fix: correctly detect errors from vm

lib/client.js

@@ -366,7 +366,7 @@ extend(Raven.prototype, {
       kwargs = utils.isPlainObject(kwargs) ? extend({}, kwargs) : {};
     }
 
-    if (!(err instanceof Error)) {
+    if (!utils.isError(err)) {
       if (utils.isPlainObject(err)) {
         // This will allow us to group events based on top-level keys
         // which is much better than creating new group when any key/value change
@@ -451,7 +451,7 @@ extend(Raven.prototype, {
     var self = this;
     var wrapped = function() {
       var err = arguments[0];
-      if (err instanceof Error) {
+      if (utils.isError(err)) {
         self.captureException(err, options);
       } else {
         func.apply(null, arguments);

lib/utils.js

@@ -31,6 +31,14 @@ function jsonSize(value) {
   return utf8Length(JSON.stringify(value));
 }
 
+function isError(what) {
+  return (
+    Object.prototype.toString.call(what) === '[object Error]' || what instanceof Error
+  );
+}
+
+module.exports.isError = isError;
+
 function isPlainObject(what) {
   return Object.prototype.toString.call(what) === '[object Object]';
 }

test/raven.utils.js

@@ -566,4 +566,37 @@ describe('raven.utils', function() {
       raven.utils.serializeKeysForMessage('foo').should.eql('foo');
     });
   });
+
+  describe('isError', function() {
+    it('should work as advertised', function() {
+      function RavenError(message) {
+        this.name = 'RavenError';
+        this.message = message;
+      }
+      RavenError.prototype = new Error();
+      RavenError.prototype.constructor = RavenError;
+
+      raven.utils.isError(new Error()).should.be.true;
+      raven.utils.isError(new RavenError()).should.be.true;
+      raven.utils.isError({}).should.be.false;
+      raven.utils.isError({
+        message: 'A fake error',
+        stack: 'no stack here'
+      }).should.be.false;
+      raven.utils.isError('').should.be.false;
+      raven.utils.isError(true).should.be.false;
+    });
+
+    it('should work with errors from different contexts, eg. vm module', function(done) {
+      var vm = require('vm');
+      var script = new vm.Script("throw new Error('this is the error')");
+
+      try {
+        script.runInNewContext();
+      } catch (e) {
+        raven.utils.isError(e).should.be.true;
+        done();
+      }
+    });
+  });
 });