From 5c9d7d80265820a9e90b2e89542a4cc51a548226 Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Sun, 8 Nov 2020 12:58:49 +0000
Subject: [PATCH] js: Limit number of consecutive error trace entries being
 printed

    > function f(){f()}f()
    Uncaught exception: [RuntimeError]: Call stack size limit exceeded
     -> f
     1234 more calls
     -> (global execution context)
    > function a(x){if(x>0){a(x-1)}else{throw Error()}}function b(x){if(x>0){b(x-1)}else{a(5)}}function c(){b(2)}c()
    Uncaught exception: [Error]
     -> a
     5 more calls
     -> b
     -> b
     -> b
     -> c
     -> (global execution context)
---
 Userland/js.cpp | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/Userland/js.cpp b/Userland/js.cpp
index 316160e0d7..9170c7526e 100644
--- a/Userland/js.cpp
+++ b/Userland/js.cpp
@@ -363,8 +363,25 @@ static bool parse_and_run(JS::Interpreter& interpreter, const StringView& source
         print(vm->exception()->value());
         auto trace = vm->exception()->trace();
         if (trace.size() > 1) {
-            for (auto& function_name : trace)
-                printf(" -> %s\n", function_name.characters());
+            unsigned repetitions = 0;
+            for (size_t i = 0; i < trace.size(); ++i) {
+                auto& function_name = trace[i];
+                if (i + 1 < trace.size() && trace[i + 1] == function_name) {
+                    repetitions++;
+                    continue;
+                }
+                if (repetitions > 4) {
+                    // If more than 5 (1 + >4) consecutive function calls with the same name, print
+                    // the name only once and show the number of repetitions instead. This prevents
+                    // printing ridiculously large call stacks of recursive functions.
+                    outln(" -> {}", function_name);
+                    outln(" {} more calls", repetitions);
+                } else {
+                    for (size_t j = 0; j < repetitions + 1; ++j)
+                        outln(" -> {}", function_name);
+                }
+                repetitions = 0;
+            }
         }
         vm->clear_exception();
         return false;