Allow varying ExpressiveUrlGeneratorFactory behavior

This patch adds a new optional constructor argument to the
`ExpressiveUrlGeneratorFactory`, a string `$urlHelperServiceName`. By
default, it uses `Zend\Expressive\Helper\UrlHelper` for the value. Users
can, however, specify an alternate service class. This allows users to
vary the `ExpressiveUrlGenerator` per module or path-segregated
middleware pipeline:

```php
// In configuration:
return [
    'dependencies' => [
        'factories' => [
            \Api\Router::class => FastRouteRouterFactory::class,
            \Api\RouteMiddleware::class => new RouteMiddlewareFactory(\Api\Router::class),
            \Api\UrlHelper::class => new UrlHelperFactory('/api', \Api\Router::class),
            \Api\UrlHelperMiddleware::class => new UrlHelperMiddlewareFactory(\Api\UrlHelper::class),
            \Api\UrlGenerator::class => new ExpressiveUrlGeneratorFactory(\Api\UrlHelper::class),
        ],
    ],
],
```

The factory implements `__set_state()`, allowing serialization via
`var_export()` (the mechanism used by the default expressive
configuration caching mechanism).

Author: weierophinney

src/LinkGenerator/ExpressiveUrlGeneratorFactory.php

@@ -1,7 +1,7 @@
 <?php
 /**
  * @see       https://github.com/zendframework/zend-expressive-hal for the canonical source repository
- * @copyright Copyright (c) 2017 Zend Technologies USA Inc. (http://www.zend.com)
+ * @copyright Copyright (c) 2017-2018 Zend Technologies USA Inc. (http://www.zend.com)
  * @license   https://github.com/zendframework/zend-expressive-hal/blob/master/LICENSE.md New BSD License
  */
 
@@ -16,19 +16,40 @@
 
 class ExpressiveUrlGeneratorFactory
 {
+    /** @var string */
+    private $urlHelperServiceName;
+
+    /**
+     * Allow serialization
+     */
+    public static function __set_state(array $data) : self
+    {
+        return new self(
+            $data['urlHelperServiceName'] ?? UrlHelper::class
+        );
+    }
+
+    /**
+     * Vary behavior based on the URL helper service name.
+     */
+    public function __construct(string $urlHelperServiceName = UrlHelper::class)
+    {
+        $this->urlHelperServiceName = $urlHelperServiceName;
+    }
+
     public function __invoke(ContainerInterface $container) : ExpressiveUrlGenerator
     {
-        if (! $container->has(UrlHelper::class)) {
+        if (! $container->has($this->urlHelperServiceName)) {
             throw new RuntimeException(sprintf(
                 '%s requires a %s in order to generate a %s instance; none found',
                 __CLASS__,
-                UrlHelper::class,
+                $this->urlHelperServiceName,
                 ExpressiveUrlGenerator::class
             ));
         }
 
         return new ExpressiveUrlGenerator(
-            $container->get(UrlHelper::class),
+            $container->get($this->urlHelperServiceName),
             $container->has(ServerUrlHelper::class) ? $container->get(ServerUrlHelper::class) : null
         );
     }

test/LinkGenerator/ExpressiveUrlGeneratorFactoryTest.php

@@ -1,7 +1,7 @@
 <?php
 /**
  * @see       https://github.com/zendframework/zend-expressive-hal for the canonical source repository
- * @copyright Copyright (c) 2017 Zend Technologies USA Inc. (http://www.zend.com)
+ * @copyright Copyright (c) 2017-2018 Zend Technologies USA Inc. (http://www.zend.com)
  * @license   https://github.com/zendframework/zend-expressive-hal/blob/master/LICENSE.md New BSD License
  */
 
@@ -67,4 +67,30 @@ public function testFactoryCanCreateUrlGeneratorWithBothUrlHelperAndServerUrlHel
         $this->assertAttributeSame($urlHelper, 'urlHelper', $generator);
         $this->assertAttributeSame($serverUrlHelper, 'serverUrlHelper', $generator);
     }
+
+    public function testFactoryCanAcceptUrlHelperServiceNameToConstructor()
+    {
+        $urlHelper = $this->prophesize(UrlHelper::class)->reveal();
+
+        $this->container->has(CustomUrlHelper::class)->willReturn(true);
+        $this->container->get(CustomUrlHelper::class)->willReturn($urlHelper);
+        $this->container->has(ServerUrlHelper::class)->willReturn(false);
+
+        $factory = new ExpressiveUrlGeneratorFactory(CustomUrlHelper::class);
+        $generator = $factory($this->container->reveal());
+
+        $this->assertInstanceOf(ExpressiveUrlGenerator::class, $generator);
+        $this->assertAttributeSame($urlHelper, 'urlHelper', $generator);
+        $this->assertAttributeEmpty('serverUrlHelper', $generator);
+    }
+
+    public function testFactoryIsSerializable()
+    {
+        $factory = ExpressiveUrlGeneratorFactory::__set_state([
+            'urlHelperServiceName' => CustomUrlHelper::class,
+        ]);
+
+        $this->assertInstanceOf(ExpressiveUrlGeneratorFactory::class, $factory);
+        $this->assertAttributeSame(CustomUrlHelper::class, 'urlHelperServiceName', $factory);
+    }
 }