From 6fbe4b93d1dccdb305148164660d756ebd58c9d8 Mon Sep 17 00:00:00 2001
From: Milutin Kristofic <milutin@google.com>
Date: Wed, 4 Sep 2019 11:39:43 +0200
Subject: [PATCH] Reporting top 3 lines of stack for js errors

This should help investigating js errors. It includes line, column
and names of two functions who calls method with js error.

Change-Id: Icc893161e9c9bb0cde4ec2aecd96fe5e71d780f3
---
 .../app/elements/core/gr-reporting/gr-reporting.js     |  8 +++++++-
 .../elements/core/gr-reporting/gr-reporting_test.html  | 10 ++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js
index ca494d2f2c..397189a52d 100644
--- a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js
@@ -116,7 +116,13 @@
     if (error) {
       line = line || error.lineNumber;
       column = column || error.columnNumber;
-      msg = msg || error.toString();
+      let shortenedErrorStack = msg;
+      if (error.stack) {
+        const errorStackLines = error.stack.split('\n');
+        shortenedErrorStack = errorStackLines.slice(0,
+            Math.min(3, errorStackLines.length)).join('\n');
+      }
+      msg = shortenedErrorStack || error.toString();
     }
     const payload = {
       url,
diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html
index f5053117ec..a0a25b3831 100644
--- a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html
@@ -341,6 +341,7 @@ limitations under the License.
 
       test('is reported', () => {
         const error = new Error('bar');
+        error.stack = undefined;
         emulateThrow('bar', 'http://url', 4, 2, error);
         assert.isTrue(reporter.calledWith('error', 'exception', 'bar'));
         const payload = reporter.lastCall.args[3];
@@ -352,6 +353,15 @@ limitations under the License.
         });
       });
 
+      test('is reported with 3 lines of stack', () => {
+        const error = new Error('bar');
+        emulateThrow('bar', 'http://url', 4, 2, error);
+        const expectedStack = error.stack.split('\n').slice(0, 3)
+            .join('\n');
+        assert.isTrue(reporter.calledWith('error', 'exception',
+            expectedStack));
+      });
+
       test('prevent default event handler', () => {
         assert.isTrue(emulateThrow());
       });