nodejs / nodejs/cjs-module-lexer

Not work well with TypeScript export default as output

Open
#69 2 comments 3 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

edge case wontfix
Dominant language
JavaScript
Stars
262
Forks
31
Avg merge
9d 2h
Merged PRs (30d)
5

Description

Hi,

TypeScript export default as syntax seems not working with this module. Considering the following TS code:

export { default as fs } from 'fs'; 

Test its output with cjs-module-lexer:

const { parse } = require('cjs-module-lexer');

const result = parse(`
"use strict";
var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };
};
Object.defineProperty(exports, "__esModule", { value: true });
exports.fs = void 0;
var fs_1 = require("fs");
Object.defineProperty(exports, "fs", { enumerable: true, get: function () { return __importDefault(fs_1).default; } });
`);

console.log(result);

It prints:

{ exports: [ '__esModule' ], reexports: [] }

fs do not be considered as exports in the above case.

And I also figure out that changing the place of the __importDefault call

var fs_1 = require("fs");
Object.defineProperty(exports, "fs", { enumerable: true, get: function () { return __importDefault(fs_1).default; } });

to something like this one (what babel does):

var fs_1 = __importDefault(require("fs"));
Object.defineProperty(exports, "fs", { enumerable: true, get: function () { return fs_1.default; } });

The result will become:

{ exports: [ '__esModule', 'fs'], reexports: [] }

Is this an expected behavior?

Ref:

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by running the shown cjs-module-lexer parse example and compare its result for the TypeScript-generated and Babel-generated output forms. Trace how the parser handles the Object.defineProperty getter, then establish the expected export result and cover that behavior with a regression test.

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, typescript
Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.