BUG Fix nesting bug in Kernel

src/Core/Config/ConfigLoader.php

@@ -37,6 +37,11 @@ public static function inst()
      */
     public function getManifest()
     {
+        if ($this !== self::$instance) {
+            throw new BadMethodCallException(
+                "Non-current config manifest cannot be accessed. Please call ->activate() first"
+            );
+        }
         if (empty($this->manifests)) {
             throw new BadMethodCallException("No config manifests available");
         }

src/Core/Injector/InjectorLoader.php

@@ -36,6 +36,11 @@ public static function inst()
      */
     public function getManifest()
     {
+        if ($this !== self::$instance) {
+            throw new BadMethodCallException(
+                "Non-current injector manifest cannot be accessed. Please call ->activate() first"
+            );
+        }
         if (empty($this->manifests)) {
             throw new BadMethodCallException("No injector manifests available");
         }
@@ -87,8 +92,8 @@ public function countManifests()
      */
     public function nest()
     {
-        // Nest config
-        $manifest = $this->getManifest()->nest();
+        // Nest injector (note: Don't call getManifest()->nest() since that self-pushes a new manifest)
+        $manifest = clone $this->getManifest();
 
         // Create new blank loader with new stack (top level nesting)
         $newLoader = new static;
@@ -101,9 +106,12 @@ public function nest()
 
     /**
      * Mark this instance as the current instance
+     *
+     * @return $this
      */
     public function activate()
     {
         static::$instance = $this;
+        return $this;
     }
 }

tests/php/Core/KernelTest.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace SilverStripe\Core\Tests;
+
+use BadMethodCallException;
+use SilverStripe\Control\Director;
+use SilverStripe\Core\Config\Config;
+use SilverStripe\Core\Config\ConfigLoader;
+use SilverStripe\Core\Injector\Injector;
+use SilverStripe\Core\Injector\InjectorLoader;
+use SilverStripe\Core\Kernel;
+use SilverStripe\Dev\SapphireTest;
+
+class KernelTest extends SapphireTest
+{
+    public function testNesting()
+    {
+        /** @var Kernel $kernel */
+        $kernel = Injector::inst()->get(Kernel::class);
+
+        $nested1 = $kernel->nest();
+        Director::config()->set('alternate_base_url', '/mysite/');
+        $this->assertEquals($nested1->getConfigLoader(), ConfigLoader::inst());
+        $this->assertEquals($nested1->getInjectorLoader(), InjectorLoader::inst());
+        $this->assertEquals(1, ConfigLoader::inst()->countManifests());
+        $this->assertEquals(1, InjectorLoader::inst()->countManifests());
+
+        // Re-nest
+        $nested2 = $nested1->nest();
+
+        // Nesting config / injector should increase this count
+        Injector::nest();
+        Config::nest();
+        $this->assertEquals($nested2->getConfigLoader(), ConfigLoader::inst());
+        $this->assertEquals($nested2->getInjectorLoader(), InjectorLoader::inst());
+        $this->assertEquals(2, ConfigLoader::inst()->countManifests());
+        $this->assertEquals(2, InjectorLoader::inst()->countManifests());
+        Director::config()->set('alternate_base_url', '/anothersite/');
+
+        // Nesting always resets sub-loaders to 1
+        $nested2->nest();
+        $this->assertEquals(1, ConfigLoader::inst()->countManifests());
+        $this->assertEquals(1, InjectorLoader::inst()->countManifests());
+
+        // Calling ->activate() on a previous kernel restores
+        $nested1->activate();
+        $this->assertEquals($nested1->getConfigLoader(), ConfigLoader::inst());
+        $this->assertEquals($nested1->getInjectorLoader(), InjectorLoader::inst());
+        $this->assertEquals('/mysite/', Director::config()->get('alternate_base_url'));
+        $this->assertEquals(1, ConfigLoader::inst()->countManifests());
+        $this->assertEquals(1, InjectorLoader::inst()->countManifests());
+    }
+
+    public function testInvalidInjectorDetection()
+    {
+        $this->expectException(BadMethodCallException::class);
+        $this->expectExceptionMessage(
+            "Non-current injector manifest cannot be accessed. Please call ->activate() first"
+        );
+
+        /** @var Kernel $kernel */
+        $kernel = Injector::inst()->get(Kernel::class);
+        $kernel->nest(); // $kernel is no longer current kernel
+
+        $kernel->getInjectorLoader()->getManifest();
+    }
+
+    public function testInvalidConfigDetection()
+    {
+        $this->expectException(BadMethodCallException::class);
+        $this->expectExceptionMessage(
+            "Non-current config manifest cannot be accessed. Please call ->activate() first"
+        );
+
+        /** @var Kernel $kernel */
+        $kernel = Injector::inst()->get(Kernel::class);
+        $kernel->nest(); // $kernel is no longer current kernel
+
+        $kernel->getConfigLoader()->getManifest();
+    }
+}