codemirror v6 couldn't be installed with snowpack 2.18.3

[twop]

codemirror@next is shipped as esmodule package with import map
https://github.com/codemirror/codemirror.next/blob/master/package.json

Note that there is no package.json in the exports map
Relevant snippet:

{
  "name": "@codemirror/next",
  "version": "0.15.0",
  "type": "module",
  "exports": {
    "./state": "./state/dist/index.js",
    "./text": "./text/dist/index.js",
    "./view": "./view/dist/index.js",
    "./commands": "./commands/dist/index.js",
    "./history": "./history/dist/index.js",
    "./collab": "./collab/dist/index.js",
    "./gutter": "./gutter/dist/index.js",
    "./rangeset": "./rangeset/dist/index.js",
    "./language": "./language/dist/index.js",
    "./language-desc": "./language-desc/dist/index.js",
    "./fold": "./fold/dist/index.js",
    "./matchbrackets": "./matchbrackets/dist/index.js",
    "./closebrackets": "./closebrackets/dist/index.js",
    "./panel": "./panel/dist/index.js",
    "./tooltip": "./tooltip/dist/index.js",
    "./search": "./search/dist/index.js",
    "./goto-line": "./goto-line/dist/index.js",
    "./lint": "./lint/dist/index.js",
    "./highlight": "./highlight/dist/index.js",
    "./stream-parser": "./stream-parser/dist/index.js",
    "./autocomplete": "./autocomplete/dist/index.js",
    "./comment": "./comment/dist/index.js",
    "./rectangular-selection": "./rectangular-selection/dist/index.js",
    "./highlight-selection": "./highlight-selection/dist/index.js",
    "./basic-setup": "./basic-setup/dist/index.js",
    "./lang-javascript": "./lang-javascript/dist/index.js",
    "./lang-java": "./lang-java/dist/index.js",
    "./lang-json": "./lang-json/dist/index.js",
    "./lang-cpp": "./lang-cpp/dist/index.js",
    "./lang-python": "./lang-python/dist/index.js",
    "./lang-css": "./lang-css/dist/index.js",
    "./lang-html": "./lang-html/dist/index.js",
    "./lang-sql": "./lang-sql/dist/index.js",
    "./lang-rust": "./lang-rust/dist/index.js",
    "./lang-xml": "./lang-xml/dist/index.js",
    "./lang-markdown": "./lang-markdown/dist/index.js",
    "./theme-one-dark": "./theme-one-dark/dist/index.js"
  },
}

After I upgraded to version 2.18.3 I started to get this error:

No "exports" main defined in /Users/twop/work/scry-play/node_modules/@codemirror/next/package.json

Which is true :)

I'm not sure why it is required though, I read node docs https://nodejs.org/api/packages.html#packages_exports and skypack https://docs.skypack.dev/package-authors/package-checks#export-map and I can't find a mention about package.json.

Thus it seems that the logic here https://github.com/snowpackjs/snowpack/blob/5e22dae6825d24a375b56bf2dd7141c5f19b9a1b/skypack/src/util.ts#L88 is incomplete.

I want to upgrade to 2.18.3 because it seems to support webworkers in dev mode but I can't because of this issue.

NOTE: version 2.17.1 seems to have no issues with that

[FredKSchott]

You're right, it's failing here:

const fullPath = fs.realpathSync.native(require.resolve(dep, {paths: [cwd]}));

We're kind of stuck here, tbh. We have two ways to fetch a package.json manifest for a package by name:

• require.resolve(${dep}/package.json) Works if no export map, or if export map contains package.json
• require.resolve(dep) + traverse up the file system to closest package.json Works if export map with '.' entry

I actually don't think there's any possible way to do this without either ['.'] or ['./package.json'] in your export map. We need to use require.resolve() at some point in the resolution logic because otherwise yarn v2 / PnP mode will break. Curious if anyone has any ideas for how to solve this.

@twop for now, the package will either need to add a 'package.json' or a '.' entrypoint to thier export map for it to work in Snowpack.

[twop]

I submitted a PR codemirror/dev#349 to CodeMirror

But it seems that a lot of packages might be affected by this, meaning that a normally looking package on npm might not work with snowpack (and I assume skypack?)

[FredKSchott]

See issue here: nodejs/modules#445

this is a node.js limitation, I'm actually not sure what the workaround is here (it sounds like one may not exist)