RFC for npm run to traverse directory tree up to the root before failing

[agorovyi]

Let npm run traverse monorepo directory tree up to the root before failing

With this request I would like to be able to execute npm run command that will traverse the directory tree up to the root level if it can't find a required /node_modules/.bin with executable command in subdirectory where it was executed from.

A detailed explanation and the rationale is covered in the .md file.

[isaacs]

Ah! I had missed this PR, but I was working on the implementation for #90 today, saw the bit of code that sets up the PATH environ, and had a suspicion that this would be an issue.

In fact, rather than splitting on node_modules, it should append node_modules/.bin to every parent path. Eg, a module at /x/y/z/node_modules/a/node_modules/b would have a PATH containing:

/x/y/z/node_modules/a/node_modules/b/node_modules/.bin
/x/y/z/node_modules/a/node_modules/node_modules/.bin
/x/y/z/node_modules/a/node_modules/.bin
/x/y/z/node_modules/node_modules/.bin
/x/y/z/node_modules/.bin
/x/y/node_modules/.bin
/x/node_modules/.bin
/node_modules/.bin

I think it might be good to set a "project root" dir to not walk up past (ie, /x/y/z in this example), but getting that reliably is a little bit tricky, and I'm not sure it matters much.

So, I think npm v7 will satisfy you there by default.

As a corollary (which I'm not sure how or if to take advantage of?) is that we could put metadeps in ./node_modules/node_modules/, so they're accessible to anything in node_modules, but not to the root project. That could prevent unlisted deps, which are a problem in some cases.