Package subpath './package.json' is not defined by "exports"

[zwz]

I was using this package in https://github.com/sveltejs/sapper-template/tree/rollup
But it reports error:

Package subpath './package.json' is not defined by "exports" 
in <my-project-path>/node_modules/w3c-keyname/package.json

[marijnh]

Do you have a stack trace for the error? I guess someone is directly requiring package.json, which worked fine in a pre-node-14 world, but is likely to cause this error for packages that declare an exports field now. The best way to fix it is probably to adjust that package to just load and parse the file properly.

[zwz]

What I did is adding at the beginning of the file sapper-template-rollup/src/routes/index.svelte:

<script>
 import * as Key from  "w3c-keyname"   
</script>

And when I run npm run dev, it reports:

✗ server
Package subpath './package.json' is not defined by "exports" in /Users/rbx0999/project/sapper-template-rollup/node_modules/w3c-keyname/package.json
✗ client
Package subpath './package.json' is not defined by "exports" in /Users/rbx0999/project/sapper-template-rollup/node_modules/w3c-keyname/package.json
internal/modules/cjs/loader.js:1032
  throw err;
  ^

Error: Cannot find module 'sapper-template-rollup/__sapper__/dev/server/server.js'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:1029:15)
    at Function.Module._load (internal/modules/cjs/loader.js:898:27)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12)
    at internal/main/run_main_module.js:17:47 {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}

[marijnh]

This seems to be an issue with rollup-plugin-svelte (see this pr, for example). I'm going to close this here.