Can I make TypeScript include node_modules for transpilation?

Question

OK so I have an interesting situation in setting up my Node.js TypeScript project. I want to be able to refer to my local modules using a non-relative require reference. The way TypeScript and Node.js look up modules is to look for a node_modules directory in the current directory and then each parent directory until they find such a directory containing the reference. So let's say I have a module I want to reference in the following directory structure:

/node_modules        <-- Main NPM modules dir
    /...
/package.json
/src
    /node_modules    <-- My local modules dir
        /modules
            /myModule.ts
    /scripts
        /init.ts

... and in init.ts I reference myModule like this:

import myModule from "modules/myModule";

As I understand it, I want TypeScript to transpile my node_modules directory over to the output dist directory along with all my other .ts file directories, so that the dist directory looks like this:

/node_modules        <-- Main NPM modules dir
    /...
/package.json
/dist
    /node_modules    <-- My local modules dir
        /modules
            /myModule.js
    /scripts
        /init.js

Then, when Node.js looks for the module it will find it at dist/node_modules/modules/myModule.js. So in this case I actually do want TypeScript to include the node_modules directory in its input files. I seem to be missing something fundamental, though, because TypeScript actually ignores this directory by default.

Is my scenario a legitimate one for including the node_modules directory, and if so, how can I make TypeScript include it in the transpilation when I just run tsc (and therefore it will use my tsconfig.json file)?

UPDATE: I have found that I can make it include my node_modules directory by explicitly putting it in the include directive in the .tsconfig.json like so:

"include": [
    "./src/node_modules/**/*",
    "./src/**/*"
]

The question remains; am I getting something fundamentally wrong here, because I am having to override something TypeScript excludes by default? I've tested this and when I make it transpile node_modules, it does indeed find my local modules correctly.

Answer 1

That's not correct to include node_modules for transpilation. Because node_modules contains javascript and doesn't requires second transpilation in case of ts libraries, they should have declarations in .d.ts.

If you have custom types, or you want to add types to some libraries that don't have them, you need to use own declarations or @types/* packages.

in your tsconfig.json you can define type roots (where to load declarations from).

{
    "compilerOptions": {
        "typeRoots": ["./declarations", "./node_modules/@types"],
        "types": ["node"],
    }
}

then you can install npm i --save-dev @types/node@^12 for example to get declarations of nodejs v12.

and define your own declarations in declarations for express for example: ./declarations/express/index.d.ts

import * as express from 'express';

declare module 'express' {
    export interface Request {
        user?: {
            id: string;
            name: string;
        }
    }
}