Inconsistencies in ESM-style imports of accessibility-modified properties from CJS-exported classes

Acknowledgement

• I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

Search terms

import AND class AND (protected OR private OR modifier)

Description

Given the following CJS module:

class X {
  public static a = 1;
  protected static b = 2;
  private static c = 3;
}
export = X;

then the behaviour of the static properties when using ESM-style imports is variable. For example,

import { a, b, c } from "module.cjs";

is permitted, but

import * as m from "module.cjs";
const { a, b, c } = m;

is not (m is an alias to the CJS export X, so this counts as a class property access and is subject to accessibility checks).

Protected and private class properties are also offered by tsserver for Intellisense suggestions when using ESM-style imports, but are obviously hidden when offering properties of the "namespace" object created by import * (since it's just an alias to the exported class), and do not appear in its keyof.

(The same would also apply if the CJS export were an instance of a class with accessibility-modified prototype properties, but exporting a class constructor is the more likely scenario encountered in the wild.)

Exposing intended-to-be-hidden properties in this way is almost always going to have been unintentional, and the alternative behaviour is fairly straightforward: add accessibility checks for NamedImports elements when the import target is a CJS export.

Inizia con l’esempio di classe CJS-exported nell’issue e segui il modo in cui TypeScript gestisce NamedImports rispetto a un import-star namespace quando la destinazione è una classe esportata. Riproduci il diverso comportamento di accessibilità, quindi verifica che anche i named imports impongano controlli di accessibilità senza esporre proprietà protected o private.