Feature: disable extensionless imports

I’d like there to be a way to always require the file extension to be specified for relative import statements. At the moment extensionless imports always just work. Even ‘Go to Definition’ just assumes it should open the JS file.

src/
 - index.js
 - foo.js

// index.js
import { Foo } from './foo'; // extensionless

I’d like there to be a jsconfig option to disable this behavior and require a file extension to be specified.

import { Foo } from './foo';
                    ^^^^^^^ No definition found for 'foo'

// fix
- import { Foo } from './foo';
+ import { Foo } from './foo.js';

I’m asking because extensionless imports don’t really work in the browser if you’re not using a module bundler. It can only work if the HTTP server supports extensionless imports, which is a big ask.

[fatcerberus]

I’m going to put my support behind seeing a fix for this. Browsers support ES modules natively now and TS isn’t a nice experience for web development because:

1. Automatic imports are added without an extension
2. Browsers don’t support extensionless imports
3. TS doesn’t support module specifiers rewriting

…which creates a perfect storm in which it’s possible to write several modules with a nontrivial dependency graph before realizing that the whole thing is broken because none of the import statements have extensions. Fixing it is then an exercise in patience as you hunt through the project looking for offending imports—and the browser won’t help you here because it stops short at the first one that fails to load. It’s not a good development experience, which sucks because TS is so, so nice otherwise. 😦

Even if TS just rewrote imports in the generated code to append a .js to any specifiers without it, that would be a good interim solution, I think.

[thw0rted]

It’s weird but I don’t think this issue has any links yet to the ur-issue, https://github.com/microsoft/TypeScript/issues/16577. Technically, providing a flag to error out is different from providing a flag to append the correct extension, but it’s pretty similar.