From 4ea4e72870f794044b7c98fd8aa0e8f829ca4fc7 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Mon, 12 Apr 2021 11:42:54 +0200
Subject: [PATCH] repl: fix error message printing

The REPL implementation would strip away the first and last character
of a formatted error message if it ended with `]` (but with the
obviously missing check for a starting `]`), leading to things like
`Uncaught rror: foo[a` being printed for input like `Error: foo[a]`.

Refs: https://github.com/nodejs/node/pull/22436

PR-URL: https://github.com/nodejs/node/pull/38209
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
---
 lib/repl.js                                   |  2 +-
 .../test-repl-pretty-stack-custom-writer.js   | 23 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 test/parallel/test-repl-pretty-stack-custom-writer.js

diff --git a/lib/repl.js b/lib/repl.js
index 4787107929d949..cf408516c6fce1 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -651,7 +651,7 @@ function REPLServer(prompt,
         errStack = self.writer(e);
 
         // Remove one line error braces to keep the old style in place.
-        if (errStack[errStack.length - 1] === ']') {
+        if (errStack[0] === '[' && errStack[errStack.length - 1] === ']') {
           errStack = StringPrototypeSlice(errStack, 1, -1);
         }
       }
diff --git a/test/parallel/test-repl-pretty-stack-custom-writer.js b/test/parallel/test-repl-pretty-stack-custom-writer.js
new file mode 100644
index 00000000000000..877f8cb8077597
--- /dev/null
+++ b/test/parallel/test-repl-pretty-stack-custom-writer.js
@@ -0,0 +1,23 @@
+'use strict';
+require('../common');
+const { PassThrough } = require('stream');
+const assert = require('assert');
+const repl = require('repl');
+
+{
+  const input = new PassThrough();
+  const output = new PassThrough();
+
+  const r = repl.start({
+    prompt: '',
+    input,
+    output,
+    writer: String,
+    terminal: false,
+    useColors: false
+  });
+
+  r.write('throw new Error("foo[a]")\n');
+  r.close();
+  assert.strictEqual(output.read().toString(), 'Uncaught Error: foo[a]\n');
+}