LibDatabase: Allow String values to contain embedded null bytes

LibDatabase previously truncated String values at the first '\0' when
round-tripping through SQLite due to the use of strlen.

This is something which we should support according to WPT:

https://wpt.live/webstorage/storage_setitem.window.html

The above test works fine when run through our test-web harness
as we have the SQL database disabled, so this instead adds a C++
test.

Libraries/LibDatabase/Database.cpp

@@ -170,8 +170,9 @@ ValueType Database::result_column(StatementID statement_id, int column)
     auto* statement = prepared_statement(statement_id);
 
     if constexpr (IsSame<ValueType, String>) {
+        auto length = sqlite3_column_bytes(statement, column);
         auto const* text = reinterpret_cast<char const*>(sqlite3_column_text(statement, column));
-        return MUST(String::from_utf8(StringView { text, strlen(text) }));
+        return MUST(String::from_utf8(StringView { text, static_cast<size_t>(length) }));
     } else if constexpr (IsSame<ValueType, ByteString>) {
         auto length = sqlite3_column_bytes(statement, column);
         auto const* text = sqlite3_column_blob(statement, column);

Tests/CMakeLists.txt

@@ -2,6 +2,7 @@ add_subdirectory(AK)
 add_subdirectory(LibCompress)
 add_subdirectory(LibCore)
 add_subdirectory(LibCrypto)
+add_subdirectory(LibDatabase)
 add_subdirectory(LibDiff)
 add_subdirectory(LibDNS)
 add_subdirectory(LibGC)

Tests/LibDatabase/CMakeLists.txt

@@ -0,0 +1,7 @@
+set(TEST_SOURCES
+    TestDatabase.cpp
+)
+
+foreach(source IN LISTS TEST_SOURCES)
+    ladybird_test("${source}" LibDatabase LIBS LibDatabase)
+endforeach()

Tests/LibDatabase/TestDatabase.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2026, Shannon Booth <shannon@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+#include <Libraries/LibDatabase/Database.h>
+
+TEST_CASE(string_can_contain_null_bytes)
+{
+    auto database = TRY_OR_FAIL(Database::Database::create_memory_backed());
+
+    database->execute_statement(TRY_OR_FAIL(database->prepare_statement(R"#(
+        CREATE TABLE WebStorage (
+            key TEXT PRIMARY KEY,
+            value TEXT
+        );
+    )#"sv)),
+        {});
+
+    auto get_item_statement = TRY_OR_FAIL(database->prepare_statement("SELECT value FROM WebStorage WHERE key = ?;"sv));
+    auto set_item_statement = TRY_OR_FAIL(database->prepare_statement("INSERT OR REPLACE INTO WebStorage VALUES (?, ?);"sv));
+    auto delete_item_statement = TRY_OR_FAIL(database->prepare_statement("DELETE FROM WebStorage WHERE key = ?;"sv));
+
+    auto get_item = [&](String const& key) {
+        Optional<String> result;
+        database->execute_statement(
+            get_item_statement,
+            [&](auto statement_id) {
+                result = database->result_column<String>(statement_id, 0);
+            },
+            key);
+        return result;
+    };
+
+    auto set_item = [&](String const& key, String const& value) {
+        database->execute_statement(
+            set_item_statement,
+            {},
+            key,
+            value);
+    };
+
+    auto remove_item = [&](String const& key) {
+        database->execute_statement(
+            delete_item_statement,
+            {},
+            key);
+    };
+
+    EXPECT_EQ(get_item("my_key"_string), Optional<String> {});
+    set_item("my_key"_string, "my_value"_string);
+    EXPECT_EQ(get_item("my_key"_string), Optional<String> { "my_value"_string });
+    set_item("my_key"_string, "my_value_with_\0_null"_string);
+    EXPECT_EQ(get_item("my_key"_string), Optional<String> { "my_value_with_\0_null"_string });
+    remove_item("my_key"_string);
+    EXPECT_EQ(get_item("my_key"_string), Optional<String> {});
+}