Unload uninstalled plugins from Electron cache

Summary: Electron/Node.js does not garbage collects unloaded modules by default. Need to cleanup require.cache to fully unload them.

Reviewed By: passy

Differential Revision: D25545962

fbshipit-source-id: 4dce32f39e22adcd2b4f5a55853551379e786e7b

desktop/app/src/store.tsx

@@ -28,6 +28,7 @@ import {_SandyPluginDefinition} from 'flipper-plugin';
 import BaseDevice from './devices/BaseDevice';
 import {State as PluginStates} from './reducers/pluginStates';
 import {ActivatablePluginDetails} from 'flipper-plugin-lib';
+import {unloadModule} from './utils/electronModuleCache';
 
 export const store: Store = createStore<StoreState, Actions, any, any>(
   rootReducer,
@@ -168,6 +169,11 @@ function updateClientPlugin(
       ];
     });
     cleanupPluginStates(draft.pluginStates, plugin.id);
+    const previousVersion = draft.plugins.clientPlugins.get(plugin.id);
+    if (previousVersion) {
+      // unload previous version from Electron cache
+      unloadPluginModule(previousVersion.details);
+    }
     // update plugin definition
     draft.plugins.clientPlugins.set(plugin.id, plugin);
     // start plugin for each client
@@ -191,6 +197,7 @@ function uninstallPlugin(state: StoreState, plugin: PluginDefinition) {
       delete draft.pluginMessageQueue[pluginKey];
     });
     cleanupPluginStates(draft.pluginStates, plugin.id);
+    unloadPluginModule(plugin.details);
     draft.plugins.clientPlugins.delete(plugin.id);
     draft.plugins.devicePlugins.delete(plugin.id);
     draft.pluginManager.uninstalledPlugins.add(plugin.details.name);
@@ -207,6 +214,11 @@ function updateDevicePlugin(state: StoreState, plugin: DevicePluginDefinition) {
       d.unloadDevicePlugin(plugin.id);
     });
     cleanupPluginStates(draft.pluginStates, plugin.id);
+    const previousVersion = draft.plugins.devicePlugins.get(plugin.id);
+    if (previousVersion) {
+      // unload previous version from Electron cache
+      unloadPluginModule(previousVersion.details);
+    }
     draft.plugins.devicePlugins.set(plugin.id, plugin);
     devicesWithEnabledPlugin.forEach((d) => {
       d.loadDevicePlugin(plugin);
@@ -245,3 +257,11 @@ function cleanupPluginStates(pluginStates: PluginStates, pluginId: string) {
     }
   });
 }
+
+function unloadPluginModule(plugin: ActivatablePluginDetails) {
+  if (plugin.isBundled) {
+    // We cannot unload bundled plugin.
+    return;
+  }
+  unloadModule(plugin.entry);
+}

desktop/app/src/utils/electronModuleCache.tsx

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+export function unloadModule(path: string) {
+  const resolvedPath = global.electronRequire.resolve(path);
+  if (!resolvedPath || !global.electronRequire.cache[resolvedPath]) {
+    return;
+  }
+  delete global.electronRequire.cache[resolvedPath];
+}

desktop/types/nodejs.d.ts

@@ -11,7 +11,11 @@ declare module NodeJS {
   interface Global {
     __REVISION__: string | undefined;
     __VERSION__: string;
-    electronRequire: (name: string) => any;
+    electronRequire: {
+      (name: string): any;
+      resolve: (module: string) => string;
+      cache: {[module: string]: any};
+    };
     window: Window | undefined;
     WebSocket: any;
     fetch: any;