fix(arborist): tag spec should install the exact version

[gemwuu]

Given package.json below:

{
  "dependencies": {
    "kewu": "1.0.0",
    "wuke": "1.0.1"
  }
}

The two npm package dependencies are:

1. [email protected] has only one dependency wuke@stable
2. wuke@stable refers to [email protected]

Run code below, would only install [email protected] into the root dir of node_modules.

const arborist = new Arborist({
  path: process.cwd(),
})
const idealTree = await arborist.buildIdealTree({})

console.log('idealTree wuke: %s', idealTree.children.get('kewu').children.get('wuke'))

@npmcli/arborist treats [email protected] as the matched version of wuke@stable, which is wrong.

The PR intends to fix this.

As tested, this bug exists from the very beginning implement of arborist.

References

[wraithgar]

I think there is a very specific reason this works the way it does. I am pretty sure this will break every npm ci out there if implemented, and the deps they have referenced by tag publish new versions under that tag. The tag resolution with a lockfile works the same way as git resolution. A tag is not idempotent, so once it's in the tree we can't re-evaluate it without making older installations invalid.

The way npm works now is that if you give it a tag, it resolves that tag and then "remembers" that resolution via lockfile. Whether the tag came from the package.json or part of add is irrelevant.

This does outline another issue and that is package.json files really should not have tags in them, for this very reason. A tag does not obey semver, and can point to anything. It can easily move out from under you and should be considered an antipattern.

This change would be a breaking change, and I don't think it's on the roadmap for 9.0. We're trying to make a 9.0 that works for most people who are already using 8, and this would definitely not fall under that criteria.

[gemwuu]

@wraithgar So, this behavior change will file for now, and integrate on the next major version(npm 10.0)? Should I create an RRFC for further discussion?

[wraithgar]

Yes at the very least this needs further discussion.

[gemwuu]

Yes at the very least this needs further discussion.

RRFC: npm/rfcs#640