Plugins: Don't add file extensions automatically

[Rich-Harris]

_This issue was transferred from rollup-plugin-alias, which lacked an issue template_

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Reviewing the various PRs for rollup/rollup-plugin-alias#11, I was struck by how much extra work is created for the sake of allowing users to do this...

alias({
  foo: 'bar'
})

...when they mean this:

alias({
  foo: 'bar.js'
})

In my view there's no good reason to support that. Extension-less imports is a bad habit encouraged by Node's ill-conceived module resolution algorithm. Being explicit and obvious (rather than relying on scattered bits of magic) makes life easier for whichever developer inherits a project, and it would allow us to remove a lot of moving parts (including the resolve option).

Breaking, obviously, so would have to be a version 2. Thoughts?

[hansemannn]

@Rich-Harris I'd love to see this integrated, even if it requires a major bump. Otherwise, an alternative or workaround would be appreciated!

[andrezsanchez]

This is preventing me from using this in a TypeScript build setup because it is automatically adding .js when I just want to put .ts

[gluons]

This also break my import './some-my-style.css';.

[shellscape]

@Rich-Harris is this one still relevant?

[dumbmatter]

I just ran into this problem too, when I want to alias a JSON file and then load it with rollup-plugin-json, it fails because this configuration:

{find: 'aliased-json', replacement: './test.json'},

makes it look for test.json.js.

So I have to create a dummy JS test.js next to test.json that just imports and exports test.json, and then alias to that rather than my JSON file.

If a non-breaking change was desired, an option could be added to disable the automatic file extension.

EDIT: Sorry, I just realized what the resolve option does. Still seems like it'd be better to change the default behavior :)

[northkode]

webpack has a similar thing that allows us to alias directories so we can even alias to asset files that might be images.

Currently my config is

alias({
            '@assets': __dirname + '/src/assets'
        }),

And i'm doing
import png from "@assets/icon.png";

but this adds .js to the end of the file.. which is not ideal. it seems alias shouldnt be bound to a file type assumption.

[lukastaegert]

Another approach could be to use the this.resolve context function to resolve this. If someone were to use rollup-plugin-node-resolve, they get the resolution algorithm they know and love, otherwise just what is built-in. @Acionyx has been contacting me because he is working on a fork to do just that but I did not yet find time to have a look.

[chopfitzroy]

@lukastaegert could you give a small example of using this.resolve?

Cheers.

[lukastaegert]

Here is a real-world example, though it is probably not a simple one: https://github.com/rollup/rollup-plugin-commonjs/blob/535e8117607731e1e8688be84c3aeb6e5c3b6fa5/src/resolve-id.js#L54

Here it is taking an import of the form commonjs-proxy:./some-imports.js, removes the prefix and uses this.resolve to find out what path the import of ./some-import.js resolves to.

[shellscape]

34 was merged and published a little while back. It now uses this.resolve() and should alleviate this issue. If it still pops up with the new version, please respond and we'll reopen.