add processor to backport const keyword for open api < 3.1

src/Generator.php

@@ -191,6 +191,7 @@ public function getProcessors(): array
  new Processors\MergeXmlContent(),
  new Processors\OperationId(),
  new Processors\CleanUnmerged(),
+ new Processors\BackportConstants(),
  ];
  }
 

src/Processors/BackportConstants.php

@@ -0,0 +1,37 @@
+<?php declare(strict_types=1);
+
+/**
+ * @license Apache 2.0
+ */
+
+namespace OpenApi\Processors;
+
+use OpenApi\Analysis;
+use OpenApi\Annotations\OpenApi;
+use OpenApi\Annotations\Property as AnnotationSchema;
+use OpenApi\Attributes\Property as AttributeSchema;
+use OpenApi\Generator;
+
+/**
+ * Transform const keywords to enum in OpenApi versions < 3.1.0
+ */
+class BackportConstants
+{
+ public function __invoke(Analysis $analysis)
+ {
+ /** @var AnnotationSchema[] $schemas */
+ $schemas = $analysis->getAnnotationsOfType([AnnotationSchema::class, AttributeSchema::class], true);
+
+ foreach ($schemas as $schema) {
+ if (Generator::isDefault($schema->const)) {
+ continue;
+ }
+
+ if (version_compare($analysis->context->version, OpenApi::VERSION_3_1_0, '<')) {
+ $schema->type = 'enum';
+ $schema->enum = [$schema->const];
+ $schema->const = Generator::UNDEFINED;
+ }
+ }
+ }
+}