Resolve 156 with introduce a simple cache and build a new ReferenceContext only when needed

Author: marcelthole

src/spec/Reference.php

@@ -29,6 +29,9 @@
  */
 class Reference implements SpecObjectInterface, DocumentContextInterface
 {
+    /** @var array<string, mixed>  */
+    private static $relativeReferencesCache = [];
+
     /**
      * @var string
      */
@@ -296,14 +299,18 @@ private function resolveTransitiveReference(Reference $referencedObject, Referen
      */
     private function adjustRelativeReferences($referencedDocument, $basePath, $baseDocument = null, $oContext = null)
     {
-        $context = new ReferenceContext(null, $basePath);
         if ($baseDocument === null) {
             $baseDocument = $referencedDocument;
         }
 
         foreach ($referencedDocument as $key => $value) {
             // adjust reference URLs
             if ($key === '$ref' && is_string($value)) {
+                $fullPath = $basePath . $value;
+                if (array_key_exists($fullPath, self::$relativeReferencesCache)) {
+                    return self::$relativeReferencesCache[$fullPath];
+                }
+
                 if (isset($value[0]) && $value[0] === '#') {
                     // direcly inline references in the same document,
                     // these are not going to be valid in the new context anymore
@@ -315,8 +322,10 @@ private function adjustRelativeReferences($referencedDocument, $basePath, $baseD
                     $this->_recursingInsideFile = true;
                     $return = $this->adjustRelativeReferences($inlineDocument, $basePath, $baseDocument, $oContext);
                     $this->_recursingInsideFile = false;
+                    self::$relativeReferencesCache[$fullPath] = $return;
                     return $return;
                 }
+                $context = new ReferenceContext(null, $basePath);
                 $referencedDocument[$key] = $context->resolveRelativeUri($value);
                 $parts = explode('#', $referencedDocument[$key], 2);
                 if ($parts[0] === $oContext->getUri()) {
@@ -329,6 +338,7 @@ private function adjustRelativeReferences($referencedDocument, $basePath, $baseD
             // adjust URLs for 'externalValue' references in Example Objects
             // https://spec.openapis.org/oas/v3.0.3#example-object
             if ($key === 'externalValue' && is_string($value)) {
+                $context = new ReferenceContext(null, $basePath);
                 $referencedDocument[$key] = $this->makeRelativePath($oContext->getUri(), $context->resolveRelativeUri($value));
                 continue;
             }