Import issue where file 2 is not running

[apacheli]

Oddly, I seem to be getting a "not defined error" despite having the code correct. I would assume that this is likely a compile issue as I was able to replicate it almost instantly.

// test1.ts
import { A } from "./test2.ts";

console.log("test 1");

console.log(A.B);

// test2.ts
export const enum A {
  B
}

console.log("Is this even running");

Running these examples yields these results:

From the logs, it seems like test2.ts doesn't run at all. The runtime seems to die here.

(If needed, I can move this to the issue tracker, which I probably should've done at first.)

[apacheli]

Update:

Importing test2.ts without importing any of its exports logs this:

import { A } from "./test2.ts";
import "./test2.ts";

It is running, though the export still doesn't happen.

I tried again with import as a function, and that works. However, I don't think that this is the solution.

const { A } = await import("./test2.ts");

I also checked to see if const enum was the problem, and it is not.

[kitsonk]

const enum are not supported in Deno. We need to make that clearer in the documentation. We only support TypeScript in the isolatedModules mode, which is enabled by default. I has assumed that isolateModules would report errors with const enum but it appears it doesn't. const enum aren't ever exported, because they are fully erased from the emit and the emitted code ends up with a "hardcoded" value. Because it is a type directed emit (e.g. what the type information is impacts what the emitted code is, which is really a TypeScript anti-pattern) they are not supported in Deno. TypeScript/tsc continues to support it, though it runs afoul of the TypeScript design principles, because they don't want to break backwards compatibility.

[apacheli]

const enum are not supported in Deno. We need to make that clearer in the documentation. We only support TypeScript in the isolatedModules mode, which is enabled by default. I has assumed that isolateModules would report errors with const enum but it appears it doesn't. const enum aren't ever exported, because they are fully erased from the emit and the emitted code ends up with a "hardcoded" value. Because it is a type directed emit (e.g. what the type information is impacts what the emitted code is, which is really a TypeScript anti-pattern) they are not supported in Deno. TypeScript/tsc continues to support it, though it runs afoul of the TypeScript design principles, because they don't want to break backwards compatibility.

Removing const enum seemed to have solved the issue for the most part, but I'm still confused on why the compiled code seems to be inconsistent whether I include const or not. I checked the compiled code in %appdata%/local/deno and it doesn't include any import statements:

// These 2 results are without `const enum` in test2.ts
// test1.ts.js
console.log(A.B);
export {};

// test2.ts.js
export var A;
(function (A) {
    A[A["B"] = 10] = "B";
})(A || (A = {}));

It seems like Deno is ignoring the fact that test1.js is not being edited, therefore it doesn't re-compile?

This is what I did to replicate the error:

• Create both files with the initial code samples
• Expect error when running test1.ts, intended yes because isolatedModules
• Remove const from enum in test2.ts, and run test1.ts again. This also errors, which is probably unintended?
• Edit test1.ts however you wish, run again, and it doesn't error

[nayeemrmn]

This is a tsc transpilation bug tracked in microsoft/TypeScript#40499, #7605.