__importStar can result in undefined imports when importing cyclical dependencies

[VeriClock-Bryce]

I've run across what appears to be a bug with __importStar when cyclical dependencies are involved.

I've replicated the issue this sandbox: https://codesandbox.io/s/eloquent-khayyam-nn14o?file=/src/tsFile.ts

Which contains 3 key files:

index.js

const jsFile = require("./jsFile");
jsFile.doMainThingInJsFile();
console.log("All is good!");

tsFile.ts

//this fails
import * as jsFile from "./jsFile";

//this works
// import jsFile = require("./jsFile");

export function doSomethingInTsFile() {
  console.log("tsFile.doSomethingInTsFile()");
  jsFile.doSomethingInJsFile2();
}

jsFile.js

const tsFile = require("./tsFile");

function doMainThingInJsFile() {
  console.log("jsFile: in doMainThingInJsFile()");
  tsFile.doSomethingInTsFile();
}
exports.doMainThingInJsFile = doMainThingInJsFile;
exports.doSomethingInJsFile2 = function() {
  console.log("jsFile.doSomethingInJsFile2()");
};

tsFile.ts and jsFile.js are cyclical dependencies.

When the 'fail' version of the code runs, doSomethingInTsFile() inside of tsFile.ts is undefined.

Looking at the source code for __importStar it becomes clear what is happening: the reference returned from require(...) is replaced with a new container object. It is unclear to me why this occurs and instead the original isn't used, but I suspect its related to emitting code that will ultimately work with other code that goes looking for a 'default' export in that output.

I would chalk this up to me misusing import * or other settings being incorrect, but if the cyclical dependency is removed, then the module imports just fine with an import *. It's this differing behaviour that leads me to think there is a bug here. We encountered this in our project when some code that rarely ran failed at runtime because a cyclical dependency had been added elsewhere that ultimately caused the member functions of the imported library (old commonjs code) to be undefined.