Coverage Report cache makes PHP report memory usage explode

[Slamdunk]

Q	A
php-code-coverage version	10.1.3
PHP version	8.2
PHPUnit version (if used)	10.3.3

Changes merged in #1005 and released 10.1.3 made Report\PHP unusable as now it always consumes too much memory.

Our coverage.php file went from 29 Mb to 737 Mb, re-processing it with phpcov or any other tool skyrockets the memory used from < 1 Gb to > 4 Gb, with no control over it and, most important, no real benefit for the purposes of re-processing many times the Report\PHP file.

#1005 is good because when you use many Report\*, the Directory is build only once and PHPUnit's report generation is faster, but Report\PHP should serialize the CodeCoverage object without the $this->cachedReport property filled.

I suggest the following improvements:

• Report\PHP should serialize the CodeCoverage object with the cache cleared using a new @internal API such as CodeCoverage::clearCache (different from the currently present CodeCoverage::clear which has another purpose)
  • Avoid serialization of cache data in PHP report #1011
• PHPUnit\Runner\CodeCoverage should generate the Report\PHP as first in the list, so that when it's processed no cache has been already built; the aforementioned API CodeCoverage::clearCache would be practically useless, but it's still needed to ensure consistency of php-code-coverage package
  • PHPUnit 9.6: Generate code coverage report in PHP format as first in list to avoid serializing cache data phpunit#5508
  • PHPUnit 10.3: Generate code coverage report in PHP format as first in list to avoid serializing cache data phpunit#5509
• SebastianBergmann\PHPCOV\Command should generate the Report\PHP as first in the list for the same reason
  • Generate code coverage report in PHP format as first in list to avoid serializing cache data phpcov#134

[sebastianbergmann]

All of your suggestions make sense to me, at least as short-term solutions.

Once #874 has been implemented, we should have a long-term solution.