经常在 Cider 中看到 "REPL command timed out" with shadow-cljs 和 React Native。必须重启模拟器才能修复

Question

我正在使用带有 Cider 和 ShadowCLJS 的 Emacs 来开发一个基本的 ReactNative 应用程序。我可以非常一致地使用 REPL 进行开发，但是一旦我不小心保存了一个有语法错误的文件，我就会失去与 REPL 的通信。我键入的任何内容都会导致延迟，然后是 "REPL command timed out"。我发现修复它的唯一方法是使用 npx react-native run-android 重新启动模拟器。但是后来我失去了我在 REPL 中的所有状态。

Answer 1

这可能是许多不同的事情。

这可能与 Metro（或 Expo）提供的实时加载有关。在模拟器中按 Ctrl-M（Mac 上的 Cmd-M）调出关闭快速刷新的选项。

https://facebook.github.io/react-native/docs/fast-refresh

https://github.com/thheller/shadow-cljs/issues/469

如果禁用快速刷新后仍然出现此错误，可能是因为 ReactNative 在重新加载时没有完全断开旧的 websockets。这是 shadow-cljs 创建者的评论。

its a bug in react-native in that it doesn't disconnect websockets when reloading the app so shadow-cljs thinks the "old" app is still running and tries talking to it (but it never replies) I opened an issue on the RN repo but it was closed due do inactivity for a year or so. nobody cared I guess.

我找到了使用 ReactNative 的 AppState 和从 shadow-cljs dev 命名空间引用 websocket 的解决方法。

https://facebook.github.io/react-native/docs/appstate.html

https://github.com/thheller/shadow-cljs/blob/master/src/main/shadow/cljs/devtools/client/react_native.cljs

(defn on-app-state-change
  "Fixes issue with shadow-cljs repl losing connection to websocket.

  Put this in some root component's `component-did-mount`.
  
  "
  [state]
  (cond
    (= state "background")
    (.close @shadow-rn/socket-ref)

    (and (= state "active")
         (nil? @shadow-rn/socket-ref))
    (shadow-rn/ws-connect)))

(defn make-reloader
  [component]
  (let [component-ref (r/atom component)]
    (letfn [(render []
              (let [component @component-ref]
                (if (fn? component)
                  (component)
                  component)))]
      (let [wrapper (r/create-class
                     {:render render
                      :component-did-mount
                      (fn []
                        (.addEventListener rn/AppState "change" on-app-state-change))

                      :component-will-unmount
                      (fn []
                        (.removeEventListener rn/AppState "change" on-app-state-change))})]

        (rn/AppRegistry.registerComponent "Ezmonic" (fn [] wrapper))
        (fn [comp]
          (reset! component-ref comp))))))

经常在 Cider 中看到 "REPL command timed out" with shadow-cljs 和 React Native。必须重启模拟器才能修复

Often seeing "REPL command timed out" in Cider with shadow-cljs and React Native. Must restart emulator to fix

cider

react-native

shadow-cljs