fix: add missing support for oneOf directive in schema printer

src/Utils/ASTDefinitionBuilder.php

@@ -536,16 +536,42 @@ private function makeScalarDef(ScalarTypeDefinitionNode $def): CustomScalarType
         ]);
     }
 
-    /** @throws InvariantViolation */
+    /**
+     * @throws \Exception
+     * @throws \ReflectionException
+     * @throws InvariantViolation
+     */
     private function makeInputObjectDef(InputObjectTypeDefinitionNode $def): InputObjectType
     {
         $name = $def->name->value;
         /** @var array<InputObjectTypeExtensionNode> $extensionASTNodes (proven by schema validation) */
         $extensionASTNodes = $this->typeExtensionsMap[$name] ?? [];
 
+        $oneOfDirective = Directive::oneOfDirective();
+
+        // Check for @oneOf directive in the definition node
+        $isOneOf = Values::getDirectiveValues(
+            $oneOfDirective,
+            $def
+        ) !== null;
+
+        // Check for @oneOf directive in extension nodes
+        if (! $isOneOf) {
+            foreach ($extensionASTNodes as $extensionNode) {
+                if (Values::getDirectiveValues(
+                    $oneOfDirective,
+                    $extensionNode
+                ) !== null) {
+                    $isOneOf = true;
+                    break;
+                }
+            }
+        }
+
         return new InputObjectType([
             'name' => $name,
             'description' => $def->description->value ?? null,
+            'isOneOf' => $isOneOf,
             'fields' => fn (): array => $this->makeInputFields([$def, ...$extensionASTNodes]),
             'astNode' => $def,
             'extensionASTNodes' => $extensionASTNodes,

src/Utils/SchemaPrinter.php

@@ -563,6 +563,7 @@ protected static function printInputObject(InputObjectType $type, array $options
 
         return static::printDescription($options, $type)
             . "input {$type->name}"
+            . ($type->isOneOf() ? ' @oneOf' : '')
             . static::printBlock($fields);
     }
 

tests/Utils/BuildSchemaTest.php

@@ -1042,6 +1042,39 @@ public function testCorrectlyExtendInputObjectType(): void
         self::assertSame($inputSDL, $this->printAllASTNodes($someInput));
     }
 
+    /** @see it('Correctly extend input object type with @oneOf directive') */
+    public function testCorrectlyExtendInputObjectTypeWithOneOfDirective(): void
+    {
+        $inputSDL = <<<'GRAPHQL'
+            input SomeInput {
+              first: String
+            }
+
+            extend input SomeInput @oneOf {
+              second: Int
+            }
+
+            GRAPHQL;
+
+        $schema = BuildSchema::build($inputSDL);
+
+        $someInput = $schema->getType('SomeInput');
+        assert($someInput instanceof InputObjectType);
+
+        // Verify that the @oneOf directive from the extension is properly applied
+        self::assertTrue($someInput->isOneOf());
+
+        $expectedSomeInputSDL = <<<'GRAPHQL'
+            input SomeInput @oneOf {
+              first: String
+              second: Int
+            }
+            GRAPHQL;
+
+        self::assertSame($expectedSomeInputSDL, SchemaPrinter::printType($someInput));
+        self::assertSame($inputSDL, $this->printAllASTNodes($someInput));
+    }
+
     /** @see it('Correctly assign AST nodes') */
     public function testCorrectlyAssignASTNodes(): void
     {

tests/Utils/SchemaPrinterTest.php

@@ -764,6 +764,32 @@ public function testInputType(): void
         );
     }
 
+    /** @see it('Print Input Type with @oneOf directive') */
+    public function testInputTypeWithOneOfDirective(): void
+    {
+        $inputType = new InputObjectType([
+            'name' => 'InputType',
+            'isOneOf' => true,
+            'fields' => [
+                'int' => Type::int(),
+            ],
+        ]);
+
+        $schema = new Schema([
+            'types' => [$inputType],
+        ]);
+
+        self::assertPrintedSchemaEquals(
+            <<<'GRAPHQL'
+            input InputType @oneOf {
+              int: Int
+            }
+
+            GRAPHQL,
+            $schema
+        );
+    }
+
     /** @see it('Custom Scalar') */
     public function testCustomScalar(): void
     {