Introduce a factory for the Doctype view helper.

This factory and default configuration preserves the historic method of configuring the doctype for an MVC application

composer.json

@@ -28,6 +28,7 @@
         "php": "^7.4 || ~8.0.0 || ~8.1.0",
         "laminas/laminas-http": "^2.15",
         "laminas/laminas-servicemanager": "^3.16.0",
+        "laminas/laminas-view": "^2.22.0",
         "psr/container": "^1 || ^2",
         "webmozart/assert": "^1.11.0"
     },

src/ConfigProvider.php

@@ -5,6 +5,7 @@
 namespace Laminas\Mvc\View;
 
 use Laminas\ServiceManager\ConfigInterface;
+use Laminas\View\Helper as ViewHelper;
 
 /** @psalm-import-type ServiceManagerConfigurationType from ConfigInterface */
 final class ConfigProvider
@@ -27,6 +28,16 @@ public function __invoke(): array
                  */
                 'server_url' => null, // i.e 'https://example.com'
             ],
+            /**
+             * MVC has historically used the `view_manager` top-level key for a range of configuration options
+             */
+            'view_manager' => [
+                /**
+                 * Configure a doctype for HTML views by selecting one of the available constants in the
+                 * {@link ViewHelper\Doctype} helper class.
+                 */
+                'doctype' => null,
+            ],
         ];
     }
 
@@ -42,6 +53,10 @@ public function getViewHelperConfig(): array
         return [
             'factories' => [
                 Helper\ServerUrl::class => Helper\Factory\ServerUrlFactory::class,
+                /**
+                 * Factories for helpers in Laminas\View
+                 */
+                ViewHelper\Doctype::class => Helper\Factory\DoctypeFactory::class,
             ],
             'aliases'   => [
                 'serverUrl' => Helper\ServerUrl::class,

src/Helper/Factory/DoctypeFactory.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Laminas\Mvc\View\Helper\Factory;
+
+use ArrayAccess;
+use Laminas\View\Helper\Doctype;
+use Psr\Container\ContainerInterface;
+
+use function assert;
+use function is_array;
+use function is_string;
+
+final class DoctypeFactory
+{
+    public function __invoke(ContainerInterface $container): Doctype
+    {
+        $helper = new Doctype();
+
+        if (! $container->has('config')) {
+            return $helper;
+        }
+
+        $config = $container->get('config');
+        assert(is_array($config) || $config instanceof ArrayAccess);
+
+        $options = $config['view_manager'] ?? [];
+        assert(is_array($options));
+
+        /** @var mixed $doctype */
+        $doctype = $options['doctype'] ?? null;
+        if (is_string($doctype)) {
+            $helper->setDoctype($doctype);
+        }
+
+        return $helper;
+    }
+}

test/Helper/Factory/DoctypeFactoryTest.php

@@ -0,0 +1,95 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LaminasTest\Mvc\View\Helper\Factory;
+
+use Laminas\Mvc\View\Helper\Factory\DoctypeFactory;
+use Laminas\View\Helper\Doctype;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Psr\Container\ContainerInterface;
+
+final class DoctypeFactoryTest extends TestCase
+{
+    private DoctypeFactory $factory;
+    /** @var MockObject&ContainerInterface */
+    private ContainerInterface $container;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        $this->factory   = new DoctypeFactory();
+        $this->container = $this->createMock(ContainerInterface::class);
+        Doctype::unsetDoctypeRegistry(); // Overcome nasty static state
+    }
+
+    public function testAHelperWillBeReturnedWhenNoConfigIsFound(): void
+    {
+        $this->container->expects(self::once())
+            ->method('has')
+            ->with('config')
+            ->willReturn(false);
+
+        $this->container->expects(self::never())
+            ->method('get');
+
+        $this->factory->__invoke($this->container);
+    }
+
+    public function testThatTheDoctypeWillBeAsConfiguredWhenAppropriateConfigCanBeFound(): void
+    {
+        $config = [
+            'view_manager' => [
+                'doctype' => Doctype::HTML4_FRAMESET,
+            ],
+        ];
+
+        $this->container->expects(self::once())
+            ->method('has')
+            ->with('config')
+            ->willReturn(true);
+
+        $this->container->expects(self::once())
+            ->method('get')
+            ->with('config')
+            ->willReturn($config);
+
+        $helper = $this->factory->__invoke($this->container);
+
+        self::assertEquals(Doctype::HTML4_FRAMESET, $helper->getDoctype());
+    }
+
+    /** @return array<string, array{0: iterable<mixed>, 1: string}> */
+    public function configProvider(): array
+    {
+        $helper  = new Doctype();
+        $default = $helper->getDoctype();
+
+        return [
+            'Empty Config'          => [[], $default],
+            'Missing Doctype Key'   => [['view_manager' => []], $default],
+            'Doctype Configured'    => [['view_manager' => ['doctype' => Doctype::XHTML1_RDFA]], Doctype::XHTML1_RDFA],
+            'Doctype Explicit Null' => [['view_manager' => ['doctype' => null]], $default],
+        ];
+    }
+
+    /** @dataProvider configProvider */
+    public function testConfigScenarios(iterable $config, string $expectedDoctype): void
+    {
+        $this->container->expects(self::once())
+            ->method('has')
+            ->with('config')
+            ->willReturn(true);
+
+        $this->container->expects(self::once())
+            ->method('get')
+            ->with('config')
+            ->willReturn($config);
+
+        $helper = $this->factory->__invoke($this->container);
+
+        self::assertEquals($expectedDoctype, $helper->getDoctype());
+    }
+}