Declaration emit from javascript doesn't respect optional properties in function parameters

[dbellavista]

Bug Report

🔎 Search Terms

• javascript declaration
• optional object parameters

🕗 Version & Regression Information

• typescript 4.0
• typescript 4.1
• typescript@beta

• This changed between versions 3.x and 4.x

⏯ Playground Link

Playground link with relevant code (check .D.TS tab)

💻 Code

jsconfig.json

{
  "compilerOptions": {
    "module": "es6",
    "moduleResolution": "node",
    "target": "es2020",
    "checkJs": true,
    "declaration": true,
    "noEmit": false,
    "emitDeclarationOnly": true
  }
}

test.js

/**
 * test
 *
 * @public
 * @param {object} opts
 * @param {number} opts.a
 * @param {number} [opts.b]
 * @param {number} [opts.c]
 * @returns {number}
 */
function test({a, b, c}) {
  return a + b + c;
}

npx tsc  -p jsconfig.json

🙁 Actual behavior

The definition file doesn't mark b and c as optional

test.d.ts

/**
 * test
 *
 * @public
 * @param {object} opts
 * @param {number} opts.a
 * @param {number} [opts.b]
 * @param {number} [opts.c]
 * @returns {number}
 */
declare function test({ a, b, c }: {
    a: number;
    b: number;
    c: number;
}): number;

🙂 Expected behavior

The definition file should mark b and c as optional (so that projects importing the definitions will be checked properly)

test.d.ts

/**
 * test
 *
 * @public
 * @param {object} opts
 * @param {number} opts.a
 * @param {number} [opts.b]
 * @param {number} [opts.c]
 * @returns {number}
 */
declare function test({ a, b, c }: {
    a: number;
    b?: number;
    c?: number;
}): number;