From b2889c31fc7dad533bd1594e553bd9c9bc6c0226 Mon Sep 17 00:00:00 2001
From: Andreas Tolfsen <ato@mozilla.com>
Date: Fri, 30 Dec 2016 13:07:54 +0000
Subject: [PATCH] Bug 1326534 - Propagate stacktraces for WebDriver errors;
 r=automatedtester

When we currently create new WebDriver errors we throw away the stacktrace
generated by `WebDriverError`'s prototype, `Error`.  This change stores
the stacktrace, which will cause it to be serialised and returned to
the client.

This change is not as valuable as storing the stacktraces of internal
errors, but brings symmetry to our error handling and may be useful if
only to navigate to the source of an error.

MozReview-Commit-ID: LCFMwKxxcTp

--HG--
extra : rebase_source : 56947805f29000a64c2daef0fd774ea90330c09e
---
 testing/marionette/error.js      |  3 ++-
 testing/marionette/test_error.js | 22 ++++++++++++++++------
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/testing/marionette/error.js b/testing/marionette/error.js
index 97e3f2183410..ddd81344d961 100644
--- a/testing/marionette/error.js
+++ b/testing/marionette/error.js
@@ -211,7 +211,7 @@ error.fromJson = function (json) {
  *     to propagate.
  */
 this.WebDriverError = function (err) {
-  Error.call(this, err);
+  const proto = Error.call(this, err);
   this.name = "WebDriverError";
   this.status = "webdriver error";
 
@@ -220,6 +220,7 @@ this.WebDriverError = function (err) {
     this.stack = err.stack;
   } else {
     this.message = err;
+    this.stack = proto.stack;
   }
 };
 WebDriverError.prototype = Object.create(Error.prototype);
diff --git a/testing/marionette/test_error.js b/testing/marionette/test_error.js
index acb37dbb59c0..3f36902a46ee 100644
--- a/testing/marionette/test_error.js
+++ b/testing/marionette/test_error.js
@@ -81,12 +81,15 @@ add_test(function test_toJson() {
       /Unserialisable error type: [object Error]/);
 
   let e0 = new WebDriverError();
-  deepEqual({error: e0.status, message: "", stacktrace: ""},
-      error.toJson(e0));
+  let e0s = error.toJson(e0);
+  equal(e0s.error, "webdriver error");
+  equal(e0s.message, "");
+  equal(e0s.stacktrace, e0.stack);
 
   let e1 = new WebDriverError("a");
-  deepEqual({error: e1.status, message: "a", stacktrace: ""},
-      error.toJson(e1));
+  let e1s = error.toJson(e1);
+  equal(e1s.message, e1.message);
+  equal(e1s.stacktrace, e1.stack);
 
   let e2 = new JavaScriptError("first", "second", "third", "fourth");
   let e2s = error.toJson(e2);
@@ -107,10 +110,17 @@ add_test(function test_fromJson() {
   Assert.throws(() => error.fromJson({}),
       /Undeserialisable error type: undefined/);
 
+  // stacks will be different
   let e1 = new WebDriverError("1");
-  deepEqual(e1, error.fromJson({error: "webdriver error", message: "1"}));
+  let e1r = error.fromJson({error: "webdriver error", message: "1"});
+  equal(e1r.status, e1.status);
+  equal(e1r.message, e1.message);
+
+  // stacks will be different
   let e2 = new InvalidArgumentError("2");
-  deepEqual(e2, error.fromJson({error: "invalid argument", message: "2"}));
+  let e2r = error.fromJson({error: "invalid argument", message: "2"});
+  equal(e2r.status, e2.status);
+  equal(e2r.message, e2.message);
 
   let e3 = new JavaScriptError("first", "second", "third", "fourth");
   let e3s = error.toJson(e3);