--experimental-specifier-resolution=node doesn't follow the `main` field in package.json

[hronro]

• Version: v16.1.0
• Platform: Linux ArchLinux 5.12.4-arch1-2 deps: update openssl to 1.0.1j #1 SMP PREEMPT Sat, 15 May 2021 20:58:02 +0000 x86_64 GNU/Linux
• Subsystem:

What steps will reproduce the bug?

project structure:

├── package.json
└── src
   ├── foo
   │  ├── package.json
   │  └── src
   │     └── index.js
   └── index.js

// package.json
{
  "main": "src/index.js",
  "type": "module"
}

// src/foo/package.json
{
  "main": "src/index.js",
  "type": "module"
}

// src/foo/src/index.js
export default 'foo'

// src/index.js
import foo from './foo'

console.log(`hello from ${foo}`)

Run node --experimental-specifier-resolution=node .

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior?

Should see hello from foo in the terminal

What do you see instead?

node:internal/process/esm_loader:74
    internalBinding('errors').triggerUncaughtException(
                              ^

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/xxx/src/foo' imported from /xxx/src/index.js
    at new NodeError (node:internal/errors:363:5)
    at finalizeResolution (node:internal/modules/esm/resolve:296:11)
    at moduleResolve (node:internal/modules/esm/resolve:742:10)
    at Loader.defaultResolve [as _resolve] (node:internal/modules/esm/resolve:853:11)
    at Loader.resolve (node:internal/modules/esm/loader:89:40)
    at Loader.getModuleJob (node:internal/modules/esm/loader:242:28)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:73:40)
    at link (node:internal/modules/esm/module_job:72:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}

Additional information

[aduh95]

@nodejs/modules

[ljharb]

I believe this is quite intentional; see #36918.

Especially when using ESM, the intention is to use "exports" and not "main" (altho a published package should ofc provide both, for back compat).