fix: Fix npm install --prefix on windows

[nipunn1313]

I found that globalDir/localDir and globalPrefix/localPrefix end up being the same value when --prefix is set. This was surprising to me, but it does appear that globalPrefix is set to match prefix at the end of loading.

This means that the globalTop logic is actually incorrect here. It accidentally worked on non-windows machines.

For example if running npm i --prefix scripts

On non-windows this.npm.globalDir = $CWD/scripts/lib/node_modules

On windows this.npm.globalDir = $CWD/scripts/node_modules

IMHO, the logic inside of npmconfig is also incorrect here, since globalDir is being set to this bogus $CWD/scripts/lib/node_modules

However, this fix should work regardless - since it stops relying on the specific values of globalDir.

I manually tested npm install and npm install --prefix on both windows and mac. Everything works now.

References

Fixes #7722

[wraithgar]

This needs tests

[nipunn1313]

good idea. I'll see when I can make some time for it. install.test.js has some examples which I had taken a quick pass over. It was a little hard to figure out how to get the equivalent of --prefix to happen since the tests don't take command line args directly. I'll have to dive a bit to figure out how to get coverage.

If anyone out there reading this has time to offer help, I'd take it.

[mbtools]

Closed by https://github.com/npm/cli/pull/8269