Refactor bridge.js for lazy loading and boot sequence improvement

Author: appurva21

.github/workflows/ci.yml

@@ -60,7 +60,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [16, 18]
+        node-version: [16, 18, 22]
         os: [ubuntu-latest, windows-latest]
         include:
           - coverage: true

lib/bridge.js

@@ -31,15 +31,35 @@ const Flatted = require('flatted'),
 
         ${bridgeClientCode()}
 
-        (function (emit, id) {
+        __uvm_startBoot = (function (uvmEmit, uvmTimeout) {
+            return function () {
+                // A 5ms delay is added to ensure the required modules are loaded.
+                uvmTimeout(() => {
+                    try {
+                        ${bootCode};
+                    } catch (error) {
+                       uvmTimeout(() => { throw error; }, 0);
+                    }
+                    uvmEmit('${Flatted.stringify(['load.' + id])}');
+                }, 5);
+
+            };
+        }(__uvm_emit, setTimeout));
+
+        (function (emit, boot, id) {
             __uvm_addEventListener("message", function (e) {
                 const { __emit_uvm, __id_uvm } = e?.data || e || {};
                 if (typeof __emit_uvm === 'string' && __id_uvm === id) {
-                    emit(__emit_uvm);
+                    if (__emit_uvm === '${Flatted.stringify(['boot-start'])}') {
+                        boot();
+                    } else {
+                        emit(__emit_uvm);
+                    }
                 }
             });
-        }(__uvm_dispatch, "${id}"));
+        }(__uvm_dispatch, __uvm_startBoot,  "${id}"));
         __uvm_dispatch = null; delete __uvm_dispatch;
+        __uvm_startBoot = null; delete __uvm_startBoot;
         __uvm_addEventListener = null; delete __uvm_addEventListener;
 
         (function (self, bridge, setTimeout) {
@@ -48,16 +68,12 @@ const Flatted = require('flatted'),
         __self = null; delete __self;
 
         // boot code starts hereafter
-        __uvm_setTimeout = setTimeout;
-        try {
-            ${bootCode};
-        } catch (error) {
-            __uvm_setTimeout(() => { throw error; }, 0);
-        }
-
-        __uvm_emit('${Flatted.stringify(['load.' + id])}');
+        // Post node v22.3.0, node uses undici's MessageEvent class which is
+        // loaded lazily and reads certain modules from the global scope when loaded.
+        // We are doing a round trip to main thread to ensure the everything required
+        // for uvm to work is loaded before running the boot code, which might mutate the global scope.
+         __uvm_emit('${Flatted.stringify(['boot-ready.' + id])}');
         __uvm_emit = null; delete __uvm_emit;
-        __uvm_setTimeout = null; delete __uvm_setTimeout;
         `;
     };
 
@@ -133,6 +149,17 @@ module.exports = function (bridge, options, callback) {
         callback(null, bridge);
     });
 
+    bridge.once('boot-ready.' + id, () => {
+        if (!worker) {
+            return callback(new Error('uvm : boot sequence failed due to worker termination.'));
+        }
+
+        worker.postMessage({
+            __emit_uvm: Flatted.stringify(['boot-start']),
+            __id_uvm: id
+        });
+    });
+
     // get firmware code string with boot code
     firmwareCode = sandboxFirmware(options.bootCode, id, options.debug);