Angular/Typescript: "export const" cannot be compiled

Issue

I've just started to build my own library for Angular. First I added a service; I can build the lib problem-free.

For this service, however, I have moved a constant to a file called tokens.ts to which the service now references. J

Now the build fails with the following message:

------------------------------------------------------------------------------
Building entry point 'mylib'
------------------------------------------------------------------------------
√ Compiling with Angular sources in Ivy partial compilation mode.
× Generating FESM2020
'SOME_VALUE' is not exported by dist\mylib\esm2020\lib\tokens.mjs, imported by dist\mylib\esm2020\lib\services\mysuperservice.service.mjs
Process finished with exit code 1

The tokens.ts:

export declare const SOME_VALUE: ...

The mentioned service:

import {SOME_VALUE} from "../tokens";

@Injectable({
  providedIn: 'root',
})
export class MySuperService{
//...

My tsconfig.lib.json:

{
  "extends": "../../tsconfig.json",
  "compilerOptions": {
    "outDir": "../../out-tsc/lib",
    "declaration": true,
    "declarationMap": true,
    "inlineSources": true,
    "types": []
  },
  "exclude": [
    "src/test.ts",
    "**/*.spec.ts"
  ]
}

My tsconfig.json:

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": "./",
    "paths": {
      "common": [
        "dist/mylib/mylib",
        "dist/mylib"
      ]
    },
    "outDir": "./dist/out-tsc",
    "forceConsistentCasingInFileNames": true,
    "strict": true,
    "noImplicitOverride": true,
    "noPropertyAccessFromIndexSignature": true,
    "noImplicitReturns": true,
    "noFallthroughCasesInSwitch": true,
    "sourceMap": true,
    "declaration": false,
    "downlevelIteration": true,
    "experimentalDecorators": true,
    "moduleResolution": "node",
    "importHelpers": true,
    "target": "es2017",
    "module": "es2020",
    "lib": [
      "es2020",
      "dom"
    ]
  },
  "angularCompilerOptions": {
    "enableI18nLegacyMessageIdFormat": false,
    "strictInjectionParameters": true,
    "strictInputAccessModifiers": true,
    "strictTemplates": true
  }
}

My public-api.ts:

export * from './lib/tokens';
export * from './lib/mylib/mysuperservice.service';
export * from './lib/mylib.module';

My project-tree:

I could imagine that this has something to do with my TS compiler options, since the error message mentions .mjs files. However, I have no idea where the problem could be.

Can you help me with that?

Solution

As @jboot mentioned, the problem was indeed that I was declaring a type; not a concret instance.

Correct way:

export const SOME_VALUE= new InjectionToken<SomeType>('some description');

Thanks for that!

Answered By - EchtFettigerKeks