[BUG] `npm install` silently fails to create symlinks for workspaces when "`main`" is added in parent `package.json`

Is there an existing issue for this?

• I have searched the existing issues

This issue exists in the latest npm version

• I am using the latest npm

Current Behavior

When I am trying to bootstrap a project with workspaces and main is present the installation fails to symlink the workspaces.

Expected Behavior

Symlinking the workspaces or showing a warning message.

Steps To Reproduce

1. Create a project with npm init -y, main should be present inside the parent package.json
2. Add one or more workspaces
3. Run npm install
4. Workspaces are not properly symlinked, no error or warning is thrown.

Example structure:

+-- package.json
`-- workspace-a
   `-- package.json

Example parent package.json :

{
  "name": "my-workspaces-powered-project",
  "main": "index.js",
  "workspaces": [
    "workspace-a"
  ],
  "devDependencies": {
    "typescript": "4.3.5",
    "@types/node": "16.7.5",
  }
}

Environment

• npm: 8.0.0
• Node: v16.11.1
• OS: MacOS
• npm config:

; "builtin" config from /opt/homebrew/lib/node_modules/npm/npmrc

prefix = "/opt/homebrew"

; node bin location = /opt/homebrew/Cellar/node/16.11.1/bin/node
; cwd = /Users/vorillaz
; HOME = /Users/vorillaz
; Run `npm config ls -l` to show all defaults.

Start by reproducing the workspace layout and parent package.json shown in the issue, then run npm install with the reported npm and Node versions. Trace the workspace installation path to determine why the symlink is skipped when main is present; done means the workspace is symlinked or npm emits a warning.