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Should preserve unique symbols when re‑assigning module.exports #37403
Description
TypeScript Version:
3.9.0-dev.20200315
Search Terms:
- object property preserve unique symbol
- module.exports preserve unique symbol
Code
// @target: ES2015
// @module: CommonJS
// @allowJs
// @checkJs
// @noEmit
// @filename: index.js
const customSymbol = Symbol("custom");
// ^?
// This is a common pattern in Node’s built-in modules:
module.exports = {
customSymbol,
// ^?
};Also, the following requires a // @ts‑ignore comment, but otherwise works:
// some-module.js
const customSymbol = Symbol("custom");
// This is a common pattern in Node’s built-in modules:
module.exports = {
/** @type {typeof customSymbol} */
// @ts-ignore
customSymbol,
// ~~~~~~~~~~~~ TS2322: Type 'symbol' is not assignable to type 'unique symbol'.
};Expected behavior:
// some-module.d.ts
declare const customSymbol: unique symbol;
declare const _default: {
customSymbol: typeof customSymbol;
};
export = _default;Actual behavior:
// some-module.d.ts
declare const _default: {
customSymbol: symbol;
};
export = _default;
Activity
ExE-Boss commentedon May 3, 2020
Also, the following requires a
// @ts‑ignorecomment, but otherwise works:1 remaining item
typescript-bot commentedon Mar 10, 2021
👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of the 2 repros in this issue running against the nightly TypeScript.
Issue body code block by ExE Boss (@ExE-Boss)
Comment by ExE Boss (@ExE-Boss)const customSymbol: typeof customSymbol(property) customSymbol: symbol(property) customSymbol: symbolHistorical Information
Issue body code block by ExE Boss (@ExE-Boss)
const customSymbol: typeof customSymbol(alias) const customSymbol: typeof customSymbol import customSymbolconst customSymbol: typeof customSymbol(property) customSymbol: symbolComment by ExE Boss (@ExE-Boss)
(property) customSymbol: symbolExE-Boss commentedon Mar 10, 2021
Looks like this got fixed at some point in TypeScript 4.1 with the changes to
module.exportshandling.weswigham commentedon Mar 10, 2021
Yeah, #42655 probably got this as a drive by?
ExE-Boss commentedon Mar 11, 2021
Note that this breaks if you do:
Workbench Repro