Declare subpath exports for bundled plugins, Eleventy-maintained data, .d.ts typings, etc.

[noelforte]

Upfront note: I'd be willing to submit a PR to help out with this.

Is your feature request related to a problem? Please describe.

Commit c505822 inadvertantly introduced some breaking changes to subpath exports when Eleventy is consumed as a dependency. By adding the exports key to package.json with only 1 conditional import (import/requre keys), any attempt to import a subpath throws a ERR_PACKAGE_PATH_NOT_EXPORTED error. (source)

Describe the solution you'd like

This is more specific to @11ty/eleventy/src/Engines/Util/ContextAugmenter.js (#3355 (comment)) but is applicable to any exports in Eleventy that could be consumed by outside packages, including (but not limited to):

• Plugins bundled with Eleventy
• .d.ts declaration files (#3097, #3296)
• Eleventy-maintained global data and methods like augmentKeys

Syntax I'm thinking of could be something like:

"exports": {
  ".": {
    "import": "./src/Eleventy.js",
    "require": "./src/EleventyCommonJs.cjs",
  },
  "./user-config": {
    "types": "./types/UserConfig.d.ts"
  },
  "./plugins/*": "./src/Plugins/*",
}

The above declarations can be consumed as so:

import type UserConfig from '@11ty/eleventy/user-config';
import Eleventy from '@11ty/eleventy';
import HtmlBasePlugin from '@11ty/eleventy/plugins/HtmlBasePlugin.js';
// ...

Or via an aggregator:

"exports": {
  "./internal-plugins": "./src/Plugins/index.js",
}

import {
  HtmlBasePlugin,
  RenderPlugin,
  InputPathToUrlPlugin,
} from '@11ty/eleventy/internal-plugins';

Describe alternatives you've considered

It is possible to import something from a package with an "exports" key directly via node_modules, for instance this doesn't throw an error:

import { augmentKeys } from 'node_modules/@11ty/eleventy/src/Engines/Util/ContextAugmenter.js';

...however I'm cautious to use that pattern because it's 1) not terribly erganomic, and 2) I'm not sure if there's any resolution errors that could stem from that syntax. In my case specifically, augmentKeys is a 2-element array so my solve is copy-pasting the array into my code to achieve the same result.

Additional context

Subpath exports are supported by Node 18 which is the required minimum for 3.0.

Additionally, when an exports field is present the main field is ignored by Node v12.7.0 and later, so to alleviate any confusion in Node's entry-point resolution, it might be worth removing the "main" key from Eleventy's package.json entirely. (source)

[Ryuno-Ki]

Related to #3097

[noelforte]

Related to #3097

@Ryuno-Ki yep, I mentioned that issue in my original post. I opened a new issue since while .d.ts files can be referenced through subpath imports, the implementation of subpath imports isn't directly dependent on typings. I'm ok closing in favor of the other issue, but there's my explanation 😄

[Ryuno-Ki]

Ah, missed the nuance.