From 644094e88f352ddb13b78278e01dfe4dc00c6b4e Mon Sep 17 00:00:00 2001
From: Jillian Crossley <jillianc@twitter.com>
Date: Thu, 21 Dec 2023 23:06:56 +0000
Subject: [PATCH] util/util-app: Include the exception in the error message
 printed when the application encounters an error on startup

Problem

When the application exits prematurely due to an exception encountered on startup, this
exception is not printed to stderr, only the message "Exception thrown in main on startup".
The exception stack trace is printed to stdout, but this is unintuitive for the user.

Solution

Include the exception and stack trace in the exception printed to stderr.

Differential Revision: https://phabricator.twitter.biz/D1116753
---
 CHANGELOG.rst                                         |  7 +++++++
 PROJECT.yml                                           |  1 -
 util-app/src/main/scala/com/twitter/app/App.scala     | 10 +++++++++-
 util-app/src/test/scala/com/twitter/app/AppTest.scala |  2 +-
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 43fa096fe4..51b4ff60d0 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -7,6 +7,13 @@ Note that ``PHAB_ID=#`` and ``RB_ID=#`` correspond to associated messages in com
 Unreleased
 ----------
 
+Runtime Behavior Changes
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+* util-app: When the application exits due to an error on startup, the error and
+  and stack trace are printed to stderr in addition to the existing stdout. ``PHAB_ID=D1116753``
+
+
 23.11.0
 -------
 
diff --git a/PROJECT.yml b/PROJECT.yml
index c9d152767c..675c29685a 100644
--- a/PROJECT.yml
+++ b/PROJECT.yml
@@ -4,4 +4,3 @@ owners:
   - csl-team:ldap
   - jillianc
   - mbezoyan
-  - nvong
diff --git a/util-app/src/main/scala/com/twitter/app/App.scala b/util-app/src/main/scala/com/twitter/app/App.scala
index cb4c916550..167fa1b6ec 100644
--- a/util-app/src/main/scala/com/twitter/app/App.scala
+++ b/util-app/src/main/scala/com/twitter/app/App.scala
@@ -3,6 +3,8 @@ package com.twitter.app
 import com.twitter.app.lifecycle.Event._
 import com.twitter.conversions.DurationOps._
 import com.twitter.util._
+import java.io.PrintWriter
+import java.io.StringWriter
 import java.lang.reflect.InvocationTargetException
 import java.util.concurrent.ConcurrentLinkedQueue
 import java.util.concurrent.atomic.AtomicReference
@@ -82,7 +84,13 @@ trait App extends ClosableOnce with CloseOnceAwaitably with Lifecycle {
         System.err.println(throwable.getMessage)
         System.exit(1)
       case _ =>
-        exitOnError("Exception thrown in main on startup")
+        util.Using(new StringWriter) { stringWriter =>
+          util.Using(new PrintWriter(stringWriter)) { printWriter =>
+            throwable.printStackTrace(printWriter)
+            printWriter.flush()
+            exitOnError(s"Exception thrown in main on startup: ${stringWriter.toString}")
+          }
+        }
     }
   }
 
diff --git a/util-app/src/test/scala/com/twitter/app/AppTest.scala b/util-app/src/test/scala/com/twitter/app/AppTest.scala
index 5c70b2f126..a6c9eedcdb 100644
--- a/util-app/src/test/scala/com/twitter/app/AppTest.scala
+++ b/util-app/src/test/scala/com/twitter/app/AppTest.scala
@@ -67,7 +67,7 @@ class AppTest extends AnyFunSuite {
 
     test1.main(Array())
 
-    assert(test1.reason.contains("Exception thrown in main on startup"))
+    assert(test1.reason.exists(_.contains("Exception thrown in main on startup")))
   }
 
   test("App: propagate underlying exception from fields in app") {