Functions wrapped in `__importDefault` with allowSyntheticDefaultImports emit incorrect function calls

[borekb]

The following code:

import allSettled from "promise.allsettled";

const resolved = Promise.resolve(42);
const rejected = Promise.reject(-1);

allSettled([resolved, rejected]).then(results => {
 console.log(results);
});

Is transpiled into the following JS with esModuleInterop & allowSyntheticDefaultImports:

"use strict";
var __importDefault =
 (this && this.__importDefault) ||
 function(mod) {
 return mod && mod.__esModule ? mod : { default: mod };
 };
Object.defineProperty(exports, "__esModule", { value: true });
const promise_allsettled_1 = __importDefault(require("promise.allsettled"));
const resolved = Promise.resolve(42);
const rejected = Promise.reject(-1);
promise_allsettled_1.default([resolved, rejected]).then(results => {
 console.log(results);
});

Full tsconfig.json:

{
 "compilerOptions": {
 "target": "es2018",
 "module": "commonjs",
 "strict": true,
 "allowSyntheticDefaultImports": true,
 "esModuleInterop": true,
 },
 "include": [
 "src"
 ]
}

(CodeSandbox.)

Executing this code leads to:

TypeError: #<Object> is not a constructor
 at Object.resolve (<anonymous>)
 at Object.PromiseResolve (/sandbox/node_modules/es-abstract/es2018.js:160:10)
 at /sandbox/node_modules/promise.allsettled/implementation.js:26:24
 at Function.from (<anonymous>)
 at Object.allSettled (/sandbox/node_modules/promise.allsettled/implementation.js:19:22)
 at Object.allSettled [as default] (/sandbox/node_modules/promise.allsettled/index.js:16:9)
 at Object.<anonymous> (/sandbox/src/demo.ts:6:11)
 at Module._compile (internal/modules/cjs/loader.js:776:30)
 at Module.m._compile (/sandbox/node_modules/ts-node/src/index.ts:536:23)
 at Module._extensions..js (internal/modules/cjs/loader.js:787:10)

That is because the promise.allsettled package handles this according to the spec, see es-shims/Promise.allSettled#5. The author of that library is Jordan Harband (@ljharb) who will have deeper understanding of the specifics than I do. (Also, thanks for nudging me to report this issue!)

The problem is most likely the emitted function call, which looks like this:

promise_allsettled_1.default([resolved, rejected]).then(results => {
 console.log(results);
});

In comparison, Babel + TS emits this (which works):

(0, _promise.default)([resolved, rejected]).then(function (results) {
 console.log(results);
});

Babel playground.

TypeScript Version: 3.7.2

Search Terms: esModuleInterop, allowSyntheticDefaultImports, emit, transpile, downlevel compile, ES Modules, default, wrapper, Node.js, module.

[ljharb]

A simpler repro case would be importing module.exports = function () { 'use strict'; return !!this; } (with esModuleInterop and synthetic imports enabled, of course) - a correct downleveling would make invoking this function with no implied receiver return false; TS’s output currently seems to make it return true.

[ajafff]

AFAICT the same bug exists for named imports.

// foo.ts
export function foo() { return !!this; }

// bar.ts
import { foo } from './foo.js';
foo();

// transpiled bar.js
var foo_js_1 = require('./foo.js');
foo_js_1.foo(); // this line should be `(0, foo_js_1.foo)()`

Jordan Harband (@ljharb) please correct me if I'm wrong.

[ljharb]

Yes, that’s the same bug, thanks.

[ajafff]

Fix is up at #35877