feat: expose open string enum branches

README.md

@@ -158,6 +158,21 @@ if ($schema instanceof ReferenceSchema) {
 
 This makes valid recursive schemas safe to parse.
 
+An `anyOf` that combines one string enum with another string branch documents
+suggested values without closing the set. The canonical composite exposes the
+enum-bearing branch without requiring consumers to inspect the union shape:
+
+```php
+use Utopia\OpenAPI\Model\CompositeSchema;
+
+if ($schema instanceof CompositeSchema) {
+    $suggestedValues = $schema->openStringEnumBranch()?->enum ?? [];
+}
+```
+
+`oneOf`, unions with non-string branches, and unions with multiple enum branches
+are not treated as open string enums.
+
 ### Parameters and request bodies
 
 Path-level parameters are inherited by operations. An operation-level parameter with the same case-sensitive `name` and `in` value replaces the inherited parameter.

src/Model/CompositeSchema.php

@@ -26,4 +26,40 @@ public function __construct(
     ) {
         parent::__construct($title, $description, $nullable, $default, $enum, $format, $readOnly, $writeOnly, $deprecated, $example, $extensions);
     }
+
+    /**
+     * Return the documented values from an open string enum.
+     *
+     * An open string enum uses anyOf to combine one string enum with one or
+     * more string branches that accept values outside the documented set.
+     */
+    public function openStringEnumBranch(): ?StringSchema
+    {
+        if ($this->composition !== Composition::ANY_OF) {
+            return null;
+        }
+
+        $enumBranch = null;
+        $hasOpenBranch = false;
+
+        foreach ($this->schemas as $schema) {
+            if (! $schema instanceof StringSchema) {
+                return null;
+            }
+
+            if ($schema->enum === []) {
+                $hasOpenBranch = true;
+
+                continue;
+            }
+
+            if ($enumBranch !== null) {
+                return null;
+            }
+
+            $enumBranch = $schema;
+        }
+
+        return $hasOpenBranch ? $enumBranch : null;
+    }
 }

tests/Schema/ReaderTest.php

@@ -105,6 +105,66 @@ public function test_composition_and_not(): void
         self::assertInstanceOf(StringSchema::class, $negated->not);
     }
 
+    public function test_open_string_enum_branch_is_exposed_regardless_of_branch_order(): void
+    {
+        $reader = $this->reader(Version::V3_0);
+        $enum = ['type' => 'string', 'enum' => ['network.requests', 'network.inbound']];
+        $open = ['type' => 'string'];
+
+        foreach ([[$enum, $open], [$open, $enum]] as $branches) {
+            $schema = $reader->read(['anyOf' => $branches], '#/x');
+
+            self::assertInstanceOf(CompositeSchema::class, $schema);
+            self::assertSame(['network.requests', 'network.inbound'], $schema->openStringEnumBranch()?->enum);
+        }
+    }
+
+    public function test_open_string_enum_requires_any_of(): void
+    {
+        $reader = $this->reader(Version::V3_0);
+        $branches = [
+            ['type' => 'string', 'enum' => ['known']],
+            ['type' => 'string'],
+        ];
+
+        foreach ([Composition::ONE_OF, Composition::ALL_OF] as $composition) {
+            $schema = $reader->read([$composition->value => $branches], '#/x');
+
+            self::assertInstanceOf(CompositeSchema::class, $schema);
+            self::assertNull($schema->openStringEnumBranch());
+        }
+    }
+
+    public function test_open_string_enum_requires_one_enum_and_an_open_string_branch(): void
+    {
+        $reader = $this->reader(Version::V3_0);
+        $invalidUnions = [
+            [['type' => 'string', 'enum' => ['known']]],
+            [['type' => 'string'], ['type' => 'string']],
+            [
+                ['type' => 'string', 'enum' => ['first']],
+                ['type' => 'string', 'enum' => ['second']],
+                ['type' => 'string'],
+            ],
+            [
+                ['type' => 'integer', 'enum' => [1]],
+                ['type' => 'string'],
+            ],
+            [
+                ['type' => 'string', 'enum' => ['known']],
+                ['type' => 'string'],
+                ['type' => 'integer'],
+            ],
+        ];
+
+        foreach ($invalidUnions as $branches) {
+            $schema = $reader->read(['anyOf' => $branches], '#/x');
+
+            self::assertInstanceOf(CompositeSchema::class, $schema);
+            self::assertNull($schema->openStringEnumBranch());
+        }
+    }
+
     public function test_discriminator_is_read_from_both_the_string_and_object_forms(): void
     {
         $reader = $this->reader(Version::V3_0);