possibly 'undefined'. emitted after Boolean constructor check in Visual Studio

[kdevay]

🔎 Search Terms

• possibly 'undefined'
• visual studio code
• VS code
• Boolean wrapper not supported
• Boolean constructor not supported

🕗 Version & Regression Information

• This is the behavior in TS Version 5.4.3, and I reviewed the FAQ for entries about undefined values after a boolean check

⏯ Playground Link

https://replit.com/join/cwiubczice-kdevay

💻 Code

interface Message {
  text: string;
  isBot: boolean;
}

interface ConversationProps {
  messages?: Message[];
}

const Conversation: React.FC<ConversationProps> = ({ messages }) => {
  return (
    <div
      id="conversation"
      className="flex flex-col gap-2 h-conversation overflow-y-scroll text-white"
    >
      {Boolean(messages && messages.length) &&
        messages.map((message, index) => (
          <div
            key={index}
            className="flex flex-row w-full"
          >
            <div>
              `${message.isBot ? '🤖' : 'you'}: ${message.text}`
            </div>
          </div>
        ))}
    </div>
  );
};

export default Conversation;

🙁 Actual behavior

I am seeing a red squiggle on messages.map stating that it is possibly undefined

🙂 Expected behavior

I should not see any error, because I performed this check: Boolean(messages && messages.length) .

I do not see an error message when I add the check without the Boolean constructor, like

      {(messages && messages.length) &&
        messages.map((message, index) => (

Additional information about the issue

TypeScript
Version 5.4.3

Visual Studio Code
Version: 1.89.0 (Universal)
Commit: b58957e67ee1e712cebf466b995adf4c5307b2bd
Date: 2024-05-01T02:10:10.196Z
Electron: 28.2.8
ElectronBuildId: 27744544
Chromium: 120.0.6099.291
Node.js: 18.18.2
V8: 12.0.267.19-electron.0
OS: Darwin arm64 23.4.0

My Machine
Model: Macbook pro
Chip: Apple M2
OS: Sonoma 14.4

[fatcerberus]

More or less the same as #16655

[typescript-bot]

This issue has been marked as "Duplicate" and has seen no recent activity. It has been automatically closed for house-keeping purposes.