Replace node vm with worker_threads

CHANGELOG.yaml

@@ -1,4 +1,6 @@
 unreleased:
+  new feature:
+    - Replaced Node VM with Worker threads
   chores:
     - Add GitHub CI and remove Travis
 

README.md

@@ -1,6 +1,6 @@
 # UVM [![CI](https://github.com/postmanlabs/uvm/actions/workflows/ci.yml/badge.svg?branch=develop)](https://github.com/postmanlabs/uvm/actions/workflows/ci.yml) [![codecov](https://codecov.io/gh/postmanlabs/uvm/branch/develop/graph/badge.svg)](https://codecov.io/gh/postmanlabs/uvm)
 
-Module that exposes an event emitter to send data across contexts ([VM](https://nodejs.org/api/vm.html) in Node.js and [Web Workers](https://www.w3.org/TR/workers/) in browser).
+Module that exposes an event emitter to send data across contexts ([Worker threads](https://nodejs.org/api/worker_threads.html) in Node.js and [Web Workers](https://www.w3.org/TR/workers/) in browser).
 
 ## Installation
 UVM can be installed using NPM or directly from the git repository within your NodeJS projects. If installing from NPM, the following command installs the module and saves in your `package.json`

firmware/sandbox-base.browser.js

@@ -0,0 +1,11 @@
+module.exports = `
+(function (self) {
+    var init = function (e) {
+        self.removeEventListener('message', init);
+        const __init_uvm = e && (e.__init_uvm || (e.data && e.data.__init_uvm));
+        // eslint-disable-next-line no-eval
+        (typeof __init_uvm === 'string') && eval(__init_uvm);
+    };
+    self.addEventListener('message', init);
+}(self));
+`;

firmware/sandbox-base.js

@@ -1,10 +1,9 @@
 module.exports = `
-(function (self) {
-    var init = function (e) {
-        self.removeEventListener('message', init);
+(function (parentPort) {
+    var init = function (m) {
         // eslint-disable-next-line no-eval
-        (e && e.data && (typeof e.data.__init_uvm === 'string')) && eval(e.data.__init_uvm);
+        m && m.__init_uvm && (typeof m.__init_uvm === 'string') && eval(m.__init_uvm);
     };
-    self.addEventListener('message', init);
-}(self));
+    parentPort.once('message', init);
+}(require('worker_threads').parentPort));
 `;

lib/bridge-client.js

@@ -11,7 +11,7 @@
 const toString = String.prototype.toString;
 
 /**
- * Generate code to be executed inside a VM for bootstrap.
+ * Generate code to be executed inside a worker for bootstrap.
  *
  * @param {String|Buffer} bootCode
  * @return {String}
@@ -31,11 +31,15 @@ module.exports = function (bootCode) {
         emit: function (name) {
             var self = this,
                 args = arrayProtoSlice.call(arguments, 1);
-            this._events[name] && [...this._events[name]].forEach(function (listener) {
+            [...this.listeners(name)].forEach(function (listener) {
                 listener.apply(self, args);
             });
         },
 
+        listeners: function (name) {
+            return this._events[name] || [];
+        },
+
         dispatch: function () {
             emit(Flatted.stringify(arrayProtoSlice.call(arguments)));
         },
@@ -55,7 +59,7 @@ module.exports = function (bootCode) {
         },
 
         off: function (name, listener) {
-            var e = this._events[name],
+            var e = this.listeners(name),
                 i = e && e.length || 0;
 
             if (!e) { return; }

lib/bridge.browser.js

@@ -1,36 +1,58 @@
 /* istanbul ignore file */
-/*
- * @note options.dispatchTimeout is not implemented in browser sandbox because
- * there is no way to interrupt an infinite loop.
- * Maybe terminate and restart the worker or execute in nested worker.
- */
 const Flatted = require('flatted'),
     { randomNumber } = require('./utils'),
 
