Can not build with --isolatedModules

[neelance]

Describe the Bug
Can not build with TypeScript compiler option isolatedModules.

Steps to Reproduce
Add cloudevents as a dependency to a project that uses isolatedModules and run a build.

You get:

node_modules/cloudevents/dist/index.d.ts:7:60 - error TS2748: Cannot access ambient const enums when the '--isolatedModules' flag is provided.

The problem is with export declare const enum Version. One way to solve this would be to drop the const modifier.

Expected Behavior
Build passes.

[github-actions]

This issue is stale because it has been open 30 days with no activity.

[jketcham]

I'm running into this issue as well in a Typescript project being transpiled with babel.

For reference, it looks like there are two places where const enum is being used:

• sdk-javascript/src/event/cloudevent.ts

  Line 17 in 2ac731e

  export const enum Version {

• sdk-javascript/src/transport/protocols.ts

  Line 10 in 80d987c

  export const enum Protocol {

Could a change to remove the const declaration from those enums be accepted?

Or I think setting preserveConstEnums to true may fix the problem too, info on that option here: https://www.typescriptlang.org/tsconfig#preserveConstEnums.

I tried both changes in a fork and all tests passed if anyone is interested in taking a look. I can open a PR if either change is reasonable.

• https://github.com/jketcham/sdk-javascript/tree/456-remove-const-enums
• https://github.com/jketcham/sdk-javascript/tree/456-set-preserve-const-enums

[grant]

@lance Do you think we could simply remove const from our enums here?

Seeing a downstream issue.

[lance]

@lance Do you think we could simply remove const from our enums here?

That should be part of it. But I think the resolution should be more comprehensive. I found this article a good read on the problem, as I was unaware of exactly why this was an issue. https://ncjamieson.com/dont-export-const-enums/

We should add "isolatedModules": "true" to our tsconfig.json. I did this locally, and it actually exposes a number of problems besides just this.

❯ npm run build

> cloudevents@5.3.1 build /home/lanceball/src/github.com/cloudevents/sdk-javascript
> tsc --project tsconfig.json && tsc --project tsconfig.browser.json && webpack

src/index.ts:20:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

20   CloudEventV1,
     ~~~~~~~~~~~~

src/index.ts:21:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

21   CloudEventV1Attributes,
     ~~~~~~~~~~~~~~~~~~~~~~

src/index.ts:25:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

25   Headers,
     ~~~~~~~

src/index.ts:27:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

27   Binding,
     ~~~~~~~

src/index.ts:28:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

28   Message,
     ~~~~~~~

src/index.ts:29:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

29   Deserializer,
     ~~~~~~~~~~~~

src/index.ts:30:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

30   Serializer,
     ~~~~~~~~~~

src/index.ts:33:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

33   KafkaEvent,
     ~~~~~~~~~~

src/index.ts:34:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

34   KafkaMessage,
     ~~~~~~~~~~~~

src/index.ts:36:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

36   MQTTMessage,
     ~~~~~~~~~~~

src/index.ts:39:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

39   TransportFunction,
     ~~~~~~~~~~~~~~~~~

src/index.ts:40:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

40   EmitterFunction,
     ~~~~~~~~~~~~~~~

src/index.ts:43:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

43   Options,
     ~~~~~~~

src/message/kafka/index.ts:14:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

14   KafkaMessage,
     ~~~~~~~~~~~~

src/message/kafka/index.ts:15:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

15   KafkaEvent
     ~~~~~~~~~~

src/message/mqtt/index.ts:10:3 - error TS1205: Re-exporting a type when the '--isolatedModules' flag is provided requires using 'export type'.

10   MQTTMessage,
     ~~~~~~~~~~~


Found 16 errors.

npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! cloudevents@5.3.1 build: `tsc --project tsconfig.json && tsc --project tsconfig.browser.json && webpack`
npm ERR! Exit status 2
npm ERR!
npm ERR! Failed at the cloudevents@5.3.1 build script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/lanceball/.npm/_logs/2022-02-09T20_02_30_244Z-debug.log

[lance]

By simply changing tsconfig.json to use "isolatedModules": "true", it seems TypeScript transpiles to the correct JavaScript.

exports.CloudEvent = exports.Version = void 0;
const uuid_1 = require("uuid");

/**
 * An enum representing the CloudEvent specification version
 */
var Version;
(function (Version) {
    Version["V1"] = "1.0";
    Version["V03"] = "0.3";
})(Version = exports.Version || (exports.Version = {}));