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: nodejs#22436

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);
         }
       }

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');
+}