+    // code for bridge
+    bridgeClientCode = require('./bridge-client'),
+
     ERROR = 'error',
     MESSAGE = 'message',
     UVM_ID_ = '__id_uvm_',
-
-    // code for bridge
-    bridgeClientCode = require('./bridge-client'),
+    MESSAGE_ERROR = 'messageerror',
+    UNCAUGHT_EXCEPTION = 'uncaughtException',
+
+    // code to catch uncaught exceptions and re-emit
+    // them for consumers to process the error.
+    // if no listener is attached for uncaughtException
+    // event, it will continue with the default behavior.
+    UNCAUGHT_EXCEPTION_HANDLER = `
+        ;(function (bridge) {
+            const onError = function (event, throwError) {
+                if (bridge.listeners('${UNCAUGHT_EXCEPTION}').length) {
+                    event.preventDefault();
+                    return bridge.emit('${UNCAUGHT_EXCEPTION}', event.error || event.reason);
+                }
+
+                if (throwError) {
+                    event.preventDefault();
+                    throw event.error || event.reason;
+                }
+            };
+
+            self.addEventListener('error', onError);
+            self.addEventListener('unhandledrejection', (e) => onError(e, true));
+        })(bridge);
+    `,
 
     /**
      * Returns the firmware code to be executed inside Web Worker.
      *
      * @private
      * @param {String} code -
      * @param {String} id -
+     * @param {Boolean} debug -
      * @return {String}
      */
-    sandboxFirmware = (code, id) => {
+    sandboxFirmware = (code, id, debug) => {
         // @note self.postMessage and self.addEventListener methods are cached
         // in variable or closure because bootCode might mutate the global scope
         return `
+            !${debug} && (console = new Proxy({}, { get: function () { return function () {}; } }));
             __uvm_emit = function (postMessage, args) {
                 postMessage({__id_uvm: "${id}",__emit_uvm: args});
             }.bind(null, self.postMessage);
             __uvm_addEventListener = self.addEventListener;
-            try {${code}} catch (e) { setTimeout(function () { throw e; }, 0); }
+            ${code}
             (function (emit, id) {
                 __uvm_addEventListener("message", function (e) {
                     (e && e.data && (typeof e.data.__emit_uvm === 'string') && (e.data.__id_uvm === id)) &&
@@ -55,6 +77,12 @@ module.exports = function (bridge, options, callback) {
 
     const id = UVM_ID_ + randomNumber(),
 
+        // We append the uncaught exception handler before the
+        // provided bootCode to ensure that the handler has
+        // access to `bridge` and other global values before
+        // the boot code mutates them (if at all).
+        safeBootCode = UNCAUGHT_EXCEPTION_HANDLER + options.bootCode,
+
         // function to forward messages emitted
         forwardEmits = (e) => {
             if (!(e && e.data && (typeof e.data.__emit_uvm === 'string') && (e.data.__id_uvm === id))) { return; }
@@ -72,7 +100,7 @@ module.exports = function (bridge, options, callback) {
         },
 
         // function to terminate worker
-        terminateWorker = function () {
+        terminateWorker = function (callback) {
             if (!worker) { return; }
 
             // remove event listeners for this sandbox
@@ -89,6 +117,7 @@ module.exports = function (bridge, options, callback) {
             }
 
             worker = null;
+            callback && callback();
         };
 
     // on load attach the dispatcher
@@ -112,12 +141,13 @@ module.exports = function (bridge, options, callback) {
     });
 
     // get firmware code string with boot code
-    firmwareCode = sandboxFirmware(bridgeClientCode(options.bootCode), id);
+    firmwareCode = sandboxFirmware(bridgeClientCode(safeBootCode), id, options.debug);
 
     // start boot timer, stops once we get the load signal, terminate otherwise
     bootTimer = setTimeout(() => {
-        terminateWorker();
-        callback(new Error(`uvm: boot timed out after ${options.bootTimeout}ms.`));
+        terminateWorker(() => {
+            callback(new Error(`uvm: boot timed out after ${options.bootTimeout}ms.`));
+        });
     }, options.bootTimeout);
 
     // if sandbox worker is provided, we simply need to init with firmware code
@@ -145,6 +175,7 @@ module.exports = function (bridge, options, callback) {
     // don't set `onmessage` and `onerror` as it might override external sandbox
     worker.addEventListener(MESSAGE, forwardEmits);
     worker.addEventListener(ERROR, forwardErrors);
+    worker.addEventListener(MESSAGE_ERROR, forwardErrors);
 
     // equip bridge to disconnect (i.e. terminate the worker)
     bridge._disconnect = terminateWorker;