Set XDEBUG_MODE for processes with coverage

Fixes infection#1473

src/Process/CoveredPhpProcess.php

@@ -0,0 +1,64 @@
+<?php
+/**
+ * This code is licensed under the BSD 3-Clause License.
+ *
+ * Copyright (c) 2017, Maks Rafalko
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * * Neither the name of the copyright holder nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+declare(strict_types=1);
+
+namespace Infection\Process;
+
+use function array_merge;
+use Symfony\Component\Process\Process;
+
+/**
+ * @internal
+ *
+ * Process which setups necessary environment variables to make coverage reporting happen
+ * without any extra user interaction.
+ *
+ * As of now we only cover Xdebug, adding XDEBUG_MODE environment variable to ensure it
+ * is properly activated. Since we can't know if Xdebug was offloaded, we add this env
+ * variable at all times.
+ */
+final class CoveredPhpProcess extends Process
+{
+    /**
+     * @param array<string|bool>|null $env
+     */
+    public function start(?callable $callback = null, ?array $env = null): void
+    {
+        $env = array_merge($env ?? [], [
+            'XDEBUG_MODE' => 'debug',
+        ]);
+
+        parent::start($callback, $env);
+    }
+}

src/Process/Factory/InitialTestsRunProcessFactory.php

@@ -36,6 +36,7 @@
 namespace Infection\Process\Factory;
 
 use Infection\AbstractTestFramework\TestFrameworkAdapter;
+use Infection\Process\CoveredPhpProcess;
 use Infection\Process\OriginalPhpProcess;
 use function method_exists;
 use Symfony\Component\Process\Process;
@@ -64,7 +65,7 @@ public function createProcess(
         bool $skipCoverage
     ): Process {
         // If we're expecting to receive a code coverage, test process must run in a vanilla environment
-        $processClass = $skipCoverage ? Process::class : OriginalPhpProcess::class;
+        $processClass = $skipCoverage ? CoveredPhpProcess::class : OriginalPhpProcess::class;
 
         /** @var Process $process */
         $process = new $processClass(

tests/phpunit/Process/Factory/InitialTestsRunProcessFactoryTest.php

@@ -36,6 +36,7 @@
 namespace Infection\Tests\Process\Factory;
 
 use Infection\AbstractTestFramework\TestFrameworkAdapter;
+use Infection\Process\CoveredPhpProcess;
 use Infection\Process\Factory\InitialTestsRunProcessFactory;
 use Infection\Process\OriginalPhpProcess;
 use const PHP_OS_FAMILY;
@@ -86,6 +87,7 @@ public function test_it_creates_a_process_with_coverage_skipped(): void
 
         $this->assertNull($process->getTimeout());
         $this->assertNotInstanceOf(OriginalPhpProcess::class, $process);
+        $this->assertInstanceOf(CoveredPhpProcess::class, $process);
     }
 
     public function test_it_creates_a_process_with_coverage(): void