Preserve property comment and insert @default value, if provided

Search Terms

default initial initializer value preserve comment tsdoc type options option bag

Suggestion

As the title suggests, insert a @default comment to the TSDoc AST if an initializer is provided, preserving the original comment.

Use Cases

I have a default value for an option and I want the consumer of the library to know what the default value is.

Examples

interface Options {
  /**
   * The server host.
   */
  host?: string;
  port?: number;
}

function serve({ host = 'localhost', port }: Options) {
  return { host, port };
}

Playground

Hovering over host in the return statement shows the following in vscode:

Not only is the TSDoc comment lost for this property, but it could furthermore be improved if @default "localhost" were added to it, seeing as that information is available in this context.

It should look like this:

Much ❤️ for the TS team!

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

issue ではソースファイルやテストが指定されていません。まず、TypeScript が分割代入されたパラメーターの TSDoc AST とホバー情報をどのように構築するかを追跡し、次に initializer が元のプロパティコメントを保持して @default 値を追加できる方法を確認してください。示されている host 例がコメントを保持し、出力される JavaScript を変更せずにデフォルト値を公開できれば完了です。