--require flag does not load from node_modules

[jonaskello]

As added in #181 ts-node accepts a --require flag. When trying to use this with the tsconfig-paths package it fails to locate the package. Example:

$ ts-node -r tsconfig-paths main.ts 
Error: Cannot find module 'tsconfig-paths'

The reason seems to be this line which does Module._load(id) in order to require the modules specified by --require. If it is changed to require(id)it will locate the package. It seems like Module._load(id) skips loading from node_modules.

The mocha package also has a -r option and looking here it seems they use require to load the modules rather than Module._load. So this example works:

$ mocha --compilers ts:ts-node/register -r node-tsconfig-paths mocha-example.ts

[blakeembrey]

We shouldn't technically be doing require as that could result in loading our own dependencies instead of the users, which would be a confusing situation. I believe this code was based on the node CLI itself here: nodejs/node#881. I'm not sure about the current implementation in node anymore, I'll need to find out how to do a better implementation.

[blakeembrey]

Found it. Let's use _preload_modules found here: https://github.com/nodejs/node/blob/0fb21df6e692bef9f55b9bfa876f3c59dc590332/lib/internal/bootstrap_node.js#L391. We may need to fallback to Module._load on older node.js versions (I can't recall if this ever worked now, I'll check though).

[blakeembrey]

Ok, exists all the way back to 4.0, should work well enough if you want to submit a PR. The other reason we can't use require is that it wouldn't work for relative --require ./ calls - they would resolve relative to our module instead of to the CLI execution.

[jonaskello]

Nice! I'm collaborating with @Jontem on the node-tsconfig-paths package and he'll make a PR for this.

[blakeembrey]

Looks like this should have been resolved with #258 IIRC.