Optional arguments in JSDoc types may be moved to TypeScript types quickfix

TypeScript Version: 3.4.3

• 80004
• jsdoc quickfix optional

Code

With Closure Compiler, you mark a function parameter optional by adding an = after its type (reference):

/**
 * @param a {string} Base string.
 * @param b {string=} Optional string to add
 * @return {string}
 */
function foo(a, b) {
  if (b) return a + b;
  return a;
}

TypeScript offers a quickfix to convert these jsdoc annotations to TypeScript types:

Expected behavior:

The b parameter should be optional:

/**
 * @param a {string} Base string.
 * @param b {string=} Optional string to add
 * @return {string}
 */
function foo(a: string, b?: string): string {
  if (b) return a + b;
  return a;
}

Actual behavior:

The b parameter is required but has type string | optional:

/**
 * @param a {string} Base string.
 * @param b {string=} Optional string to add
 * @return {string}
 */
function foo(a: string, b: string | undefined): string {
  if (b) return a + b;
  return a;
}

This means that all calls of the function which don't specify b will be flagged as errors.

Playground Link: link, though quickfixes are not available there

Related Issues:

Commencez par reproduire le quickfix des types JSDoc-to-TypeScript avec la fonction foo fournie et comparez le type de paramètre généré avec le paramètre optionnel attendu. Suivez le point d’entrée du quickfix et ajoutez une couverture de régression montrant que les appels omettant b sont acceptés, tandis que le type de retour généré reste string.