Ensure aliases can reference explicit services

With the most recent changes to allow unshared aliases, aliases to
explicitly registered services no longer worked. This patch adds logic
to get() to check if:

- the alias is shared, AND
- the resolved service is present

and, if so, registers the service under the alias, returning it.

Author: weierophinney

src/ServiceManager.php

@@ -166,6 +166,16 @@ public function get($name)
             return $this->services[$requestedName];
         }
 
+        // Next, if the alias should be shared, and we have cached the resolved
+        // service, use it.
+        if ($requestedName !== $name
+            && (! isset($this->shared[$requestedName]) || $this->shared[$requestedName])
+            && isset($this->services[$name])
+        ) {
+            $this->services[$requestedName] = $this->services[$name];
+            return $this->services[$name];
+        }
+
         // At this point, we need to create the instance; we use the resolved
         // name for that.
         $object = $this->doCreate($name);

test/ServiceManagerTest.php

@@ -221,4 +221,23 @@ public function testSharedServicesReferencingAliasShouldBeHonored()
 
         $this->assertNotSame($instance1, $instance2);
     }
+
+    public function testAliasToAnExplicitServiceShouldWork()
+    {
+        $config = [
+            'aliases' => [
+                'Invokable' => InvokableObject::class,
+            ],
+            'services' => [
+                InvokableObject::class => new InvokableObject(),
+            ],
+        ];
+
+        $serviceManager = new ServiceManager($config);
+
+        $service = $serviceManager->get(InvokableObject::class);
+        $alias   = $serviceManager->get('Invokable');
+
+        $this->assertSame($service, $alias);
+    }
 }