[API] `getImpliedNodeFormatForFile` can't be used because the first argument is of an internal type

[ericmorand]

🔎 Search Terms

I searched for getImpliedNodeFormatForFile. The issues I found are not related to this issue.

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about TypeScript API.

⏯ Playground Link

No response

💻 Code

const containingFile = 'foo.ts';

const mode = ts.getImpliedNodeFormatForFile(
    containingFile, // TS22345: Argument of type `string` is not assignable to parameter of type `Path`
undefined,
    ts.sys,
    {}
);

🙁 Actual behavior

The mentionned code does not compile because getImpliedNodeFormatForFile expects the first argument to be of a type that is not publicly accessible or instantiable:

type Path = string & {
    __pathBrand: any;
};

There seems to be some factories to construct a Path in the code base of the API, but they are not exposed.

🙂 Expected behavior

The mentionned code does compile, either because getImpliedNodeFormatForFile expects the first argument to be of a type string, or because there is a way to construct an instance of Path.

Additional information about the issue

Interestingly enough, even the developers of the official TypeScript plugin of Rollup did struggle with this issue:

https://github.com/rollup/plugins/blob/33174f956304ab4aad4bbaba656f627c31679dc5/packages/typescript/src/index.ts#L129

ts.getImpliedNodeFormatForFile(
  // @ts-expect-error
  containingFile,
  undefined, // eslint-disable-line no-undefined
  { ...ts.sys, ...formatHost },
  parsedOptions.options
)

They unfortunately didn't consider opening an issue here, so here I am. 😃

[ericmorand]

🙇‍♂️