From 8ca412b7a3d5e6e84441bc846c5f42e8dcd2f1b9 Mon Sep 17 00:00:00 2001
From: cjihrig <cjihrig@gmail.com>
Date: Tue, 24 Nov 2015 19:52:35 -0500
Subject: [PATCH] util: add decorateErrorStack()

This commit adds the decorateErrorStack() method. This function
uses the internal util's getHiddenValue() method to extract
arrow messages from error objects and attach them to the
error's stack trace.

PR-URL: https://github.com/nodejs/node/pull/4013
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
---
 lib/util.js                                   | 11 ++++++
 .../test-util-decorate-error-stack.js         | 35 +++++++++++++++++++
 2 files changed, 46 insertions(+)
 create mode 100644 test/parallel/test-util-decorate-error-stack.js

diff --git a/lib/util.js b/lib/util.js
index 0666300d68..40d6491e0f 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -899,3 +899,14 @@ exports._exceptionWithHostPort = function(err,
   }
   return ex;
 };
+
+
+exports.decorateErrorStack = function(err) {
+  if (!(isError(err) && err.stack))
+    return;
+
+  const arrow = internalUtil.getHiddenValue(err, 'arrowMessage');
+
+  if (arrow)
+    err.stack = arrow + err.stack;
+};
diff --git a/test/parallel/test-util-decorate-error-stack.js b/test/parallel/test-util-decorate-error-stack.js
new file mode 100644
index 0000000000..b609ee3372
--- /dev/null
+++ b/test/parallel/test-util-decorate-error-stack.js
@@ -0,0 +1,35 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const util = require('util');
+
+assert.doesNotThrow(function() {
+  util.decorateErrorStack();
+  util.decorateErrorStack(null);
+  util.decorateErrorStack(1);
+  util.decorateErrorStack(true);
+});
+
+// Verify that a stack property is not added to non-Errors
+const obj = {};
+util.decorateErrorStack(obj);
+assert.strictEqual(obj.stack, undefined);
+
+// Verify that the stack is decorated when possible
+let err;
+
+try {
+  require('../fixtures/syntax/bad_syntax');
+} catch (e) {
+  err = e;
+  assert(!/var foo bar;/.test(err.stack));
+  util.decorateErrorStack(err);
+}
+
+assert(/var foo bar;/.test(err.stack));
+
+// Verify that the stack is unchanged when there is no arrow message
+err = new Error('foo');
+const originalStack = err.stack;
+util.decorateErrorStack(err);
+assert.strictEqual(originalStack, err.stack);