how to use TypeScript in my npm library and make it usable in both Angular AND nodejs environment

Question

I would like to write in TypeScript a npm package and I want that the user will be able to use it in both Angular and node environments.

I saw that this question was asked many times, like here or here, but it's not exactly what I want. I found a lot of other responses, like this excellent article, but I still have a problem, and I don't know why. I try to solve it since two days and I think that I will soon become crazy.

Example :

My awesome package :

index.ts

import { hello } from './file-to-import';

export function sayHello() {
    hello();
}

file-to-import.ts

export function hello() {
    console.log('Hello');
}

tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "moduleResolution": "node",
        "target": "es5",
        "declaration": true,
        // ....
    }
}

Now I compile the library with tsc, publish it and try to use it in Angular for the frontend and in NodeJs for the backend.

• First try with the combination commonjs/es5 :

All is ok for the backend, but in the frontend, Angular gives a warning : ... depends on 'my-awesome-module'. CommonJS or AMD dependencies can cause optimization bailouts.. I could ask the user to solve this problem by adding my module to allowedCommonJsDependencies option in angular.json, but I think that's not a good idea.

• Second try with the combination es6/es5 or esnext/es5:

Now, all is ok for Angular, but nodejs says in the backend : SyntaxError: Cannot use import statement outside a module.

• Third try with the combination umd/es5:

All is perfect for NodeJs, but Angular throws the same error than in the first try and adds other warnings : Critical dependency: require function is used in a way in which dependencies cannot be statically extracted.

I think that it's possible to transpile the module two times, one with a tsconfig with esnext/es5 and the other with commonjs/es5, but I don't know how to do that and if it's a good idea.

Any help will be welcome !