refactor: HMR

packages/core/build/flecks.hooks.js

@@ -41,14 +41,16 @@ export const hooks = {
   }),
 
   /**
-   * Invoked when a fleck is HMR'd
+   * Invoked when a module is HMR'd. Throw to abort hot reload and restart application.
+   * Must be synchronous.
+   *
    * @param {string} path The path of the fleck
-   * @param {Module} updatedFleck The updated fleck module.
-   * @invoke
+   * @param {Module} updated The updated module.
+   * @invokeSequential
    */
-  '@flecks/core.hmr': (path, updatedFleck) => {
+  '@flecks/core.hmr': (path, updated) => {
     if ('my-fleck' === path) {
-      updatedFleck.doSomething();
+      updated.doSomething();
     }
   },
 

packages/server/build/runtime.js

@@ -70,8 +70,16 @@ module.exports = async (config, env, argv, flecks) => {
   // Hooks for each fleck.
   resolvedPaths.forEach((path) => {
     source.push(`  module.hot.accept('${path}', async () => {`);
-    source.push(`    global.flecks.refresh('${path}', require('${path}'));`);
-    source.push(`    global.flecks.invoke('@flecks/core.hmr', '${path}');`);
+    source.push(`    const M = require('${path}')`);
+    source.push('    try {');
+    source.push(`      global.flecks.invokeSequential('@flecks/core.hmr', '${path}', M);`);
+    source.push(`      global.flecks.refresh('${path}', M);`);
+    source.push('    }');
+    source.push('    catch (error) {');
+    // eslint-disable-next-line no-template-curly-in-string
+    source.push('      console.error(`HMR failed for fleck: ${error.message}`);');
+    source.push('      module.hot.invalidate();');
+    source.push('    }');
     source.push('  });');
   });
   source.push('}');

packages/server/build/start.js

@@ -85,12 +85,23 @@ class StartServerPlugin {
       args,
       ...(inspectPort && {inspectPort}),
     });
-    this.worker = cluster.fork(env);
+    const setupListeners = (worker) => {
       if (killOnExit) {
-      this.worker.on('exit', () => {
+        worker.on('exit', () => {
           process.exit();
         });
       }
+      worker.on('message', (message) => {
+        if ('hmr-restart' === message) {
+          // eslint-disable-next-line no-console
+          console.error('[HMR] Restarting application...');
+          this.worker = cluster.fork(env);
+          setupListeners(this.worker);
+        }
+      });
+    };
+    this.worker = cluster.fork(env);
+    setupListeners(this.worker);
     return new Promise((resolve, reject) => {
       this.worker.on('error', reject);
       this.worker.on('online', resolve);

packages/server/src/entry.js

@@ -1,3 +1,4 @@
+import cluster from 'cluster';
 import {mkdir} from 'fs/promises';
 import {tmpdir} from 'os';
 import {join} from 'path';
@@ -30,3 +31,14 @@ import {D, Flecks} from '@flecks/core';
     console.error(error);
   }
 })();
+
+if (module.hot) {
+  module.hot.accept('./runtime', () => {
+    if (cluster.isWorker) {
+      cluster.worker.send('hmr-restart');
+      const error = new Error('Restart requested!');
+      error.stack = '';
+      throw error;
+    }
+  });
+}

packages/server/test/server/build/listen.js

@@ -33,6 +33,18 @@ class SocketWrapper {
     });
   }
 
+  async waitForHmr() {
+    return new Promise((resolve, reject) => {
+      this.socket.on('error', reject);
+      this.socket.on('data', (data) => {
+        const action = JSON.parse(data.toString());
+        if ('hmr' === action.type) {
+          resolve(action);
+        }
+      });
+    });
+  }
+
 }
 
 export async function listen() {

packages/server/test/server/template/comm/src/server.js

@@ -5,8 +5,21 @@ const {
 } = process.env;
 
 export const hooks = {
+  '@flecks/core.hmr': async (path, M, flecks) => {
+    if (!flecks.socket) {
+      return;
+    }
+    flecks.socket.write(JSON.stringify({
+      type: 'hmr',
+      payload: path,
+    }));
+  },
   '@flecks/server.up': async (flecks) => {
+    if (!FLECKS_SERVER_TEST_SOCKET) {
+      return;
+    }
     const socket = createConnection({path: FLECKS_SERVER_TEST_SOCKET});
+    flecks.socket = socket;
     socket.on('connect', () => {
       socket.on('data', (data) => {
         const {meta, payload, type} = JSON.parse(data);