Enable xdebug manually

[uuf6429]

For XDebug, this is a bit different, as there is no "enable" option (may have to be enabled using -d zend_extension=xdebug, but this can be another issue because of extension load order).

Originally posted by @remicollet in #3506 (comment)

It is very typical for developers to run PHP without xdebug and only enable it when necessary through -d zend_extension=xdebug.
PhpStorm, for example follows this approach once properly configured: running tests does not enable xdebug. Debugging or covering tests enables xdebug.

This however does not work for process-isolated-tests (@runTestsInSeparateProcess): even though settings are now copied to the child process, xdebug will not be enabled. This is understandable since it's not trivial to find if xdebug is enabled by default (and I was also not able to find the location of the library programmatically, so PR comment below).

The objective of this PR is to do exactly that. 🙏

---

@sebastianbergmann as soon as it's decided where to go, I can also open PRs for other versions.

[uuf6429]

I'm assuming this PR will be released as that version.

[uuf6429]

getenv('TODO_USE_PHPUNIT_SETTINGS')

Should I...

1. ...just use php_xdebug since it already solves most cases
2. ...use getenv('XX') ?: 'php_xdebug' to offer a bit of flexibility (what should it be named?)
3. ...use PHPUnit xml config functionality to "do it properly"

[codecov]

Codecov Report

Merging #5135 (1c589c3) into 9.5 (954ca31) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##                9.5    #5135      +/-   ##
============================================
- Coverage     83.39%   83.38%   -0.02%     
- Complexity     4664     4666       +2     
============================================
  Files           275      275              
  Lines         13819    13821       +2     
============================================
  Hits          11524    11524              
- Misses         2295     2297       +2     

Impacted Files	Coverage Δ
src/Util/PHP/AbstractPhpProcess.php	68.88% <0.00%> (-0.78%)	⬇️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[sebastianbergmann]

Thank you for your contribution. I appreciate the time you invested in preparing this pull request. However, I have decided not to merge it. This should be handled outside of PHPUnit, sorry.

[uuf6429]

I understand it's a very specific annoyance, but I can't see it solved outside PHPUnit.

Enabling xdebug globally is terrible for day-to-day use (think installing composer packages with xdebug enabled 😆).

Additionally, #3506 feels half-baked without this - one could also argue that it was not needed if PHP was properly configured.

I've also tried hackier approaches, by the way, and nothing worked well (<php><ini...>..., modifying PHPUnit at runtime).. so not a lot of options unless I missed something.

---

Edit: in case someone sees this, I went with this ugly-ish solution for now:

    public static function setUpBeforeClass(): void
    {
        parent::setUpBeforeClass();

        self::isXdebugEnabledAutomatically() or self::enableXdebugForSubProcesses();
    }

    private static function isXdebugEnabledAutomatically(): bool
    {
        $exp = /** @lang PHP */ "var_export(extension_loaded('xdebug'));";
        $cmd = (new Runtime())->getBinary() . ' -r ' . escapeshellarg($exp) . ' 2>&1';

        return str_contains((string)shell_exec($cmd), 'true');
    }

    private static function enableXdebugForSubProcesses(): void
    {
        $runtime = new Runtime();
        // reset 'binary' property
        $ref = new ReflectionProperty($runtime, 'binary');
        $ref->setValue($runtime, null);
        $runtime->getBinary();
        // update it with xdebug extension
        $ref->setValue($runtime, $ref->getValue($runtime) . ' -d zend_extension=php_xdebug');
    }