Autoloader: add fall-back to PSR4 autoloading

This fallback will only allow loading additional files on PHPUnit >= 9.x and will throw an exception otherwise.

Includes dedicated test for the autoload exception.

Author: jrfnl

assertarraysubset-autoload.php

@@ -31,11 +31,6 @@ public static function load($className)
                         // PHPUnit >= 9.0.0.
                         require_once __DIR__ . '/src/ArraySubsetAsserts.php';
 
-                        // Straight away load the other classes needed as well.
-                        // These should only ever be loaded in this context anyway.
-                        require_once __DIR__ . '/src/ArrayAccessible.php';
-                        require_once __DIR__ . '/src/Constraint/ArraySubset.php';
-
                         return true;
                     }
 
@@ -56,6 +51,34 @@ public static function load($className)
                     require_once __DIR__ . '/src/AssertFallThrough.php';
 
                     return true;
+
+                /*
+                 * Handle arbitrary additional classes via PSR-4, but only allow loading on PHPUnit >= 9.0.0,
+                 * as additional classes should only ever _need_ to be loaded when using PHPUnit >= 9.0.0.
+                 */
+                default:
+                    if (\method_exists('\PHPUnit\Framework\Assert', 'assertArraySubset') === true) {
+                        // PHPUnit < 9.0.0.
+                        throw new \RuntimeException(
+                            \sprintf(
+                                'Using class "%s" is only supported in combination with PHPUnit >= 9.0.0',
+                                $className
+                            )
+                        );
+                    }
+
+                    // PHPUnit >= 9.0.0.
+                    $file = \realpath(
+                        __DIR__ . \DIRECTORY_SEPARATOR
+                        . 'src' . \DIRECTORY_SEPARATOR
+                        . \strtr(\substr($className, 33), '\\', \DIRECTORY_SEPARATOR) . '.php'
+                    );
+
+                    if (\file_exists($file) === true) {
+                        require_once $file;
+
+                        return true;
+                    }
             }
 
             return false;

phpcs.xml.dist

@@ -34,6 +34,7 @@
     </rule>
     <rule ref="SlevomatCodingStandard.Namespaces.ReferenceUsedNamesOnly.ReferenceViaFullyQualifiedName">
         <exclude-pattern>assertarraysubset-autoload\.php</exclude-pattern>
+        <exclude-pattern>tests/Availability/*\.php</exclude-pattern>
     </rule>
     <rule ref="SlevomatCodingStandard.TypeHints.ParameterTypeHint.MissingNativeTypeHint">
         <exclude-pattern>assertarraysubset-autoload\.php</exclude-pattern>

tests/Availability/AutoloadExceptionTest.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace DMS\PHPUnitExtensions\ArraySubset\Tests\Availibility;
+
+use DMS\PHPUnitExtensions\ArraySubset\Constraint\ArraySubset;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Testing that autoloading classes which should only ever be loaded on PHPUnit >= 9 will
+ * generate an exception when attempted on PHPUnit < 9..
+ *
+ * Note: the autoloading in combination with PHPUnit 9+ is automatically tested via the
+ * actual tests for the polyfill as the class will be called upon.
+ *
+ * {@internal The code in this file must be PHP cross-version compatible for PHP 5.4 - current!}
+ *
+ * @requires PHPUnit < 9
+ */
+final class AutoloadExceptionTest extends TestCase
+{
+    public function testAutoloadException()
+    {
+        $expection = '\RuntimeException';
+        $message   = 'Using class "DMS\PHPUnitExtensions\ArraySubset\Constraint\ArraySubset" is only supported in combination with PHPUnit >= 9.0.0';
+
+        if (\method_exists('\PHPUnit\Framework\TestCase', 'expectException') === true) {
+            $this->expectException($expection);
+            $this->expectExceptionMessage($message);
+        } else {
+            $this->setExpectedException($expection, $message);
+        }
+
+        new ArraySubset();
+    }
+}