From 684dd28a6c684532336777348875ac11305727b9 Mon Sep 17 00:00:00 2001
From: Rod Vagg <rod@vagg.org>
Date: Tue, 15 Oct 2013 12:26:18 +1100
Subject: [PATCH] util: format as Error if instanceof Error

---
 lib/util.js                     |  3 ++-
 test/simple/test-util-format.js | 10 ++++++++++
 test/simple/test-util.js        |  2 +-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/util.js b/lib/util.js
index 9901a66..b0bbdd4 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -496,7 +496,8 @@ function isDate(d) {
 exports.isDate = isDate;
 
 function isError(e) {
-  return isObject(e) && objectToString(e) === '[object Error]';
+  return isObject(e) &&
+      (objectToString(e) === '[object Error]' || e instanceof Error);
 }
 exports.isError = isError;
 
diff --git a/test/simple/test-util-format.js b/test/simple/test-util-format.js
index ee96744..1bea1bf 100644
--- a/test/simple/test-util-format.js
+++ b/test/simple/test-util-format.js
@@ -66,3 +66,13 @@ assert.equal(util.format('%%%s%%%%', 'hi'), '%hi%%');
   o.o = o;
   assert.equal(util.format('%j', o), '[Circular]');
 })();
+
+// Errors
+assert.equal(util.format(new Error('foo')), '[Error: foo]');
+function CustomError(msg) {
+  Error.call(this);
+  Object.defineProperty(this, 'message', { value: msg, enumerable: false });
+  Object.defineProperty(this, 'name', { value: 'CustomError', enumerable: false });
+}
+util.inherits(CustomError, Error);
+assert.equal(util.format(new CustomError('bar')), '[CustomError: bar]');
diff --git a/test/simple/test-util.js b/test/simple/test-util.js
index 2acdbdb..4e75d51 100644
--- a/test/simple/test-util.js
+++ b/test/simple/test-util.js
@@ -68,7 +68,7 @@ assert.equal(true, util.isError(new (context('SyntaxError'))));
 assert.equal(false, util.isError({}));
 assert.equal(false, util.isError({ name: 'Error', message: '' }));
 assert.equal(false, util.isError([]));
-assert.equal(false, util.isError(Object.create(Error.prototype)));
+assert.equal(true, util.isError(Object.create(Error.prototype)));
 
 // isObject
 assert.ok(util.isObject({}) === true);
-- 
2.7.4