Microsoft/TypeScript

JSDoc comments emitted a second time even after commenrs on type are emitted

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#62453 opened on Sep 15, 2025

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 (0 comments) (1 reaction) (0 assignees)TypeScript (48,455 stars) (6,726 forks)batch import
BugDomain: Comment EmitHelp Wanted

Description

🔎 Search Terms

JSDoc, emit, comments

🕗 Version & Regression Information

v5.9.2

  • I was unable to test this on prior versions because I was not using TS.

⏯ Playground Link

No response

💻 Code

/**
 * The template passed to generate messages
 *
 * @callback Template
 * @param {...*} args - Arguments to the template
 * @returns {any} The generated message
 */

/**
 * The arguments sent with notify become the input parameters for the template.
 *
 * @typedef {Parameters<Template>} TemplateParams
 */

/**
 * The return value from the template is yielded as the message generated from
 * the subscription. The following types help define this relationship.
 *
 * @typedef {ReturnType<Template>} Message
 */

🙁 Actual behavior

Typescript, when emitting from JSDoc, seems to want to emit the same comments for a type declaration twice:

  • once for the export (good) and
  • once just copying over the JSDoc comment (bad).
/**
 * The template passed to generate messages
 */
export type Template = (...args: any[]) => any;
/**
 * The arguments sent with notify become the input parameters for the template.
 */
export type TemplateParams = Parameters<Template>;
/**
 * The return value from the template is yielded as the message generated from
 * the subscription. The following types help define this relationship.
 */
export type Message = ReturnType<Template>;
/**
 * The template passed to generate messages
 *
 * @callback Template
 * @param {...*} args Arguments to the template
 * @returns {any} The generated message
 */
/**
 * The arguments sent with notify become the input parameters for the template.
 *
 * @typedef {Parameters<Template>} TemplateParams
 */
/**
 * The return value from the template is yielded as the message generated from
 * the subscription. The following types help define this relationship.
 *
 * @typedef {ReturnType<Template>} Message
 */

🙂 Expected behavior

It should emit the comment just once:

/**
 * The template passed to generate messages
 */
export type Template = (...args: any[]) => any;
/**
 * The arguments sent with notify become the input parameters for the template.
 */
export type TemplateParams = Parameters<Template>;
/**
 * The return value from the template is yielded as the message generated from
 * the subscription. The following types help define this relationship.
 */
export type Message = ReturnType<Template>;

or even better (See #61664)

/**
 * The template passed to generate messages
 *
 * @param Arguments to the template
 * @returns The generated message
 */
export type Template = (...args: any[]) => any;
/**
 * The arguments sent with notify become the input parameters for the template.
 */
export type TemplateParams = Parameters<Template>;
/**
 * The return value from the template is yielded as the message generated from
 * the subscription. The following types help define this relationship.
 */
export type Message = ReturnType<Template>;

Additional information about the issue

No response

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