Prevent Web API functional test installation from dropping an unrelated database (#36291)

dev/tests/api-functional/framework/Magento/TestFramework/WebApiApplication.php

@@ -5,6 +5,13 @@
  */
 namespace Magento\TestFramework;
 
+use Magento\Framework\App\DeploymentConfig;
+use Magento\Framework\App\DeploymentConfig\Reader;
+use Magento\Framework\Config\ConfigOptionsListConstants;
+use Magento\Framework\Config\File\ConfigFilePool;
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\Filesystem\DriverPool;
+
 /**
  * Provides access to the application for the tests
  *
@@ -28,6 +35,8 @@ public function run()
      */
     public function install($cleanup)
     {
+        $this->assertInstallationTargetsConfiguredDatabase();
+
         if ($cleanup) {
             $this->cleanup();
         }
@@ -71,4 +80,67 @@ protected function getCustomDirs()
     {
         return [];
     }
+
+    /**
+     * Verify that the installation is not about to destroy a database the tests are not configured to use.
+     *
+     * Unlike the integration tests framework, Web API functional tests do not have their own configuration
+     * directory - they reuse the "app/etc" of the installation that serves TESTS_BASE_URL. Both
+     * "setup:uninstall" and "setup:install" therefore operate on whatever "app/etc/env.php" points at. When
+     * that database differs from the one declared in TESTS_INSTALL_CONFIG_FILE, the installation silently
+     * drops all tables of an unrelated database instead of the configured test one.
+     *
+     * @return void
+     * @throws LocalizedException
+     */
+    private function assertInstallationTargetsConfiguredDatabase(): void
+    {
+        if (!$this->isInstalled()) {
+            return;
+        }
+
+        $configuredDbName = $this->getInstallConfig()['db-name'] ?? null;
+        $installedDbName = $this->getInstalledDbName();
+
+        if (!$configuredDbName || !$installedDbName || $configuredDbName === $installedDbName) {
+            return;
+        }
+
+        throw new LocalizedException(
+            __(
+                'Web API functional tests are configured to install Magento into the "%1" database, but the '
+                . 'installation in "%2" uses the "%3" database. Installing would drop all tables of "%3" and '
+                . 'overwrite its deployment configuration, because Web API functional tests reuse the '
+                . 'application they send requests to. Either configure the test installation to use the "%3" '
+                . 'database, or set TESTS_MAGENTO_INSTALLATION to "disabled" to run the tests against the '
+                . 'already installed application.',
+                $configuredDbName,
+                $this->_configDir,
+                $installedDbName
+            )
+        );
+    }
+
+    /**
+     * Retrieve the database name of the already installed application, if its deployment configuration exists.
+     *
+     * @return string|null
+     */
+    private function getInstalledDbName(): ?string
+    {
+        $configFilePool = new ConfigFilePool();
+        $envFile = $this->_configDir . '/' . $configFilePool->getPath(ConfigFilePool::APP_ENV);
+        // phpcs:ignore Magento2.Functions.DiscouragedFunction
+        if (!file_exists($envFile)) {
+            return null;
+        }
+
+        $reader = new Reader($this->dirList, new DriverPool(), $configFilePool);
+        $deploymentConfig = new DeploymentConfig($reader, []);
+
+        return $deploymentConfig->get(
+            ConfigOptionsListConstants::CONFIG_PATH_DB_CONNECTION_DEFAULT
+            . '/' . ConfigOptionsListConstants::KEY_NAME
+        );
+    }
 }