Bundling of .d.ts declarations of external modules

[sumbricht]

Question

My intention is to bundle TypeScript definitions of TS code written by myself with definitions of external modules residing in node_modules. The reasoning behind is that I need to supply these joint definitions to a web-based TS code editor (MonacoEditor) to allow for code completion.

What I have working quite well:

• Transpiling .ts to .js and bundling into a single .js file (note: I don't need the .js file; in the end I would turn on emitDeclarationOnly, but this isn't too relevant now). This is working for custom code, node-internal modules (such as 'path') and external modules (such as 'typeorm')
• Transpiling .ts to .d.ts only for custom code

What isn't working yet:

• Transpiling .ts to .d.ts for node-internal and external modules only references the modules but I would like to have them inlined in the same .d.ts file

Now is there any way how I can force rollup-plugin-ts to inline external type definitions as well?

For reference, I have created the following minimal repo, including the output .js and .d.ts: https://github.com/sumbricht/rollup_dts_example. In reality it would include definitions for around 100 external modules, therefore manually managing wouldn't be feasible; alternative automatable approaches are however also welcome :-).

Below the main files:
rollup.config.js:

import ts from 'rollup-plugin-ts'
import commonjs from '@rollup/plugin-commonjs'
import nodeResolve from '@rollup/plugin-node-resolve'
import polyfill from 'rollup-plugin-polyfill-node'

const config = [
    {
        input: "./src/entrypoint.ts",
        output: [{ file: "./dist/entrypoint.js", format: "es" }],
        plugins: [
            polyfill(),
            commonjs(),
            nodeResolve(),
            ts({
                tsconfig: './tsconfig.json',
                exclude: [],
            })
        ],
    },
];

export default config;

tsconfig.json:

{
  "compilerOptions": {
    /* Language and Environment */
    "target": "ESNext",

    /* Modules */
    "module": "ESNext",
    "moduleResolution": "node",
    "typeRoots": ["node_modules/@types"],
    "types": ["node"],

    /* Emit */
    "declaration": true,
  },
  "exclude": []
}

entrypoint.ts:

// code by myself: nicely reflected in .js and .d.ts
export { Foo } from './foo'

// node-internal code: nicely reflected in .js but as external reference in .d.ts
export { dirname } from 'path'

// external module: nicely reflected in .js but as external reference in .d.ts
export { createConnection } from 'typeorm'

entrypoint.js:

class Foo {
    foo;
    constructor(foo) {
        this.foo = foo;
    }
    printFoo() {
        console.log(this.foo);
    }
}

// code from 'path' and 'typeorm' (cut for brevity)

export { Foo, createConnection$1 as createConnection, dirname };

entrypoint.d.ts:

declare class Foo {
    private foo;
    constructor(foo: string);
    printFoo(): void;
}
export { Foo };
export { dirname } from 'path';
export { createConnection } from 'typeorm';