Utilizing paths feature without baseUrl #28321

Hi!

I'm trying to figure out how to use the compilerOptions.paths behavior while retaining the default behavior of compilerOptions.baseUrl.

The following examples assume a folder structure like so:

my-app/
  tsconfig.json
  package.json
  src/
    index.ts
    something.ts

For example, if we want to support absolute imports via @/, we could configure paths like so:

{
  "compilerOptions": {
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  }
}

Unfortunately, this has the side effect of permitting import 'src/something'; since baseUrl is set to ..

It appears as if you can replicate the desired behavior by using the following configuration:

{
  "compilerOptions": {
    "baseUrl": "node_modules",
    "paths": {
      "@/*": ["../src/*"]
    }
  }
}

However, I'm not sure if this is functionally equivalent to the following example for all intents and purposes (assuming this worked):

{
  "compilerOptions": {
    "baseUrl": null, // undefined, whatever
    "paths": {
      "@/*": ["./src/*"]
    }
  }
}

Can you confirm if baseUrl: 'node_modules' is identical to baseUrl: undefined? Or are these behaviors different?

Thanks!