From 107d9b4d23f8d37186513dffe5c0434122b6ae0f Mon Sep 17 00:00:00 2001
From: Christian Daguerre <cdaguerre@worldia.com>
Date: Wed, 2 Mar 2022 10:14:28 +0100
Subject: [PATCH] add processor to backport const keyword for open api < 3.1

---
 src/Generator.php                    |  1 +
 src/Processors/BackportConstants.php | 37 ++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 src/Processors/BackportConstants.php

diff --git a/src/Generator.php b/src/Generator.php
index ef0bca7d3..5b8eb2601 100644
--- a/src/Generator.php
+++ b/src/Generator.php
@@ -191,6 +191,7 @@ public function getProcessors(): array
                 new Processors\MergeXmlContent(),
                 new Processors\OperationId(),
                 new Processors\CleanUnmerged(),
+                new Processors\BackportConstants(),
             ];
         }
 
diff --git a/src/Processors/BackportConstants.php b/src/Processors/BackportConstants.php
new file mode 100644
index 000000000..2049bd06e
--- /dev/null
+++ b/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;
+            }
+        }
+    }
+}