__importDefault without tslib in output when noEmitHelpers and importHelpers set to true

[mrttrifork]

TypeScript Version: 4.0.2

Search Terms:

tslib, __importDefault

Code

Using "noEmitHelpers": true and "importHelpers": true does not always include tslib_1 in files, in the last example __importDefault is in the index.js file, without any tslib_1

tsconfig

{
  "compileOnSave": false,
  "compilerOptions": {
    "target": "es5",
    "lib": [
      "es2017", "dom", "es2018.promise"
    ],
    "module": "commonjs",
    "moduleResolution": "node",
    "rootDir": "./src",
    "declaration": true,
    "noLib": false,
    "outDir": "target/lib/ts",
    "allowSyntheticDefaultImports": true,
    "sourceMap": true,
    "strictBindCallApply": false,
    "esModuleInterop": true,
    "strictNullChecks": true,
    "noUnusedLocals": true,
    "noImplicitAny": true,
    "noEmitHelpers": true,
    "importHelpers": true
  },
  "exclude": [
    "node_modules",
    "target"
  ]
}

TypeScript 3.9.7

// index.ts
export * from "./core/Core";
export {default as HandlerManager} from "./core/HandlerManager";

// becomes

// index.js
Object.defineProperty(exports, "__esModule", { value: true });
var tslib_1 = require("tslib");
tslib_1.__exportStar(require("./core/Core"), exports);
var HandlerManager_1 = require("./core/HandlerManager");
Object.defineProperty(exports, "HandlerManager", { enumerable: true, get: function () { return HandlerManager_1.default; } });

Here tslib_1 is only used for exportStar and HandlerManager is not wrapped in __importDefault

TypeScript 4.0.2

// index.ts
export * from "./core/Core";
export {default as HandlerManager} from "./core/HandlerManager";

// becomes

// index.js
Object.defineProperty(exports, "__esModule", { value: true });
// lots of exports, removed because only HandlerManager is relevant
exports.firstExport = ... = exports.HandlerManager = void 0;
var tslib_1 = require("tslib");
tslib_1.__exportStar(require("./core/Core"), exports);
var HandlerManager_1 = require("./core/HandlerManager");
Object.defineProperty(exports, "HandlerManager", { enumerable: true, get: function () { return tslib_1.__importDefault(HandlerManager_1).default; } });

Here HandlerManager is imported correct with tslib_1, however if we remove the * import from index.ts, we have

// index.ts
// export * from "./core/Core";
export {default as HandlerManager} from "./core/HandlerManager";

// becomes

// index.js
Object.defineProperty(exports, "__esModule", { value: true });
// lots of exports, removed because only HandlerManager is relevant
exports.firstExport = ... = exports.HandlerManager = void 0;
// export * from "./core/Core";
var HandlerManager_1 = require("./core/HandlerManager");
Object.defineProperty(exports, "HandlerManager", { enumerable: true, get: function () { return __importDefault(HandlerManager_1).default; } });

Now we have __importDefault , but tslib is not imported and __importDefault doesn't come from tslib, so __importDefault is undefined

Expected behavior:

tslib should be imported in index.js and importDefault should be called like tslib_1.__importDefault

Actual behavior:

__importDefault without any tslib in index.js

Playground Link: Not possible, requires more than 1 file

Related Issues: No similar issues

[mxmauro]

Here the same, cannot get rid of __importDefaut

[mrttrifork]

I see that 4.1.2 is released. Please consider to include this issue in 4.2

[mrttrifork]

The problem still persists. As for now i have created a workaround in my index.ts

I added this at the top of the file

export * from "./noop"; // TypeScript 4.2 is bugged it won't import tslib.__importDefault without importing another tslib function

Where noop.ts looks like this

export function noop() { /* Do nothing */ }

This way i get __exportStar imported and then everything works as intended