
            },
          );
        });

        client.ws.on('error', e => {
          console.error('[Hot Module Replacement] Unexpected error', e);
          disconnect();
        });

        client.ws.on('close', () => disconnect());
      })
    .done();
  });
}

function arrayEquals(arrayA, arrayB) {
  arrayA = arrayA || [];
  arrayB = arrayB || [];
  return (
    arrayA.length === arrayB.length &&
    arrayA.every((element, index) => {
      return element === arrayB[index];
    })
  );
}

module.exports = attachHMRServer;