Generate coverage for required files passed as args in spawn

[jaridmargolin]

Imagine the following code written inside of a testcase.

spawn('node', [
   '--require',
   './lib/index.js',
    'test/fixtures/syntax-error.js'
]);

I am attempting to generate coverage for ./lib/index.js.

Expected Behavior

Coverage is generated for ./lib/index.js

Observed Behavior

No coverage is generated.

[jaridmargolin]

@bcoe do you agree that the expected behavior would be to generate coverage?

I have absolutely no insight into the inner workings of istanbul / nyc, but if you agree with the overall direction, I will take a stab at a PR. Additionally if you had any thoughts / ideas about the implementation, feel free to share :)

Thanks!

[coreyfarrell]

This is not directly possible. I think the problem is that --require modules are loaded before nyc can hook the loader system. To accomplish your goal you will need to pre-instrument your code using:

nyc instrument ${PWD}/lib/index.js > lib/index-covered.js

Then in your test:

spawn('node', [
   '--require',
   './lib/index-covered.js',
    'test/fixtures/syntax-error.js'
]);

FYI the ${PWD} is needed for now to work around #1014. Once that is fixed you'll be able to just nyc instrument lib/index.js > lib/index-covered.js.