tsconfig paths

As I've learned, the module specifiers in typescript have two audiences:

• They're used by the host when resolving modules.
• They're used by typescript to check type safety based on the imported module.

I found myself in a bit of tricky situation when I wanted to author typescript code that imports npm modules without the intention of using a bundler in the build process.

Instead, I'd like to use import maps to include the dependencies.

Consequently, my development environment is radically different than my production environment.

Since typescript does not transform the module specifier and I did not want to use a bundler to glue things together, I was prepared for a challenge.

The paths compiler option can be used as an alias to "hack" it so that we can write the module specifier as it's intended for the host while finding a way to let typescript know how to resolve the module.

  // tsconfig.json
  {
      "compilerOptions": {
          "module": "ES2022",
          "baseUrl": ".",
          "paths": {
              "emacs": ["foo/bar"] // there is a foo/bar.ts file.
          }
      }
  }

  // program.ts
  import { helloworld } from "emacs";

  import { helloworld as h } from "foo/bar.js" // XXX: we're being incredibly explicit and accurate by specifying the expected output js file instead of letting typescript perform file extension substitution guessing.


  function main() {
      helloworld()
      h()
  }

  main()