const getPluginKey = (
  plugin: WatchPlugin,
  globalConfig: Config.GlobalConfig,
) => {
  if (typeof plugin.getUsageInfo === 'function') {
    return (plugin.getUsageInfo(globalConfig) || {key: null}).key;
  }

  return null;
};

    .sort((a: WatchPlugin, b: WatchPlugin) => {
      if (a.isInternal && b.isInternal) {
        // internal plugins in the order we specify them
        return 0;
      }
      if (a.isInternal !== b.isInternal) {
        // external plugins afterwards
        return a.isInternal ? -1 : 1;
      }

      const usageInfoA = a.getUsageInfo && a.getUsageInfo(globalConfig);
      const usageInfoB = b.getUsageInfo && b.getUsageInfo(globalConfig);

      if (usageInfoA && usageInfoB) {
        // external plugins in alphabetical order
        return usageInfoA.key.localeCompare(usageInfoB.key);
      }
      return 0;
    })

export default function watch(
  initialGlobalConfig: Config.GlobalConfig,
  contexts: Array<Context>,
  outputStream: NodeJS.WriteStream,
  hasteMapInstances: Array<HasteMap>,
  stdin: NodeJS.ReadStream = process.stdin,
  hooks: JestHook = new JestHook(),
  filter?: Filter,
): Promise<void> {
  // `globalConfig` will be constantly updated and reassigned as a result of
  // watch mode interactions.
  let globalConfig = initialGlobalConfig;
  let activePlugin: WatchPlugin | null;

  globalConfig = updateGlobalConfig(globalConfig, {
    mode: globalConfig.watch ? 'watch' : 'watchAll',
    passWithNoTests: true,
  });

  const updateConfigAndRun = ({
    bail,
    changedSince,
    collectCoverage,
    collectCoverageFrom,
    collectCoverageOnlyFrom,
    coverageDirectory,
    coverageReporters,
    mode,
    notify,
    notifyMode,
    onlyFailures,
    reporters,
    testNamePattern,
    testPathPattern,
    updateSnapshot,
    verbose,
  }: AllowedConfigOptions = {}) => {
    const previousUpdateSnapshot = globalConfig.updateSnapshot;
    globalConfig = updateGlobalConfig(globalConfig, {
      bail,
      changedSince,
      collectCoverage,
      collectCoverageFrom,
      collectCoverageOnlyFrom,
      coverageDirectory,
      coverageReporters,
      mode,
      notify,
      notifyMode,
      onlyFailures,
      reporters,
      testNamePattern,
      testPathPattern,
      updateSnapshot,
      verbose,
    });

    startRun(globalConfig);
    globalConfig = updateGlobalConfig(globalConfig, {
      // updateSnapshot is not sticky after a run.
      updateSnapshot:
        previousUpdateSnapshot === 'all' ? 'none' : previousUpdateSnapshot,
    });
  };

  const watchPlugins: Array<WatchPlugin> = INTERNAL_PLUGINS.map(
    InternalPlugin => new InternalPlugin({stdin, stdout: outputStream}),
  );
  watchPlugins.forEach((plugin: WatchPlugin) => {
    const hookSubscriber = hooks.getSubscriber();
    if (plugin.apply) {
      plugin.apply(hookSubscriber);
    }
  });

  if (globalConfig.watchPlugins != null) {
    const watchPluginKeys: WatchPluginKeysMap = new Map();
    for (const plugin of watchPlugins) {
      const reservedInfo =
        RESERVED_KEY_PLUGINS.get(plugin.constructor as WatchPluginClass) ||
        ({} as ReservedInfo);
      const key = reservedInfo.key || getPluginKey(plugin, globalConfig);
      if (!key) {
        continue;
      }
      const {forbiddenOverwriteMessage} = reservedInfo;
      watchPluginKeys.set(key, {
        forbiddenOverwriteMessage,
        overwritable: forbiddenOverwriteMessage == null,
        plugin,
      });
    }

    for (const pluginWithConfig of globalConfig.watchPlugins) {
      let plugin: WatchPlugin;
      try {
        const ThirdPartyPlugin = require(pluginWithConfig.path);
        plugin = new ThirdPartyPlugin({
          config: pluginWithConfig.config,
          stdin,
//.........这里部分代码省略.........

 watchPlugins.forEach((plugin: WatchPlugin) => {
   const hookSubscriber = hooks.getSubscriber();
   if (plugin.apply) {
     plugin.apply(hookSubscriber);
   }
 });