VSCode 在 1.88 的更新日志中宣布了 Restart extensions 的功能：

在本地 VSCode 中，现在不需要 Reload Window 就可以重启插件了。这不禁让我好奇，他们到底做了些什么？

ToC

找找

让我们先用关键词 Reload Extensions 来找一找：

    this.enabled = true;
    this.class = ExtensionRuntimeStateAction.EnabledClass;
    this.tooltip = runtimeState.reason;
    this.label = runtimeState.action === ExtensionRuntimeActionType.ReloadWindow ? localize('reload window', 'Reload Window')
      : runtimeState.action === ExtensionRuntimeActionType.RestartExtensions ? localize('restart extensions', 'Restart Extensions')
        : runtimeState.action === ExtensionRuntimeActionType.QuitAndInstall ? localize('restart product', 'Restart to Update')
          : runtimeState.action === ExtensionRuntimeActionType.ApplyUpdate || runtimeState.action === ExtensionRuntimeActionType.DownloadUpdate ? localize('update product', 'Update {0}', this.productService.nameShort) : '';
  }

找到了 runtimeState.action。它是怎么定义的呢？

export const enum ExtensionRuntimeActionType {
  ReloadWindow = "reloadWindow",
  RestartExtensions = "restartExtensions",
  DownloadUpdate = "downloadUpdate",
  ApplyUpdate = "applyUpdate",
  QuitAndInstall = "quitAndInstall",
}

看来是加了个 ExtensionRuntimeActionType.RestartExtensions。继续追引用：

  override async run(): Promise<any> {
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    const runtimeState = this.extension?.runtimeState;
    if (!runtimeState?.action) {
      return;
    }
    type ExtensionRuntimeStateActionClassification = {
      owner: 'sandy081';
      comment: 'Extension runtime state action event';
      action: { classification: 'SystemMetaData'; purpose: 'FeatureInsight'; comment: 'Executed action' };
    };
    type ExtensionRuntimeStateActionEvent = {
      action: string;
    };
    this.telemetryService.publicLog2<ExtensionRuntimeStateActionEvent, ExtensionRuntimeStateActionClassification>('extensions:runtimestate:action', {
      action: runtimeState.action
    });
    if (runtimeState?.action === ExtensionRuntimeActionType.ReloadWindow) {
      return this.hostService.reload();
    }
    else if (runtimeState?.action === ExtensionRuntimeActionType.RestartExtensions) {
      return this.extensionsWorkbenchService.updateRunningExtensions();
    }
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    else if (runtimeState?.action === ExtensionRuntimeActionType.DownloadUpdate) {
      return this.updateService.downloadUpdate();
    }
    else if (runtimeState?.action === ExtensionRuntimeActionType.ApplyUpdate) {
      return this.updateService.applyUpdate();
    }
    else if (runtimeState?.action === ExtensionRuntimeActionType.QuitAndInstall) {
      return this.updateService.quitAndInstall();
    }
  }

看来核心逻辑都在 updateRunningExtensions 里了。

看看

看看 updateRunningExtensions：

  async updateRunningExtensions(): Promise<void> {
    const toAdd: ILocalExtension[] = [];
    const toRemove: string[] = [];
    const extensionsToCheck = [...this.local];
    const notExistingRunningExtensions = this.extensionService.extensions.filter(e => !this.local.some(local => areSameExtensions({ id: e.identifier.value, uuid: e.uuid }, local.identifier)));
    if (notExistingRunningExtensions.length) {
      const extensions = await this.getExtensions(notExistingRunningExtensions.map(e => ({ id: e.identifier.value })), CancellationToken.None);
      extensionsToCheck.push(...extensions);
    }
    for (const extension of extensionsToCheck) {
      const runtimeState = extension.runtimeState;
      if (!runtimeState || runtimeState.action !== ExtensionRuntimeActionType.RestartExtensions) {
        continue;
      }
      if (extension.state === ExtensionState.Uninstalled) {
        toRemove.push(extension.identifier.id);
        continue;
      }
      if (!extension.local) {
        continue;
      }
      const isEnabled = this.extensionEnablementService.isEnabled(extension.local);
      if (isEnabled) {
        const runningExtension = this.extensionService.extensions.find(e => areSameExtensions({ id: e.identifier.value, uuid: e.uuid }, extension.identifier));
        if (runningExtension) {
          toRemove.push(runningExtension.identifier.value);
        }
        toAdd.push(extension.local);
      } else {
        toRemove.push(extension.identifier.id);
      }
    }
    if (toAdd.length || toRemove.length) {
      if (await this.extensionService.stopExtensionHosts(nls.localize('restart', "Enable or Disable extensions"))) {
        await this.extensionService.startExtensionHosts({ toAdd, toRemove });
      }
    }
  }

还以为会有什么魔法，结果居然是先 Stop 再 Start？？

这里 startExtensionHosts() 的签名相比于之前的版本增加了 toAdd 和 toRemove 两个参数，传到内部之后是直接调用了 _handleDeltaExtensions：

  public async startExtensionHosts(updates?: { toAdd: IExtension[]; toRemove: string[] }): Promise<void> {
    this._doStopExtensionHosts();
    if (updates) {
      await this._handleDeltaExtensions(new DeltaExtensionsQueueItem(updates.toAdd, updates.toRemove));
    }
    const lock = await this._registry.acquireLock('startExtensionHosts');
    try {
      this._startExtensionHostsIfNecessary(false, Array.from(this._allRequestedActivateEvents.keys()));
      const localProcessExtensionHosts = this._getExtensionHostManagers(ExtensionHostKind.LocalProcess);
      await Promise.all(localProcessExtensionHosts.map(extHost => extHost.ready()));
    } finally {
      lock.dispose();
    }
  }

没意思，还以为是做了什么好东西，这样实现居然还不支持 Remote，软软没救了，散了散了）