Support turning off node_modules default exclude via flag

[hershmire]

This PR is part of resolving issue #898. The idea is to be able to turn off the default exclusion of **/node_modules/** for users that need/want to support local node_modules. As mentioned in that issue, the negateExclude (i.e. !**/node_modules/**) doesn't work for cases when you still want your exclusion list to still exclude matches within your local node_modules directory.

Related PRs for solving the above issue:

• Support turning off node_modules default exclude via flag istanbuljs#213
• Support turning off node_modules default exclude via flag babel-plugin-istanbul#172

NOTE: this test-exclude PR (istanbuljs/istanbuljs#213) will need to get merged and published before this is effective.

[bcoe]

@leslc @hershmire I'm open to this pull request, and your patches across the various Istanbul libraries are wonderful...

please help me better understand why you're running unit tests inside the node_modules folder, this feels really weird to me ... mainly because tests tend to be something people remove when publishing a module, and I think of code in node_modules as the code of your dependents, not your own code.

tldr; I'd love to better understand what motivated this pattern (partially as a product manager at npm, Inc, more so than a maintainer of nyc).

[hershmire]

@bcoe This issue I wrote up back in August might answer some of your questions – https://github.com/istanbuljs/nyc/issues/898.

[hershmire]

@bcoe Any update?

[JaKXz]

@hershmire I'm sorry for the late reply & if what I say next might be frustrating to you:

If the node_modules that are in those sub-projects/pages are actually local modules (that you hand rolled in place) and not npm installed into those sub-projects/pages, why does the folder have to be called node_modules? CJS requires can work with relative paths so I'm not sure that adding all this cyclomatic complexity to nyc/istanbul is the right approach. As @coreyfarrell said in #898 there are more complex use cases with mono-repos that are becoming more common now to support, so unless this plays nice I don't see this being implemented TBPH.

to anyone: please correct me if I'm wrong.

[bcoe]

@JaKXz @hershmire I would love to add better semantics for including node_modules, but I think we should do this work in the test-exclude module, rather than in nyc itself 👍 let's try to pick this work back up though.

[coveralls]

Coverage remained the same at 96.349% when pulling 122e9d9 on hershmire:exclude-node_modules-flag into 3eb0e37 on istanbuljs:master.

[coveralls]

Coverage remained the same at 96.349% when pulling 122e9d9 on hershmire:exclude-node_modules-flag into 3eb0e37 on istanbuljs:master.

[coveralls]

Coverage remained the same at 96.349% when pulling 122e9d9 on hershmire:exclude-node_modules-flag into 3eb0e37 on istanbuljs:master.

[coreyfarrell]

@hershmire Sorry for the long delay on this, my intent is that this feature will be available in nyc 14.

@bcoe this feature is already added to test-exclude via istanbuljs/istanbuljs#213, now we just need to expose it to users via nyc.

@AndrewFinlay we will want to add the --exclude-node-modules option to nyc instrument. I didn't add that to this change because I don't want to cause conflicts with #1007 which is nearly ready for merge.

[bcoe]

👍 LGTM with @coreyfarrell's approval.