add RectorClassValidator

src/Validator/RectorClassValidator.php

@@ -0,0 +1,45 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Validator;
+
+use Rector\Contract\Rector\RectorInterface;
+use Rector\Exception\Validator\InvalidRectorClassException;
+
+final class RectorClassValidator
+{
+    /**
+     * @param string[] $rectors
+     */
+    public function validate(array $rectors): void
+    {
+        foreach ($rectors as $rector) {
+            $this->ensureClassExists($rector);
+            $this->ensureIsRector($rector);
+        }
+    }
+
+    private function ensureClassExists(string $rector): void
+    {
+        if (class_exists($rector)) {
+            return;
+        }
+
+        throw new InvalidRectorClassException(sprintf(
+            'Rector "%s" was not found. Make sure class exists and is autoloaded.',
+            $rector
+        ));
+    }
+
+    private function ensureIsRector(string $rector): void
+    {
+        if (is_a($rector, RectorInterface::class, true)) {
+            return;
+        }
+
+        throw new InvalidRectorClassException(sprintf(
+            'Rector "%s" is not supported. Use class that implements %s.',
+            $rector,
+            RectorInterface::class
+        ));
+    }
+}