Add (relative) URL imports for modules

Search Terms

• import url
• relative url import

Suggestion

Add a new moduleResolution mode (e.g. "url") that treats non-bare specifiers in import statements and -expressions as URLs, matching the behavior of browser and node ESM. Mostly for relative URLs but potentially also for absolute URLs. It likely shouldn't change the resolution of require calls.

There's a similar issue (Add support for URI style import) that focusses on HTTP URLs but I would consider supporting HTTP URLs out of scope for this issue. It may be possible to layer HTTP support on top of the basic feature, so they aren't mutually exclusive.

Use Cases

Write code that works as-is in browsers and node, using filenames that contain characters that would typically be URL encoded (like spaces).

Examples

Right now the "classic" and "node" (~CommonJS/babel) resolution modes treat relative specifiers as file system paths and don't support absolute file:// URLs at all. For browser ESM and node ESM, these should typically be treated as relative URLs. E.g.:

// main.ts
import {name} from './dep%20file.js';
console.log(name);

// dep file.ts:
export const name = 'Robin';

TypeScript generates working code for this (if emit on error is allowed) but it will fail to trace the import correctly because it expects an imported filename that contains the literal string "%20".

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Start by tracing how the moduleResolution modes handle relative import statements and import expressions, comparing the existing classic and node behavior. The work is done when a URL-oriented mode resolves relative URL specifiers such as './dep%20file.js' correctly without changing require resolution or requiring HTTP URL support.