try to use realpath to find nvm's dir

[jchip]

From #1369

[ljharb]

Thanks! This PR needs tests before it could be accepted.

Can you elaborate on what this is fixing - ie, in what scenario does nvm-exec fail, that your change makes work?

Can this change also be made in nvm.sh so that nvm itself can also benefit from it?

[jchip]

realpath is more reliable. If I symlink /usr/local/bin/nvm-exec to nvm-exec, then only realpath can find the real dir.

I am not familiar with the way the tests are setup. Where is the existing test I can update?

[ljharb]

What's the usecase for symlinking it, as opposed to adding its directory to the PATH, or using nvm exec?

Each test has its own file - https://github.com/creationix/nvm/tree/f7763c8ba96e61825e34ebaf979811a1bde2a997/test/slow/nvm%20exec are all of the nvm exec tests atm, and https://github.com/creationix/nvm/blob/f7763c8ba96e61825e34ebaf979811a1bde2a997/test/install_script/nvm_source is the test for the install script being able to locate nvm-exec, which may be relevant here.

[ljharb]

This also might be related to #617.

[jchip]

the main use of nvm-exec is for when installing nvm some where under /usr where only root has access. symlinking so no need to mess with PATH. In this case, you can't do nvm install without sudo. sudo can't execute nvm because it's a shell function. so only way is to execute nvm with nvm-exec, which is to be added later, or in the first PR I submitted.

I don't see any test for the file `nvm-exec.

[ljharb]

nvm should be installed per-user - one separate copy of NVM_DIR for each user that wants to access it. Installing nvm to share across user accounts isn't a supported use case.

All the tests are for nvm exec, which invokes nvm-exec under the hood - nvm exec is the important thing not to break, using nvm-exec directly is also not something that's officially encouraged.

[jchip]

Installing nvm to share across user accounts isn't a supported use case.

You don't want to make that a supported use case?

All existing nvm exec tests passed.

[ljharb]

Not particularly, you're supposed to always have an entire nvm installation for each user account that wants to use nvm and node.

I don't mind improving nvm-exec and nvm.sh in concert to work better with symlinks, though.

[jchip]

work better with symlinks

This PR changes to use realpath if it's available is more reliable.

To support shared usage, you just need to make nvm-exec be able to invoke nvm itself. There was a question somewhere (stackoverflow?) in which someone suggested sudo nvm-exec, but that doesn't work w/o being able to invoke nvm using sudo somehow.

shared usage is helpful on shared machines.

[jchip]

I've been using this for more than a year to support shared usage. I just found some time now to see if there interest for this so I figured I PR it in.

[jchip]

that doesn't work w/o being able to invoke nvm using sudo somehow.

unless you login as root directly.