loadNodeModules() should be more clear about what went wrong

[krainboltgreene]

I had an error loading a library, but all it told me is that it couldn't resolve the module. That's fine, but the real issue is that the package's main file didn't exist.

Here's some payload information:

{ x: 'snabbdom-view',
  start: '/Users/krainboltgreene/Code/krainboltgreene/deushack/source/client/cycle',
  dirs: [] }

We can definitely make this better. We can say all the directories we looked in, what exact file we;'re looking for (in this case main) and then do some reading to show the user that it's the package;'s fault.

[ljharb]

What does require.resolve tell you in that scenario?

Why would the issue here just be "missing main"? Couldn't also Users/krainboltgreene/Code/krainboltgreene/deushack/source/client/cycle.js or Users/krainboltgreene/Code/krainboltgreene/deushack/source/client/cycle/index.js also be missing?

[krainboltgreene]

In this case the package had a "main": "transpiled/source/index.js" which literally didn't exist.

[krainboltgreene]

Three parts for improvement:

1. Tell the user where we looked.
2. Tell the user what we looked for.
3. Either tell the user why we failed OR send them to an FAQ.

I would love to work on this as a PR.

[ljharb]

I'm hesitant to add complexity, even in error paths - but if you're willing, taking a look at it via a PR would be helpful.

[calvinqc]

@ljharb Hi Jordan, this issue sounds very interesting even though it's been here for a long time. I'm wondering whether it's still opened and still recommended to work on now?

[ljharb]

@calvinqc yes, that'd be great! Be mindful though, that changing error message text has been semver-major in the past, so I'm highly likely to only accept the PR into v2 (the default branch) and not be able to backport it into v1 (the 1.x branch).

[krainboltgreene]

Is it still breaking if you get a generic semi-related error before and now you get a specific error?

[ljharb]

@krainboltgreene yes, potentially - there are tools that rely on the exact string and type of an error that resolve throws in specific situations. I've broken angular-cli and ember-cli before by changing an error message, and am not anxious to repeat it.

[krainboltgreene]

As the maintainer of a big project i feel that.