Enhancement: Generate test coverage reports after npm test (#2289)

[JesseCodeBones]

Signed-off-by: Jesse xiang19890319@gmail.com

Issue details: #2289

Test report screen shot:

• I've read the contributing guidelines
• I've added my name and email to the NOTICE file

[HerrCai0907]

@dcodeIO @MaxGraey. I think add coverage is helpful during feature development. wdyt?

[dcodeIO]

Looks like the test:coverage step can be included in coverage as it isn't very useful on its own. Even better perhaps, if the test step could detect that it runs under c8 (looking at process.argv or .env perhaps) and then disables parallel execution - so the test step can be reused? Then we'd have

  "coverage": "ASC_FEATURES=\"*\" c8 npm test",

A minor concern could be that sometimes, ASC_FEATURES can enable things that are not yet fully functioning, so setting it independently could make sense.

[JesseCodeBones]

Hi Dcode,
Considering the compatibility of Windows and POSIX system. I prefer the process.argv. currently the issue is, c8 need a something like zygote process process, so it cannot use && on its command line.
So I create coverage and test:coverage tasks, the test:coverage will have --coverage option for specific test test:compiler
The other option is we can create a test.js file and use it to control the environment variables and argument variables, with this option, we only need one coverage task.
What do you think?
Regards

[dcodeIO]

Toying around with c8 a little, I found that instead of having a separate --coverage option, we can detect that c8 is being used by checking process.env.NODE_V8_COVERAGE != null and then turn off parallel testing. Looks like this allows to reuse the test step?

(found this here)

[JesseCodeBones]

@dcodeIO
yes, we can use this option, I finished the modification

[dcodeIO]

For example here:

Suggested change

	if (args.parallel && coreCount > 2 && !args.coverage) {
	const isCoverage = process.env.NODE_V8_COVERAGE != null;
	if (args.parallel && coreCount > 2 && !isCoverage) {

[dcodeIO]

The slightly modified PR above is based on this PR with a few slight changes so coverage remains light / optional for now. One would manually set ASC_FEATURES, and c8 is installed on demand, whereas all the necessary configuration is provided. PTAL :)

[dcodeIO]

Initial code coverage in the spirit of this PR has been added in #2517, with the difference that it is kept optional for now. Sorry for the strange co-authored-by in the commit message, I used the signed-off credentials from the first post that apparently link to a different account, hrm.