SSR resolve always happens as require even when it's an import

[benmccann]

Describe the bug

Svelte has a package.json in each directory to support older versions of Node. On Node 12+ the exports map will be used. Even on newer versions of Node, Vite appears to be looking at the nested package.json rather than the exports map, which is incorrect. This only happens with the external config.

Originally reported in sveltejs/vite-plugin-svelte#360

Reproduction

git clone git@github.com:benmccann/context-issue.git
cd context-issue/svelte-kit-app
npm install
npm run dev

System Info

System:
    OS: macOS 12.3.1
    CPU: (10) arm64 Apple M1 Pro
    Memory: 293.67 MB / 32.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 17.9.0 - ~/.nvm/versions/node/v17.9.0/bin/node
    Yarn: 1.22.18 - ~/.nvm/versions/node/v17.9.0/bin/yarn
    npm: 8.5.5 - ~/.nvm/versions/node/v17.9.0/bin/npm
  Browsers:
    Chrome: 102.0.5005.61
    Firefox: 100.0.2
    Safari: 15.4
    Safari Technology Preview: 15.4
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.50 
    @sveltejs/kit: next => 1.0.0-next.347 
    svelte: ^3.44.0 => 3.48.0

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[benmccann]

There's at least a couple bugs here.

The first is that it appears to try multiple packages before looking for an exports field:

vite/packages/vite/src/node/plugins/resolve.ts

Line 629 in cba13e8

const possiblePkgId = nestedPath.slice(0, slashIndex)

The second is that it hardcodes isRequire: true which is wrong nearly 100% of the time for SvelteKit projects:

vite/packages/vite/src/node/ssr/ssrModuleLoader.ts

Line 129 in 65dd88b

isRequire: true,

It's possible there's still be more wrong after that, but fixing those would be a good start.

[benmccann]

Reopening since the isRequire portion of the fix was reverted: #10569

Also, @aleclarson pointed out a tweak that may be needed for the remaining piece of the fix: #10371 (comment)