Extensions loaded using -d extension or -d zend_extension are not loaded in child processes #7053

Summary

PHP extensions loaded via -d extension= are not enabled in tests that run with process isolation, which can cause an uncaught exception.

Current behavior

If you load a PHP extension not via INI files, but rather on-demand via e.g. php -dextension=pcov.so vendor/bin/phpunit ..., the -d extension option will not be passed to child processes when using process isolation. This results in extensions missing from the child process, which can cause all sort of issues. A concrete example, which is also what led me to file this report, is for coverage drivers, for which PHPUnit will throw an (uncaught) exception as described below.

This is similar/related to a bunch of previously-reported issues such as #3492 and #4664, before which options such as -d pcov.enabled=1 were not passed to subprocesses. However, this one is different in that the option that isn't being passed is not a coverage driver-specific one, but rather the extension directive. As far as I can tell, there is no existing issue covering this, but apologies if there's one I didn't see!

How to reproduce

A concrete example with PCOV:

• Create any valid test file, e.g.

$ cat tests/MyTest.php 
<?php

use PHPUnit\Framework\TestCase;

class MyTest extends TestCase {
	public function testTrue() {
		$this->assertTrue( true );
	}
}

• Install PHPUnit (for example, via composer: composer require --dev "phpunit/phpunit")
• Install https://github.com/krakjoe/pcov through your preferred means
• Make sure your PHP interpreter does NOT have pcov enabled by default, e.g. via sudo phpdismod pcov or manually editing the PHP ini file
• Run php -dextension=pcov.so -dpcov.enabled=1 vendor/bin/phpunit --coverage-html ./coverage --coverage-filter tests tests/MyTest.php (no process isolation) and confirm that everything works correctly
• Next run with process isolation: php -dextension=pcov.so -dpcov.enabled=1 vendor/bin/phpunit --coverage-html ./coverage --coverage-filter tests --process-isolation tests/MyTest.php which should give something like

1) MyTest::testTrue
PHPUnit\Framework\Exception: PHP Fatal error:  Uncaught TypeError: PHPUnit\Runner\CodeCoverage::codeCoverage(): Return value must be of type SebastianBergmann\CodeCoverage\CodeCoverage, null returned in vendor/phpunit/phpunit/src/Runner/CodeCoverage.php:187
Stack trace:
#0 Standard input code(105): PHPUnit\Runner\CodeCoverage->codeCoverage()
#1 Standard input code(166): __phpunit_run_isolated_test()
#2 {main}
  thrown in vendor/phpunit/phpunit/src/Runner/CodeCoverage.php on line 187
Fatal error: Uncaught TypeError: PHPUnit\Runner\CodeCoverage::codeCoverage(): Return value must be of type SebastianBergmann\CodeCoverage\CodeCoverage, null returned in vendor/phpunit/phpunit/src/Runner/CodeCoverage.php:187
Stack trace:
#0 Standard input code(105): PHPUnit\Runner\CodeCoverage->codeCoverage()
#1 Standard input code(166): __phpunit_run_isolated_test()
#2 {main}
  thrown in vendor/phpunit/phpunit/src/Runner/CodeCoverage.php on line 187

Expected behavior

PHPUnit should load pcov in the subprocess as well. I think it principle this should be considered for all PHP extensions, but for a start, it could be done for pcov and xdebug only by matching on the loaded extension name.