detect DOMExceptions accross contexts as errors in isError

Author: Thomas Grainger

src/utils.js

@@ -4,14 +4,15 @@ function isObject(what) {
     return typeof what === 'object' && what !== null;
 }
 
-// Sorta yanked from https://github.com/joyent/node/blob/aa3b4b4/lib/util.js#L560
+// Yanked from https://git.io/vS8DV re-used under CC0
 // with some tiny modifications
-function isError(what) {
-    var toString = {}.toString.call(what);
-    return isObject(what) &&
-        toString === '[object Error]' ||
-        toString === '[object Exception]' || // Firefox NS_ERROR_FAILURE Exceptions
-        what instanceof Error;
+function isError(value) {
+  switch ({}.toString.call(value)) {
+    case '[object Error]': return true;
+    case '[object Exception]': return true;
+    case '[object DOMException]': return true;
+    default: return value instanceof Error;
+  }
 }
 
 module.exports = {

test/utils.test.js

@@ -66,11 +66,39 @@ describe('utils', function () {
     });
 
     describe('isError', function() {
+      function testErrorFromDifferentContext(createError) {
+          var iframe = document.createElement('iframe');
+          document.body.appendChild(iframe);
+          try {
+              return createError(iframe.contentWindow);
+          } finally {
+              iframe.parentElement.removeChild(iframe);
+          }
+      }
+
+      function fromContext(win) {
+          return new win.Error();
+      }
+
+      function domException(win) {
+          try {
+              win.document.querySelectorAll('');
+          } catch(e) {
+              return e;
+          }
+      }
+
         it('should work as advertised', function() {
             assert.isTrue(isError(new Error()));
             assert.isTrue(isError(new ReferenceError()));
             assert.isTrue(isError(new RavenConfigError()));
+            assert.isTrue(isError(testErrorFromDifferentContext(fromContext)));
+            assert.isTrue(isError(testErrorFromDifferentContext(domException)));
             assert.isFalse(isError({}));
+            assert.isFalse(isError({
+              message: 'A fake error',
+              stack: 'no stack here'
+            }));
             assert.isFalse(isError(''));
             assert.isFalse(isError(true));
         });