When can an npm package's dependency be resolved to a workspace package?

[nicolo-ribaudo]

I'm debugging a CI failure in babel/babel#15907, and I'm surprised by how Yarn is resolving dependencies:

   ├─ @babel/preset-env@npm:7.22.14 [9548c] (via npm:latest [9548c])
   │  ├─ @babel/plugin-syntax-unicode-sets-regex@npm:7.18.6 [0d136] (via npm:^7.18.6 [0d136])
   │  │  └─ @babel/helper-create-regexp-features-plugin@workspace:packages/babel-helper-create-regexp-features-plugin [c1822] (via workspace:* [c1822])

What could be causing @babel/plugin-syntax-unicode-sets-regex to get the dependency from the local workspace rather than from npm?

[nicolo-ribaudo]

This, obviously 😛

https://github.com/babel/babel/blob/235a7accd9e3ca2958c41a3a97475c839c88b09a/package.json#L101

I'm sorry, today is not a great day for me debugging resolution, apparently.