From 794c62db5869c79785ed0ae7ec05fdb9d9cb2104 Mon Sep 17 00:00:00 2001
From: Andrew Nicols <andrew@nicols.co.uk>
Date: Wed, 3 Apr 2024 15:38:16 +0800
Subject: [PATCH] MDL-81419 core: Ensure that frames exist before checking them

---
 lib/setuplib.php | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/setuplib.php b/lib/setuplib.php
index e95897e0723..9d3808c6050 100644
--- a/lib/setuplib.php
+++ b/lib/setuplib.php
@@ -385,11 +385,13 @@ function get_whoops(): ?\Whoops\Run {
 
     // Append a custom handler to add some more information to the frames.
     $whoops->appendHandler(function ($exception, $inspector, $run) {
-        // Moodle exceptions often have a link to the Moodle docs pages for them.
-        // Add that to the first frame in the stack.
         $collection = $inspector->getFrames();
 
-        $isdebugging = str_ends_with($collection[1]->getFile(), '/lib/weblib.php');
+        // Detect if the Whoops handler was immediately invoked by a call to `debugging()`.
+        // If so, we remove the top frames in the collection to avoid showing the inner
+        // workings of debugging, and the point that we trigger the error that is picked up by Whoops.
+        $isdebugging = count($collection) > 2;
+        $isdebugging = $isdebugging && str_ends_with($collection[1]->getFile(), '/lib/weblib.php');
         $isdebugging = $isdebugging && $collection[2]->getFunction() === 'debugging';
 
         if ($isdebugging) {
@@ -398,6 +400,8 @@ function get_whoops(): ?\Whoops\Run {
                 return array_search($frame, $remove) === false;
             });
         } else {
+            // Moodle exceptions often have a link to the Moodle docs pages for them.
+            // Add that to the first frame in the stack.
             $info = get_exception_info($exception);
             if ($info->moreinfourl) {
                 $collection[0]->addComment("{$info->moreinfourl}", 'More info');