From 2d603c7c3fb21c0a16298cfc490f8fb3c1979875 Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Mon, 1 Apr 2024 22:00:29 -0400
Subject: [PATCH] LibJS: Support computed member expressions in nullish object
 exceptions

---
 Userland/Libraries/LibJS/Bytecode/Generator.cpp   |  7 ++++---
 .../LibJS/Tests/null-or-undefined-access.js       | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.cpp b/Userland/Libraries/LibJS/Bytecode/Generator.cpp
index 122a6c9b549..5a7c3b1a0a2 100644
--- a/Userland/Libraries/LibJS/Bytecode/Generator.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Generator.cpp
@@ -461,9 +461,10 @@ static Optional<ByteString> expression_identifier(Expression const& expression)
             builder.append(*identifer);
 
         if (auto identifer = expression_identifier(member_expression.property()); identifer.has_value()) {
-            if (!builder.is_empty())
-                builder.append('.');
-            builder.append(*identifer);
+            if (member_expression.is_computed())
+                builder.appendff("[{}]", *identifer);
+            else
+                builder.appendff(".{}", *identifer);
         }
 
         return builder.to_byte_string();
diff --git a/Userland/Libraries/LibJS/Tests/null-or-undefined-access.js b/Userland/Libraries/LibJS/Tests/null-or-undefined-access.js
index c5a1a754cdc..b4d6c7425ae 100644
--- a/Userland/Libraries/LibJS/Tests/null-or-undefined-access.js
+++ b/Userland/Libraries/LibJS/Tests/null-or-undefined-access.js
@@ -43,6 +43,7 @@ test("null/undefined object key", () => {
 test("null/undefined array index", () => {
     [null, undefined].forEach(value => {
         let foo = [value];
+        let index = 0;
 
         expect(() => {
             foo[0].bar;
@@ -51,5 +52,19 @@ test("null/undefined array index", () => {
         expect(() => {
             foo[0].bar = 1;
         }).toThrowWithMessage(TypeError, `Cannot access property "bar" on ${value} object`);
+
+        expect(() => {
+            foo[index].bar;
+        }).toThrowWithMessage(
+            TypeError,
+            `Cannot access property "bar" on ${value} object "foo[index]"`
+        );
+
+        expect(() => {
+            foo[index].bar = 1;
+        }).toThrowWithMessage(
+            TypeError,
+            `Cannot access property "bar" on ${value} object "foo[index]"`
+        );
     });
 });