resolve.getNpmPaths - nvm prefix

[mklabs]

Might be related to #52

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I'm running into an issue when trying to load installed generators with env#getGeneratorsMeta(), and I think it's related to nvm and npm prefix being different than the defaults.

My test sample is something like:

var env = require('yeoman-environment').createEnv();
env.lookup((err) => {
  console.log(env.getGeneratorsMeta());
});

Looking at the getNpmPaths() method, I can see that $NODE_PATH is used when defined, and I can get the env lookup working with:

NODE_PATH="/home/user/.nvm/versions/nodes/v6.0.0/lib/node_modules" node test.js

My question is, would you agree on adding the result of npm prefix to the lookup paths automatically ?

env.lookup() is asynchronous, so we might be able to introduce a call to .exec('npm prefix -g') if you don't mind the performance penalty it might introduce.

Alternatively, if you don't want it to be the default behavior, would it be possible to define custom paths? something like:

// env.lookup([paths, ], cb);

env.lookup(['/home/user/.nvm/versions/node/v6.0.0/lib/node_modules'], function() {});

Either way, it would fix the lookup for nvm installed yeoman and generators. This doesn't apply when yeoman-environment is installed globally, yo works fine in this case.

[mklabs]

$NVM_PATH can also be used if defined in environment variables, might avoid spawning npm to run npm prefix

[SBoudrias]

Yeah, spawning a command is really, but reallllly SLOW. It's not a good option.

I'm okay with using $NVM_PATH

[mklabs]

Great! I'll probably send you a PR with this update.

[mklabs]

btw, really good job on extracting the environment in its own lib, very pleasant to work with and useful

[SBoudrias]

Thanks!

Also, FWIW, issues might arise more often now that npm behavior is to flatten dependencies. Right now we're always loading {yeoman-environment root}/../../../.. as the global search path (yeoman-environment -> yo -> global root), but now that assumption might be wrong.

[mklabs]

yep, I had some issues with yo npm linked, but using the NODE_PATH trick I was able to work around.