Ambient const enums are not allowed when the '--isolatedModules' flag is provided (with typescript)

[steabert]

Bug Report

Current Behavior
When compiling a typescript file that imports something from rxjs with the isolatedModules option for typescript set to true, the following error occurs:

node_modules/rxjs/internal/Notification.d.ts:3:27 - error TS1209: Ambient const enums are not allowed when the '--isolatedModules' flag is provided.

3 export declare const enum NotificationKind {

Reproduction

Create minimal project

yarn add --dev typescript rxjs
ts 

Create test.ts:

import {Observable} from 'rxjs'

Run Typescript compiler

yarn tsc --lib esnext --isolatedModules test.ts

Expected behavior
No error.

Environment

• Runtime: Node v10.15.0
• RxJS version: 6.4.0
• (If bug is related) Loader, build configuration: typescript 3.3.1

Possible Solution

Additional context/Screenshots
Add any other context about the problem here. If applicable, add screenshots to help explain.

[cartant]

I'm not familiar with the error, but I have a hunch that it might be addressed by the enum being exported in this PR: #4514

[BrianMitchL]

This also causes compilation errors with @babel/plugin-transform-typescript (the TypeScript compiler used in create-react-app), which does not support const enums.

EDIT: I've created issue #4555 to track this separately.

[cartant]

@BrianMitchL Although it also pertains to const enums, your issue is unrelated to this one. Please open an issue and fill out the template - including all relevant version information.

IIRC, TypeScript 2.4 is the version in which const enums were introduced, so I'd be more than a little surprised if the current version of the transform does not support them.

Anyway, please move all discussion to a new issue.

[am17torres]

@steabert I just ran into this issue after running a yarn upgrade

./node_modules/rxjs/internal/Notification.d.ts
Type error: Ambient const enums are not allowed when the '--isolatedModules' flag is provided.  TS1209

    1 | import { PartialObserver } from './types';
    2 | import { Observable } from './Observable';
  > 3 | export declare const enum NotificationKind {
      |                           ^
    4 |     NEXT = "N",
    5 |     ERROR = "E",
    6 |     COMPLETE = "C"

Downgrading rxjs from 6.4.0 to 6.3.3 removed that error.
This looks like the problem line

@cartant - I think you can simply export * from './internal/Notification';

I'm not sure if this is helpful 🤷‍♂️
DefinitelyTyped/DefinitelyTyped#28744 (comment)
https://github.com/DefinitelyTyped/DefinitelyTyped/pull/29783/files#diff-ec9dabea74600f252c17af9dbe837891R30

One last thought, I'm not too sure if you need to export const enum vs export enum. There is a pretty in-depth explanation on stack overflow

[cartant]

@am17torres Yeah, exporting won't solve this. See this comment.

[mrmckeb]

We're facing this issue too, and I think it's going to affect a lot of people sadly.

Any ideas for workarounds? For now we're forcing the last release (using Yarn's resolutions).

Would the quick fix be to remove const?

[cartant]

@mrmckeb I think pinning your resolution to 6.3.3 would be the quickest, simplest solution, for now.