Fix invalidate cache

Related to def176a

src/EncoderProvider.php

@@ -174,6 +174,9 @@ private function getVocab(string $encodingName): Vocab
             $loader = $this->vocabLoader = new DefaultVocabLoader($this->vocabCacheDir);
         }
 
-        return $this->vocabs[$encodingName] = $loader->load(self::ENCODINGS[$encodingName]['vocab']);
+        return $this->vocabs[$encodingName] = $loader->load(
+            self::ENCODINGS[$encodingName]['vocab'],
+            self::ENCODINGS[$encodingName]['hash'] ?? null,
+        );
     }
 }

tests/EncoderProviderTest.php

@@ -4,11 +4,13 @@
 
 namespace Yethee\Tiktoken\Tests;
 
+use org\bovigo\vfs\vfsStream;
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 use Yethee\Tiktoken\EncoderProvider;
 
 use function dirname;
+use function hash;
 
 final class EncoderProviderTest extends TestCase
 {
@@ -39,6 +41,24 @@ public function testEncode(): void
         self::assertSame([15339, 1917], $encoder->encode('hello world'));
     }
 
+    public function testUseHashWhenLoadVocab(): void
+    {
+        $cache = vfsStream::setup('cache');
+        $vocabCacheFilename = hash('sha1', EncoderProvider::ENCODINGS['p50k_base']['vocab']);
+
+        $cacheFile = vfsStream::newFile($vocabCacheFilename)
+            ->withContent('broken cache')
+            ->at($cache);
+
+        $provider = new EncoderProvider();
+        /** @psalm-suppress ArgumentTypeCoercion */
+        $provider->setVocabCache($cache->url());
+
+        $provider->get('p50k_base');
+
+        self::assertNotEquals('broken cache', $cacheFile->getContent());
+    }
+
     /**
      * @return iterable<array{non-empty-string, non-empty-string}>
      *