Xstate: [4.7.0] Property 'observable' does not exist on type 'SymbolConstructor'.

[wKovacs64]

Description

TypeScript is throwing an error as of [email protected].

Expected Result

No errors.

Actual Result

node_modules/xstate/lib/interpreter.d.ts(171,13): Error TS2339: Property 'observable' does not exist on type 'SymbolConstructor'.

Reproduction

• CodeSandbox template

The default reproduction example includes the problem, but you have to download it from CodeSandbox and run tsc locally to see it, as far as I know.

Additional context

xstate v4.6.7 is OK, but v4.7.0 and v4.7.1 (at the time of this writing) exhibit the error.

[davidkpiano]

When building locally, if you change this in packages/core/src/interpreter.ts:1216, does it fix the problem?

- public [Symbol.observable]() {
+ public [(Symbol as any).observable]() {
    return this;
  }

[wKovacs64]

Yes, it appears so. Rebuilding after making that change completely removes the offending line from the built types (packages/core/lib/interpreter.d.ts:171):

    toJSON(): {
        id: string;
    };
-   [Symbol.observable](): this;
}
export declare function spawn<TC, TE extends EventObject>(entity: StateMachine<TC, any, TE>, nameOrOptions?: string | SpawnOptions): Interpreter<TC, any, TE>;
export declare function spawn(entity: Spawnable, nameOrOptions?: string | SpawnOptions): Actor;

[davidkpiano]

That's fine; that line is for run-time compatibility with TC39 observables anyway.

[qtiki]

That's fine; that line is for run-time compatibility with TC39 observables anyway.

I don't think this is fine. Creating an empty TypeScript project with xstate doesn't compile so basically the whole package in NPM is broken for TypeScript users:

package.json:

{
  "name": "xstate-test",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "dependencies": {
    "xstate": "^4.7.1"
  },
  "devDependencies": {
    "typescript": "^3.7.2"
  }
}

tsconfig.json:

{
  "compilerOptions": {
    "lib": [
      "dom",
      "es2015"
    ]
  },
  "include": [
    "test.ts"
  ]
}

test.ts:

import * as xstate from 'xstate';

Trying to compile this project with tsc gives the error mentioned in the issue title.

[wKovacs64]

@qtiki The fix hasn't made it into a published version, yet.

[qtiki]

Oh I thought you were discussing a local workaround and not a fix to the package. I'll revert to an older version then while waiting for the fix. Thanks.

[wKovacs64]

You can patch it yourself with patch-package if you want to use the latest version until the fix is released (that's what I'm doing). Or revert, yeah.

[davidkpiano]

Published as 4.7.2 @qtiki

[qtiki]

Published as 4.7.2 @qtiki

Can confirm it's working now. 👍